Corley, Richard A.; Minard, Kevin R.; Kabilan, Senthil; Einstein, Daniel R.; Kuprat, Andrew P.; harkema, J. R.; Kimbell, Julia; Gargas, M. L.; Kinzell, John H.
2009-06-01
The percentages of total air?ows over the nasal respiratory and olfactory epithelium of female rabbits were cal-culated from computational ?uid dynamics (CFD) simulations of steady-state inhalation. These air?ow calcula-tions, along with nasal airway geometry determinations, are critical parameters for hybrid CFD/physiologically based pharmacokinetic models that describe the nasal dosimetry of water-soluble or reactive gases and vapors in rabbits. CFD simulations were based upon three-dimensional computational meshes derived from magnetic resonance images of three adult female New Zealand White (NZW) rabbits. In the anterior portion of the nose, the maxillary turbinates of rabbits are considerably more complex than comparable regions in rats, mice, mon-keys, or humans. This leads to a greater surface area to volume ratio in this region and thus the potential for increased extraction of water soluble or reactive gases and vapors in the anterior portion of the nose compared to many other species. Although there was considerable interanimal variability in the ?ne structures of the nasal turbinates and air?ows in the anterior portions of the nose, there was remarkable consistency between rabbits in the percentage of total inspired air?ows that reached the ethmoid turbinate region (~50%) that is presumably lined with olfactory epithelium. These latter results (air?ows reaching the ethmoid turbinate region) were higher than previous published estimates for the male F344 rat (19%) and human (7%). These di?erences in regional air?ows can have signi?cant implications in interspecies extrapolations of nasal dosimetry.
Gasification CFD Modeling for Advanced Power Plant Simulations
Zitney, S.E.; Guenther, C.P.
2005-09-01
In this paper we have described recent progress on developing CFD models for two commercial-scale gasifiers, including a two-stage, coal slurry-fed, oxygen-blown, pressurized, entrained-flow gasifier and a scaled-up design of the PSDF transport gasifier. Also highlighted was NETL’s Advanced Process Engineering Co-Simulator for coupling high-fidelity equipment models with process simulation for the design, analysis, and optimization of advanced power plants. Using APECS, we have coupled the entrained-flow gasifier CFD model into a coal-fired, gasification-based FutureGen power and hydrogen production plant. The results for the FutureGen co-simulation illustrate how the APECS technology can help engineers better understand and optimize gasifier fluid dynamics and related phenomena that impact overall power plant performance.
Dr. Chenn Zhou
2008-10-15
Pulverized coal injection (PCI) into the blast furnace (BF) has been recognized as an effective way to decrease the coke and total energy consumption along with minimization of environmental impacts. However, increasing the amount of coal injected into the BF is currently limited by the lack of knowledge of some issues related to the process. It is therefore important to understand the complex physical and chemical phenomena in the PCI process. Due to the difficulty in attaining trus BF measurements, Computational fluid dynamics (CFD) modeling has been identified as a useful technology to provide such knowledge. CFD simulation is powerful for providing detailed information on flow properties and performing parametric studies for process design and optimization. In this project, comprehensive 3-D CFD models have been developed to simulate the PCI process under actual furnace conditions. These models provide raceway size and flow property distributions. The results have provided guidance for optimizing the PCI process.
A simplified DEM-CFD approach for pebble bed reactor simulations
Li, Y.; Ji, W.
2012-07-01
In pebble bed reactors (PBR's), the pebble flow and the coolant flow are coupled with each other through coolant-pebble interactions. Approaches with different fidelities have been proposed to simulate similar phenomena. Coupled Discrete Element Method-Computational Fluid Dynamics (DEM-CFD) approaches are widely studied and applied in these problems due to its good balance between efficiency and accuracy. In this work, based on the symmetry of the PBR geometry, a simplified 3D-DEM/2D-CFD approach is proposed to speed up the DEM-CFD simulation without significant loss of accuracy. Pebble flow is simulated by a full 3-D DEM, while the coolant flow field is calculated with a 2-D CFD simulation by averaging variables along the annular direction in the cylindrical geometry. Results show that this simplification can greatly enhance the efficiency for cylindrical core, which enables further inclusion of other physics such as thermal and neutronic effect in the multi-physics simulations for PBR's. (authors)
Thermal hydraulic simulations, error estimation and parameter sensitivity studies in Drekar::CFD
Smith, Thomas Michael; Shadid, John N.; Pawlowski, Roger P.; Cyr, Eric C.; Wildey, Timothy Michael
2014-01-01
This report describes work directed towards completion of the Thermal Hydraulics Methods (THM) CFD Level 3 Milestone THM.CFD.P7.05 for the Consortium for Advanced Simulation of Light Water Reactors (CASL) Nuclear Hub effort. The focus of this milestone was to demonstrate the thermal hydraulics and adjoint based error estimation and parameter sensitivity capabilities in the CFD code called Drekar::CFD. This milestone builds upon the capabilities demonstrated in three earlier milestones; THM.CFD.P4.02 [12], completed March, 31, 2012, THM.CFD.P5.01 [15] completed June 30, 2012 and THM.CFD.P5.01 [11] completed on October 31, 2012.
Using Process/CFD Co-Simulation for the Design and Analysis of Advanced Energy Systems
Zitney, S.E.
2007-04-01
In this presentation we describe the major features and capabilities of NETL’s Advanced Process Engineering Co-Simulator (APECS) and highlight its application to advanced energy systems, ranging from small fuel cell systems to commercial-scale power plants including the coal-fired, gasification-based electricity and hydrogen plant in the DOE’s $1 billion, 10-year FutureGen demonstration project. APECS is an integrated software suite which allows the process and energy industries to optimize overall plant performance with respect to complex thermal and fluid flow phenomena by combining process simulation (e.g., Aspen Plus®) with high-fidelity equipment simulations based on computational fluid dynamics (CFD) models (e.g., FLUENT®).
Development of CFD-Based Simulation Tools for In-Situ Thermal...
Office of Scientific and Technical Information (OSTI)
Processing of Oil ShaleSands Citation Details In-Document Search Title: Development of CFD-Based Simulation Tools for In-Situ Thermal Processing of Oil ShaleSands In our ...
Development of CFD-Based Simulation Tools for In-Situ Thermal...
Office of Scientific and Technical Information (OSTI)
CFD-Based Simulation Tools for In-Situ Thermal Processing of Oil ShaleSands None 04 OIL SHALES AND TAR SANDS In our research, we are taking the novel approach of developing and...
Coupled full core neutron transport/CFD simulations of pressurized water reactors
Kochunas, B.; Stimpson, S.; Collins, B.; Downar, T.; Brewster, R.; Baglietto, E.; Yan, J.
2012-07-01
Recently as part of the CASL project, a capability to perform 3D whole-core coupled neutron transport and computational fluid dynamics (CFD) calculations was demonstrated. This work uses the 2D/1D transport code DeCART and the commercial CFD code STAR-CCM+. It builds on previous CASL work demonstrating coupling for smaller spatial domains. The coupling methodology is described along with the problem simulated and results are presented for fresh hot full power conditions. An additional comparison is made to an equivalent model that uses lower order T/H feedback to assess the importance and cost of high fidelity feedback to the neutronics problem. A simulation of a quarter core Combustion Engineering (CE) PWR core was performed with the coupled codes using a Fixed Point Gauss-Seidel iteration technique. The total approximate calculation requirements are nearly 10,000 CPU hours and 1 TB of memory. The problem took 6 coupled iterations to converge. The CFD coupled model and low order T/H feedback model compared well for global solution parameters, with a difference in the critical boron concentration and average outlet temperature of 14 ppm B and 0.94 deg. C, respectively. Differences in the power distribution were more significant with maximum relative differences in the core-wide pin peaking factor (Fq) of 5.37% and average relative differences in flat flux region power of 11.54%. Future work will focus on analyzing problems more relevant to CASL using models with less approximations. (authors)
Pitz, William J.; McNenly, Matt J.; Whitesides, Russell; Mehl, Marco; Killingsworth, Nick J.; Westbrook, Charles K.
2015-12-17
Predictive chemical kinetic models are needed to represent next-generation fuel components and their mixtures with conventional gasoline and diesel fuels. These kinetic models will allow the prediction of the effect of alternative fuel blends in CFD simulations of advanced spark-ignition and compression-ignition engines. Enabled by kinetic models, CFD simulations can be used to optimize fuel formulations for advanced combustion engines so that maximum engine efficiency, fossil fuel displacement goals, and low pollutant emission goals can be achieved.
Wardle, K.E.
2013-07-01
Liquid-liquid contacting equipment used in solvent extraction processes has the dual purpose of mixing and separating two immiscible fluids. Consequently, such devices inherently encompass a wide variety of multiphase flow regimes. A hybrid multiphase computational fluid dynamics (CFD) solver which combines the Eulerian multi-fluid method with VOF (volume of fluid) sharp interface capturing has been developed for application to annular centrifugal contactors. This solver has been extended to enable prediction of mean droplet size and liquid-liquid interfacial area through a single moment population balance method. Simulations of liquid-liquid mixing in a simplified geometry and a model annular centrifugal contactor are reported with droplet breakup/coalescence models being calibrated versus available experimental data. Quantitative comparison is made for two different housing vane geometries and it is found that the predicted droplet size is significantly smaller for vane geometries which result in higher annular liquid holdup.
Designing high power targets with computational fluid dynamics (CFD)
Covrig, S. D.
2013-11-07
High power liquid hydrogen (LH2) targets, up to 850 W, have been widely used at Jefferson Lab for the 6 GeV physics program. The typical luminosity loss of a 20 cm long LH2 target was 20% for a beam current of 100 μA rastered on a square of side 2 mm on the target. The 35 cm long, 2500 W LH2 target for the Qweak experiment had a luminosity loss of 0.8% at 180 μA beam rastered on a square of side 4 mm at the target. The Qweak target was the highest power liquid hydrogen target in the world and with the lowest noise figure. The Qweak target was the first one designed with CFD at Jefferson Lab. A CFD facility is being established at Jefferson Lab to design, build and test a new generation of low noise high power targets.
Designing high power targets with computational fluid dynamics (CFD)
Covrig, Silviu D.
2013-11-01
High power liquid hydrogen (LH2) targets, up to 850 W, have been widely used at Jefferson Lab for the 6 GeV physics program. The typical luminosity loss of a 20 cm long LH2 target was 20% for a beam current of 100 {micro}A rastered on a square of side 2 mm on the target. The 35 cm long, 2500 W LH2 target for the Qweak experiment had a luminosity loss of 0.8% at 180 {micro}A beam rastered on a square of side 4 mm at the target. The Qweak target was the highest power liquid hydrogen target in the world and with the lowest noise figure. The Qweak target was the first one designed with CFD at Jefferson Lab. A CFD facility is being established at Jefferson Lab to design, build and test a new generation of low noise high power targets.
Coupling DAEM and CFD for simulating biomass fast pyrolysis in fluidized beds
Xiong, Qingang; Zhang, Jingchao; Wiggins, Gavin; Daw, C. Stuart; Xu, Fei
2015-12-03
We report results from computational simulations of an experimental, lab-scale bubbling bed biomass pyrolysis reactor that include a distributed activation energy model (DAEM) for the kinetics. In this study, we utilized multiphase computational fluid dynamics (CFD) to account for the turbulent hydrodynamics, and this was combined with the DAEM kinetics in a multi-component, multi-step reaction network. Our results indicate that it is possible to numerically integrate the coupled CFD–DAEM system without significantly increasing computational overhead. It is also clear, however, that reactor operating conditions, reaction kinetics, and multiphase flow dynamics all have major impacts on the pyrolysis products exiting the reactor. We find that, with the same pre-exponential factors and mean activation energies, inclusion of distributed activation energies in the kinetics can shift the predicted average value of the exit vapor-phase tar flux and its statistical distribution, compared to single-valued activation-energy kinetics. Perhaps the most interesting observed trend is that increasing the diversity of the DAEM activation energies appears to increase the mean tar yield, all else being equal. As a result, these findings imply that accurate resolution of the reaction activation energy distributions will be important for optimizing biomass pyrolysis processes.
Coupling DAEM and CFD for simulating biomass fast pyrolysis in fluidized beds
Xiong, Qingang; Zhang, Jingchao; Wiggins, Gavin; Daw, C. Stuart; Xu, Fei
2015-12-03
We report results from computational simulations of an experimental, lab-scale bubbling bed biomass pyrolysis reactor that include a distributed activation energy model (DAEM) for the kinetics. In this study, we utilized multiphase computational fluid dynamics (CFD) to account for the turbulent hydrodynamics, and this was combined with the DAEM kinetics in a multi-component, multi-step reaction network. Our results indicate that it is possible to numerically integrate the coupled CFD–DAEM system without significantly increasing computational overhead. It is also clear, however, that reactor operating conditions, reaction kinetics, and multiphase flow dynamics all have major impacts on the pyrolysis products exiting themore » reactor. We find that, with the same pre-exponential factors and mean activation energies, inclusion of distributed activation energies in the kinetics can shift the predicted average value of the exit vapor-phase tar flux and its statistical distribution, compared to single-valued activation-energy kinetics. Perhaps the most interesting observed trend is that increasing the diversity of the DAEM activation energies appears to increase the mean tar yield, all else being equal. As a result, these findings imply that accurate resolution of the reaction activation energy distributions will be important for optimizing biomass pyrolysis processes.« less
Arastoopour, Hamid; Abbasian, Javad
2014-07-31
This project describes the work carried out to prepare a highly reactive and mechanically strong MgO based sorbents and to develop a Population Balance Equations (PBE) approach to describe the evolution of the particle porosity distribution that is linked with Computational Fluid Dynamics (CFD) to perform simulations of the CO2 capture and sorbent regeneration. A large number of MgO-based regenerable sorbents were prepared using low cost and abundant dolomite as the base material. Among various preparation parameters investigated the potassium/magnesium (K/Mg) ratio was identified as the key variable affecting the reactivity and CO2 capacity of the sorbent. The optimum K/Mg ratio is about 0.15. The sorbent formulation HD52-P2 was identified as the “best” sorbent formulation and a large batch (one kg) of the sorbent was prepared for the detailed study. The results of parametric study indicate the optimum carbonation and regeneration temperatures are 360° and 500°C, respectively. The results also indicate that steam has a beneficial effect on the rate of carbonation and regeneration of the sorbent and that the reactivity and capacity of the sorbent decreases in the cycling process (sorbent deactivation). The results indicate that to achieve a high CO2 removal efficiency, the bed of sorbent should be operated at a temperature range of 370-410°C which also favors production of hydrogen through the WGS reaction. To describe the carbonation reaction kinetics of the MgO, the Variable Diffusivity shrinking core Model (VDM) was developed in this project, which was shown to accurately fit the experimental data. An important advantage of this model is that the changes in the sorbent conversion with time can be expressed in an explicit manner, which will significantly reduce the CFD computation time. A Computational Fluid Dynamic/Population Balance Equations (CFD/PBE) model was developed that accounts for the particle (sorbent) porosity distribution and a new version of
Richard W. Johnson; Hugh M. McIlroy
2010-08-01
The U. S. Department of Energy (DOE) is supporting the development of a next generation nuclear plant (NGNP), which will be based on a very high temperature reactor (VHTR) design. The VHTR is a single-phase helium-cooled reactor wherein the helium will be heated initially to 750 °C and later to temperatures approaching 1000 °C. The high temperatures are desired to increase reactor efficiency and to provide a heat source for the manufacture of hydrogen and other applications. While computational fluid dynamics (CFD) has not been used in the past to design or license nuclear reactors in the U. S., it is expected that CFD will be used in the design and safety analysis of forthcoming designs. This is partly because of the maturity of CFD and partly because detailed information is desired of the flow and heat transfer inside the reactor to avoid hot spots and other conditions that might compromise reactor safety. Numerical computations of turbulent flow should be validated against experimental data for flow conditions that contain some or all of the physics expected in the thermal fluid machinery of interest. To this end, a scaled model of a narrow slice of the lower plenum of the prismatic VHTR was constructed and installed in the Idaho National Laboratory’s (INL) matched index of refraction (MIR) test facility and data were taken. The data were then studied and compared to CFD calculations to help determine their suitability for validation data. One of the main findings was that the inlet data, which were measured and controlled by calibrated mass flow rotameters and were also measured using detailed stereo particle image velocimetry (PIV) showed considerable discrepancies in mass flow rate between the two methods. The other finding was that a randomly unstable recirculation zone occurs in the flow. This instability has a very significant effect on the flow field in the vicinity of the inlet jets. Because its time scale is long and because it is apparently a
Office of Energy Efficiency and Renewable Energy (EERE)
Presentation given by Argonne National Laboratory at 2014 DOE Hydrogen and Fuel Cells Program and Vehicle Technologies Office Annual Merit Review and Peer Evaluation Meeting about CFD simulations...
JACKSON VL
2011-08-31
The primary purpose of the tank mixing and sampling demonstration program is to mitigate the technical risks associated with the ability of the Hanford tank farm delivery and celtification systems to measure and deliver a uniformly mixed high-level waste (HLW) feed to the Waste Treatment and Immobilization Plant (WTP) Uniform feed to the WTP is a requirement of 24590-WTP-ICD-MG-01-019, ICD-19 - Interface Control Document for Waste Feed, although the exact definition of uniform is evolving in this context. Computational Fluid Dynamics (CFD) modeling has been used to assist in evaluating scaleup issues, study operational parameters, and predict mixing performance at full-scale.
CFD Simulation of 3D Flow field in a Gas Centrifuge
Dongjun Jiang; Shi Zeng
2006-07-01
A CFD method was used to study the whole flow field in a gas centrifuge. In this paper, the VSM (Vector Splitting Method) of the FVM (Finite Volume Method) was used to solve the 3D Navier-Stokes equations. An implicit second-order upwind scheme was adopted. The numerical simulation was successfully performed on a parallel cluster computer and a convergence result was obtained. The simulation shows that: in the withdrawal chamber, a strong detached shock wave is formed in front of the scoop; as the radial position increases, the shock becomes stronger and the distance to scoop front surface is smaller. An oblique shock forms in the clearance between the scoop and the centrifuge wall; behind the shock-wave, the radially-inward motion of gas is induced because of the imbalance of the pressure gradient and the centrifugal force. In the separation chamber, a countercurrent is introduced. This indicates that CFD method can be used to study the complex three-dimensional flow field of gas centrifuges. (authors)
Leishear, Robert A.; Lee, Si Y.; Poirier, Michael R.; Steeper, Timothy J.; Ervin, Robert C.; Giddings, Billy J.; Stefanko, David B.; Harp, Keith D.; Fowley, Mark D.; Van Pelt, William B.
2012-10-07
Computational fluid dynamics (CFD) is recognized as a powerful engineering tool. That is, CFD has advanced over the years to the point where it can now give us deep insight into the analysis of very complex processes. There is a danger, though, that an engineer can place too much confidence in a simulation. If a user is not careful, it is easy to believe that if you plug in the numbers, the answer comes out, and you are done. This assumption can lead to significant errors. As we discovered in the course of a study on behalf of the Department of Energy's Savannah River Site in South Carolina, CFD models fail to capture some of the large variations inherent in complex processes. These variations, or scatter, in experimental data emerge from physical tests and are inadequately captured or expressed by calculated mean values for a process. This anomaly between experiment and theory can lead to serious errors in engineering analysis and design unless a correction factor, or safety factor, is experimentally validated. For this study, blending times for the mixing of salt solutions in large storage tanks were the process of concern under investigation. This study focused on the blending processes needed to mix salt solutions to ensure homogeneity within waste tanks, where homogeneity is required to control radioactivity levels during subsequent processing. Two of the requirements for this task were to determine the minimum number of submerged, centrifugal pumps required to blend the salt mixtures in a full-scale tank in half a day or less, and to recommend reasonable blending times to achieve nearly homogeneous salt mixtures. A full-scale, low-flow pump with a total discharge flow rate of 500 to 800 gpm was recommended with two opposing 2.27-inch diameter nozzles. To make this recommendation, both experimental and CFD modeling were performed. Lab researchers found that, although CFD provided good estimates of an average blending time, experimental blending times varied
CFD simulation of MSW combustion and SNCR in a commercial incinerator
Xia, Zihong; Li, Jian; Wu, Tingting; Chen, Caixia; Zhang, Xiaoke
2014-09-15
Highlights: • Presented a CFD scheme for modeling MSW incinerator including SNCR process. • Performed a sensitivity analysis of SNCR operating conditions. • Non-uniform distributions of gas velocity, temperature and NO{sub x} in the incinerator. • The injection position of reagent was critical for a desirable performance of SNCR. • A NSR 1.5 was recommended as a compromise of NO{sub x} reduction rates and NH{sub 3} slip. - Abstract: A CFD scheme was presented for modeling municipal solid waste (MSW) combustion in a moving-grate incinerator, including the in-bed burning of solid wastes, the out-of-bed burnout of gaseous volatiles, and the selective non-catalytic reduction (SNCR) process between urea (CO(NH{sub 2}){sub 2}) and NO{sub x}. The in-bed calculations provided 2-D profiles of the gas–solid temperatures and the gas species concentrations along the bed length, which were then used as inlet conditions for the out-of-bed computations. The over-bed simulations provided the profiles of incident radiation heat flux on the top of bed. A 3-dimensional benchmark simulation was conducted with a 750 t/day commercial incinerator using the present coupling scheme incorporating with a reduced SNCR reduction mechanism. Numerical tests were performed to investigate the effects of operating parameters such as injection position, injection speed and the normalized stoichiometric ratio (NSR) on the SNCR performance. The simulation results showed that the distributions of gas velocity, temperature and NO{sub x} concentration were highly non-uniform, which made the injection position one of the most sensitive operating parameters influencing the SNCR performance of moving grate incinerators. The simulation results also showed that multi-layer injections were needed to meet the EU2000 standard, and a NSR 1.5 was suggested as a compromise of a satisfactory NO{sub x} reduction and reasonable NH{sub 3} slip rates. This work provided useful guides to the design and
Energy Science and Technology Software Center (OSTI)
2015-10-20
Look-ahead dynamic simulation software system incorporates the high performance parallel computing technologies, significantly reduces the solution time for each transient simulation case, and brings the dynamic simulation analysis into on-line applications to enable more transparency for better reliability and asset utilization. It takes the snapshot of the current power grid status, functions in parallel computing the system dynamic simulation, and outputs the transient response of the power system in real time.
Sun Qi; Groth, Alexandra; Bertram, Matthias; Waechter, Irina; Bruijns, Tom; Hermans, Roel; Aach, Til
2010-09-15
Purpose: Recently, image-based computational fluid dynamics (CFD) simulation has been applied to investigate the hemodynamics inside human cerebral aneurysms. The knowledge of the computed three-dimensional flow fields is used for clinical risk assessment and treatment decision making. However, the reliability of the application specific CFD results has not been thoroughly validated yet. Methods: In this work, by exploiting a phantom aneurysm model, the authors therefore aim to prove the reliability of the CFD results obtained from simulations with sufficiently accurate input boundary conditions. To confirm the correlation between the CFD results and the reality, virtual angiograms are generated by the simulation pipeline and are quantitatively compared to the experimentally acquired angiograms. In addition, a parametric study has been carried out to systematically investigate the influence of the input parameters associated with the current measuring techniques on the flow patterns. Results: Qualitative and quantitative evaluations demonstrate good agreement between the simulated and the real flow dynamics. Discrepancies of less than 15% are found for the relative root mean square errors of time intensity curve comparisons from each selected characteristic position. The investigated input parameters show different influences on the simulation results, indicating the desired accuracy in the measurements. Conclusions: This study provides a comprehensive validation method of CFD simulation for reproducing the real flow field in the cerebral aneurysm phantom under well controlled conditions. The reliability of the CFD is well confirmed. Through the parametric study, it is possible to assess the degree of validity of the associated CFD model based on the parameter values and their estimated accuracy range.
Cantera Aerosol Dynamics Simulator
Energy Science and Technology Software Center (OSTI)
2004-09-01
The Cantera Aerosol Dynamics Simulator (CADS) package is a general library for aerosol modeling to address aerosol general dynamics, including formation from gas phase reactions, surface chemistry (growth and oxidation), bulk particle chemistry, transport by Brownian diffusion, thermophoresis, and diffusiophoresis with linkage to DSMC studies, and thermal radiative transport. The library is based upon Cantera, a C++ Cal Tech code that handles gas phase species transport, reaction, and thermodynamics. The method uses a discontinuous galerkinmore » formulation for the condensation and coagulation operator that conserves particles, elements, and enthalpy up to round-off error. Both O-D and 1-D time dependent applications have been developed with the library. Multiple species in the solid phase are handled as well. The O-D application, called Tdcads (Time Dependent CADS) is distributed with the library. Tdcads can address both constant volume and constant pressure adiabatic homogeneous problems. An extensive set of sample problems for Tdcads is also provided.« less
Energy Science and Technology Software Center (OSTI)
2015-09-14
GridDyn is a part of power grid simulation toolkit. The code is designed using modern object oriented C++ methods utilizing C++11 and recent Boost libraries to ensure compatibility with multiple operating systems and environments.
Computational Fluid Dynamics Simulation of Fluidized Bed Polymerization Reactors
Rong Fan
2006-08-09
, monovariate population balance, bivariate population balance, aggregation and breakage equation and DQMOM-Multi-Fluid model are described. In the last section of Chapter 3, numerical methods involved in the multi-fluid model and time-splitting method are presented. Chapter 4 is based on a paper about application of DQMOM to polydisperse gas-solid fluidized beds. Results for a constant aggregation and breakage kernel and a kernel developed from kinetic theory are shown. The effect of the aggregation success factor and the fragment distribution function are investigated. Chapter 5 shows the work on validation of mixing and segregation phenomena in gas-solid fluidized beds with a binary mixture or a continuous size distribution. The simulation results are compared with available experiment data and discrete-particle simulation. Chapter 6 presents the project with Univation Technologies on CFD simulation of a Polyethylene pilot-scale FB reactor, The fluid dynamics, mass/heat transfer and particle size distribution are investigated through CFD simulation and validated with available experimental data. The conclusions of this study and future work are discussed in Chapter 7.
Dynamic Simulation Nuclear Power Plants
Energy Science and Technology Software Center (OSTI)
1992-03-03
DSNP (Dynamic Simulator for Nuclear Power-Plants) is a system of programs and data files by which a nuclear power plant, or part thereof, can be simulated. The acronym DSNP is used interchangeably for the DSNP language, the DSNP libraries, the DSNP precompiler, and the DSNP document generator. The DSNP language is a special-purpose, block-oriented, digital-simulation language developed to facilitate the preparation of dynamic simulations of a large variety of nuclear power plants. It is amore » user-oriented language that permits the user to prepare simulation programs directly from power plant block diagrams and flow charts by recognizing the symbolic DSNP statements for the appropriate physical components and listing these statements in a logical sequence according to the flow of physical properties in the simulated power plant. Physical components of nuclear power plants are represented by functional blocks, or modules. Many of the more complex components are represented by several modules. The nuclear reactor, for example, has a kinetic module, a power distribution module, a feedback module, a thermodynamic module, a hydraulic module, and a radioactive heat decay module. These modules are stored in DSNP libraries in the form of a DSNP subroutine or function, a block of statements, a macro, or a combination of the above. Basic functional blocks such as integrators, pipes, function generators, connectors, and many auxiliary functions representing properties of materials used in nuclear power plants are also available. The DSNP precompiler analyzes the DSNP simulation program, performs the appropriate translations, inserts the requested modules from the library, links these modules together, searches necessary data files, and produces a simulation program in FORTRAN.« less
Dynamics of Molecular Clouds: Observations, Simulations, and...
Office of Scientific and Technical Information (OSTI)
Simulations, and NIF Experiments Citation Details In-Document Search Title: Dynamics of Molecular Clouds: Observations, Simulations, and NIF Experiments You are ...
The MAX facility for CFD code validation
Lomperski, S.; Merzari, E.; Obabko, A.; Pointer, W. D.; Fischer, P.
2012-07-01
ANL has recently completed construction of a fluid dynamics test facility devised to provide validation data for CFD simulation tools used to evaluate various aspects of nuclear power plant design and safety. Experiments with the facility involve mixing air jets within a 1x1x1.7m long glass tank at atmospheric pressure. A particle image velocimetry system measures flow velocity and turbulence quantities within the tank while a high-speed infrared camera records temperatures across the tank lid. The tandem of high fidelity thermal and turbulence data is particularly useful for benchmarking transient heat transfer phenomena such as thermal striping. This paper describes the MAX facility, preliminary data obtained during shakedown tests, and the results of companion CFD calculations employing RANS-based Star-CCM+ and large eddy simulations with Nek 5000. (authors)
Simulation and sequential dynamical systems
Mortveit, H.S.; Reidys, C.M.
1999-06-01
Computer simulations have a generic structure. Motivated by this the authors present a new class of discrete dynamical systems that captures this structure in a mathematically precise way. This class of systems consists of (1) a loopfree graph {Upsilon} with vertex set {l_brace}1,2,{hor_ellipsis},n{r_brace} where each vertex has a binary state, (2) a vertex labeled set of functions (F{sub i,{Upsilon}}:F{sub 2}{sup n} {yields} F{sub 2}{sup n}){sub i} and (3) a permutation {pi} {element_of} S{sub n}. The function F{sub i,{Upsilon}} updates the state of vertex i as a function of the states of vertex i and its {Upsilon}-neighbors and leaves the states of all other vertices fixed. The permutation {pi} represents the update ordering, i.e., the order in which the functions F{sub i,{Upsilon}} are applied. By composing the functions F{sub i,{Upsilon}} in the order given by {pi} one obtains the dynamical system (equation given in paper), which the authors refer to as a sequential dynamical system, or SDS for short. The authors will present bounds for the number of functionally different systems and for the number of nonisomorphic digraphs {Gamma}[F{sub {Upsilon}},{pi}] that can be obtained by varying the update order and applications of these to specific graphs and graph classes.
Communication: Quantum molecular dynamics simulation of liquid...
Office of Scientific and Technical Information (OSTI)
Communication: Quantum molecular dynamics simulation of liquid para-hydrogen by nuclear and electron wave packet approach Citation Details In-Document Search Title: Communication:...
Dynamics Simulation in a Wave Environment
U.S. Department of Energy (DOE) all webpages (Extended Search)
focus: Advanced Naval concepts Also have projects in: Offshore Platforms Wave Energy Converters Wind Power 3 Coupled Dynamics (AEGIR Co-simulation Capability) * Interprocess ...
Nonequilibrium molecular dynamics simulations of confined fluids...
Office of Scientific and Technical Information (OSTI)
A nonequilibrium molecular dynamics (MD) ... in a single simulation upon compression, whereas fluid molecules in the bulk ... for weak fluid -- wall interactions. ...
Thermoacoustic engine simulations with lattice Boltzmann CFD. Tasks 3, 4 and 5 progress report
1995-02-06
Advanced Projects Research Incorporated has completed tasks number 3, 4 and 5 of the specified tasks in the LANL subcontract. Task 3 required measurement of the acoustic attenuation for various thermoacoustic conditions and Task 4 involved the analysis of the energy transfer mechanisms for the geometries of Task 3. Finally, Task 5 specified that simulations of thermoacoustic engine configurations used at LANL were to be performed. Discussion of all 3 task results is presented.
simulate the dynamic distribution of lithium in the electrode
U.S. Department of Energy (DOE) all webpages (Extended Search)
simulate the dynamic distribution of lithium in the electrode - Sandia Energy Energy ... simulate the dynamic distribution of lithium in the electrode HomeTag:simulate the ...
Parallel Implementation of Power System Dynamic Simulation
Jin, Shuangshuang; Huang, Zhenyu; Diao, Ruisheng; Wu, Di; Chen, Yousu
2013-07-21
Dynamic simulation of power system transient stability is important for planning, monitoring, operation, and control of electrical power systems. However, modeling the system dynamics and network involves the computationally intensive time-domain solution of numerous differential and algebraic equations (DAE). This results in a transient stability implementation that may not maintain the real-time constraints of an online security assessment. This paper presents a parallel implementation of the dynamic simulation on a high-performance computing (HPC) platform using parallel simulation algorithms and computation architectures. It enables the simulation to run even faster than real time, enabling the look-ahead capability of upcoming stability problems in the power grid.
The Dalles Dam, Columbia River: Spillway Improvement CFD Study
Cook, Chris B.; Richmond, Marshall C.; Serkowski, John A.
2006-06-01
This report documents development of computational fluid dynamics (CFD) models that were applied to The Dalles spillway for the US Army Corps of Engineers, Portland District. The models have been successfully validated against physical models and prototype data, and are suitable to support biological research and operations management. The CFD models have been proven to provide reliable information in the turbulent high-velocity flow field downstream of the spillway face that is typically difficult to monitor in the prototype. In addition, CFD data provides hydraulic information throughout the solution domain that can be easily extracted from archived simulations for later use if necessary. This project is part of an ongoing program at the Portland District to improve spillway survival conditions for juvenile salmon at The Dalles. Biological data collected at The Dalles spillway have shown that for the original spillway configuration juvenile salmon passage survival is lower than desired. Therefore, the Portland District is seeking to identify operational and/or structural changes that might be implemented to improve fish passage survival. Pacific Northwest National Laboratory (PNNL) went through a sequence of steps to develop a CFD model of The Dalles spillway and tailrace. The first step was to identify a preferred CFD modeling package. In the case of The Dalles spillway, Flow-3D was as selected because of its ability to simulate the turbulent free-surface flows that occur downstream of each spilling bay. The second step in development of The Dalles CFD model was to assemble bathymetric datasets and structural drawings sufficient to describe the dam (powerhouse, non-overflow dam, spillway, fish ladder entrances, etc.) and tailrace. These datasets are documented in this report as are various 3-D graphical representations of The Dalles spillway and tailrace. The performance of the CFD model was then validated for several cases as the third step. The validated model
Xu, Chuanfu; Deng, Xiaogang; Zhang, Lilun; Fang, Jianbin; Wang, Guangxue; Jiang, Yi; Cao, Wei; Che, Yonggang; Wang, Yongxian; Wang, Zhenghua; Liu, Wei; Cheng, Xinghua
2014-12-01
Programming and optimizing complex, real-world CFD codes on current many-core accelerated HPC systems is very challenging, especially when collaborating CPUs and accelerators to fully tap the potential of heterogeneous systems. In this paper, with a tri-level hybrid and heterogeneous programming model using MPI + OpenMP + CUDA, we port and optimize our high-order multi-block structured CFD software HOSTA on the GPU-accelerated TianHe-1A supercomputer. HOSTA adopts two self-developed high-order compact definite difference schemes WCNS and HDCS that can simulate flows with complex geometries. We present a dual-level parallelization scheme for efficient multi-block computation on GPUs and perform particular kernel optimizations for high-order CFD schemes. The GPU-only approach achieves a speedup of about 1.3 when comparing one Tesla M2050 GPU with two Xeon X5670 CPUs. To achieve a greater speedup, we collaborate CPU and GPU for HOSTA instead of using a naive GPU-only approach. We present a novel scheme to balance the loads between the store-poor GPU and the store-rich CPU. Taking CPU and GPU load balance into account, we improve the maximum simulation problem size per TianHe-1A node for HOSTA by 2.3×, meanwhile the collaborative approach can improve the performance by around 45% compared to the GPU-only approach. Further, to scale HOSTA on TianHe-1A, we propose a gather/scatter optimization to minimize PCI-e data transfer times for ghost and singularity data of 3D grid blocks, and overlap the collaborative computation and communication as far as possible using some advanced CUDA and MPI features. Scalability tests show that HOSTA can achieve a parallel efficiency of above 60% on 1024 TianHe-1A nodes. With our method, we have successfully simulated an EET high-lift airfoil configuration containing 800M cells and China's large civil airplane configuration containing 150M cells. To our best knowledge, those are the largest-scale CPU–GPU collaborative simulations that
Molecular dynamics simulation studies of electrolytes andelectrolyte...
Merit Review and Peer Evaluation Meeting, May 18-22, 2009 -- Washington D.C. es40smith.pdf (4 MB) More Documents & Publications Molecular Dynamics Simulation Studies of ...
CFD code development for performance evaluation of a pilot-scale FCC riser reactor
Chang, S.L.; Lottes, S.A.; Zhou, C.Q.; Golchert, B.; Petrick, M.
1997-09-01
Fluid Catalytic Cracking (FCC) is an important conversion process for the refining industry. The improvement of FCC technology could have a great impact on the public in general by lowering the cost of transportation fuel. A recent review of the FCC technology development by Bienstock et al. of Exxon indicated that the use of computational fluid dynamics (CFD) simulation can be very effective in the advancement of the technology. Theologos and Markatos used a commercial CFD code to model an FCC riser reactor. National Laboratories of the U.S. Department of Energy (DOE) have accumulated immense CFD expertise over the years for various engineering applications. A recent DOE survey showed that National Laboratories are using their CFD expertise to help the refinery industry improve the FCC technology under DOE`s Cooperative Research and Development Agreement (CRADA). Among them are Los Alamos National Laboratory with Exxon and Amoco and Argonne National Laboratory (ANL) with Chevron and UOP. This abstract briefly describes the current status of ANL`s work. The objectives of the ANL CRADA work are (1) to use a CFD code to simulate FCC riser reactor flow and (2) to evaluate the impacts of operating conditions and design parameters on the product yields. The CFD code used in this work was originally developed for spray combustion simulation in early 1980 at Argonne. It has been successfully applied to diagnosing a number of multi-phase reacting flow problems in a magneto-hydrodynamic power train. A new version of the CFD code developed for the simulation of the FCC riser flow is called Integral CRacKing FLOw (ICRKFLO). The CFD code solves conservation equations of general flow properties for three phases: gaseous species, liquid droplets, and solid particles. General conservation laws are used in conjunction with rate equations governing the mass, momentum, enthalpy, and species for a multi-phase flow with gas species, liquid droplets, and solid particles.
CFD analysis of laminar oscillating flows
Booten, C. W. Charles W.); Konecni, S.; Smith, B. L.; Martin, R. A.
2001-01-01
This paper describes a numerical simulations of oscillating flow in a constricted duct and compares the results with experimental and theoretical data. The numerical simulations were performed using the computational fluid dynamics (CFD) code CFX4.2. The numerical model simulates an experimental oscillating flow facility that was designed to test the properties and characteristics of oscillating flow in tapered ducts, also known as jet pumps. Jet pumps are useful devices in thermoacoustic machinery because they produce a secondary pressure that can counteract an unwanted effect called streaming, and significantly enhance engine efficiency. The simulations revealed that CFX could accurately model velocity, shear stress and pressure variations in laminar oscillating flow. The numerical results were compared to experimental data and theoretical predictions with varying success. The least accurate numerical results were obtained when laminar flow approached transition to turbulent flow.
Sandia Energy - Molecular Dynamics Simulations Predict Fate of...
U.S. Department of Energy (DOE) all webpages (Extended Search)
Molecular Dynamics Simulations Predict Fate of Uranium in Sediments Home Highlights - Energy Research Molecular Dynamics Simulations Predict Fate of Uranium in Sediments Previous...
Dynamic procedure for filtered gyrokinetic simulations
Morel, P.; Banon Navarro, A.; Albrecht-Marc, M.; Carati, D.; Merz, F.; Goerler, T.; Jenko, F.
2012-01-15
Large eddy simulations (LES) of gyrokinetic plasma turbulence are investigated as interesting candidates to decrease the computational cost. A dynamic procedure is implemented in the gene code, allowing for dynamic optimization of the free parameters of the LES models (setting the amplitudes of dissipative terms). Employing such LES methods, one recovers the free energy and heat flux spectra obtained from highly resolved direct numerical simulations. Systematic comparisons are performed for different values of the temperature gradient and magnetic shear, parameters which are of prime importance in ion temperature gradient driven turbulence. Moreover, the degree of anisotropy of the problem, which can vary with parameters, can be adapted dynamically by the method that shows gyrokinetic large eddy simulation to be a serious candidate to reduce numerical cost of gyrokinetic solvers.
Dynamic Fracture Simulations of Explosively Loaded Cylinders
Arthur, Carly W.; Goto, D. M.
2015-11-30
This report documents the modeling results of high explosive experiments investigating dynamic fracture of steel (AerMet® 100 alloy) cylinders. The experiments were conducted at Lawrence Livermore National Laboratory (LLNL) during 2007 to 2008 [10]. A principal objective of this study was to gain an understanding of dynamic material failure through the analysis of hydrodynamic computer code simulations. Two-dimensional and three-dimensional computational cylinder models were analyzed using the ALE3D multi-physics computer code.
Dynamic simulation gives 20-20 foresight
Womack, J.W.
1986-04-07
Dynamic simulation is being increasingly recognized as a viable tool for system analysis and design. Its use by Mobil Research and Development Corp. (MRDC) has grown steadily. Applications fall into three major categories: Support of major capital projects, mostly in the form of high-fidelity models capable of answering many of the ''what-if'' questions which arise during the engineering design, construction, and commissioning phases of a project; Simulators for operator training, which have been acquired for an increasing fraction of both new and existing facilities over the past 10 years; Solution of operational problems, evaluate process changes, and in debottlenecking studies of existing facilities. A number of dynamic simulations have been done by contractors or system vendors. MRDC involvement was limited to review and/or acceptance of the work. MRDC did not write any of the training simulator programs, for example, although its inputs often influenced their development.
Predicting aerodynamic characteristic of typical wind turbine airfoils using CFD
Wolfe, W.P. [Sandia National Labs., Albuquerque, NM (United States); Ochs, S.S. [Iowa State Univ., Ames, IA (United States). Aerospace Engineering Dept.
1997-09-01
An investigation was conducted into the capabilities and accuracy of a representative computational fluid dynamics code to predict the flow field and aerodynamic characteristics of typical wind-turbine airfoils. Comparisons of the computed pressure and aerodynamic coefficients were made with wind tunnel data. This work highlights two areas in CFD that require further investigation and development in order to enable accurate numerical simulations of flow about current generation wind-turbine airfoils: transition prediction and turbulence modeling. The results show that the laminar-to turbulent transition point must be modeled correctly to get accurate simulations for attached flow. Calculations also show that the standard turbulence model used in most commercial CFD codes, the k-e model, is not appropriate at angles of attack with flow separation. 14 refs., 28 figs., 4 tabs.
Gebraad, P. M. O.; Teeuwisse, F. W.; van Wingerden, J. W.; Fleming, Paul A.; Ruben, S. D.; Marden, J. R.; Pao, L. Y.
2016-01-01
This article presents a wind plant control strategy that optimizes the yaw settings of wind turbines for improved energy production of the whole wind plant by taking into account wake effects. The optimization controller is based on a novel internal parametric model for wake effects, called the FLOw Redirection and Induction in Steady-state (FLORIS) model. The FLORIS model predicts the steady-state wake locations and the effective flow velocities at each turbine, and the resulting turbine electrical energy production levels, as a function of the axial induction and the yaw angle of the different rotors. The FLORIS model has a limited number of parameters that are estimated based on turbine electrical power production data. In high-fidelity computational fluid dynamics simulations of a small wind plant, we demonstrate that the optimization control based on the FLORIS model increases the energy production of the wind plant, with a reduction of loads on the turbines as an additional effect.
Gebraad, P. M. O.; Teeuwisse, F. W.; van Wingerden, J. W.; Fleming, Paul A.; Ruben, S. D.; Marden, J. R.; Pao, L. Y.
2016-01-01
This article presents a wind plant control strategy that optimizes the yaw settings of wind turbines for improved energy production of the whole wind plant by taking into account wake effects. The optimization controller is based on a novel internal parametric model for wake effects, called the FLOw Redirection and Induction in Steady-state (FLORIS) model. The FLORIS model predicts the steady-state wake locations and the effective flow velocities at each turbine, and the resulting turbine electrical energy production levels, as a function of the axial induction and the yaw angle of the different rotors. The FLORIS model has a limitedmore » number of parameters that are estimated based on turbine electrical power production data. In high-fidelity computational fluid dynamics simulations of a small wind plant, we demonstrate that the optimization control based on the FLORIS model increases the energy production of the wind plant, with a reduction of loads on the turbines as an additional effect.« less
On Extended-Term Dynamic Simulations
U.S. Department of Energy (DOE) all webpages (Extended Search)
Extended-Term Dynamic Simulations with High Penetrations of Photovoltaic Generation Ricky Concepcion, Ryan Elliott Sandia National Laboratories Albuquerque, NM 87185 {rconcep, rtellio}@sandia.gov Matt Donnelly Montana Tech Butte, MT 59701 mdonnelly@mtech.edu Juan Sanchez-Gasca GE Energy Schenectady, NY 12345 juan1.sanchez@ge.com Abstract-The uncontrolled intermittent availability of renew- able energy sources makes integration of such devices into today's grid a challenge. Thus, it is imperative
Integrated computer simulation on FIR FEL dynamics
Furukawa, H.; Kuruma, S.; Imasaki, K.
1995-12-31
An integrated computer simulation code has been developed to analyze the RF-Linac FEL dynamics. First, the simulation code on the electron beam acceleration and transport processes in RF-Linac: (LUNA) has been developed to analyze the characteristics of the electron beam in RF-Linac and to optimize the parameters of RF-Linac. Second, a space-time dependent 3D FEL simulation code (Shipout) has been developed. The RF-Linac FEL total simulations have been performed by using the electron beam data from LUNA in Shipout. The number of particles using in a RF-Linac FEL total simulation is approximately 1000. The CPU time for the simulation of 1 round trip is about 1.5 minutes. At ILT/ILE, Osaka, a 8.5MeV RF-Linac with a photo-cathode RF-gun is used for FEL oscillation experiments. By using 2 cm wiggler, the FEL oscillation in the wavelength approximately 46 {mu}m are investigated. By the simulations using LUNA with the parameters of an ILT/ILE experiment, the pulse shape and the energy spectra of the electron beam at the end of the linac are estimated. The pulse shape of the electron beam at the end of the linac has sharp rise-up and it slowly decays as a function of time. By the RF-linac FEL total simulations with the parameters of an ILT/ILE experiment, the dependencies of the start up of the FEL oscillations on the pulse shape of the electron beam at the end of the linac are estimated. The coherent spontaneous emission effects and the quick start up of FEL oscillations have been observed by the RF-Linac FEL total simulations.
Computational simulation of dynamic impact problems
Muenz, T.W.; Rix, K.S.; Willam, K.J.
1996-12-31
Recent advances of computing methods make it possible to examine dynamic failure and complicated contact-impact load scenarios in time and space. The response simulation for these extreme load conditions needs to capture dynamic contact between the impactor and the deformable target and progressive failure in the target. Independently from the impact scenario, two basic approaches may be used to describe the failure process in an appropriate manner, namely the Discrete Failure Approach and the Smeared Failure Approach. In the contribution the dynamic impact of a pendulum test and the failure scenario in notched cylindrical specimens (Charpy-type IZOD test) are examined using the explicit dynamic finite element code DYNA3D. The study focuses on the question, whether the smeared crack approach is able to capture the dynamic failure process using von Mises plasticity with a plastic strain-based failure limiter. The computational results indicate that upon consistent mesh refinement the overall energy dissipation approaches the value observed in laboratory experiments.
Multi-phase CFD modeling of solid sorbent carbon capture system
Ryan, E. M.; DeCroix, D.; Breault, Ronald W.; Xu, W.; Huckaby, E. David
2013-01-01
Computational fluid dynamics (CFD) simulations are used to investigate a low temperature post-combustion carbon capture reactor. The CFD models are based on a small scale solid sorbent carbon capture reactor design from ADA-ES and Southern Company. The reactor is a fluidized bed design based on a silica-supported amine sorbent. CFD models using both Eulerian–Eulerian and Eulerian–Lagrangian multi-phase modeling methods are developed to investigate the hydrodynamics and adsorption of carbon dioxide in the reactor. Models developed in both FLUENT® and BARRACUDA are presented to explore the strengths and weaknesses of state of the art CFD codes for modeling multi-phase carbon capture reactors. The results of the simulations show that the FLUENT® Eulerian–Lagrangian simulations (DDPM) are unstable for the given reactor design; while the BARRACUDA Eulerian–Lagrangian model is able to simulate the system given appropriate simplifying assumptions. FLUENT® Eulerian–Eulerian simulations also provide a stable solution for the carbon capture reactor given the appropriate simplifying assumptions.
Multi-Phase CFD Modeling of Solid Sorbent Carbon Capture System
Ryan, Emily M.; DeCroix, David; Breault, Ronald W.; Xu, Wei; Huckaby, E. D.; Saha, Kringan; Darteville, Sebastien; Sun, Xin
2013-07-30
Computational fluid dynamics (CFD) simulations are used to investigate a low temperature post-combustion carbon capture reactor. The CFD models are based on a small scale solid sorbent carbon capture reactor design from ADA-ES and Southern Company. The reactor is a fluidized bed design based on a silica-supported amine sorbent. CFD models using both Eulerian-Eulerian and Eulerian-Lagrangian multi-phase modeling methods are developed to investigate the hydrodynamics and adsorption of carbon dioxide in the reactor. Models developed in both FLUENT® and BARRACUDA are presented to explore the strengths and weaknesses of state of the art CFD codes for modeling multi-phase carbon capture reactors. The results of the simulations show that the FLUENT® Eulerian-Lagrangian simulations (DDPM) are unstable for the given reactor design; while the BARRACUDA Eulerian-Lagrangian model is able to simulate the system given appropriate simplifying assumptions. FLUENT® Eulerian-Eulerian simulations also provide a stable solution for the carbon capture reactor given the appropriate simplifying assumptions.
A texture-based framework for improving CFD data visualization in a virtual environment
Gerrick O'Ron Bivins
2005-05-05
In the field of computational fluid dynamics (CFD) accurate representations of fluid phenomena can be simulated hut require large amounts of data to represent the flow domain. Most datasets generated from a CFD simulation can be coarse, {approx}10,000 nodes or cells, or very fine with node counts on the order of 1,000,000. A typical dataset solution can also contain multiple solutions for each node, pertaining to various properties of the flow at a particular node. Scalar properties such as density, temperature, pressure, and velocity magnitude are properties that are typically calculated and stored in a dataset solution. Solutions are not limited to just scalar properties. Vector quantities, such as velocity, are also often calculated and stored for a CFD simulation. Accessing all of this data efficiently during runtime is a key problem for visualization in an interactive application. Understanding simulation solutions requires a post-processing tool to convert the data into something more meaningful. Ideally, the application would present an interactive visual representation of the numerical data for any dataset that was simulated while maintaining the accuracy of the calculated solution. Most CFD applications currently sacrifice interactivity for accuracy, yielding highly detailed flow descriptions hut limiting interaction for investigating the field.
Brownian Dynamics Simulation of Protein Solutions: Structural and Dynamical Properties
Mereghetti, Paolo; Gabdoulline, Razif; Wade, Rebecca C.
2010-12-01
The study of solutions of biomacromolecules provides an important basis for understanding the behavior of many fundamental cellular processes, such as protein folding, self-assembly, biochemical reactions, and signal transduction. Here, we describe a Brownian dynamics simulation procedure and its validation for the study of the dynamic and structural properties of protein solutions. In the model used, the proteins are treated as atomically detailed rigid bodies moving in a continuum solvent. The protein-protein interaction forces are described by the sum of electrostatic interaction, electrostatic desolvation, nonpolar desolvation, and soft-core repulsion terms. The linearized Poisson-Boltzmann equation is solved to compute electrostatic terms. Simulations of homogeneous solutions of three different proteins with varying concentrations, pH, and ionic strength were performed. The results were compared to experimental data and theoretical values in terms of long-time self-diffusion coefficients, second virial coefficients, and structure factors. The results agree with the experimental trends and, in many cases, experimental values are reproduced quantitatively. There are no parameters specific to certain protein types in the interaction model, and hence the model should be applicable to the simulation of the behavior of mixtures of macromolecules in cell-like crowded environments.
Experimental and CFD Analysis of Advanced Convective Cooling Systems
Hassan, Yassin A; Ugaz, Victor M
2012-06-27
The objective of this project is to study the fundamental physical phenomena in the reactor cavity cooling system (RCCS) of very high-temperature reactors (VHTRs). One of the primary design objectives is to assure that RCCS acts as an ultimate heat sink capable of maintaining thermal integrity of the fuel, vessel, and equipment within the reactor cavity for the entire spectrum of postulated accident scenarios. Since construction of full-scale experimental test facilities to study these phenomena is impractical, it is logical to expect that computational fluid dynamics (CFD) simulations will play a key role in the RCCS design process. An important question then arises: To what extent are conventional CFD codes able to accurately capture the most important flow phenomena, and how can they be modified to improve their quantitative predictions? Researchers are working to tackle this problem in two ways. First, in the experimental phase, the research team plans to design and construct an innovative platform that will provide a standard test setting for validating CFD codes proposed for the RCCS design. This capability will significantly advance the state of knowledge in both liquid-cooled and gas-cooled (e.g., sodium fast reactor) reactor technology. This work will also extend flow measurements to micro-scale levels not obtainable in large-scale test facilities, thereby revealing previously undetectable phenomena that will complement the existing infrastructure. Second, in the computational phase of this work, numerical simulation of the flow and temperature profiles will be performed using advanced turbulence models to simulate the complex conditions of flows in critical zones of the cavity. These models will be validated and verified so that they can be implemented into commercially available CFD codes. Ultimately, the results of these validation studies can then be used to enable a more accurate design and safety evaluation of systems in actual nuclear power
A Study of the Role of Adjoint-Equipped CFD in VUQ Analysis of...
U.S. Department of Energy (DOE) all webpages (Extended Search)
Study of the Role of Adjoint- Equipped CFD in VUQ Analysis of Channel Boiling Simulations Krzysztof Fidkowski University of Michigan Milestone L3:THM.CFD.P7.08 November 21, 2013 ...
On sequential dynamical systems and simulation
Barrett, C.L.; Mortveit, H.S.; Reidys, C.M.
1999-06-01
The generic structure of computer simulations motivates a new class of discrete dynamical systems that captures this structure in a mathematically precise way. This class of systems consists of (1) a loopfree graph {Upsilon} with vertex set {l_brace}1,2,{hor_ellipsis},n{r_brace} where each vertex has a binary state, (2) a vertex labeled set of functions (F{sub i,{Upsilon}}:F{sub 2}{sup n} {r_arrow} F{sub 2}{sup n}){sub i} and (3) a permutation {pi} {element_of} S{sub n}. The function F{sub i,{Upsilon}} updates the state of vertex i as a function of the states of vertex i and its {Upsilon}-neighbors and leaves the states of all other vertices fixed. The permutation {pi} represents the update ordering, i.e., the order in which the functions F{sub i,{Upsilon}} are applied. By composing the functions F{sub i,{Upsilon}} in the order given by {pi} one obtains the dynamical system (equation given in paper) which the authors refer to as a sequential dynamical system, or SDS for short. The authors will present bounds for the number of functionally different systems and for the number of nonisomorphic digraphs {Gamma}[F{sub {Upsilon}},{pi}] that can be obtained by varying the update order and applications of these to specific graphs and graph classes. This will be done using both combinatorial/algebraic techniques and probabilistic techniques. Finally the authors give results on dynamical system properties for some special systems.
Lee, S.
2011-05-05
The Savannah River Remediation (SRR) Organization requested that Savannah River National Laboratory (SRNL) develop a Computational Fluid Dynamics (CFD) method to mix and blend the miscible contents of the blend tanks to ensure the contents are properly blended before they are transferred from the blend tank; such as, Tank 50H, to the Salt Waste Processing Facility (SWPF) feed tank. The work described here consists of two modeling areas. They are the mixing modeling analysis during miscible liquid blending operation, and the flow pattern analysis during transfer operation of the blended liquid. The transient CFD governing equations consisting of three momentum equations, one mass balance, two turbulence transport equations for kinetic energy and dissipation rate, and one species transport were solved by an iterative technique until the species concentrations of tank fluid were in equilibrium. The steady-state flow solutions for the entire tank fluid were used for flow pattern analysis, for velocity scaling analysis, and the initial conditions for transient blending calculations. A series of the modeling calculations were performed to estimate the blending times for various jet flow conditions, and to investigate the impact of the cooling coils on the blending time of the tank contents. The modeling results were benchmarked against the pilot scale test results. All of the flow and mixing models were performed with the nozzles installed at the mid-elevation, and parallel to the tank wall. From the CFD modeling calculations, the main results are summarized as follows: (1) The benchmark analyses for the CFD flow velocity and blending models demonstrate their consistency with Engineering Development Laboratory (EDL) and literature test results in terms of local velocity measurements and experimental observations. Thus, an application of the established criterion to SRS full scale tank will provide a better, physically-based estimate of the required mixing time, and
Lopez, A.R.; Gritzo, L.A.; Hassan, B.
1997-06-01
For the purposes of designing improved Halon-alternative fire suppression strategies for aircraft applications, Computational Fluid Dynamics (CFD) simulations of the air flow, suppressant transport, and air-suppressant mixing within an uncluttered F18 engine nacelle were performed. The release of inert gases from a Solid Propellant Gas Generator (SPGG) was analyzed at two different injection locations in order to understand the effect of injection position on the flow patterns and the mixing of air and suppression agent. An uncluttered engine nacelle was simulated to provide insight into the global flow features as well as to promote comparisons with previous nacelle fire tests and recent water tunnel tests which included little or no clutter. Oxygen concentration levels, fuel/air residence times that would exist if a small fuel leak were present, velocity contours, and streamline patterns are presented inside the engine nacelle. The numerical results show the influence of the gent release location on regions of potential flame extinction due to oxygen inerting and high flame strain. The occurrence of inflow through the exhaust ducts on the aft end of the nacelle is also predicted. As expected, the predicted oxygen concentration levels were consistently higher than the measured levels since a fire was not modeled in this analysis. Despite differences in the conditions of these simulations and the experiments, good agreement was obtained between the CFD predictions and the experimental measurements.
Molecular dynamics simulations of microscale fluid transport
Wong, C.C.; Lopez, A.R.; Stevens, M.J.; Plimpton, S.J.
1998-02-01
Recent advances in micro-science and technology, like Micro-Electro-Mechanical Systems (MEMS), have generated a group of unique liquid flow problems that involve characteristic length scales of a Micron. Also, in manufacturing processes such as coatings, current continuum models are unable to predict microscale physical phenomena that appear in these non-equilibrium systems. It is suspected that in these systems, molecular-level processes can control the interfacial energy and viscoelastic properties at the liquid/solid boundary. A massively parallel molecular dynamics (MD) code has been developed to better understand microscale transport mechanisms, fluid-structure interactions, and scale effects in micro-domains. Specifically, this MD code has been used to analyze liquid channel flow problems for a variety of channel widths, e.g. 0.005-0.05 microns. This report presents results from MD simulations of Poiseuille flow and Couette flow problems and addresses both scaling and modeling issues. For Poiseuille flow, the numerical predictions are compared with existing data to investigate the variation of the friction factor with channel width. For Couette flow, the numerical predictions are used to determine the degree of slip at the liquid/solid boundary. Finally, the results also indicate that shear direction with respect to the wall lattice orientation can be very important. Simulation results of microscale Couette flow and microscale Poiseuille flow for two different surface structures and two different shear directions will be presented.
CFD modeling of entrained-flow coal gasifiers with improved physical and chemical sub-models
Ma, J.; Zitney, S.
2012-01-01
Optimization of an advanced coal-fired integrated gasification combined cycle system requires an accurate numerical prediction of gasifier performance. While the turbulent multiphase reacting flow inside entrained-flow gasifiers has been modeled through computational fluid dynamic (CFD), the accuracy of sub-models requires further improvement. Built upon a previously developed CFD model for entrained-flow gasification, the advanced physical and chemical sub-models presented here include a moisture vaporization model with consideration of high mass transfer rate, a coal devolatilization model with more species to represent coal volatiles and heating rate effect on volatile yield, and careful selection of global gas phase reaction kinetics. The enhanced CFD model is applied to simulate two typical oxygen-blown entrained-flow configurations including a single-stage down-fired gasifier and a two-stage up-fired gasifier. The CFD results are reasonable in terms of predicted carbon conversion, syngas exit temperature, and syngas exit composition. The predicted profiles of velocity, temperature, and species mole fractions inside the entrained-flow gasifier models show trends similar to those observed in a diffusion-type flame. The predicted distributions of mole fractions of major species inside both gasifiers can be explained by the heterogeneous combustion and gasification reactions and the homogeneous gas phase reactions. It was also found that the syngas compositions at the CFD model exits are not in chemical equilibrium, indicating the kinetics for both heterogeneous and gas phase homogeneous reactions are important. Overall, the results achieved here indicate that the gasifier models reported in this paper are reliable and accurate enough to be incorporated into process/CFD co-simulations of IGCC power plants for systemwide design and optimization.
Sandia Energy - Simulations Reveal Ion Dynamics in Polymer Electrolyte
U.S. Department of Energy (DOE) all webpages (Extended Search)
and their effects on material properties is important for improved design. Recent molecular-dynamics simulations have revealed new details of ion motion in model ionomers....
Molecular Dynamics Simulations of Gas Selectivity in Amorphous...
U.S. Department of Energy (DOE) all webpages (Extended Search)
Dynamics Simulations of Gas Selectivity in Amorphous Porous Molecular Solids Previous Next List Shan Jiang, Kim E. Jelfs, Daniel Holden, Tom Hasell, Samantha Y. Chong, Maciej...
Dynamic System Simulation of the KRUSTY Experiment (Technical...
Office of Scientific and Technical Information (OSTI)
Technical Report: Dynamic System Simulation of the KRUSTY Experiment Citation Details ... Have feedback or suggestions for a way to improve these results? Save Share this ...
Molecular dynamics simulation and ab intio studies of electrolytes...
Office of Energy Efficiency and Renewable Energy (EERE) (indexed site)
More Documents & Publications High Voltage Electrolytes for Li-ion Batteries Molecular Dynamics Simulation Studies of Electrolytes and ElectrolyteElectrode Interfaces
Molecular dynamics simulation and ab intio studies of electrolytes...
and Vehicle Technologies Program Annual Merit Review and Peer Evaluation es058smith2011o.pdf (854.25 KB) More Documents & Publications Molecular Dynamics Simulation ...
Rotational Brownian Dynamics simulations of clathrin cage formation
Ilie, Ioana M.; Briels, Wim J.; Otter, Wouter K. den
2014-08-14
The self-assembly of nearly rigid proteins into ordered aggregates is well suited for modeling by the patchy particle approach. Patchy particles are traditionally simulated using Monte Carlo methods, to study the phase diagram, while Brownian Dynamics simulations would reveal insights into the assembly dynamics. However, Brownian Dynamics of rotating anisotropic particles gives rise to a number of complications not encountered in translational Brownian Dynamics. We thoroughly test the Rotational Brownian Dynamics scheme proposed by Naess and Elsgaeter [Macromol. Theory Simul. 13, 419 (2004); Naess and Elsgaeter Macromol. Theory Simul. 14, 300 (2005)], confirming its validity. We then apply the algorithm to simulate a patchy particle model of clathrin, a three-legged protein involved in vesicle production from lipid membranes during endocytosis. Using this algorithm we recover time scales for cage assembly comparable to those from experiments. We also briefly discuss the undulatory dynamics of the polyhedral cage.
Simulation of spray drying in superheated steam using computational fluid dynamics
Frydman, A.; Vasseur, J.; Ducept, F.; Sionneau, M.; Moureh, J.
1999-09-01
This paper presents a numerical simulation and experimental validation of a spray dryer using superheated steam instead of air as drying medium, modeled with a computational fluid dynamics (CFD) code. The model describes momentum, heat and mass transfer between two phases--a discrete phase of droplets, and a continuous gas phase--through a finite volume method. For the simulation, droplet size distribution is represented by 6 discrete classes of diameter, fitting to the experimental distribution injected from the nozzle orifice, taking into account their peculiar shrinkage during drying. This model is able to predict the most important features of the dryer: fields of gas temperature and gas velocity inside the chamber, droplets trajectories and eventual deposits on to the wall. The results of simulation are compared to a pilot scale dryer, using water. In the absence of risk of power ignition in steam, the authors have tested rather high steam inlet temperature (973K), thus obtaining a high volumic efficiency. The model is validated by comparison between experimental and predicted values of temperature inside the chamber, verifying the coupling between the 3 different types of transfer without adjustment. This type of model can be used for chamber design, or scale up. Using superheated steam instead of air in a spray dryer can allow a high volumic evaporation rate (20 k.h.m{sup 3}), high energy recovery and better environment control.
Expansion techniques for collisionless stellar dynamical simulations
Meiron, Yohai; Li, Baile; Holley-Bockelmann, Kelly; Spurzem, Rainer
2014-09-10
We present graphics processing unit (GPU) implementations of two fast force calculation methods based on series expansions of the Poisson equation. One method is the self-consistent field (SCF) method, which is a Fourier-like expansion of the density field in some basis set; the other method is the multipole expansion (MEX) method, which is a Taylor-like expansion of the Green's function. MEX, which has been advocated in the past, has not gained as much popularity as SCF. Both are particle-field methods and optimized for collisionless galactic dynamics, but while SCF is a 'pure' expansion, MEX is an expansion in just the angular part; thus, MEX is capable of capturing radial structure easily, while SCF needs a large number of radial terms. We show that despite the expansion bias, these methods are more accurate than direct techniques for the same number of particles. The performance of our GPU code, which we call ETICS, is profiled and compared to a CPU implementation. On the tested GPU hardware, a full force calculation for one million particles took ∼0.1 s (depending on expansion cutoff), making simulations with as many as 10{sup 8} particles fast for a comparatively small number of nodes.
Kinetic simulations of plasmoid chain dynamics
Markidis, S. [High Performance Computing and Visualization (HPCViz) Department, KTH Royal Institute of Technology, Stockholm (Sweden)] [High Performance Computing and Visualization (HPCViz) Department, KTH Royal Institute of Technology, Stockholm (Sweden); Henri, P. [Universit de Nice Sophia Antipolis, CNRS, Observatoire de la Cte d'Azur, Nice (France)] [Universit de Nice Sophia Antipolis, CNRS, Observatoire de la Cte d'Azur, Nice (France); Lapenta, G. [Centrum voor Plasma-Astrofysica, Department Wiskunde, Katholieke Universiteit Leuven, Leuven (Belgium)] [Centrum voor Plasma-Astrofysica, Department Wiskunde, Katholieke Universiteit Leuven, Leuven (Belgium); Divin, A. [Swedish Institute of Space Physics, Uppsala (Sweden)] [Swedish Institute of Space Physics, Uppsala (Sweden); Goldman, M.; Newman, D. [Department of Physics and CIPS, University of Colorado, Boulder 80309-0390 (United States)] [Department of Physics and CIPS, University of Colorado, Boulder 80309-0390 (United States); Laure, E. [PDC and High Performance Computing and Visualization (HPCViz) Department, KTH Royal Institute of Technology, Stockholm (Sweden)] [PDC and High Performance Computing and Visualization (HPCViz) Department, KTH Royal Institute of Technology, Stockholm (Sweden)
2013-08-15
The dynamics of a plasmoid chain is studied with three dimensional Particle-in-Cell simulations. The evolution of the system with and without a uniform guide field, whose strength is 1/3 the asymptotic magnetic field, is investigated. The plasmoid chain forms by spontaneous magnetic reconnection: the tearing instability rapidly disrupts the initial current sheet generating several small-scale plasmoids that rapidly grow in size coalescing and kinking. The plasmoid kink is mainly driven by the coalescence process. It is found that the presence of guide field strongly influences the evolution of the plasmoid chain. Without a guide field, a main reconnection site dominates and smaller reconnection regions are included in larger ones, leading to an hierarchical structure of the plasmoid-dominated current sheet. On the contrary in presence of a guide field, plasmoids have approximately the same size and the hierarchical structure does not emerge, a strong core magnetic field develops in the center of the plasmoid in the direction of the existing guide field, and bump-on-tail instability, leading to the formation of electron holes, is detected in proximity of the plasmoids.
Dynamic Simulation over Long Time Periods with 100% Solar Generation.
Concepcion, Ricky James; Elliott, Ryan Thomas
2015-12-01
This project aimed to identify the path forward for dynamic simulation tools to accommodate these needs by characterizing the properties of power systems (with high PV penetration), analyzing how these properties affect dynamic simulation software, and offering solutions for potential problems.
Software Framework for Advanced Power Plant Simulations
John Widmann; Sorin Munteanu; Aseem Jain; Pankaj Gupta; Mark Moales; Erik Ferguson; Lewis Collins; David Sloan; Woodrow Fiveland; Yi-dong Lang; Larry Biegler; Michael Locke; Simon Lingard; Jay Yun
2010-08-01
This report summarizes the work accomplished during the Phase II development effort of the Advanced Process Engineering Co-Simulator (APECS). The objective of the project is to develop the tools to efficiently combine high-fidelity computational fluid dynamics (CFD) models with process modeling software. During the course of the project, a robust integration controller was developed that can be used in any CAPE-OPEN compliant process modeling environment. The controller mediates the exchange of information between the process modeling software and the CFD software. Several approaches to reducing the time disparity between CFD simulations and process modeling have been investigated and implemented. These include enabling the CFD models to be run on a remote cluster and enabling multiple CFD models to be run simultaneously. Furthermore, computationally fast reduced-order models (ROMs) have been developed that can be 'trained' using the results from CFD simulations and then used directly within flowsheets. Unit operation models (both CFD and ROMs) can be uploaded to a model database and shared between multiple users.
Bonneville Project: CFD of the Spillway Tailrace
Rakowski, Cynthia L.; Serkowski, John A.; Richmond, Marshall C.; Romero Gomez, Pedro DJ
2012-11-19
US Army Corps of Engineers, Portland District (CENWP) operates the Bonneville Lock and Dam Project on the Columbia River. High spill flows that occurred during 2011 moved a large volume of rock from downstream of the spillway apron to the stilling basin and apron. Although 400 cubic yards of rocks were removed from the stilling basin, there are still large volumes of rock downstream of the apron that could, under certain flow conditions, move upstream into the stilling basin. CENWP is investigating operational changes that could be implemented to minimize future movement of rock into the stilling basin. A key analysis tool to develop these operational changes is a computational fluid dynamics (CFD) model of the spillway. A free-surface CFD model of the Bonneville spillway tailrace was developed and applied for four flow scenarios. These scenarios looked at the impact of flow volume and flow distribution on tailrace hydraulics. The simulation results showed that areas of upstream flow existed near the river bed downstream of the apron, on the apron, and within the stilling basin for all flows. For spill flows of 300 kcfs, the cross-stream and downstream extent of the recirculation zones along Cascade and Bradford Island was very dependent on the spill pattern. The center-loaded pattern had much larger recirculation zones than the flat or bi-modal pattern. The lower flow (200 kcfs) with a flat pattern had a very large recirculation zone that extended half way across the channel near the river bed. A single flow scenario (300 kcfs of flow in a relatively flat spill pattern) was further interrogated using Lagrangian particle tracking. The tracked particles (with size and mass) showed the upstream movement of sediments onto the concrete apron and against the vertical wall between the apron and the stilling basin from seed locations downstream of the apron and on the apron.
Validation of Hydrodynamic Load Models Using CFD for the OC4-DeepCwind Semisubmersible: Preprint
Benitz, M. A.; Schmidt, D. P.; Lackner, M. A.; Stewart, G. M.; Jonkman, J.; Robertson, A.
2015-03-01
Computational fluid dynamics (CFD) simulations were carried out on the OC4-DeepCwind semi-submersible to obtain a better understanding of how to set hydrodynamic coefficients for the structure when using an engineering tool such as FAST to model the system. The focus here was on the drag behavior and the effects of the free-surface, free-ends and multi-member arrangement of the semi-submersible structure. These effects are investigated through code-to-code comparisons and flow visualizations. The implications on mean load predictions from engineering tools are addressed. The work presented here suggests that selection of drag coefficients should take into consideration a variety of geometric factors. Furthermore, CFD simulations demonstrate large time-varying loads due to vortex shedding, which FAST's hydrodynamic module, HydroDyn, does not model. The implications of these oscillatory loads on the fatigue life needs to be addressed.
Lee, S.
2011-05-17
The process of recovering the waste in storage tanks at the Savannah River Site (SRS) typically requires mixing the contents of the tank to ensure uniformity of the discharge stream. Mixing is accomplished with one to four dual-nozzle slurry pumps located within the tank liquid. For the work, a Tank 48 simulation model with a maximum of four slurry pumps in operation has been developed to estimate flow patterns for efficient solid mixing. The modeling calculations were performed by using two modeling approaches. One approach is a single-phase Computational Fluid Dynamics (CFD) model to evaluate the flow patterns and qualitative mixing behaviors for a range of different modeling conditions since the model was previously benchmarked against the test results. The other is a two-phase CFD model to estimate solid concentrations in a quantitative way by solving the Eulerian governing equations for the continuous fluid and discrete solid phases over the entire fluid domain of Tank 48. The two-phase results should be considered as the preliminary scoping calculations since the model was not validated against the test results yet. A series of sensitivity calculations for different numbers of pumps and operating conditions has been performed to provide operational guidance for solids suspension and mixing in the tank. In the analysis, the pump was assumed to be stationary. Major solid obstructions including the pump housing, the pump columns, and the 82 inch central support column were included. The steady state and three-dimensional analyses with a two-equation turbulence model were performed with FLUENT{trademark} for the single-phase approach and CFX for the two-phase approach. Recommended operational guidance was developed assuming that local fluid velocity can be used as a measure of sludge suspension and spatial mixing under single-phase tank model. For quantitative analysis, a two-phase fluid-solid model was developed for the same modeling conditions as the single
Soria, José; Gauthier, Daniel; Flamant, Gilles; Rodriguez, Rosa; Mazza, Germán
2015-09-15
Highlights: • A CFD two-scale model is formulated to simulate heavy metal vaporization from waste incineration in fluidized beds. • MSW particle is modelled with the macroscopic particle model. • Influence of bed dynamics on HM vaporization is included. • CFD predicted results agree well with experimental data reported in literature. • This approach may be helpful for fluidized bed reactor modelling purposes. - Abstract: Municipal Solid Waste Incineration (MSWI) in fluidized bed is a very interesting technology mainly due to high combustion efficiency, great flexibility for treating several types of waste fuels and reduction in pollutants emitted with the flue gas. However, there is a great concern with respect to the fate of heavy metals (HM) contained in MSW and their environmental impact. In this study, a coupled two-scale CFD model was developed for MSWI in a bubbling fluidized bed. It presents an original scheme that combines a single particle model and a global fluidized bed model in order to represent the HM vaporization during MSW combustion. Two of the most representative HM (Cd and Pb) with bed temperatures ranging between 923 and 1073 K have been considered. This new approach uses ANSYS FLUENT 14.0 as the modelling platform for the simulations along with a complete set of self-developed user-defined functions (UDFs). The simulation results are compared to the experimental data obtained previously by the research group in a lab-scale fluid bed incinerator. The comparison indicates that the proposed CFD model predicts well the evolution of the HM release for the bed temperatures analyzed. It shows that both bed temperature and bed dynamics have influence on the HM vaporization rate. It can be concluded that CFD is a rigorous tool that provides valuable information about HM vaporization and that the original two-scale simulation scheme adopted allows to better represent the actual particle behavior in a fluid bed incinerator.
Molecular Dynamics Simulation Studies of Electrolytes andElectrolyte...
Review and Peer Evaluation Meeting, June 7-11, 2010 -- Washington D.C. PDF icon es058smith2010p.pdf More Documents & Publications Molecular dynamics simulation and ab intio ...
First-principles molecular dynamics simulations of condensed...
Office of Scientific and Technical Information (OSTI)
phase V-type nerve agent reaction pathways and energy barriers Citation Details In-Document Search Title: First-principles molecular dynamics simulations of condensed phase V-type ...
Dynamic System Simulation of the KRUSTY Experiment (Technical Report) |
Office of Scientific and Technical Information (OSTI)
SciTech Connect Technical Report: Dynamic System Simulation of the KRUSTY Experiment Citation Details In-Document Search Title: Dynamic System Simulation of the KRUSTY Experiment The proposed KRUSTY experiment is a demonstration of a reactor operating at power. The planned experimental configuration includes a highly enriched uranium (HEU) reflected core, cooled by multiple heat pipes leading to Stirling engines for primary heat rejection. Operating power is expected to be approximately four
Sandia Energy - Computational Fluid Dynamics Simulations Provide...
U.S. Department of Energy (DOE) all webpages (Extended Search)
from a VWiS large-eddy simulation. One of the primary roles of Sandia's Scaled Wind Farm Technology (SWiFT) facility will be to conduct detailed experiments on turbine wakes and...
Dynamic extension of the Simulation Problem Analysis Kernel (SPANK)
Sowell, E.F. . Dept. of Computer Science); Buhl, W.F. )
1988-07-15
The Simulation Problem Analysis Kernel (SPANK) is an object-oriented simulation environment for general simulation purposes. Among its unique features is use of the directed graph as the primary data structure, rather than the matrix. This allows straightforward use of graph algorithms for matching variables and equations, and reducing the problem graph for efficient numerical solution. The original prototype implementation demonstrated the principles for systems of algebraic equations, allowing simulation of steady-state, nonlinear systems (Sowell 1986). This paper describes how the same principles can be extended to include dynamic objects, allowing simulation of general dynamic systems. The theory is developed and an implementation is described. An example is taken from the field of building energy system simulation. 2 refs., 9 figs.
Reduced order model based on principal component analysis for process simulation and optimization
Lang, Y.; Malacina, A.; Biegler, L.; Munteanu, S.; Madsen, J.; Zitney, S.
2009-01-01
It is well-known that distributed parameter computational fluid dynamics (CFD) models provide more accurate results than conventional, lumped-parameter unit operation models used in process simulation. Consequently, the use of CFD models in process/equipment co-simulation offers the potential to optimize overall plant performance with respect to complex thermal and fluid flow phenomena. Because solving CFD models is time-consuming compared to the overall process simulation, we consider the development of fast reduced order models (ROMs) based on CFD results to closely approximate the high-fidelity equipment models in the co-simulation. By considering process equipment items with complicated geometries and detailed thermodynamic property models, this study proposes a strategy to develop ROMs based on principal component analysis (PCA). Taking advantage of commercial process simulation and CFD software (for example, Aspen Plus and FLUENT), we are able to develop systematic CFD-based ROMs for equipment models in an efficient manner. In particular, we show that the validity of the ROM is more robust within well-sampled input domain and the CPU time is significantly reduced. Typically, it takes at most several CPU seconds to evaluate the ROM compared to several CPU hours or more to solve the CFD model. Two case studies, involving two power plant equipment examples, are described and demonstrate the benefits of using our proposed ROM methodology for process simulation and optimization.
U.S. Department of Energy (DOE) all webpages (Extended Search)
6 Implementation and validation of the new RPI boiling models using STAR-CCM+ as CFD Platform Victor Petrov, Annalisa Manera UMICH September 30, 2013 CASL-U-2013-0193-000 L3.THM.CFD.P7.06 iii EXECUTIVE SUMMARY This milestone is focused on the assessment of the new boiling models developed by the RPI team. The RPI models have been originally developed and tested using NPHASE as the base Computational Fluid Dynamics (CFD) solver. In order to gain experience for the further implementation of these
Numerical simulation of undersea cable dynamics
Ablow, C.M.; Schechter, S.
1983-01-01
A fully three-dimensional code has been written to compute the motion of a towed cable. The code is based on a robust and stable finite difference approximation to the differential equations derived from basic dynamics. A 3500-ft cable pulled at 18.5 knots (hr/sup -1/) through a circular turn of 700 yd radius has been computed in about half of the real time of the maneuver. The computed displacements are close to the measured ones; the changes in depth are within 2%.
Chombo-Crunch Sinks Its Teeth into Fluid Dynamics
U.S. Department of Energy (DOE) all webpages (Extended Search)
Their work has yielded a high-performance computational fluid dynamics (CFD) and reactive ... Using CFD tools based on embedded boundary technology, Trebotich found that he could ...
Use dynamic simulation to model HPU reactor depressuring
Ernest, J.B.; Depew, C.A. )
1995-01-01
Dynamic simulation is the best available method for the analysis of hydroprocessing unit (HPU) depressuring. Depressuring is crucial for the safe operation of hydrocracking and other HPUs with catalysts that have hydrocracking activity. Effective design for depressuring is valuable for all types of HPUs, both grass-roots and revamps. Reactor loop depressuring can set design temperatures and pressures for the reactor effluent cooling train and other equipment and piping in an HPU. Unfortunately, usual methods for determining equipment and piping design conditions during depressuring leave much room for improvement because they poorly account for time-dependent temperature and pressure changes. Dynamic simulation makes it practical to more accurately estimate these transient conditions. The paper discusses depressuring design, including the nature of depressuring, the impact of depressuring on design, and depressuring calculation methods. The author then describes modeling of hydroprocessing unit depressuring by discussing the general and particular correspondence of simulation modules to physical equipment using the base case of total electrical power failure. The special data that is required for dynamic simulation is described and typical simulation results are given. Lastly, the advantages of dynamic simulation are summarized.
CFD Combustion Modeling with Conditional Moment Closure using Tabulated
Office of Energy Efficiency and Renewable Energy (EERE) (indexed site)
Chemistry | Department of Energy Combustion Modeling with Conditional Moment Closure using Tabulated Chemistry CFD Combustion Modeling with Conditional Moment Closure using Tabulated Chemistry A method is presented that allows for efficient conditional moment closure combustion simulations through the use of a progress variable based parameterization of the combustion chemistry. p-15_borg.pdf (228.78 KB) More Documents & Publications Advanced CFD Models for High Efficiency Compression
Modeling and simulation of consumer response to dynamic pricing.
Valenzuela, J.; Thimmapuram, P.; Kim, J
2012-08-01
Assessing the impacts of dynamic-pricing under the smart grid concept is becoming extremely important for deciding its full deployment. In this paper, we develop a model that represents the response of consumers to dynamic pricing. In the model, consumers use forecasted day-ahead prices to shift daily energy consumption from hours when the price is expected to be high to hours when the price is expected to be low while maintaining the total energy consumption as unchanged. We integrate the consumer response model into the Electricity Market Complex Adaptive System (EMCAS). EMCAS is an agent-based model that simulates restructured electricity markets. We explore the impacts of dynamic-pricing on price spikes, peak demand, consumer energy bills, power supplier profits, and congestion costs. A simulation of an 11-node test network that includes eight generation companies and five aggregated consumers is performed for a period of 1 month. In addition, we simulate the Korean power system.
Processes and Procedures for Application of CFD to Nuclear Reactor Safety Analysis
Richard W. Johnson; Richard R. Schultz; Patrick J. Roache; Ismail B. Celik; William D. Pointer; Yassin A. Hassan
2006-09-01
Traditionally, nuclear reactor safety analysis has been performed using systems analysis codes such as RELAP5, which was developed at the INL. However, goals established by the Generation IV program, especially the desire to increase efficiency, has lead to an increase in operating temperatures for the reactors. This increase pushes reactor materials to operate towards their upper temperature limits relative to structural integrity. Because there will be some finite variation of the power density in the reactor core, there will be a potential for local hot spots to occur in the reactor vessel. Hence, it has become apparent that detailed analysis will be required to ensure that local hot spots do not exceed safety limits. It is generally accepted that computational fluid dynamics (CFD) codes are intrinsically capable of simulating fluid dynamics and heat transport locally because they are based on first principles. Indeed, CFD analysis has reached a fairly mature level of development, including the commercial level. However, CFD experts are aware that even though commercial codes are capable of simulating local fluid and thermal physics, great care must be taken in their application to avoid errors caused by such things as inappropriate grid meshing, low-order discretization schemes, lack of iterative convergence and inaccurate time-stepping. Just as important is the choice of a turbulence model for turbulent flow simulation. Turbulence models model the effects of turbulent transport of mass, momentum and energy, but are not necessarily applicable for wide ranges of flow types. Therefore, there is a well-recognized need to establish practices and procedures for the proper application of CFD to simulate flow physics accurately and establish the level of uncertainty of such computations. The present document represents contributions of CFD experts on what the basic practices, procedures and guidelines should be to aid CFD analysts to obtain accurate estimates of
Computational Fluid Dynamics & Large-Scale Uncertainty Quantification...
U.S. Department of Energy (DOE) all webpages (Extended Search)
... (CFD) simulations and uncertainty analyses. The project developed new mathematical uncertainty quantification techniques and applied them, in combination with high-fidelity CFD ...
Kinetic Simulations of Fusion Energy Dynamics at the Extreme Scale |
U.S. Department of Energy (DOE) all webpages (Extended Search)
Argonne Leadership Computing Facility Kinetic Simulations of Fusion Energy Dynamics at the Extreme Scale PI Name: William Tang PI Email: tang@pppl.gov Institution: Princeton Plasma Physics Laboratory Allocation Program: INCITE Allocation Hours at ALCF: 40 Million Year: 2013 Research Domain: Physics To build the scientific foundations needed to develop fusion power as a clean and sustainable energy source, the timely development of a high-physics-fidelity predictive simulation capability for
CFD analysis of coverplate receiver flow
Popp, O.; Zimmermann, H.; Kutz, J.
1998-01-01
The flow field in a preswirled cooling air supply to a turbine rotor has been investigated by means of CFD simulations. Coefficients for system efficiency are derived. The influences of various geometric parameters for different configurations have been correlated with the help of appropriate coefficients. For some of the most important geometric parameters of the coverplate receiver, design recommendations have been made. For the preswirl nozzles, the potential of efficiency improvement by contour design is highlighted.
Reactor physics simulations with coupled Monte Carlo calculation and computational fluid dynamics.
Seker, V.; Thomas, J. W.; Downar, T. J.; Purdue Univ.
2007-01-01
A computational code system based on coupling the Monte Carlo code MCNP5 and the Computational Fluid Dynamics (CFD) code STAR-CD was developed as an audit tool for lower order nuclear reactor calculations. This paper presents the methodology of the developed computer program 'McSTAR'. McSTAR is written in FORTRAN90 programming language and couples MCNP5 and the commercial CFD code STAR-CD. MCNP uses a continuous energy cross section library produced by the NJOY code system from the raw ENDF/B data. A major part of the work was to develop and implement methods to update the cross section library with the temperature distribution calculated by STARCD for every region. Three different methods were investigated and implemented in McSTAR. The user subroutines in STAR-CD are modified to read the power density data and assign them to the appropriate variables in the program and to write an output data file containing the temperature, density and indexing information to perform the mapping between MCNP and STAR-CD cells. Preliminary testing of the code was performed using a 3x3 PWR pin-cell problem. The preliminary results are compared with those obtained from a STAR-CD coupled calculation with the deterministic transport code DeCART. Good agreement in the k{sub eff} and the power profile was observed. Increased computational capabilities and improvements in computational methods have accelerated interest in high fidelity modeling of nuclear reactor cores during the last several years. High-fidelity has been achieved by utilizing full core neutron transport solutions for the neutronics calculation and computational fluid dynamics solutions for the thermal-hydraulics calculation. Previous researchers have reported the coupling of 3D deterministic neutron transport method to CFD and their application to practical reactor analysis problems. One of the principal motivations of the work here was to utilize Monte Carlo methods to validate the coupled deterministic neutron
Combining molecular dynamics with mesoscopic Green’s function reaction dynamics simulations
Vijaykumar, Adithya; Bolhuis, Peter G.; Rein ten Wolde, Pieter
2015-12-07
In many reaction-diffusion processes, ranging from biochemical networks, catalysis, to complex self-assembly, the spatial distribution of the reactants and the stochastic character of their interactions are crucial for the macroscopic behavior. The recently developed mesoscopic Green’s Function Reaction Dynamics (GFRD) method enables efficient simulation at the particle level provided the microscopic dynamics can be integrated out. Yet, many processes exhibit non-trivial microscopic dynamics that can qualitatively change the macroscopic behavior, calling for an atomistic, microscopic description. We propose a novel approach that combines GFRD for simulating the system at the mesoscopic scale where particles are far apart, with a microscopic technique such as Langevin dynamics or Molecular Dynamics (MD), for simulating the system at the microscopic scale where reactants are in close proximity. This scheme defines the regions where the particles are close together and simulated with high microscopic resolution and those where they are far apart and simulated with lower mesoscopic resolution, adaptively on the fly. The new multi-scale scheme, called MD-GFRD, is generic and can be used to efficiently simulate reaction-diffusion systems at the particle level.
CFD modeling of commercial-scale entrained-flow coal gasifiers
Ma, J.; Zitney, S.
2012-01-01
Optimization of an advanced coal-fired integrated gasification combined cycle system requires an accurate numerical prediction of gasifier performance. Computational fluid dynamics (CFD) has been used to model the turbulent multiphase reacting flow inside commercial-scale entrained-flow coal gasifiers. Due to the complexity of the physical and chemical processes involved, the accuracy of sub-models requires further improvement. Built upon a previously developed CFD model for entrained-flow gasification, the advanced physical and chemical sub-models presented in this paper include a moisture vaporization model with consideration of high mass transfer rate and a coal devolatilization model with more species to represent coal volatiles and the heating rate effect on volatile yield. The global gas phase reaction kinetics is also carefully selected. To predict a reasonable peak temperature of the coal/O{sub 2} flame inside an entrained-flow gasifier, the reserve reaction of H{sub 2} oxidation is included in the gas phase reaction model. The enhanced CFD model is applied to simulate two typical commercial-scale oxygen-blown entrained-flow configurations including a single-stage down-fired gasifier and a two-stage up-fired gasifier. The CFD results are reasonable in terms of predicted carbon conversion, syngas exit temperature, and syngas exit composition. The predicted profiles of velocity, temperature, and species mole fractions inside the entrained-flow gasifier models show trends similar to those observed in a diffusion-type flame. The predicted distributions of mole fractions of major species inside both gasifiers can be explained by the heterogeneous combustion and gasification reactions and the homogeneous gas phase reactions. It was also found that the syngas compositions at the CFD model exits are not in chemical equilibrium, indicating the kinetics for both heterogeneous and gas phase homogeneous reactions are important. Overall, the results achieved here
Generic solar photovoltaic system dynamic simulation model specification.
Ellis, Abraham; Behnke, Michael Robert; Elliott, Ryan Thomas
2013-10-01
This document is intended to serve as a specification for generic solar photovoltaic (PV) system positive-sequence dynamic models to be implemented by software developers and approved by the WECC MVWG for use in bulk system dynamic simulations in accordance with NERC MOD standards. Two specific dynamic models are included in the scope of this document. The first, a Central Station PV System model, is intended to capture the most important dynamic characteristics of large scale (> 10 MW) PV systems with a central Point of Interconnection (POI) at the transmission level. The second, a Distributed PV System model, is intended to represent an aggregation of smaller, distribution-connected systems that comprise a portion of a composite load that might be modeled at a transmission load bus.
Advanced beam-dynamics simulation tools for RIA.
Garnett, R. W.; Wangler, T. P.; Billen, J. H.; Qiang, J.; Ryne, R.; Crandall, K. R.; Ostroumov, P.; York, R.; Zhao, Q.; Physics; LANL; LBNL; Tech Source; Michigan State Univ.
2005-01-01
We are developing multi-particle beam-dynamics simulation codes for RIA driver-linac simulations extending from the low-energy beam transport (LEBT) line to the end of the linac. These codes run on the NERSC parallel supercomputing platforms at LBNL, which allow us to run simulations with large numbers of macroparticles. The codes have the physics capabilities needed for RIA, including transport and acceleration of multiple-charge-state beams, beam-line elements such as high-voltage platforms within the linac, interdigital accelerating structures, charge-stripper foils, and capabilities for handling the effects of machine errors and other off-normal conditions. This year will mark the end of our project. In this paper we present the status of the work, describe some recent additions to the codes, and show some preliminary simulation results.
Beam Dynamics Design and Simulation in Ion Linear Accelerators (
Energy Science and Technology Software Center (OSTI)
2006-08-01
Orginally, the ray tracing code TRACK has been developed to fulfill the many special requirements for the Rare Isotope Accelerator Facility known as RIA. Since no available beam-dynamics code met all the necessary requirements, modifications to the code TRACK were introduced to allow end-to-end (from the ion souce to the production target) simulations of the RIA machine, TRACK is a general beam-dynamics code and can be applied for the design, commissioning and operation of modernmore » ion linear accelerators and beam transport systems.« less
V&V Of CFD Modeling Of The Argonne Bubble Experiment: FY15 Summary Report
Hoyt, Nathaniel C.; Wardle, Kent E.; Bailey, James L.; Basavarajappa, Manjunath
2015-09-30
In support of the development of accelerator-driven production of the fission product Mo 99, computational fluid dynamics (CFD) simulations of an electron-beam irradiated, experimental-scale bubble chamber have been conducted in order to aid in interpretation of existing experimental results, provide additional insights into the physical phenomena, and develop predictive thermal hydraulic capabilities that can be applied to full-scale target solution vessels. Toward that end, a custom hybrid Eulerian-Eulerian-Lagrangian multiphase solver was developed, and simulations have been performed on high-resolution meshes. Good agreement between experiments and simulations has been achieved, especially with respect to the prediction of the maximum temperature of the uranyl sulfate solution in the experimental vessel. These positive results suggest that the simulation methodology that has been developed will prove to be suitable to assist in the development of full-scale production hardware.
Simulating the Dynamic Coupling of Market and Physical System Operations
Widergren, Steven E.; Roop, Joseph M.; Guttromson, Ross T.; Huang, Zhenyu
2004-06-01
Abstract-As energy trading products cover shorter time periods and demand response programs move toward real-time pricing, financial market-based activity impacts ever more directly the physical operation of the system. To begin to understand the complex interactions between the market-driven operation signals, the engineered controlled schemes, and the laws of physics, new system modeling and simulation techniques must be explored. This discussion describes requirements for new simulation tools to address such market transaction control interactions and an approach to capture the dynamic coupling between energy markets and the physical operation of the power system appropriate for dispatcher reaction time frames.
Dislocation dynamics simulations of plasticity at small scales
Zhou, Caizhi
2010-12-15
As metallic structures and devices are being created on a dimension comparable to the length scales of the underlying dislocation microstructures, the mechanical properties of them change drastically. Since such small structures are increasingly common in modern technologies, there is an emergent need to understand the critical roles of elasticity, plasticity, and fracture in small structures. Dislocation dynamics (DD) simulations, in which the dislocations are the simulated entities, offer a way to extend length scales beyond those of atomistic simulations and the results from DD simulations can be directly compared with the micromechanical tests. The primary objective of this research is to use 3-D DD simulations to study the plastic deformation of nano- and micro-scale materials and understand the correlation between dislocation motion, interactions and the mechanical response. Specifically, to identify what critical events (i.e., dislocation multiplication, cross-slip, storage, nucleation, junction and dipole formation, pinning etc.) determine the deformation response and how these change from bulk behavior as the system decreases in size and correlate and improve our current knowledge of bulk plasticity with the knowledge gained from the direct observations of small-scale plasticity. Our simulation results on single crystal micropillars and polycrystalline thin films can march the experiment results well and capture the essential features in small-scale plasticity. Furthermore, several simple and accurate models have been developed following our simulation results and can reasonably predict the plastic behavior of small scale materials.
CASL - CFD-Based Turbulence Force Evaluation for Grid-to-Rod Fretting
U.S. Department of Energy (DOE) all webpages (Extended Search)
Phenomena CFD-Based Turbulence Force Evaluation for Grid-to-Rod Fretting Phenomena Article Background: Roger Lu - #83 - L1:CASL.P5.02 - Determine extent structural analysis amplifies (or damps) differences in pressure forces between different CFD codes for analysis of GTRF phenomenon (CASL.012) based on "CASL report CFD Turbulence Force Calculations and Grid-to-Rod Fretting Simulation" CFD-Based Turbulence Force Evaluation for Grid-to-Rod Fretting Phenomena R. Y. Lu and Z. Karoutas
Molecular dynamics simulation of radiation damage cascades in diamond
Buchan, J. T.; Robinson, M.; Christie, H. J.; Roach, D. L.; Ross, D. K.; Marks, N. A.
2015-06-28
Radiation damage cascades in diamond are studied by molecular dynamics simulations employing the Environment Dependent Interaction Potential for carbon. Primary knock-on atom (PKA) energies up to 2.5 keV are considered and a uniformly distributed set of 25 initial PKA directions provide robust statistics. The simulations reveal the atomistic origins of radiation-resistance in diamond and provide a comprehensive computational analysis of cascade evolution and dynamics. As for the case of graphite, the atomic trajectories are found to have a fractal-like character, thermal spikes are absent and only isolated point defects are generated. Quantitative analysis shows that the instantaneous maximum kinetic energy decays exponentially with time, and that the timescale of the ballistic phase has a power-law dependence on PKA energy. Defect recombination is efficient and independent of PKA energy, with only 50% of displacements resulting in defects, superior to graphite where the same quantity is nearly 75%.
Molecular dynamics simulations of Si etching in Cl- and Br-based...
Office of Scientific and Technical Information (OSTI)
Citation Details In-Document Search Title: Molecular dynamics simulations of Si etching in ... thickness, surface stoichiometry, and depth profile of surface products simulated for ...
Multi million-to-Billion Atom Molecular Dynamics Simulations of
U.S. Department of Energy (DOE) all webpages (Extended Search)
Cavitation-Induced Damage on a Silica Slab | Argonne Leadership Computing Facility Multi million-to-Billion Atom Molecular Dynamics Simulations of Cavitation-Induced Damage on a Silica Slab Authors: Shekhar, A., Nomura, K., Rajiv, K., Nakano, A., Vashishta, P Cavitation bubble collapse causes severe damage to materials. For example, cavitation erosion is a major threat to the safety of nuclear power plants. The cavitation bubbles may also be utilized for preventing stress corrosion cracking
ParaDiS-FEM dislocation dynamics simulation code primer (Technical...
Office of Scientific and Technical Information (OSTI)
ParaDiS-FEM dislocation dynamics simulation code primer Citation Details In-Document Search Title: ParaDiS-FEM dislocation dynamics simulation code primer You are accessing a ...
Lawson, M. J.; Li, Y.; Sale, D. C.
2011-10-01
This paper describes the development of a computational fluid dynamics (CFD) methodology to simulate the hydrodynamics of horizontal-axis tidal current turbines. Qualitative measures of the CFD solutions were independent of the grid resolution. Conversely, quantitative comparisons of the results indicated that the use of coarse computational grids results in an under prediction of the hydrodynamic forces on the turbine blade in comparison to the forces predicted using more resolved grids. For the turbine operating conditions considered in this study, the effect of the computational timestep on the CFD solution was found to be minimal, and the results from steady and transient simulations were in good agreement. Additionally, the CFD results were compared to corresponding blade element momentum method calculations and reasonable agreement was shown. Nevertheless, we expect that for other turbine operating conditions, where the flow over the blade is separated, transient simulations will be required.
Bibliography for Verification and Validation in Computational Simulations
Oberkampf, W.L.
1998-10-01
A bibliography has been compiled dealing with the verification and validation of computational simulations. The references listed in this bibliography are concentrated in the field of computational fluid dynamics (CFD). However, references from the following fields are also included: operations research, heat transfer, solid dynamics, software quality assurance, software accreditation, military systems, and nuclear reactor safety. This bibliography, containing 221 references, is not meant to be comprehensive. It was compiled during the last ten years in response to the author's interest and research in the methodology for verification and validation. The emphasis in the bibliography is in the following areas: philosophy of science underpinnings, development of terminology and methodology, high accuracy solutions for CFD verification, experimental datasets for CFD validation, and the statistical quantification of model validation. This bibliography should provide a starting point for individual researchers in many fields of computational simulation in science and engineering.
Molecular dynamics simulations of hydrogen diffusion in aluminum
Zhou, X. W.; El Gabaly, F.; Stavila, V.; Allendorf, M. D.
2016-03-23
In this study, hydrogen diffusion impacts the performance of solid-state hydrogen storage materials and contributes to the embrittlement of structural materials under hydrogen-containing environments. In atomistic simulations, the diffusion energy barriers are usually calculated using molecular statics simulations where a nudged elastic band method is used to constrain a path connecting the two end points of an atomic jump. This approach requires prior knowledge of the “end points”. For alloy and defective systems, the number of possible atomic jumps with respect to local atomic configurations is tremendous. Even when these jumps can be exhaustively studied, it is still unclear howmore » they can be combined to give an overall diffusion behavior seen in experiments. Here we describe the use of molecular dynamics simulations to determine the overall diffusion energy barrier from the Arrhenius equation. This method does not require information about atomic jumps, and it has additional advantages, such as the ability to incorporate finite temperature effects and to determine the pre-exponential factor. As a test case for a generic method, we focus on hydrogen diffusion in bulk aluminum. We find that the challenge of this method is the statistical variation of the results. However, highly converged energy barriers can be achieved by an appropriate set of temperatures, output time intervals (for tracking hydrogen positions), and a long total simulation time. Our results help elucidate the inconsistencies of the experimental diffusion data published in the literature. The robust approach developed here may also open up future molecular dynamics simulations to rapidly study diffusion properties of complex material systems in multidimensional spaces involving composition and defects.« less
DOE Data Explorer [Office of Scientific and Technical Information (OSTI)]
Plimpton, Steve; Thompson, Aidan; Crozier, Paul
LAMMPS (http://lammps.sandia.gov/index.html) stands for Large-scale Atomic/Molecular Massively Parallel Simulator and is a code that can be used to model atoms or, as the LAMMPS website says, as a parallel particle simulator at the atomic, meso, or continuum scale. This Sandia-based website provides a long list of animations from large simulations. These were created using different visualization packages to read LAMMPS output, and each one provides the name of the PI and a brief description of the work done or visualization package used. See also the static images produced from simulations at http://lammps.sandia.gov/pictures.html The foundation paper for LAMMPS is: S. Plimpton, Fast Parallel Algorithms for Short-Range Molecular Dynamics, J Comp Phys, 117, 1-19 (1995), but the website also lists other papers describing contributions to LAMMPS over the years.
Molecular Dynamics Simulation of Binary Fluid in a Nanochannel
Mullick, Shanta; Ahluwalia, P. K. [Department of Physics, Himachal Pradesh University, SummerHill, Shimla - 171005 (India); Pathania, Y. [Chitkara University, Atal Shiksha Kunj, Atal Nagar, Barotiwala, Dist Solan, Himachal Pradesh - 174103 (India)
2011-12-12
This paper presents the results from a molecular dynamics simulation of binary fluid (mixture of argon and krypton) in the nanochannel flow. The computational software LAMMPS is used for carrying out the molecular dynamics simulations. Binary fluids of argon and krypton with varying concentration of atom species were taken for two densities 0.65 and 0.45. The fluid flow takes place between two parallel plates and is bounded by horizontal walls in one direction and periodic boundary conditions are imposed in the other two directions. To drive the flow, a constant force is applied in one direction. Each fluid atom interacts with other fluid atoms and wall atoms through Week-Chandler-Anderson (WCA) potential. The velocity profile has been looked at for three nanochannel widths i.e for 12{sigma}, 14{sigma} and 16{sigma} and also for the different concentration of two species. The velocity profile of the binary fluid predicted by the simulations agrees with the quadratic shape of the analytical solution of a Poiseuille flow in continuum theory.
Clustering effects in ionic polymers: Molecular dynamics simulations
Agrawal, Anupriya; Perahia, Dvora; Grest, Gary S.
2015-08-18
Ionic clusters control the structure, dynamics, and transport in soft matter. Incorporating a small fraction of ionizable groups in polymers substantially reduces the mobility of the macromolecules in melts. Furthermore, these ionic groups often associate into random clusters in melts, where the distribution and morphology of the clusters impact the transport in these materials. Here, using molecular dynamic simulations we demonstrate a clear correlation between cluster size and morphology with the polymer mobility in melts of sulfonated polystyrene. We show that in low dielectric media ladderlike clusters that are lower in energy compared with spherical assemblies are formed. Reducing themore » electrostatic interactions by enhancing the dielectric constant leads to morphological transformation from ladderlike clusters to globular assemblies. Finally, decrease in electrostatic interaction significantly enhances the mobility of the polymer.« less
Clustering effects in ionic polymers: Molecular dynamics simulations
Agrawal, Anupriya; Perahia, Dvora; Grest, Gary S.
2015-08-18
Ionic clusters control the structure, dynamics, and transport in soft matter. Incorporating a small fraction of ionizable groups in polymers substantially reduces the mobility of the macromolecules in melts. Furthermore, these ionic groups often associate into random clusters in melts, where the distribution and morphology of the clusters impact the transport in these materials. Here, using molecular dynamic simulations we demonstrate a clear correlation between cluster size and morphology with the polymer mobility in melts of sulfonated polystyrene. We show that in low dielectric media ladderlike clusters that are lower in energy compared with spherical assemblies are formed. Reducing the electrostatic interactions by enhancing the dielectric constant leads to morphological transformation from ladderlike clusters to globular assemblies. Finally, decrease in electrostatic interaction significantly enhances the mobility of the polymer.
Dynamic simulation of the in-tank precipitation process
Hang, T.; Shanahan, K.L.; Gregory, M.V.; Walker, D.D.
1993-12-31
As part of the High-Level Waste Tank Farm at the Savannah River Site (SRS), the In-Tank Precipitation (ITP) facility was designed to decontaminate the radioactive waste supernate by removing cesium as precipitated cesium tetraphenylborate. A dynamic computer model of the ITP process was developed using SPEEDUP{sup TM} software to provide guidance in the areas of operation and production forecast, production scheduling, safety, air emission, and process improvements. The model performs material balance calculations in all phase (solid, liquid, and gas) for 50 key chemical constituents to account for inventory accumulation, depletion, and dilution. Calculations include precipitation, benzene radiolytic reactions, evaporation, dissolution, adsorption, filtration, and stripping. To control the ITP batch operation a customized FORTRAN program was generated and linked to SPEEDUP{sup TM} simulation This paper summarizes the model development and initial results of the simulation study.
Extracting the diffusion tensor from molecular dynamics simulation with Milestoning
Mugnai, Mauro L.; Elber, Ron
2015-01-07
We propose an algorithm to extract the diffusion tensor from Molecular Dynamics simulations with Milestoning. A Kramers-Moyal expansion of a discrete master equation, which is the Markovian limit of the Milestoning theory, determines the diffusion tensor. To test the algorithm, we analyze overdamped Langevin trajectories and recover a multidimensional Fokker-Planck equation. The recovery process determines the flux through a mesh and estimates local kinetic parameters. Rate coefficients are converted to the derivatives of the potential of mean force and to coordinate dependent diffusion tensor. We illustrate the computation on simple models and on an atomically detailed system—the diffusion along the backbone torsions of a solvated alanine dipeptide.
RIAPMTQ/Impact : beam-dynamics simulation tool for RIA.
Wangler, T. P.; Billen, J. H.; Garnett, R. W.; Qiang, J.; Ryne, R.; Crandall, K. R.; Ostroumov, P.; Aseev, V. N.; Mustapha, B.; York, R. C.; Wu, X.; Zhao, Q.; Gorelov, D.; Doleans, M.; Physics; LANL; Tech Source; Michigan State Univ.
2006-01-01
We have developed a pair of multiparticle beam dynamics codes for end-to-end computer simulations of the proposed RIA heavy-ion driver linac. The two codes are: (1) an adaptation of PARMTEQ called RIAPMTQ for the normal-conducting-linac front end, and (2) IMPACT for the superconducting linac. The codes run on a PC as well as on parallel supercomputing platforms such as NERSC at LBNL. The parallel capability allows us to run simulations with large numbers of macroparticles for the computation of beam halo and beam-losses. The codes are being benchmarked for rms beam properties against previously existing codes at ANL and MSU. The work is being performed by a collaboration including LANL, LBNL, ANL, and Michigan State University (MSU). In this paper we present an overview, the status of the work, comparison of simulation results from RIAPMTQ and the ANL code TRACK for the ANL front-end design, and the first RIAPMTQ/IMPACT end-to-end multiprocessor simulation for the MSU design.
Description of waste pretreatment and interfacing systems dynamic simulation model
Garbrick, D.J.; Zimmerman, B.D.
1995-05-01
The Waste Pretreatment and Interfacing Systems Dynamic Simulation Model was created to investigate the required pretreatment facility processing rates for both high level and low level waste so that the vitrification of tank waste can be completed according to the milestones defined in the Tri-Party Agreement (TPA). In order to achieve this objective, the processes upstream and downstream of the pretreatment facilities must also be included. The simulation model starts with retrieval of tank waste and ends with vitrification for both low level and high level wastes. This report describes the results of three simulation cases: one based on suggested average facility processing rates, one with facility rates determined so that approximately 6 new DSTs are required, and one with facility rates determined so that approximately no new DSTs are required. It appears, based on the simulation results, that reasonable facility processing rates can be selected so that no new DSTs are required by the TWRS program. However, this conclusion must be viewed with respect to the modeling assumptions, described in detail in the report. Also included in the report, in an appendix, are results of two sensitivity cases: one with glass plant water recycle steams recycled versus not recycled, and one employing the TPA SST retrieval schedule versus a more uniform SST retrieval schedule. Both recycling and retrieval schedule appear to have a significant impact on overall tank usage.
A simple model simulating a fan as a source of axial and circumferential body forces
Energy Science and Technology Software Center (OSTI)
2002-07-01
This software can be used in a computational fluids dynamics (CFD) code to represent a fan as a source of axial and circumferential body forces. The combined software can be used effectively in car design analyses that involve many underhood thermal management simulations. FANMOD uses as input the rotational speed of the fan, geometric fan data, and the lift and drag coefficients of the blades, and predicts the body forces generated by the fan inmore » the axial and circumferential directions. These forces can be used as momentum forces in a CFD code to simulate the effect of the fan in an underhood thermal management simulation.« less
Office Of Nuclear Energy Annual Review Meeting Dynamic Simulation Modeling Tool
Office of Energy Efficiency and Renewable Energy (EERE) (indexed site)
Annual Review Meeting Dynamic Simulation Modeling Tool Lou Qualls ORNL September 16-18, 2014 2 Work Package SR-14OR130108 - Modeling Tools for Dynamic Behavior Simulations of SMRs 2 ü FY14 molten salt cooled model deliverable due. n FY15 web application deliverable due. n FY15 model repository establishment due. n FY15 working collaboration with University partners. n Simplified Dynamic Modeling for Advanced SMRs - Numerous dynamic models are needed to simulate plant behavior
Large-Scale Condensed Matter and Fluid Dynamics Simulations in Three
U.S. Department of Energy (DOE) all webpages (Extended Search)
Diverse Areas: Part II: Molecular Dynamics Study of Clay-Polymer Nanocomposites | Argonne Leadership Computing Facility Snapshot from a molecular dynamics simulation of a system containing 16 isolated clay sheets immersed in a polymer melt. , Snapshot from a molecular dynamics simulation of an isolated clay platelet (consisting of two sheets) immersed in water. Top image: Snapshot from a molecular dynamics simulation of a system containing 16 isolated clay sheets immersed in a polymer melt.
U.S. Department of Energy (DOE) all webpages (Extended Search)
scour-tracc-cfd TRACC RESEARCH Computational Fluid Dynamics Computational Structural Mechanics Transportation Systems Modeling Computational Fluid Dynamics Overview of CFD: Video Clip with Audio Computational fluid dynamics (CFD) research uses mathematical and computational models of flowing fluids to describe and predict fluid response in problems of interest, such as the flow of air around a moving vehicle or the flow of water and sediment in a river. Coupled with appropriate and prototypical
Standard Problems for CFD Validation for NGNP - Status Report
Richard W. Johnson; Richard R. Schultz
2010-08-01
The U.S. Department of Energy (DOE) is conducting research and development to support the resurgence of nuclear power in the United States for both electrical power generation and production of process heat required for industrial processes such as the manufacture of hydrogen for use as a fuel in automobiles. The project is called the Next Generation Nuclear Plant (NGNP) Project, which is based on a Generation IV reactor concept called the very high temperature reactor (VHTR). The VHTR will be of the prismatic or pebble bed type; the former is considered herein. The VHTR will use helium as the coolant at temperatures ranging from 250°C to perhaps 1000°C. While computational fluid dynamics (CFD) has not previously been used for the safety analysis of nuclear reactors in the United States, it is being considered for existing and future reactors. It is fully recognized that CFD simulation codes will have to be validated for flow physics reasonably close to actual fluid dynamic conditions expected in normal operational and accident situations. The “Standard Problem” is an experimental data set that represents an important physical phenomenon or phenomena, whose selection is based on a phenomena identification and ranking table (PIRT) for the reactor in question. It will be necessary to build a database that contains a number of standard problems for use to validate CFD and systems analysis codes for the many physical problems that will need to be analyzed. The first two standard problems that have been developed for CFD validation consider flow in the lower plenum of the VHTR and bypass flow in the prismatic core. Both involve scaled models built from quartz and designed to be installed in the INL’s matched index of refraction (MIR) test facility. The MIR facility employs mineral oil as the working fluid at a constant temperature. At this temperature, the index of refraction of the mineral oil is the same as that of the quartz. This provides an advantage to the
A CFD/CSD interaction methodology for aircraft wings
Bhardwaj, M.K.; Kapania, R.K.; Reichenbach, E.; Guruswamy, G.P.
1998-01-01
With advanced subsonic transports and military aircraft operating in the transonic regime, it is becoming important to determine the effects of the coupling between aerodynamic loads and elastic forces. Since aeroelastic effects can significantly impact the design of these aircraft, there is a strong need in the aerospace industry to predict these interactions computationally. Such an analysis in the transonic regime requires high fidelity computational fluid dynamics (CFD) analysis tools, due to the nonlinear behavior of the aerodynamics in the transonic regime and also high fidelity computational structural dynamics (CSD) analysis tools. Also, there is a need to be able to use a wide variety of CFD and CSD methods to predict aeroelastic effects. Since source codes are not always available, it is necessary to couple the CFD and CSD codes without alteration of the source codes. In this study, an aeroelastic coupling procedure is developed to determine the static aeroelastic response of aircraft wings using any CFD and CSD code with little code integration. The aeroelastic coupling procedure is demonstrated on an F/A-18 Stabilator using NASTD (an in-house McDonnell Douglas CFD code) and NASTRAN. In addition, the Aeroelastic Research Wing (ARW-2) is used for demonstration of the aeroelastic coupling procedure by using ENSAERO (NASA Ames Research Center CFD code) and a finite element wing-box code. The results obtained from the present study are compared with those available from an experimental study conducted at NASA Langley Research Center and a study conducted at NASA Ames Research Center using ENSAERO and modal superposition. The results compare well with experimental data.
Extensions to Dynamic System Simulation of Fissile Solution Systems
Klein, Steven Karl; Bernardin, John David; Kimpland, Robert Herbert; Spernjak, Dusan
2015-08-24
Previous reports have documented the results of applying dynamic system simulation (DSS) techniques to model a variety of fissile solution systems. The SUPO (Super Power) aqueous homogeneous reactor (AHR) was chosen as the benchmark for comparison of model results to experimental data for steadystate operation.1 Subsequently, DSS was applied to additional AHR to verify results obtained for SUPO and extend modeling to prompt critical excursions, ramp reactivity insertions of various magnitudes and rate, and boiling operations in SILENE and KEWB (Kinetic Experiment Water Boiler).2 Additional models for pressurized cores (HRE: Homogeneous Reactor Experiment), annular core geometries, and accelerator-driven subcritical systems (ADAHR) were developed and results reported.3 The focus of each of these models is core dynamics; neutron kinetics, thermal hydraulics, radiolytic gas generation and transport are coupled to examine the time-based evolution of these systems from start-up through transition to steady-state. A common characteristic of these models is the assumption that (a) core cooling system inlet temperature and flow and (b) plenum gas inlet pressure and flow are held constant; no external (to core) component operations that may result in dynamic change to these parameters are considered. This report discusses extension of models to include explicit reference to cooling structures and radiolytic gas handling. The accelerator-driven subcritical generic system model described in References 3 and 4 is used as a basis for this extension.
Dynamic simulation models and performance of an OTEC power plant
Wormley, D.N.; Carmichael, D.A.; Umans, S.
1983-08-01
In this study, the aspects of plant performance which influence the potential for integration of an OTEC plant into a utility grid are considered. A set of simulation models have been developed for the evaluation of OTEC dynamic plant performance. A detailed nonlinear dynamic model has been forumlated which is useful for the assessment of component performance including heat exchangers, turbines, pumps and control systems. A reduced order linear model has been developed which is useful for studies of plant stability, control system development and transient performance of the plant connected to a utility grid. This model is particularly suitable for transient dynamic studies of an OTEC plant as a unit in a utility grid. A quasi-steady power availability model has also been developed which is useful to determine plant ouput power as a function of ocean thermal gradients so that the influence of daily and seasonal temperature variations may be easily computed. The study has found no fundamental technical barriers which would prohibit the interconnection of an OTEC plant into a utility grid. It has also shown that detailed consideration of turbine nozzle angle control is merited and such a control has the potential to provide superior performance in comparison to turbine bypass valve control.
Microsoft Word - Advanced Solution Verification of CFD Solutions for LES of GTRF_Rider_August23.docx
U.S. Department of Energy (DOE) all webpages (Extended Search)
VUQ.VVDA.P4.03 Jim Stewart SNL Completed: 8/31/2012 CASL-U-2012-0132-000 Advanced Solution Verification of CFD Solutions for LES o f R elevance t o GTRF Estimates. William J. Rider and James R. Kamm Sandia N ational L aboratories Albuquerque, NM 87185 August 31, 2012 SAND 2 012---7199P Summary The purpose of this work is to d emonstrate advanced solution verification (i.e., numerical error estimation) techniques on computational fluid dynamics simulations of interest to CASL. The specific case
Non-equilibrium dynamics in disordered materials: Ab initio molecular dynamics simulations
Ohmura, Satoshi; Nagaya, Kiyonobu; Yao, Makoto; Shimojo, Fuyuki
2015-08-17
The dynamic properties of liquid B{sub 2}O{sub 3} under pressure and highly-charged bromophenol molecule are studied by using molecular dynamics (MD) simulations based on density functional theory (DFT). Diffusion properties of covalent liquids under high pressure are very interesting in the sense that they show unexpected pressure dependence. It is found from our simulation that the magnitude relation of diffusion coefficients for boron and oxygen in liquid B{sub 2}O{sub 3} shows the anomalous pressure dependence. The simulation clarified the microscopic origin of the anomalous diffusion properties. Our simulation also reveals the dissociation mechanism in the coulomb explosion of the highly-charged bromophenol molecule. When the charge state n is 6, hydrogen atom in the hydroxyl group dissociates at times shorter than 20 fs while all hydrogen atoms dissociate when n is 8. After the hydrogen dissociation, the carbon ring breaks at about 100 fs. There is also a difference on the mechanism of the ring breaking depending on charge states, in which the ring breaks with expanding (n = 6) or shrink (n = 8)
Development of a CFD Analysis Plan for the first VHTR Standard Problem
Richard W. Johnson
2008-09-01
Data from a scaled model of a portion of the lower plenum of the helium-cooled very high temperature reactor (VHTR) are under consideration for acceptance as a computational fluid dynamics (CFD) validation data set or standard problem. A CFD analysis will help determine if the scaled model is a suitable geometry for validation data. The present article describes the development of an analysis plan for the CFD model. The plan examines the boundary conditions that should be used, the extent of the computational domain that should be included and which turbulence models need not be examined against the data. Calculations are made for a closely related 2D geometry to address these issues. It was found that a CFD model that includes only the inside of the scaled model in its computational domain is adequate for CFD calculations. The realizable k~e model was found not to be suitable for this problem because it did not predict vortex-shedding.
Beam dynamics simulations of the NML photoinjector at Fermilab
Piot, P.; Sun, Y.-E.; Church, M.; /Fermilab
2010-08-01
Fermilab is currently constructing a superconducting RF (SRF) test linear accelerator at the New Muon Lab (NML). Besides testing SRF accelerating modules for ILC and Project-X, NML will also eventually support a variety of advanced accelerator R&D experiments. The NML incorporates a 40 MeV photoinjector capable of providing electron bunches with variable parameters. The photoinjector is based on the 1+1/2 cell DESY-type gun followed by two superconducting cavities. It also includes a magnetic bunch compressor, a round-to-flat beam transformer and a low-energy experimental area for beam physics experiments and beam diagnostics R&D. In this paper, we explore, via beam dynamics simulations, the performance of the photoinjector for different operating scenarios.
Dynamic simulation of a direct carbonate fuel cell power plant
Ernest, J.B.; Ghezel-Ayagh, H.; Kush, A.K.
1996-12-31
Fuel Cell Engineering Corporation (FCE) is commercializing a 2.85 MW Direct carbonate Fuel Cell (DFC) power plant. The commercialization sequence has already progressed through construction and operation of the first commercial-scale DFC power plant on a U.S. electric utility, the 2 MW Santa Clara Demonstration Project (SCDP), and the completion of the early phases of a Commercial Plant design. A 400 kW fuel cell stack Test Facility is being built at Energy Research Corporation (ERC), FCE`s parent company, which will be capable of testing commercial-sized fuel cell stacks in an integrated plant configuration. Fluor Daniel, Inc. provided engineering, procurement, and construction services for SCDP and has jointly developed the Commercial Plant design with FCE, focusing on the balance-of-plant (BOP) equipment outside of the fuel cell modules. This paper provides a brief orientation to the dynamic simulation of a fuel cell power plant and the benefits offered.
Molecular dynamics simulation of annealed ZnO surfaces
Min, Tjun Kit; Yoon, Tiem Leong; Lim, Thong Leng
2015-04-24
The effect of thermally annealing a slab of wurtzite ZnO, terminated by two surfaces, (0001) (which is oxygen-terminated) and (0001{sup ¯}) (which is Zn-terminated), is investigated via molecular dynamics simulation by using reactive force field (ReaxFF). We found that upon heating beyond a threshold temperature of ∼700 K, surface oxygen atoms begin to sublimate from the (0001) surface. The ratio of oxygen leaving the surface at a given temperature increases as the heating temperature increases. A range of phenomena occurring at the atomic level on the (0001) surface has also been explored, such as formation of oxygen dimers on the surface and evolution of partial charge distribution in the slab during the annealing process. It was found that the partial charge distribution as a function of the depth from the surface undergoes a qualitative change when the annealing temperature is above the threshold temperature.
Molecular dynamics simulations of methane hydrate using polarizable force fields
Jiang, H.N.; Jordan, K.D.; Taylor, C.E.
2007-03-01
Molecular dynamics simulations of methane hydrate have been carried out using the AMOEBA and COS/G2 polarizable force fields. Properties examined include the temperature dependence of the lattice constant, the OC and OO radial distribution functions and the vibrational spectra. Both the AMOEBA and COS/G2 models are found to successfully account for the available experimental data, with overall slightly better agreement with experiment being found for the AMOEBA model. Several properties calculated using the AMOEBA and COS/G2 models differ appreciable from the corresponding results obtained previously using the polarizable TIP4P-FQ model. This appears to be due to the inadequacy of the treatment of polarization, especially, the restriction of polarization to in-plane only, in the TIP4P-FQ model.
Relationship between nanocrystalline and amorphous microstructures by molecular dynamics simulation
Keblinski, P.; Phillpot, S.R.; Wolf, D.; Gleiter, H.
1996-08-01
A recent molecular dynamics simulation method for growth of fully dense nanocrystalline materials crystallized from melt was used with the Stillinger-Weber three-body potential to synthesize nanocrystalline Si with a grain size up to 75{Angstrom}. Structures of the highly constrained grain boundaries (GBs), triple lines, and point grain junctions were found to be highly disordered and similar to the structure of amorphous Si. These and earlier results for fcc metals suggest that a nanocrystalline microstructure may be viewed as a two-phase system, namely an ordered crystalline phase in the grain interiors connected by an amorphous, intergranular, glue-like phase. Analysis of the structures of bicrystalline GBs in the same materials reveals the presence of an amorphous intergranular equilibrium phase only in the high-energy but not the low-energy GBs, suggesting that only high-energy boundaries are present in nanocrystalline microstructures.
Gayathri Devi, V.; Sircar, A.; Sarkar, B.
2015-03-15
One of the most challenging tasks in the design of the fuel cycle system lies in the effective design of Tritium Extraction System (TES) which involves proper extraction and purification of tritium in the fuel cycle of the fusion reactor. Indian Lead Lithium cooled Ceramic Breeder Test Blanket Module (LLCB-TBM) would extract hydrogen isotopes through Cryogenic Molecular Sieve Bed (CMSB) adsorber system. A prototype Hydrogen Isotopes Recovery System (HIRS) is being developed to validate the concepts for tritium extraction by adsorption mass transfer mechanism. In this study, a design model has been developed and analyzed to simulate the adsorption mass transfer kinetics in a fixed bed adsorption column. The simulation leads primarily to effective design of HIRS, which is a state-of-the-art technology. The paper describes the process simulation approach and the results of Computational Fluid Dynamics (CFD) analysis. The effects of different operating conditions are studied to investigate their influence on the hydrogen isotopes adsorption capacity. The results of the present simulation study would be used to understand the best optimized transport phenomenon before realizing the TES as a system for LLCB-TBM. (authors)
Technical Review of the CENWP Computational Fluid Dynamics Model of the John Day Dam Forebay
Rakowski, Cynthia L.; Serkowski, John A.; Richmond, Marshall C.
2010-12-01
The US Army Corps of Engineers Portland District (CENWP) has developed a computational fluid dynamics (CFD) model of the John Day forebay on the Columbia River to aid in the development and design of alternatives to improve juvenile salmon passage at the John Day Project. At the request of CENWP, Pacific Northwest National Laboratory (PNNL) Hydrology Group has conducted a technical review of CENWP's CFD model run in CFD solver software, STAR-CD. PNNL has extensive experience developing and applying 3D CFD models run in STAR-CD for Columbia River hydroelectric projects. The John Day forebay model developed by CENWP is adequately configured and validated. The model is ready for use simulating forebay hydraulics for structural and operational alternatives. The approach and method are sound, however CENWP has identified some improvements that need to be made for future models and for modifications to this existing model.
Enhanced molecular dynamics for simulating porous interphase layers in batteries.
Zimmerman, Jonathan A.; Wong, Bryan Matthew; Jones, Reese E.; Templeton, Jeremy Alan; Lee, Jonathan
2009-10-01
Understanding charge transport processes at a molecular level using computational techniques is currently hindered by a lack of appropriate models for incorporating anistropic electric fields in molecular dynamics (MD) simulations. An important technological example is ion transport through solid-electrolyte interphase (SEI) layers that form in many common types of batteries. These layers regulate the rate at which electro-chemical reactions occur, affecting power, safety, and reliability. In this work, we develop a model for incorporating electric fields in MD using an atomistic-to-continuum framework. This framework provides the mathematical and algorithmic infrastructure to couple finite element (FE) representations of continuous data with atomic data. In this application, the electric potential is represented on a FE mesh and is calculated from a Poisson equation with source terms determined by the distribution of the atomic charges. Boundary conditions can be imposed naturally using the FE description of the potential, which then propagates to each atom through modified forces. The method is verified using simulations where analytical or theoretical solutions are known. Calculations of salt water solutions in complex domains are performed to understand how ions are attracted to charged surfaces in the presence of electric fields and interfering media.
Molecular Dynamics Simulation of Thermodynamic Properties in Uranium Dioxide
Wang, Xiangyu; Wu, Bin; Gao, Fei; Li, Xin; Sun, Xin; Khaleel, Mohammad A.; Akinlalu, Ademola V.; Liu, L.
2014-03-01
In the present study, we investigated the thermodynamic properties of uranium dioxide (UO2) by molecular dynamics (MD) simulations. As for solid UO2, the lattice parameter, density, and enthalpy obtained by MD simulations were in good agreement with existing experimental data and previous theoretical predictions. The calculated thermal conductivities matched the experiment results at the midtemperature range but were underestimated at very low and very high temperatures. The calculation results of mean square displacement represented the stability of uranium at all temperatures and the high mobility of oxygen toward 3000 K. By fitting the diffusivity constant of oxygen with the Vogel-Fulcher-Tamman law, we noticed a secondary phase transition near 2006.4 K, which can be identified as a strong to fragile supercooled liquid or glass phase transition in UO2. By fitting the oxygen diffusion constant with the Arrhenius equation, activation energies of 2.0 and 2.7 eV that we obtained were fairly close to the recommended values of 2.3 to 2.6 eV. Xiangyu Wang, Bin Wu, Fei Gao, Xin Li, Xin Sun, Mohammed A. Khaleel, Ademola V. Akinlalu and Li Liu
Direct Dynamics Simulation of Dissociation of the [CH3--I--OH...
Office of Scientific and Technical Information (OSTI)
Ion-Molecule Complex Citation Details In-Document Search Title: Direct Dynamics Simulation of Dissociation of the CH3--I--OH- Ion-Molecule Complex Direct dynamics ...
Nucleation Rate Analysis of Methane Hydrate from Molecular Dynamics Simulations
Yuhara, Daisuke; Barnes, Brian C.; Suh, Donguk; Knott, Brandon C.; Beckham, Gregg T.; Yasuoka, Kenji; Wu, David T.; Amadeu K. Sum
2015-01-06
Clathrate hydrates are solid crystalline structures most commonly formed from solutions that have nucleated to form a mixed solid composed of water and gas. Understanding the mechanism of clathrate hydrate nucleation is essential to grasp the fundamental chemistry of these complex structures and their applications. Molecular dynamics (MD) simulation is an ideal method to study nucleation at the molecular level because the size of the critical nucleus and formation rate occur on the nano scale. Moreover, various analysis methods for nucleation have been developed through MD to analyze nucleation. In particular, the mean first-passage time (MFPT) and survival probability (SP)more » methods have proven to be effective in procuring the nucleation rate and critical nucleus size for monatomic systems. This study assesses the MFPT and SP methods, previously used for monatomic systems, when applied to analyzing clathrate hydrate nucleation. Because clathrate hydrate nucleation is relatively difficult to observe in MD simulations (due to its high free energy barrier), these methods have yet to be applied to clathrate hydrate systems. In this study, we have analyzed the nucleation rate and critical nucleus size of methane hydrate using MFPT and SP methods from data generated by MD simulations at 255 K and 50 MPa. MFPT was modified for clathrate hydrate from the original version by adding the maximum likelihood estimate and growth effect term. The nucleation rates were calculated by MFPT and SP methods and are within 5%; the critical nucleus size estimated by the MFPT method was 50% higher, than values obtained through other more rigorous but computationally expensive estimates. These methods can also be extended to the analysis of other clathrate hydrates.« less
Needs and opportunities for CFD-code validation
Smith, B.L. |
1996-06-01
The conceptual design for the ESS target consists of a horizontal cylinder containing a liquid metal - mercury is considered in the present study - which circulates by forced convection and carries away the waste heat generated by the spallation reactions. The protons enter the target via a beam window, which must withstand the thermal, mechanical and radiation loads to which it is subjected. For a beam power of 5MW, it is estimated that about 3.3MW of waste heat would be deposited in the target material and associated structures. it is intended to confirm, by detailed thermal-hydraulics calculations, that a convective flow of the liquid metal target material can effectively remove the waste heat. The present series of Computational Fluid Dynamics (CFD) calculations has indicated that a single-inlet Target design leads to excessive local overheating, but a multiple-inlet design, is coolable. With this option, inlet flow streams, two from the sides and one from below, merge over the target window, cooling the window itself in crossflow and carrying away the heat generated volumetrically in the mercury with a strong axial flow down the exit channel. The three intersecting streams form a complex, three-dimensional, swirling flow field in which critical heat transfer processes are taking place. In order to produce trustworthy code simulations, it is necessary that the mesh resolution is adequate for the thermal-hydraulic conditions encountered and that the physical models used by the code are appropriate to the fluid dynamic environment. The former relies on considerable user experience in the application of the code, and the latter assurance is best gained in the context of controlled benchmark activities where measured data are available. Such activities will serve to quantify the accuracy of given models and to identify potential problem area for the numerical simulation which may not be obvious from global heat and mass balance considerations.
Large-Scale Condensed Matter and Fluid Dynamics Simulations in...
U.S. Department of Energy (DOE) all webpages (Extended Search)
Simulations in Three Diverse Areas: Whole Brain Blood Flow Simulations PI Name: Peter ... blood flow behavior in the neighborhood of bifurcations and aneurysms within the brain. ...
On theoretical issues of computer simulations sequential dynamical systems
Barrett, C.L.; Mortveit, H.S.; Reidys, C.M.
1998-12-01
The authors study a class of discrete dynamical systems that is motivated by the generic structure of simulations. The systems consist of the following data: (a) a finite graph Y with vertex set {l_brace}1,...,n{r_brace} where each vertex has a binary state, (b) functions F{sub i}:F{sub 2}{sup n} {r_arrow} F{sub 2}{sup n} and (c) an update ordering {pi}. The functions F{sub i} update the binary state of vertex i as a function of the state of vertex i and its Y-neighbors and leave the states of all other vertices fixed. The update ordering is a permutation of the Y-vertices. They derive a decomposition result, characterize invertible SDS and study fixed points. In particular they analyze how many different SDS that can be obtained by reordering a given multiset of update functions and give a criterion for when one can derive concentration results on this number. Finally, some specific SDS are investigated.
Implementation of Parallel Dynamic Simulation on Shared-Memory vs. Distributed-Memory Environments
Jin, Shuangshuang; Chen, Yousu; Wu, Di; Diao, Ruisheng; Huang, Zhenyu
2015-12-09
Power system dynamic simulation computes the system response to a sequence of large disturbance, such as sudden changes in generation or load, or a network short circuit followed by protective branch switching operation. It consists of a large set of differential and algebraic equations, which is computational intensive and challenging to solve using single-processor based dynamic simulation solution. High-performance computing (HPC) based parallel computing is a very promising technology to speed up the computation and facilitate the simulation process. This paper presents two different parallel implementations of power grid dynamic simulation using Open Multi-processing (OpenMP) on shared-memory platform, and Message Passing Interface (MPI) on distributed-memory clusters, respectively. The difference of the parallel simulation algorithms and architectures of the two HPC technologies are illustrated, and their performances for running parallel dynamic simulation are compared and demonstrated.
CFD analyses of natural circulation in the air-cooled reactor cavity cooling system
Hu, R.; Pointer, W. D.
2013-07-01
The Natural Convection Shutdown Heat Removal Test Facility (NSTF) is currently being built at Argonne National Laboratory, to evaluate the feasibility of the passive Reactor Cavity Cooling System (RCCS) for Next Generation Nuclear Plant (NGNP). CFD simulations have been applied to evaluate the NSTF and NGNP RCCS designs. However, previous simulations found that convergence was very difficult to achieve in simulating the complex natural circulation. To resolve the convergence issue and increase the confidence of the CFD simulation results, additional CFD simulations were conducted using a more detailed mesh and a different solution scheme. It is found that, with the use of coupled flow and coupled energy models, the convergence can be greatly improved. Furthermore, the effects of convection in the cavity and the effects of the uncertainty in solid surface emissivity are also investigated. (authors)
SciDAC advances in beam dynamics simulation: from light sources to colliders
Qiang, Ji; Qiang, J.; Borland, M.; Kabel, A.; Li, R.; Ryne, R.; Stern, E.; Wang, Y.; Wasserman, H.; Zhang, Y.
2008-06-16
In this paper, we report on progress that has been made in beam dynamics simulation, from light sources to colliders, during the first year of SciDAC-II accelerator project,"Community Petascale Project for Accelerator Science and Simulation (ComPASS)." Several parallel computational tools for beam dynamics simulation will be described. A number of applications in current and future accelerator facilities, e.g., LCLS, RHIC, Tevatron, LHC, ELIC, are presented.
Extreme Scale Unstructured Adaptive CFD: From Multiphase Flow to
U.S. Department of Energy (DOE) all webpages (Extended Search)
Aerodynamic Flow Control | Argonne Leadership Computing Facility Isosurface of instantaneous Q criterion colored by speed over a vertical tail Isosurface of instantaneous Q criterion colored by speed over a vertical tail at Re=3.5\ 10^5 of a DES simulation with a rudder deflection angle of 30 degrees and 12 unsteady jets active. Kenneth Jansen, University of Colorado at Boulder Extreme Scale Unstructured Adaptive CFD: From Multiphase Flow to Aerodynamic Flow Control PI Name: Kenneth Jansen
Dynamic simulation of kinematic Stirling engines: Coupled and...
Office of Scientific and Technical Information (OSTI)
Subject: 42 ENGINEERING NOT INCLUDED IN OTHER CATEGORIES; STIRLING ENGINES; MATHEMATICAL MODELS; COMPUTERIZED SIMULATION; CALCULATION METHODS; COMPARATIVE EVALUATIONS; PRESSURE ...
Lawson, Mi. J.; Li, Y.; Sale, D. C.
2011-01-01
This paper describes the development of a computational fluid dynamics (CFD) methodology to simulate the hydrodynamics of horizontal-axis tidal current turbines (HATTs). First, an HATT blade was designed using the blade element momentum method in conjunction with a genetic optimization algorithm. Several unstructured computational grids were generated using this blade geometry and steady CFD simulations were used to perform a grid resolution study. Transient simulations were then performed to determine the effect of time-dependent flow phenomena and the size of the computational timestep on the numerical solution. Qualitative measures of the CFD solutions were independent of the grid resolution. Conversely, quantitative comparisons of the results indicated that the use of coarse computational grids results in an under prediction of the hydrodynamic forces on the turbine blade in comparison to the forces predicted using more resolved grids. For the turbine operating conditions considered in this study, the effect of the computational timestep on the CFD solution was found to be minimal, and the results from steady and transient simulations were in good agreement. Additionally, the CFD results were compared to corresponding blade element momentum method calculations and reasonable agreement was shown. Nevertheless, we expect that for other turbine operating conditions, where the flow over the blade is separated, transient simulations will be required.
Experimental characterization of energetic material dynamics for multiphase blast simulation.
Beresh, Steven Jay; Wagner, Justin L.; Kearney, Sean Patrick; Wright, Elton K.; Baer, Melvin R.; Pruett, Brian Owen Matthew
2011-09-01
Currently there is a substantial lack of data for interactions of shock waves with particle fields having volume fractions residing between the dilute and granular regimes, which creates one of the largest sources of uncertainty in the simulation of energetic material detonation. To close this gap, a novel Multiphase Shock Tube has been constructed to drive a planar shock wave into a dense gas-solid field of particles. A nearly spatially isotropic field of particles is generated in the test section by a gravity-fed method that results in a spanwise curtain of spherical 100-micron particles having a volume fraction of about 19%. Interactions with incident shock Mach numbers of 1.66, 1.92, and 2.02 were achieved. High-speed schlieren imaging simultaneous with high-frequency wall pressure measurements are used to reveal the complex wave structure associated with the interaction. Following incident shock impingement, transmitted and reflected shocks are observed, which lead to differences in particle drag across the streamwise dimension of the curtain. Shortly thereafter, the particle field begins to propagate downstream and spread. For all three Mach numbers tested, the energy and momentum fluxes in the induced flow far downstream are reduced about 30-40% by the presence of the particle field. X-Ray diagnostics have been developed to penetrate the opacity of the flow, revealing the concentrations throughout the particle field as it expands and spreads downstream with time. Furthermore, an X-Ray particle tracking velocimetry diagnostic has been demonstrated to be feasible for this flow, which can be used to follow the trajectory of tracer particles seeded into the curtain. Additional experiments on single spherical particles accelerated behind an incident shock wave have shown that elevated particle drag coefficients can be attributed to increased compressibility rather than flow unsteadiness, clarifying confusing results from the historical database of shock tube
Simulation studies on the standing and traveling wave thermoacoustic prime movers
Skaria, Mathew; Rasheed, K. K. Abdul; Shafi, K. A.; Kasthurirengan, S.; Behera, Upendra
2014-01-29
Thermoacoustic systems have been a focus of recent research due to its structural simplicity, high reliability due to absence of moving parts, and can be driven by low grade energy such as fuel, gas, solar energy, waste heat etc. There has been extensive research on both standing wave and traveling wave systems. Towards the development of such systems, simulations can be carried out by several methods such as (a) solving the energy equation, (b) enthalpy flow model, (c) DeltaEC, a free software available from LANL, USA (d) Computational Fluid Dynamics (CFD) etc. We present here the simulation studies of standing wave and traveling wave thermoacoustic prime movers using CFD and DeltaEC. The CFD analysis is carried out using Fluent 6.3.26, incorporating the necessary boundary conditions with different working fluids at different operating pressures. The results obtained by CFD are compared with those obtained using DeltaEC. Also, the CFD simulation of the thermoacoustically driven refrigerator is presented.
First Principals and Classical Molecular Dynamics Simulations of Solvated Benzene
Allesch, M; Lightstone, F; Schwegler, E; Galli, G
2007-09-11
We have performed extensive ab initio and classical MD simulations of benzene in water in order to examine the unique solvation structures that are formed. Qualitative differences between classical and ab initio MD simulations are found and the importance of various technical simulation parameters is examined. Our comparison indicates that non-polarizable classical models are not capable of describing the solute-water interface correctly if local interactions become energetically comparable to water hydrogen bonds. In addition, a comparison is made between a rigid water model and fully flexible water within ab initio MD simulations which shows that both models agree qualitatively for this challenging system.
Office Of Nuclear Energy Annual Review Meeting Dynamic Simulation...
Office of Energy Efficiency and Renewable Energy (EERE) (indexed site)
cooled model deliverable due. n FY15 web application deliverable due. n FY15 ... with user friendly interfaces (Excel Web) allow common simulation environment and ...
Gerhard Strydom; Su-Jong Yoon
2014-04-01
Computational Fluid Dynamics (CFD) evaluation of homogeneous and heterogeneous fuel models was performed as part of the Phase I calculations of the International Atomic Energy Agency (IAEA) Coordinate Research Program (CRP) on High Temperature Reactor (HTR) Uncertainties in Modeling (UAM). This study was focused on the nominal localized stand-alone fuel thermal response, as defined in Ex. I-3 and I-4 of the HTR UAM. The aim of the stand-alone thermal unit-cell simulation is to isolate the effect of material and boundary input uncertainties on a very simplified problem, before propagation of these uncertainties are performed in subsequent coupled neutronics/thermal fluids phases on the benchmark. In many of the previous studies for high temperature gas cooled reactors, the volume-averaged homogeneous mixture model of a single fuel compact has been applied. In the homogeneous model, the Tristructural Isotropic (TRISO) fuel particles in the fuel compact were not modeled directly and an effective thermal conductivity was employed for the thermo-physical properties of the fuel compact. On the contrary, in the heterogeneous model, the uranium carbide (UCO), inner and outer pyrolytic carbon (IPyC/OPyC) and silicon carbide (SiC) layers of the TRISO fuel particles are explicitly modeled. The fuel compact is modeled as a heterogeneous mixture of TRISO fuel kernels embedded in H-451 matrix graphite. In this study, a steady-state and transient CFD simulations were performed with both homogeneous and heterogeneous models to compare the thermal characteristics. The nominal values of the input parameters are used for this CFD analysis. In a future study, the effects of input uncertainties in the material properties and boundary parameters will be investigated and reported.
CFD Modeling of Thermal Effects of Nuclear Waste Vitrification Processes
Rayner, Chris; Soltani, Mehdi; Barringer, Chris; Knight, Kelly
2006-07-01
The Waste Treatment Plant (WTP) at Hanford, WA will vitrify nuclear waste stored at the DOE Hanford facility. The vitrification process will take place in two large concrete buildings where the glass is poured into stainless steel canisters or containers and allowed to cool. Computational Fluid Dynamics (CFD) was used extensively to calculate the effects of the heat released by molten glass as it is poured and cooled, on the HVAC system and the building structure. CFD studies of the glass cooling in these facilities were used to predict canister temperatures, HVAC air temperatures, concrete temperatures and insulation requirements, and design temperatures for canister handling equipment and instrumentation at various stages of the process. These predictions provided critical input in the design of the HVAC system, specification of insulation, the design of canister handling equipment, and the selection of instrumentation. (authors)
The legacy and future of CFD at Los Alamos
Johnson, N.L.
1996-06-01
The early history is presented of the prolific development of CFD methods in the Fluid Dynamics Group (T-3) at Los Alamos National Laboratory in the years from 1958 to the late 1960`s. Many of the currently used numerical methods--PIC, MAC, vorticity-stream-function, ICE, ALE methods and the {kappa}-{var_epsilon} method for turbulence--originated during this time. The rest of the paper summarizes the current research in T-3 for CFD, turbulence and solids modeling. The research areas include reactive flows, multimaterial flows, multiphase flows and flows with spatial discontinuities. Also summarized are modern particle methods and techniques developed for large scale computing on massively parallel computing platforms and distributed processors.
A New CFD Model for understanding and Managing Diesel Particulate...
Office of Energy Efficiency and Renewable Energy (EERE) (indexed site)
CFD Model for understanding and Managing Diesel Particulate Filter Regeneration A New CFD Model for understanding and Managing Diesel Particulate Filter Regeneration ...
Petascale, Adaptive CFD (ALCF ESP Technical Report): ALCF-2 Early...
Office of Scientific and Technical Information (OSTI)
Petascale, Adaptive CFD (ALCF ESP Technical Report): ALCF-2 Early Science Program Technical Report Citation Details In-Document Search Title: Petascale, Adaptive CFD (ALCF ESP ...
Extended-Term Dynamic Simulations with High Penetrations of Photovoltaic Generation.
Concepcion, Ricky James; Elliott, Ryan Thomas; Donnelly, Matt; Sanchez-Gasca, Juan
2016-01-01
The uncontrolled intermittent availability of renewable energy sources makes integration of such devices into today's grid a challenge. Thus, it is imperative that dynamic simulation tools used to analyze power system performance are able to support systems with high amounts of photovoltaic (PV) generation. Additionally, simulation durations expanding beyond minutes into hours must be supported. This report aims to identify the path forward for dynamic simulation tools to accom- modate these needs by characterizing the properties of power systems (with high PV penetration), analyzing how these properties affect dynamic simulation software, and offering solutions for po- tential problems. We present a study of fixed time step, explicit numerical integration schemes that may be more suitable for these goals, based on identified requirements for simulating high PV penetration systems. We also present the alternative of variable time step integration. To help determine the characteristics of systems with high PV generation, we performed small signal sta- bility studies and time domain simulations of two representative systems. Along with feedback from stakeholders and vendors, we identify the current gaps in power system modeling including fast and slow dynamics and propose a new simulation framework to improve our ability to model and simulate longer-term dynamics.
ParaDiS-FEM dislocation dynamics simulation code primer (Technical...
Office of Scientific and Technical Information (OSTI)
When we try to perform discrete dislocation dynamics simulations for finite systems such as thin films or cylinders, the ParaDiS code must be extended. First, dislocations need to ...
Kinetic Simulations of Fusion Energy Dynamics at the Extreme Scale |
U.S. Department of Energy (DOE) all webpages (Extended Search)
Argonne Leadership Computing Facility Electrostatic potential in a particle-in-cell simulation of a tokamak plasma. The tokamak fusion device uses magnetic fields to contain a heated plasma in a toroidal shape. Pictured is the electrostatic potential in the simulated tokamak. The plasma, being made up of charged particles, is driven by the potential; the two evolve self-consistently. Chad Jones and Kwan-Liu Ma, University of California, Davis; Stephane Ethier, Princeton Plasma Physics
Dynamic simulation of the Hanford tank waste remediation system
Harmsen, R.W., Westinghouse Hanford
1996-05-03
Cleaning up and disposing of approximately 50 years of nuclear waste is the main mission at the U.S. Department of Energy`s Hanford Nuclear Reservation, located in the southeastern part of the state of Washington. A major element of the total cleanup effort involves retrieving, processing, and disposing of radioactive and hazardous waste stored in 177 underground storage tanks. This effort, referred to as the Tank Waste Remediation System (TWRS), is expected to cost billions of dollars and take approximately 25 years to complete. Several computer simulations of this project are being created, focusing on both programmatic and detailed engineering issues. This paper describes one such simulation activity, using the ithink(TM)computer simulation software. The ithink(TM) simulation includes a representation of the complete TWRS cleanup system, from retrieval of waste through intermediate processing and final vitrification of waste for disposal. Major issues addressed to date by the simulation effort include the need for new underground storage tanks to support TWRS activities, and the estimated design capacities for various processing facilities that are required to support legally mandated program commitment dates. This paper discusses how the simulation was used to investigate these questions.
AMIP Simulation with the CAM4 Spectral Element Dynamical Core
Evans, Katherine J; Lauritzen, Peter; Mishra, Saroj; Neale, Rich; Taylor, Mark; Tribbia, Joe
2013-01-01
We evaluate the climate produced by the Community Earth System Model, version 1, running with the new spectral-element atmospheric dynamical core option. The spectral-element method is congured to use a cubed-sphere grid, providing quasi-uniform resolution over the sphere, increased parallel scalability and removing the need for polar filters. It uses a fourth order accurate spatial discretization which locally conserves mass and moist total energy. Using the Atmosphere Model Intercomparison Project protocol, we compare the results from the spectral-element dy- namical core with those produced by the default nite-volume dynamical core and with observations.
Carbon atom, dimer and trimer chemistry on diamond surfaces from molecular dynamics simulations
Valone, S.M.
1995-07-01
Spectroscopic studies of various atmospheres appearing in diamond film synthesis suggest evidence for carbon atoms, dimers, or trimers. Molecular dynamics simulations with the Brenner hydrocarbon potential are being used to investigate the elementary reactions of these species on a hydrogen-terminated diamond (111) surface. In principle these types of simulations can be extended to simulations of growth morphologies, in the 1-2 monolayer regime presently.
Nonadiabatic molecular dynamics simulation: An approach based on quantum measurement picture
Feng, Wei; Xu, Luting; Li, Xin-Qi; Fang, Weihai; Yan, YiJing
2014-07-15
Mixed-quantum-classical molecular dynamics simulation implies an effective quantum measurement on the electronic states by the classical motion of atoms. Based on this insight, we propose a quantum trajectory mean-field approach for nonadiabatic molecular dynamics simulations. The new protocol provides a natural interface between the separate quantum and classical treatments, without invoking artificial surface hopping algorithm. Moreover, it also bridges two widely adopted nonadiabatic dynamics methods, the Ehrenfest mean-field theory and the trajectory surface-hopping method. Excellent agreement with the exact results is illustrated with representative model systems, including the challenging ones for traditional methods.
L3:THM.CFD.P5.02 J.N. Shadid, T.M. Smith, R.P. Pawlowski, E....
U.S. Department of Energy (DOE) all webpages (Extended Search)
Smith, R.P. Pawlowski, E. C. Cyr, P.D. Weber SNL Completed: October 31, 2012 CASL-U-2012-0164-000 RANS CFD SIMULATIONS FOR CASL THM USING DREKAR::CFD J. N. Shadid, T. M. Smith, R. ...
Simulating Collisions for Hydrokinetic Turbines. FY2010 Annual Progress Report.
Richmond, Marshall C.; Rakowski, Cynthia L.; Perkins, William A.; Serkowski, John A.
2010-11-30
Computational fluid dynamics (CFD) simulations of turbulent flow and particle motion are being conducted to evaluate the frequency and severity of collisions between marine and hydrokinetic (MHK) energy devices and debris or aquatic organisms. The work is part of a collaborative research project between Pacific Northwest National Laboratory (PNNL) and Sandia National Laboratories , funded by the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy Wind and Water Power Program. During FY2010 a reference design for an axial flow MHK turbine was used to develop a computational geometry for inclusion into a CFD model. Unsteady simulations of turbulent flow and the moving MHK turbine blades are being performed and the results used for simulation of particle trajectories. Preliminary results and plans for future work are presented.
Min, Tjun Kit; Yoon, Tiem Leong; Lim, Thong Leng
2015-04-24
Molecular dynamics (MD) simulation with simulated annealing method is used to study the growth process of bi- and tri-layered graphene on a 6H-SiC (0001) substrate via molecular dynamics simulation. Tersoff-Albe-Erhart (TEA) potential is used to describe the inter-atomic interactions among the atoms in the system. The formation temperature, averaged carbon-carbon bond length, pair correlation function, binding energy and the distance between the graphene formed and the SiC substrate are quantified. The growth mechanism, graphitization of graphene on the SiC substrate and characteristics of the surface morphology of the graphene sheet obtained in our MD simulation compare well to that observed in epitaxially grown graphene experiments and other simulation works.
CFD Modeling for Mercury Control Technology
Madsen, J.I.
2006-12-01
Compliance with the Clean Air Mercury Rule will require implementation of dedicated mercury control solutions at a significant portion of the U.S. coal-fired utility fleet. Activated Carbon Injection (ACI) upstream of a particulate control device (ESP or baghouse) remains one of the most promising near-term mercury control technologies. The DOE/NETL field testing program has advanced the understanding of mercury control by ACI, but a persistent need remains to develop predictive models that may improve the understanding and practical implementation of this technology. This presentation describes the development of an advanced model of in-flight mercury capture based on Computational Fluid Dynamics (CFD). The model makes detailed predictions of the induct spatial distribution and residence time of sorbent, as well as predictions of mercury capture efficiency for particular sorbent flow rates and injection grid configurations. Hence, CFD enables cost efficient optimization of sorbent injection systems for mercury control to a degree that would otherwise be impractical both for new and existing plants. In this way, modeling tools may directly address the main cost component of operating an ACI system the sorbent expense. A typical 300 MW system is expected to require between $1 and $2 million of sorbent per year, and so even modest reductions (say 10-20%) in necessary sorbent feed injection rates will quickly make any optimization effort very worthwhile. There are few existing models of mercury capture, and these typically make gross assumptions of plug gas flow, zero velocity slip between particle and gas phase, and uniform sorbent dispersion. All of these assumptions are overcome with the current model, which is based on first principles and includes mass transfer processes occurring at multiple scales, ranging from the large-scale transport in the duct to transport within the porous structure of a sorbent particle. In principle any single one of these processes
Link, S.O.; Kickert, R.N.; Fayer, M.J.; Gee, G.W.
1993-06-01
This report describes the results of simulation models used to predict soil water storage dynamics at the Field Lysimeter Test Facility (FLTF) weighing lysimeters. The objectives of this research is to develop the capability to predict soil water storage dynamics with plants in support of water infiltration control studies for the Hanford Permanent Isolation Barrier Development Program. It is important to gain confidence in one`s ability to simulate soil water dynamics over long time periods to assess the barrier`s ability to prevent drainage. Two models were compared for their ability to simulate soil water storage dynamics with and without plants in weighing lysimeters, the soil water infiltration and movement (SWIM) and the simulation of production and utilization of rangelands (SPUR-91) models. These models adequately simulated soil water storage dynamics for the weighing lysimeters. The range of root mean square error values for the two models was 7.0 to 19.8. This compares well with the range reported by Fayer et al. (1992) for the bare soil data sets of 8.1 to 22.1. Future research will test the predictive capability of these models for longer term lysimeter data sets and for historical data sets collected in various plant community types.
Fast Dynamic Simulation-Based Small Signal Stability Assessment and Control
Acharya, Naresh; Baone, Chaitanya; Veda, Santosh; Dai, Jing; Chaudhuri, Nilanjan; Leonardi, Bruno; Sanches-Gasca, Juan; Diao, Ruisheng; Wu, Di; Huang, Zhenyu; Zhang, Yu; Jin, Shuangshuang; Zheng, Bin; Chen, Yousu
2014-12-31
Power grid planning and operation decisions are made based on simulation of the dynamic behavior of the system. Enabling substantial energy savings while increasing the reliability of the aging North American power grid through improved utilization of existing transmission assets hinges on the adoption of wide-area measurement systems (WAMS) for power system stabilization. However, adoption of WAMS alone will not suffice if the power system is to reach its full entitlement in stability and reliability. It is necessary to enhance predictability with "faster than real-time" dynamic simulations that will enable the dynamic stability margins, proactive real-time control, and improve grid resiliency to fast time-scale phenomena such as cascading network failures. Present-day dynamic simulations are performed only during offline planning studies, considering only worst case conditions such as summer peak, winter peak days, etc. With widespread deployment of renewable generation, controllable loads, energy storage devices and plug-in hybrid electric vehicles expected in the near future and greater integration of cyber infrastructure (communications, computation and control), monitoring and controlling the dynamic performance of the grid in real-time would become increasingly important. The state-of-the-art dynamic simulation tools have limited computational speed and are not suitable for real-time applications, given the large set of contingency conditions to be evaluated. These tools are optimized for best performance of single-processor computers, but the simulation is still several times slower than real-time due to its computational complexity. With recent significant advances in numerical methods and computational hardware, the expectations have been rising towards more efficient and faster techniques to be implemented in power system simulators. This is a natural expectation, given that the core solution algorithms of most commercial simulators were developed
Large scale condensed matter and fluid dynamics simulations | Argonne
U.S. Department of Energy (DOE) all webpages (Extended Search)
Leadership Computing Facility , (a)Snapshots of the vorticity field of a UPO located in weakly turbulent flow with Re=371 and period equal to 26864 LB time steps. The quantity shown is the magnitude of vorticity above a given cut-off level. Red corresponds to large negative vorticity (clockwise rotation), and blue to large positive vorticity (counter-clockwise rotation). (b)Initial stucture of the large LDH-nucleic acid models, (a) System, at the start of the simulation. For clarity, water
Dynamic simulation of kinematic Stirling engines: Coupled and decoupled analysis
Fischer, K.; Lemrani, H.; Stouffs, P.
1995-12-31
A coupled analysis modelling method of Stirling engines is presented. The main feature of this modelling method is the use of a software package combining the capabilities of a pre-/post-processor with a differential algebraic equations solver. As a result, modelling is merely a matter of linking appropriate objects from a model library and the outcoming tool is very flexible and powerful. Some simulation results are presented and compared with those obtained from a decoupled analysis. It clearly appears that the main imperfection of the model does not come from the modelling process itself but from their incomplete knowledge of the physics behind the Stirling engine operation.
CFD Calculations of S809 Aerodynamic Characteristics
U.S. Department of Energy (DOE) all webpages (Extended Search)
pressure and aerodynamic coefficients were made with wind tunnel data from the Delft University 1.8m x 1.25m low-turbulence wind tunnel. This work highlights two areas in CFD...
Computational fluid dynamics modeling of coal gasification in a pressurized spout-fluid bed
Zhongyi Deng; Rui Xiao; Baosheng Jin; He Huang; Laihong Shen; Qilei Song; Qianjun Li
2008-05-15
Computational fluid dynamics (CFD) modeling, which has recently proven to be an effective means of analysis and optimization of energy-conversion processes, has been extended to coal gasification in this paper. A 3D mathematical model has been developed to simulate the coal gasification process in a pressurized spout-fluid bed. This CFD model is composed of gas-solid hydrodynamics, coal pyrolysis, char gasification, and gas phase reaction submodels. The rates of heterogeneous reactions are determined by combining Arrhenius rate and diffusion rate. The homogeneous reactions of gas phase can be treated as secondary reactions. A comparison of the calculated and experimental data shows that most gasification performance parameters can be predicted accurately. This good agreement indicates that CFD modeling can be used for complex fluidized beds coal gasification processes. 37 refs., 7 figs., 5 tabs.
Modeling ramp compression experiments using large-scale molecular dynamics simulation.
Mattsson, Thomas Kjell Rene; Desjarlais, Michael Paul; Grest, Gary Stephen; Templeton, Jeremy Alan; Thompson, Aidan Patrick; Jones, Reese E.; Zimmerman, Jonathan A.; Baskes, Michael I.; Winey, J. Michael; Gupta, Yogendra Mohan; Lane, J. Matthew D.; Ditmire, Todd; Quevedo, Hernan J.
2011-10-01
Molecular dynamics simulation (MD) is an invaluable tool for studying problems sensitive to atomscale physics such as structural transitions, discontinuous interfaces, non-equilibrium dynamics, and elastic-plastic deformation. In order to apply this method to modeling of ramp-compression experiments, several challenges must be overcome: accuracy of interatomic potentials, length- and time-scales, and extraction of continuum quantities. We have completed a 3 year LDRD project with the goal of developing molecular dynamics simulation capabilities for modeling the response of materials to ramp compression. The techniques we have developed fall in to three categories (i) molecular dynamics methods (ii) interatomic potentials (iii) calculation of continuum variables. Highlights include the development of an accurate interatomic potential describing shock-melting of Beryllium, a scaling technique for modeling slow ramp compression experiments using fast ramp MD simulations, and a technique for extracting plastic strain from MD simulations. All of these methods have been implemented in Sandia's LAMMPS MD code, ensuring their widespread availability to dynamic materials research at Sandia and elsewhere.
Holkundkar, Amol R.
2013-11-15
The objective of this article is to report the parallel implementation of the 3D molecular dynamic simulation code for laser-cluster interactions. The benchmarking of the code has been done by comparing the simulation results with some of the experiments reported in the literature. Scaling laws for the computational time is established by varying the number of processor cores and number of macroparticles used. The capabilities of the code are highlighted by implementing various diagnostic tools. To study the dynamics of the laser-cluster interactions, the executable version of the code is available from the author.
SciDAC Advances in Beam Dynamics Simulation: From Light Sources to Colliders
Qiang, J.; Borland, M.; Kabel, A.; Li, R.; Ryne, R.; Stern, E.; Wang, Y.; Wasserman, H.; Zhang, Y.; /SLAC
2011-11-14
In this paper, we report on progress that has been made in beam dynamics simulation, from light sources to colliders, during the first year of the SciDAC-2 accelerator project 'Community Petascale Project for Accelerator Science and Simulation (ComPASS).' Several parallel computational tools for beam dynamics simulation are described. Also presented are number of applications in current and future accelerator facilities (e.g., LCLS, RHIC, Tevatron, LHC, and ELIC). Particle accelerators are some of most important tools of scientific discovery. They are widely used in high-energy physics, nuclear physics, and other basic and applied sciences to study the interaction of elementary particles, to probe the internal structure of matter, and to generate high-brightness radiation for research in materials science, chemistry, biology, and other fields. Modern accelerators are complex and expensive devices that may be several kilometers long and may consist of thousands of beamline elements. An accelerator may transport trillions of charged particles that interact electromagnetically among themselves, that interact with fields produced by the accelerator components, and that interact with beam-induced fields. Large-scale beam dynamics simulations on massively parallel computers can help provide understanding of these complex physical phenomena, help minimize design cost, and help optimize machine operation. In this paper, we report on beam dynamics simulations in a variety of accelerators ranging from next generation light sources to high-energy ring colliders that have been studied during the first year of the SciDAC-2 accelerator project.
Not Available
2006-03-01
This fact sheet describes a subcontract with Massachusetts Institute of Technology to study dynamic response simulations to evaluate floating platform concepts for offshore wind turbines.
L3:THM.CFD.P9.02 Native Conjugate Heat
U.S. Department of Energy (DOE) all webpages (Extended Search)
2 Native Conjugate Heat Transfer (CHT) in Hydra-TH Alan K. Stagg Oak Ridge National Laboratory Mark A. Christon Los Alamos National Laboratory Konor Frick North Carolina State University October 22, 2014 CASL-U-2014-0214-000 CASL-U-2014-0214-000 L3:THM.CFD.P9.02 Native Conjugate Heat Transfer (CHT) in Hydra-TH (L3 Milestone THM.CFD.P9.02) CASL-U-2014-0214-000 A. K. Stagg Modeling and Simulation Group Computational Sciences and Engineering Division Oak Ridge National Laboratory Oak Ridge, TN
A coupled RELAPS-3D/CFD methodology with a proof-of-principle calculation
Aumiller, D.L.; Tomlinson, E.T.; Bauer, R.C.
2000-01-01
The RELAP5-3D computer code was modified to make the explicit coupling capability in the code fully functional. As a test of the modified code, a coupled RELAP5/RELAP5 analysis of the Edwards-O'Brien blowdown problem was performed which showed no significant deviations from the standard RELAP5-3D predictions. In addition, a multiphase Computational Fluid Dynamics (CFD) code was modified to permit explicit coupling to RELAP5-3D. Several calculations were performed with this code. The first analysis used the experimental pressure history from a point just upstream of the break as a boundary condition. This analysis showed that a multiphase CFD code could calculate the thermodynamic and hydrodynamic conditions during a rapid blowdown transient. Finally, a coupled RELAP5/CFD analysis was performed. The results are presented in this paper.
Molecular dynamics simulations of soliton-like structures in a dusty plasma medium
Tiwari, Sanat Kumar Das, Amita; Sen, Abhijit; Kaw, Predhiman
2015-03-15
The existence and evolution of soliton-like structures in a dusty plasma medium are investigated in a first principles approach using molecular dynamic (MD) simulations of particles interacting via a Yukawa potential. These localized structures are found to exist in both weakly and strongly coupled regimes with their structures becoming sharper as the correlation effects between the dust particles get stronger. A surprising result, compared to fluid simulations, is the existence of rarefactive soliton-like structures in our non-dissipative system, a feature that arises from the charge conjugation symmetry property of the Yukawa fluid. Our simulation findings closely resemble many diverse experimental results reported in the past.
Martini, Matus; Gustafson, William I.; Yang, Qing; Xiao, Heng
2014-11-27
Organized mesoscale cellular convection (MCC) is a common feature of marine stratocumulus that forms in response to a balance between mesoscale dynamics and smaller scale processes such as cloud radiative cooling and microphysics. We use the Weather Research and Forecasting model with chemistry (WRF-Chem) and fully coupled cloud-aerosol interactions to simulate marine low clouds during the VOCALS-REx campaign over the southeast Pacific. A suite of experiments with 3- and 9-km grid spacing indicates resolution-dependent behavior. The simulations with finer grid spacing have smaller liquid water paths and cloud fractions, while cloud tops are higher. The observed diurnal cycle is reasonably well simulated. To isolate organized MCC characteristics we develop a new automated method, which uses a variation of the watershed segmentation technique that combines the detection of cloud boundaries with a test for coincident vertical velocity characteristics. This ensures that the detected cloud fields are dynamically consistent for closed MCC, the most common MCC type over the VOCALS-REx region. We demonstrate that the 3-km simulation is able to reproduce the scaling between horizontal cell size and boundary layer height seen in satellite observations. However, the 9-km simulation is unable to resolve smaller circulations corresponding to shallower boundary layers, instead producing invariant MCC horizontal scale for all simulated boundary layers depths. The results imply that climate models with grid spacing of roughly 3 km or smaller may be needed to properly simulate the MCC structure in the marine stratocumulus regions.
Ensemble Sampling vs. Time Sampling in Molecular Dynamics Simulations of Thermal Conductivity
Gordiz, Kiarash; Singh, David J.; Henry, Asegun
2015-01-29
In this report we compare time sampling and ensemble averaging as two different methods available for phase space sampling. For the comparison, we calculate thermal conductivities of solid argon and silicon structures, using equilibrium molecular dynamics. We introduce two different schemes for the ensemble averaging approach, and show that both can reduce the total simulation time as compared to time averaging. It is also found that velocity rescaling is an efficient mechanism for phase space exploration. Although our methodology is tested using classical molecular dynamics, the ensemble generation approaches may find their greatest utility in computationally expensive simulations such asmore » first principles molecular dynamics. For such simulations, where each time step is costly, time sampling can require long simulation times because each time step must be evaluated sequentially and therefore phase space averaging is achieved through sequential operations. On the other hand, with ensemble averaging, phase space sampling can be achieved through parallel operations, since each ensemble is independent. For this reason, particularly when using massively parallel architectures, ensemble sampling can result in much shorter simulation times and exhibits similar overall computational effort.« less
Accelerated molecular dynamics and equation-free methods for simulating diffusion in solids.
Deng, Jie; Zimmerman, Jonathan A.; Thompson, Aidan Patrick; Brown, William Michael; Plimpton, Steven James; Zhou, Xiao Wang; Wagner, Gregory John; Erickson, Lindsay Crowl
2011-09-01
Many of the most important and hardest-to-solve problems related to the synthesis, performance, and aging of materials involve diffusion through the material or along surfaces and interfaces. These diffusion processes are driven by motions at the atomic scale, but traditional atomistic simulation methods such as molecular dynamics are limited to very short timescales on the order of the atomic vibration period (less than a picosecond), while macroscale diffusion takes place over timescales many orders of magnitude larger. We have completed an LDRD project with the goal of developing and implementing new simulation tools to overcome this timescale problem. In particular, we have focused on two main classes of methods: accelerated molecular dynamics methods that seek to extend the timescale attainable in atomistic simulations, and so-called 'equation-free' methods that combine a fine scale atomistic description of a system with a slower, coarse scale description in order to project the system forward over long times.
Computational Particle Dynamic Simulations on Multicore Processors (CPDMu) Final Report ?? Phase I
Mark S. Schmalz
2011-07-24
Statement of Problem - Department of Energy has many legacy codes for simulation of computational particle dynamics and computational fluid dynamics applications that are designed to run on sequential processors and are not easily parallelized. Emerging high-performance computing architectures employ massively parallel multicore architectures (e.g., graphics processing units) to increase throughput. Parallelization of legacy simulation codes is a high priority, to achieve compatibility, efficiency, accuracy, and extensibility. General Statement of Solution - A legacy simulation application designed for implementation on mainly-sequential processors has been represented as a graph G. Mathematical transformations, applied to G, produce a graph representation {und G} for a high-performance architecture. Key computational and data movement kernels of the application were analyzed/optimized for parallel execution using the mapping G {yields} {und G}, which can be performed semi-automatically. This approach is widely applicable to many types of high-performance computing systems, such as graphics processing units or clusters comprised of nodes that contain one or more such units. Phase I Accomplishments - Phase I research decomposed/profiled computational particle dynamics simulation code for rocket fuel combustion into low and high computational cost regions (respectively, mainly sequential and mainly parallel kernels), with analysis of space and time complexity. Using the research team's expertise in algorithm-to-architecture mappings, the high-cost kernels were transformed, parallelized, and implemented on Nvidia Fermi GPUs. Measured speedups (GPU with respect to single-core CPU) were approximately 20-32X for realistic model parameters, without final optimization. Error analysis showed no loss of computational accuracy. Commercial Applications and Other Benefits - The proposed research will constitute a breakthrough in solution of problems related to efficient
Strategic Plan for Nuclear Energy -- Knowledge Base for Advanced Modeling and Simulation (NE-KAMS)
Kimberlyn C. Mousseau
2011-10-01
The Nuclear Energy Computational Fluid Dynamics Advanced Modeling and Simulation (NE-CAMS) system is being developed at the Idaho National Laboratory (INL) in collaboration with Bettis Laboratory, Sandia National Laboratory (SNL), Argonne National Laboratory (ANL), Utah State University (USU), and other interested parties with the objective of developing and implementing a comprehensive and readily accessible data and information management system for computational fluid dynamics (CFD) verification and validation (V&V) in support of nuclear energy systems design and safety analysis. The two key objectives of the NE-CAMS effort are to identify, collect, assess, store and maintain high resolution and high quality experimental data and related expert knowledge (metadata) for use in CFD V&V assessments specific to the nuclear energy field and to establish a working relationship with the U.S. Nuclear Regulatory Commission (NRC) to develop a CFD V&V database, including benchmark cases, that addresses and supports the associated NRC regulations and policies on the use of CFD analysis. In particular, the NE-CAMS system will support the Department of Energy Office of Nuclear Energy Advanced Modeling and Simulation (NEAMS) Program, which aims to develop and deploy advanced modeling and simulation methods and computational tools for reliable numerical simulation of nuclear reactor systems for design and safety analysis. Primary NE-CAMS Elements There are four primary elements of the NE-CAMS knowledge base designed to support computer modeling and simulation in the nuclear energy arena as listed below. Element 1. The database will contain experimental data that can be used for CFD validation that is relevant to nuclear reactor and plant processes, particularly those important to the nuclear industry and the NRC. Element 2. Qualification standards for data evaluation and classification will be incorporated and applied such that validation data sets will result in well
Jakse, N.; Pasturel, A.
2014-12-21
In the present work, the structural and dynamic properties of liquid and undercooled boron are investigated by means of ab initio molecular dynamics simulation. Our results show that both liquid and undercooled states present a well pronounced short-range order (SRO) mainly due to the formation of inverted umbrella structural units. Moreover, we observe the development of a medium-range order (MRO) in the undercooling regime related to the increase of inverted umbrella structural units and of their interconnection as the temperature decreases. We also evidence that this MRO leads to a partial crystallization in the β-rhombohedral crystal below T = 1900 K. Finally, we discuss the role played by the SRO and MRO in the nearly Arrhenius evolution of the diffusion and the non-Arrhenius temperature dependence of the shear viscosity, in agreement with the experiment.
Atomistic Simulation of Nafion Membrane: 2. Dynamics of Water Molecules and Hydronium Ions
Devanathan, Ram; Venkatnathan, Arun; Dupuis, Michel
2007-10-20
We have performed a detailed and comprehensive analysis of the dynamics of water molecules and hydronium ions in hydrated Nafion using classical molecular dynamics simulations with the DREIDING force field. In addition to calculating diffusion coefficients as a function of hydration level, we have also determined mean residence time of H2O molecules and H3O+ ions in the first solvation shell of SO3- groups. The diffusion coefficient of H2O molecules increases with increasing hydration level and is in good agreement with experiment. The mean residence time of H2O molecules decreases with increasing membrane hydration from 1 ns at a low hydration level to 75 ps at the highest hydration level studied. These dynamical changes are related to the changes in membrane nanostructure reported in the first part of this work. Our results provide insights into slow proton dynamics observed in neutron scattering experiments and are consistent with the Gebel model of Nafion structure.
Liese, E.; Zitney, S.
2012-01-01
The AVESTAR Center located at the U.S. Department of Energy’s National Energy Technology Laboratory and West Virginia University is a world-class research and training environment dedicated to using dynamic process simulation as a tool for advancing the safe, efficient and reliable operation of clean energy plants with CO{sub 2} capture. The AVESTAR Center was launched with a high-fidelity dynamic simulator for an Integrated Gasification Combined Cycle (IGCC) power plant with pre-combustion carbon capture. The IGCC dynamic simulator offers full-scope Operator Training Simulator (OTS) Human Machine Interface (HMI) graphics for realistic, real-time control room operation and is integrated with a 3D virtual Immersive Training Simulator (ITS), thus allowing joint control room and field operator training. The IGCC OTS/ITS solution combines a “gasification with CO{sub 2} capture” process simulator with a “combined cycle” power simulator into a single high-performance dynamic simulation framework. This presentation will describe progress on the development of a natural gas combined cycle (NGCC) dynamic simulator based on the syngas-fired combined cycle portion of AVESTAR’s IGCC dynamic simulator. The 574 MW gross NGCC power plant design consisting of two advanced F-class gas turbines, two heat recovery steam generators (HRSGs), and a steam turbine in a multi-shaft 2x2x1 configuration will be reviewed. Plans for integrating a post-combustion carbon capture system will also be discussed.
Liese, Eric; Zitney, Stephen E.
2013-01-01
Research in dynamic process simulation for integrated gasification combined cycles (IGCC) with carbon capture has been ongoing at the National Energy Technology Laboratory (NETL), culminating in a full operator training simulator (OTS) and immersive training simulator (ITS) for use in both operator training and research. A derivative work of the IGCC dynamic simulator has been a modification of the combined cycle section to more closely represent a typical natural gas fired combined cycle (NGCC). This paper describes the NGCC dynamic process model and highlights some of the simulator’s current capabilities through a particular startup and shutdown scenario.
Wall, Michael E.; Van Benschoten, Andrew H.; Sauter, Nicholas K.; Adams, Paul D.; Fraser, James S.; Terwilliger, Thomas C.
2014-12-01
X-ray diffraction from protein crystals includes both sharply peaked Bragg reflections and diffuse intensity between the peaks. The information in Bragg scattering is limited to what is available in the mean electron density. The diffuse scattering arises from correlations in the electron density variations and therefore contains information about collective motions in proteins. Previous studies using molecular-dynamics (MD) simulations to model diffuse scattering have been hindered by insufficient sampling of the conformational ensemble. To overcome this issue, we have performed a 1.1-?s MD simulation of crystalline staphylococcal nuclease, providing 100-fold more sampling than previous studies. This simulation enables reproducible calculations of the diffuse intensity and predicts functionally important motions, including transitions among at least eight metastable states with different active-site geometries. The total diffuse intensity calculated using the MD model is highly correlated with the experimental data. In particular, there is excellent agreement for the isotropic component of the diffuse intensity, and substantial but weaker agreement for the anisotropic component. The decomposition of the MD model into protein and solvent components indicates that proteinsolvent interactions contribute substantially to the overall diffuse intensity. In conclusion, diffuse scattering can be used to validate predictions from MD simulations and can provide information to improve MD models of protein motions.
Wall, Michael E.; Van Benschoten, Andrew H.; Sauter, Nicholas K.; Adams, Paul D.; Fraser, James S.; Terwilliger, Thomas C.
2014-12-01
X-ray diffraction from protein crystals includes both sharply peaked Bragg reflections and diffuse intensity between the peaks. The information in Bragg scattering is limited to what is available in the mean electron density. The diffuse scattering arises from correlations in the electron density variations and therefore contains information about collective motions in proteins. Previous studies using molecular-dynamics (MD) simulations to model diffuse scattering have been hindered by insufficient sampling of the conformational ensemble. To overcome this issue, we have performed a 1.1-μs MD simulation of crystalline staphylococcal nuclease, providing 100-fold more sampling than previous studies. This simulation enables reproducible calculationsmore » of the diffuse intensity and predicts functionally important motions, including transitions among at least eight metastable states with different active-site geometries. The total diffuse intensity calculated using the MD model is highly correlated with the experimental data. In particular, there is excellent agreement for the isotropic component of the diffuse intensity, and substantial but weaker agreement for the anisotropic component. The decomposition of the MD model into protein and solvent components indicates that protein–solvent interactions contribute substantially to the overall diffuse intensity. In conclusion, diffuse scattering can be used to validate predictions from MD simulations and can provide information to improve MD models of protein motions.« less
Ab initio molecular dynamics simulation of liquid water by quantum Monte Carlo
Zen, Andrea; Luo, Ye Mazzola, Guglielmo Sorella, Sandro; Guidoni, Leonardo
2015-04-14
Although liquid water is ubiquitous in chemical reactions at roots of life and climate on the earth, the prediction of its properties by high-level ab initio molecular dynamics simulations still represents a formidable task for quantum chemistry. In this article, we present a room temperature simulation of liquid water based on the potential energy surface obtained by a many-body wave function through quantum Monte Carlo (QMC) methods. The simulated properties are in good agreement with recent neutron scattering and X-ray experiments, particularly concerning the position of the oxygen-oxygen peak in the radial distribution function, at variance of previous density functional theory attempts. Given the excellent performances of QMC on large scale supercomputers, this work opens new perspectives for predictive and reliable ab initio simulations of complex chemical systems.
Adjoints and Large Data Sets in Computational Fluid Dynamics...
U.S. Department of Energy (DOE) all webpages (Extended Search)
Oana Marin Speaker(s) Title: Postdoctoral Appointee, MCS Optimal flow control and stability analysis are some of the fields within Computational Fluid Dynamics (CFD) that...
Fogarty, Aoife C. Potestio, Raffaello Kremer, Kurt
2015-05-21
A fully atomistic modelling of many biophysical and biochemical processes at biologically relevant length- and time scales is beyond our reach with current computational resources, and one approach to overcome this difficulty is the use of multiscale simulation techniques. In such simulations, when system properties necessitate a boundary between resolutions that falls within the solvent region, one can use an approach such as the Adaptive Resolution Scheme (AdResS), in which solvent particles change their resolution on the fly during the simulation. Here, we apply the existing AdResS methodology to biomolecular systems, simulating a fully atomistic protein with an atomistic hydration shell, solvated in a coarse-grained particle reservoir and heat bath. Using as a test case an aqueous solution of the regulatory protein ubiquitin, we first confirm the validity of the AdResS approach for such systems, via an examination of protein and solvent structural and dynamical properties. We then demonstrate how, in addition to providing a computational speedup, such a multiscale AdResS approach can yield otherwise inaccessible physical insights into biomolecular function. We use our methodology to show that protein structure and dynamics can still be correctly modelled using only a few shells of atomistic water molecules. We also discuss aspects of the AdResS methodology peculiar to biomolecular simulations.
MHD SIMULATIONS OF ACTIVE GALACTIC NUCLEUS JETS IN A DYNAMIC GALAXY CLUSTER MEDIUM
Mendygral, P. J.; Jones, T. W.; Dolag, K.
2012-05-10
We present a pair of three-dimensional magnetohydrodynamical simulations of intermittent jets from a central active galactic nucleus (AGN) in a galaxy cluster extracted from a high-resolution cosmological simulation. The selected cluster was chosen as an apparently relatively relaxed system, not having undergone a major merger in almost 7 Gyr. Despite this characterization and history, the intracluster medium (ICM) contains quite active 'weather'. We explore the effects of this ICM weather on the morphological evolution of the AGN jets and lobes. The orientation of the jets is different in the two simulations so that they probe different aspects of the ICM structure and dynamics. We find that even for this cluster, which can be characterized as relaxed by an observational standard, the large-scale, bulk ICM motions can significantly distort the jets and lobes. Synthetic X-ray observations of the simulations show that the jets produce complex cavity systems, while synthetic radio observations reveal bending of the jets and lobes similar to wide-angle tail radio sources. The jets are cycled on and off with a 26 Myr period using a 50% duty cycle. This leads to morphological features similar to those in 'double-double' radio galaxies. While the jet and ICM magnetic fields are generally too weak in the simulations to play a major role in the dynamics, Maxwell stresses can still become locally significant.
Chaudhari, Mangesh I.; You, Xinli; Pratt, Lawrence R.; Rempe, Susan B.
2015-11-24
Ethylene carbonate (EC) and propylene carbonate (PC) are widely used solvents in lithium (Li)-ion batteries and supercapacitors. Ion dissolution and diffusion in those media are correlated with solvent dielectric responses. Here, we use all-atom molecular dynamics simulations of the pure solvents to calculate dielectric constants and relaxation times, and molecular mobilities. The computed results are compared with limited available experiments to assist more exhaustive studies of these important characteristics. As a result, the observed agreement is encouraging and provides guidance for further validation of force-field simulation models for EC and PC solvents.
Schlesinger, Daniel; Sellberg, Jonas A.; Nilsson, Anders; Pettersson, Lars G. M.
2016-03-22
In the present study, we investigate the process of evaporative cooling of nanometer-sized droplets in vacuum using molecular dynamics simulations with the TIP4P/2005 water model. The results are compared to the temperature evolution calculated from the Knudsen theory of evaporation which is derived from kinetic gas theory. The calculated and simulation results are found to be in very good agreement for an evaporation coefficient equal to unity. Lastly, our results are of interest to experiments utilizing droplet dispensers as well as to cloud micro-physics.
Dynamical consequences of a constraint on the Langevin thermostat in molecular cluster simulation
Stinson, Jake L.; Kathmann, Shawn M.; Ford, Ian J.
2014-11-17
We investigate some unusual behaviour observed while performing molecular dynamics simulations with the DL_POLY_4.03 code. Under the standard Langevin thermostat, atoms appear to be thermalised to different temperatures, depending on their mass and on the total number of particles in the system. We find that an imposed constraint whereby no thermal noise acts on the centre of mass of the system is the cause of the unexpected behaviour. This is demonstrated by solving the stochastic dynamics for the constrained thermostat and comparing the results with simulation data. The effect of the constraint can be considerable for small systems with disparate masses. By removing the constraint the Langevin thermostat may be restored to its intended behaviour and this has been implemented as an option in DL_POLY_4.05. SMK was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences.
Dynamical properties of fractal networks: Scaling, numerical simulations, and physical realizations
Nakayama, T.; Yakubo, K. ); Orbach, R.L. )
1994-04-01
This article describes the advances that have been made over the past ten years on the problem of fracton excitations in fractal structures. The relevant systems to this subject are so numerous that focus is limited to a specific structure, the percolating network. Recent progress has followed three directions: scaling, numerical simulations, and experiment. In a happy coincidence, large-scale computations, especially those involving array processors, have become possible in recent years. Experimental techniques such as light- and neutron-scattering experiments have also been developed. Together, they form the basis for a review article useful as a guide to understanding these developments and for charting future research directions. In addition, new numerical simulation results for the dynamical properties of diluted antiferromagnets are presented and interpreted in terms of scaling arguments. The authors hope this article will bring the major advances and future issues facing this field into clearer focus, and will stimulate further research on the dynamical properties of random systems.
Fattebert, Jean-Luc; Lau, Edmond Y.; Bennion, Brian J.; Huang, Patrick; Lightstone, Felice C.
2015-10-22
Enzymes are complicated solvated systems that typically require many atoms to simulate their function with any degree of accuracy. We have recently developed numerical techniques for large scale First-Principles molecular dynamics simulations and applied them to study the enzymatic reaction catalyzed by acetylcholinesterase. We carried out Density functional theory calculations for a quantum mechanical (QM) sub- system consisting of 612 atoms with an O(N) complexity finite-difference approach. The QM sub-system is embedded inside an external potential field representing the electrostatic effect due to the environment. We obtained finite temperature sampling by First-Principles molecular dynamics for the acylation reaction of acetylcholinemore » catalyzed by acetylcholinesterase. Our calculations shows two energies barriers along the reaction coordinate for the enzyme catalyzed acylation of acetylcholine. In conclusion, the second barrier (8.5 kcal/mole) is rate-limiting for the acylation reaction and in good agreement with experiment.« less
Fattebert, Jean-Luc; Lau, Edmond Y.; Bennion, Brian J.; Huang, Patrick; Lightstone, Felice C.
2015-10-22
Enzymes are complicated solvated systems that typically require many atoms to simulate their function with any degree of accuracy. We have recently developed numerical techniques for large scale First-Principles molecular dynamics simulations and applied them to study the enzymatic reaction catalyzed by acetylcholinesterase. We carried out Density functional theory calculations for a quantum mechanical (QM) sub- system consisting of 612 atoms with an O(N) complexity finite-difference approach. The QM sub-system is embedded inside an external potential field representing the electrostatic effect due to the environment. We obtained finite temperature sampling by First-Principles molecular dynamics for the acylation reaction of acetylcholine catalyzed by acetylcholinesterase. Our calculations shows two energies barriers along the reaction coordinate for the enzyme catalyzed acylation of acetylcholine. In conclusion, the second barrier (8.5 kcal/mole) is rate-limiting for the acylation reaction and in good agreement with experiment.
Yang, L. H.; Brooks III, E. D.; Belak, J.
1992-01-01
A molecular dynamics algorithm for performing large-scale simulations using the Parallel C Preprocessor (PCP) programming paradigm on the BBN TC2000, a massively parallel computer, is discussed. The algorithm uses a linked-cell data structure to obtain the near neighbors of each atom as time evoles. Each processor is assigned to a geometric domain containing many subcells and the storage for that domain is private to the processor. Within this scheme, the interdomain (i.e., interprocessor) communication is minimized.
Dispersion curves from short-time molecular dynamics simulation. 1. Diatomic chain results
Noid, D.W.; Broocks, B.T.; Gray, S.K.; Marple, S.L.
1988-06-16
The multiple signal classification method (MUSIC) for frequency estimation is used to compute the frequency dispersion curves of a diatomic chain from the time-dependent structure factor. In this paper, the authors demonstrate that MUSIC can accurately determine the frequencies from very short time trajectories. MUSIC is also used to show how the frequencies can vary in time, i.e., along a trajectory. The method is ideally suited for analyzing molecular dynamics simulations of large systems.
Chen Shilu; Fang Weihai
2009-08-07
In the present paper we report a theoretical study on mechanistic photodissociation of acetaldehyde (CH{sub 3}CHO). Stationary structures for H{sub 2} and CO eliminations in the ground state (S{sub 0}) have been optimized with density functional theory method, which is followed by the intrinsic reaction coordinate and ab initio molecular dynamics calculations to confirm the elimination mechanism. Equilibrium geometries, transition states, and intersection structures for the C-C and C-H dissociations in excited states were determined by the complete-active-space self-consistent field (CASSCF) method. Based on the CASSCF optimized structures, the potential energy profiles for the dissociations were refined by performing the single-point calculations using the multireference configuration interaction method. Upon the low-energy irradiation of CH{sub 3}CHO (265 nm<{lambda}<318 nm), the T{sub 1} C-C bond fission following intersystem crossing from the S{sub 1} state is the predominant channel and the minor channel, the ground-state elimination to CH{sub 4}+CO after internal conversion (IC) from S{sub 1} to S{sub 0}, could not be excluded. With the photon energy increasing, another pathway of IC, achieved via an S{sub 1}/S{sub 0} intersection point resulting from the S{sub 1} C-C bond fission, becomes accessible and increases the yield of CH{sub 4}+CO.
Zhao, Tongyang; Wang, Xiaogong; Jiang, Lei; Larson, Ronald G.
2014-07-01
We examine the accuracy of dissipative particle dynamics (DPD) simulations of polymers in dilute solutions with hydrodynamic interaction (HI), at the theta point, modeled by setting the DPD conservative interaction between beads to zero. We compare the first normal-mode relaxation time extracted from the DPD simulations with theoretical predictions from a normal-mode analysis for theta chains. We characterize the influence of bead inertia within the coil by a ratio L{sub m}/R{sub g}, where L{sub m} is the ballistic distance over which bead inertia is lost, and R{sub g} is the radius of gyration of the polymer coil, while the HI strength per bead h* is determined by the ratio of bead hydrodynamic radius (r{sub H}) to the equilibrium spring length. We show how to adjust h* through the spring length and monomer mass, and how to optimize the accuracy of DPD for fixed h* by increasing the friction coefficient (γ ≥ 9) and by incorporating a nonlinear distance dependence into the frictional interaction. Even with this optimization, DPD simulations exhibit deviations of over 20% from the theoretical normal-mode predictions for high HI strength with h* ≥ 0.20, for chains with as many as 100 beads, which is a larger deviation than is found for Stochastic rotation dynamics simulations for similar chains lengths and values of h*.
Vencels, Juris; Delzanno, Gian Luca; Johnson, Alec; Peng, Ivy Bo; Laure, Erwin; Markidis, Stefano
2015-06-01
A spectral method for kinetic plasma simulations based on the expansion of the velocity distribution function in a variable number of Hermite polynomials is presented. The method is based on a set of non-linear equations that is solved to determine the coefficients of the Hermite expansion satisfying the Vlasov and Poisson equations. In this paper, we first show that this technique combines the fluid and kinetic approaches into one framework. Second, we present an adaptive strategy to increase and decrease the number of Hermite functions dynamically during the simulation. The technique is applied to the Landau damping and two-stream instabilitymore » test problems. Performance results show 21% and 47% saving of total simulation time in the Landau and two-stream instability test cases, respectively.« less
Vencels, Juris; Delzanno, Gian Luca; Johnson, Alec; Peng, Ivy Bo; Laure, Erwin; Markidis, Stefano
2015-06-01
A spectral method for kinetic plasma simulations based on the expansion of the velocity distribution function in a variable number of Hermite polynomials is presented. The method is based on a set of non-linear equations that is solved to determine the coefficients of the Hermite expansion satisfying the Vlasov and Poisson equations. In this paper, we first show that this technique combines the fluid and kinetic approaches into one framework. Second, we present an adaptive strategy to increase and decrease the number of Hermite functions dynamically during the simulation. The technique is applied to the Landau damping and two-stream instability test problems. Performance results show 21% and 47% saving of total simulation time in the Landau and two-stream instability test cases, respectively.
L3:THM.CFD.P9.05 Milestone Report Single/Multiphase CFD Assessment, Verification,
U.S. Department of Energy (DOE) all webpages (Extended Search)
Milestone Report Single/Multiphase CFD Assessment, Verification, and Validation Yidong Xia and Hong Luo North Carolina State University September 30, 2014 CASL-8-2014-0210-000 CASL-U-2014-0210-000 L3:THM.CFD.P9.05 Single/Multiphase CFD assessment, verification, and validation L3:THM.CFD.P9.05 milestone report Yidong Xia and Hong Luo Department of Mechanical and Aerospace Engineering North Carolina State University, Raleigh, NC, 27695, USA CASL-U-2014-0210-000 L3:THM.CFD.P9.05 On the performance
Computational fluid dynamics improves liner cementing operation
Barton, N.A.; Archer, G.L. ); Seymour, D.A. )
1994-09-26
The use of computational fluid dynamics (CFD), an analytical tool for studying fluid mechanics, helped plan the successful cementing of a critical liner in a North Sea extended reach well. The results from CFD analysis increased the confidence in the primary cementing of the liner. CFD modeling was used to quantify the effects of increasing the displacement rate and of rotating the liner on the mud flow distribution in the annulus around the liner.
Wangler, Thomas P.; Crandall, Kenneth R.; Garnett, Robert W.; Gorelov, Dmitry; Ostroumov, Petr; Qiang, Ji; Ryne, Robert; York, Richard
2003-08-26
Advanced Beam-Dynamics Simulation Tools for the RIA Driver Linac; Low Energy Beam Transport and Radiofrequency Quadrupole.
CFD INVESTIGATION OF EXPERIMENTAL DATA PROPOSED TO BE A VALIDATION DATA SET
Richard W. Johnson
2009-07-01
The U. S. Department of Energy (DOE) is currently supporting the development of a next generation nuclear plant (NGNP). The NGNP is based on the very high temperature reactor (VHTR), which is a Gen. IV gas-cooled reactor concept that will use helium as the coolant. Computational fluid dynamics (CFD) calculations are to be employed to estimate the details of the flow and heat transfer in the lower plenum where the heated coolant empties before exiting the reactor vessel. While it is expected that CFD will be able to provide detailed information about the flow, it must be validated using experimental data. Detailed experimental data have been taken in the INL’s matched index of refraction (MIR) facility of a scaled model of a section of the prismatic VHTR lower plenum. The present article examines the data that were taken to determine the suitability of such data to be a validation data set for CFD calculations. CFD calculations were made to compare with the experimental data to explore potential issues and make recommendations regarding the MIR data.
Pan, Jianjun [University of South Florida, Tampa (USF)] [University of South Florida, Tampa (USF); Cheng, Xiaolin [ORNL] [ORNL; Monticelli, Luca [Institut National de la Sant et de la Recherche Mdicale (INSERM) and INTS, France] [Institut National de la Sant et de la Recherche Mdicale (INSERM) and INTS, France; Heberle, Frederick A [ORNL] [ORNL; Kucerka, Norbert [Atomic Energy of Canada Limited (AECL), Canadian Neutron Beam Centre (CNBC) and Comenius University,] [Atomic Energy of Canada Limited (AECL), Canadian Neutron Beam Centre (CNBC) and Comenius University,; Tieleman, D. Peter [University of Calgary, ALberta, Canada] [University of Calgary, ALberta, Canada; Katsaras, John [ORNL] [ORNL
2014-01-01
Phosphatidylserine (PS) lipids play essential roles in biological processes, including enzyme activation and apoptosis. We report on the molecular structure and atomic scale interactions of a fluid bilayer composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylserine (POPS). A scattering density profile model, aided by molecular dynamics (MD) simulations, was developed to jointly refine different contrast small-angle neutron and X-ray scattering data, which yielded a lipid area of 62.7 A2 at 25 C. MD simulations with POPS lipid area constrained at different values were also performed using all-atom and aliphatic united-atom models. The optimal simulated bilayer was obtained using a model-free comparison approach. Examination of the simulated bilayer, which agrees best with the experimental scattering data, reveals a preferential interaction between Na+ ions and the terminal serine and phosphate moieties. Long-range inter-lipid interactions were identified, primarily between the positively charged ammonium, and the negatively charged carboxylic and phosphate oxygens. The area compressibility modulus KA of the POPS bilayer was derived by quantifying lipid area as a function of surface tension from area-constrained MD simulations. It was found that POPS bilayers possess a much larger KA than that of neutral phosphatidylcholine lipid bilayers. We propose that the unique molecular features of POPS bilayers may play an important role in certain physiological functions.
Molecular dynamics simulation of mechanical deformation of ultra-thin metal and ceramic films
Belak, J.; Glosli, J.N.; Boercker, D.B.; Stowers, I.F.
1995-04-01
We present an overview of the molecular dynamics computer simulation method as employed in the study of the mechanical properties of surfaces at the manometer scale. The embedded atom method is used to model a clean metal surface and the bond-order model is used to model ceramic surfaces. The computer experiment consists of the indentation and scraping of a hard diamond-like tool into and across the surface. Results are presented for the (111) surface of copper and silver and for the (100) surface of silicon. We explicitly demonstrate in our point indentation simulations that nanoscale plasticity in metals takes place by nondislocation mechanisms, a result suggested by recent nanoindentation experiments. We also observe the surface to accommodate nearly the entire volume of the tip and the annealing out of plastic work as the tip is removed. In our orthogonal cutting simulation, we observe an interesting phenomenon: the system dynamically reorients the gain in front of the tool tip to minimize the work performed on the shear plane (i.e. the shear plane becomes an easy slip plane). Silicon transforms into an amorphous state which then flows plastically.
A 2-D Test Problem for CFD Modeling Heat Transfer in Spent Fuel Transfer Cask Neutron Shields
Zigh, Ghani; Solis, Jorge; Fort, James A.
2011-01-14
In the United States, commercial spent nuclear fuel is typically moved from spent fuel pools to outdoor dry storage pads within a transfer cask system that provides radiation shielding to protect personnel and the surrounding environment. The transfer casks are cylindrical steel enclosures with integral gamma and neutron radiation shields. Since the transfer cask system must be passively cooled, decay heat removal from spent nuclear fuel canister is limited by the rate of heat transfer through the cask components, and natural convection from the transfer cask surface. The primary mode of heat transfer within the transfer cask system is conduction, but some cask designs incorporate a liquid neutron shield tank surrounding the transfer cask structural shell. In these systems, accurate prediction of natural convection within the neutron shield tank is an important part of assessing the overall thermal performance of the transfer cask system. The large-scale geometry of the neutron shield tank, which is typically an annulus approximately 2 meters in diameter but only 5-10 cm in thickness, and the relatively small scale velocities (typically less than 5 cm/s) represent a wide range of spatial and temporal scales that contribute to making this a challenging problem for computational fluid dynamics (CFD) modeling. Relevant experimental data at these scales are not available in the literature, but some recent modeling studies offer insights into numerical issues and solutions; however, the geometries in these studies, and for the experimental data in the literature at smaller scales, all have large annular gaps that are not prototypic of the transfer cask neutron shield. This paper presents results for a simple 2-D problem that is an effective numerical analog for the neutron shield application. Because it is 2-D, solutions can be obtained relatively quickly allowing a comparison and assessment of sensitivity to model parameter changes. Turbulence models are considered as
Tringe, J. W.; Ileri, N.; Levie, H. W.; Stroeve, P.; Ustach, V.; Faller, R.; Renaud, P.
2015-08-01
We use Molecular Dynamics and Monte Carlo simulations to examine molecular transport phenomena in nanochannels, explaining four orders of magnitude difference in wheat germ agglutinin (WGA) protein diffusion rates observed by fluorescence correlation spectroscopy (FCS) and by direct imaging of fluorescently-labeled proteins. We first use the ESPResSo Molecular Dynamics code to estimate the surface transport distance for neutral and charged proteins. We then employ a Monte Carlo model to calculate the paths of protein molecules on surfaces and in the bulk liquid transport medium. Our results show that the transport characteristics depend strongly on the degree of molecular surface coverage. Atomic force microscope characterization of surfaces exposed to WGA proteins for 1000 s show large protein aggregates consistent with the predicted coverage. These calculations and experiments provide useful insight into the details of molecular motion in confined geometries.
Tringe, J. W.; Ileri, N.; Levie, H. W.; Stroeve, P.; Ustach, V.; Faller, R.; Renaud, P.
2015-08-01
We use Molecular Dynamics and Monte Carlo simulations to examine molecular transport phenomena in nanochannels, explaining four orders of magnitude difference in wheat germ agglutinin (WGA) protein diffusion rates observed by fluorescence correlation spectroscopy (FCS) and by direct imaging of fluorescently-labeled proteins. We first use the ESPResSo Molecular Dynamics code to estimate the surface transport distance for neutral and charged proteins. We then employ a Monte Carlo model to calculate the paths of protein molecules on surfaces and in the bulk liquid transport medium. Our results show that the transport characteristics depend strongly on the degree of molecular surface coverage.more » Atomic force microscope characterization of surfaces exposed to WGA proteins for 1000 s show large protein aggregates consistent with the predicted coverage. These calculations and experiments provide useful insight into the details of molecular motion in confined geometries.« less
Varanasi, S. R. E-mail: guskova@ipfdd.de; John, A.; Guskova, O. A. E-mail: guskova@ipfdd.de; Sommer, J.-U.
2015-06-14
Fullerene C{sub 60} sub-colloidal particle with diameter ?1 nm represents a boundary case between small and large hydrophobic solutes on the length scale of hydrophobic hydration. In the present paper, a molecular dynamics simulation is performed to investigate this complex phenomenon for bare C{sub 60} fullerene and its amphiphilic/charged derivatives, so called shape amphiphiles. Since most of the unique properties of water originate from the pattern of hydrogen bond network and its dynamics, spatial, and orientational aspects of water in solvation shells around the solute surface having hydrophilic and hydrophobic regions are analyzed. Dynamical properties such as translational-rotational mobility, reorientational correlation and occupation time correlation functions of water molecules, and diffusion coefficients are also calculated. Slower dynamics of solvent moleculeswater retardationin the vicinity of the solutes is observed. Both the topological properties of hydrogen bond pattern and the dangling OH groups that represent surface defects in water network are monitored. The fraction of such defect structures is increased near the hydrophobic cap of fullerenes. Some dry regions of C{sub 60} are observed which can be considered as signatures of surface dewetting. In an effort to provide molecular level insight into the thermodynamics of hydration, the free energy of solvation is determined for a family of fullerene particles using thermodynamic integration technique.
Diallo, S. O.; Vlcek, L.; Mamontov, E.; Keum, J. K.; Chen, Jihua; Hayes, J. S.; Chialvo, A. A.
2015-02-17
When water molecules are confined to nanoscale spacings, such as in the nanometer-size pores of activated carbon fiber (ACF), their freezing point gets suppressed down to very low temperatures (~150 K), leading to a metastable liquid state with remarkable physical properties. Here we have investigated the ambient pressure diffusive dynamics of water in microporous Kynol ACF-10 (average pore size ~11.6 Å, with primarily slit-like pores) from temperature T = 280 K in its stable liquid state down to T = 230 K into the metastable supercooled phase. The observed characteristic relaxation times and diffusion coefficients are found to be, respectively, higher and lower than those in bulk water, indicating a slowing down of the water mobility with decreasing temperature. The observed temperature-dependent average relaxation time (more » $${{\\tau}}$$) when compared to previous findings indicate that it is the width of the slit pores-not their curvature-that primarily affects the dynamics of water for pore sizes larger than 10 Å. The experimental observations are compared to complementary molecular dynamics simulations of a model system, in which we studied the diffusion of water within the 11.6 Å gap of two parallel graphene sheets. We find generally a reasonable agreement between the observed and calculated relaxation times at the low momentum transfer Q (Q ≤ 0.9 Å-1). At high Q, however, where localized dynamics becomes relevant, this ideal system does not satisfactorily reproduce the measurements. Consequently, the simulations are compared to the experiments at low Q, where the two can be best reconciled. The best agreement is obtained for the diffusion parameter D associated with the hydrogen-site when a representative stretched exponential function, rather than the standard bimodal exponential model, is used to parametrize the self-correlation function I (Q,t).« less
Advanced time integration algorithms for dislocation dynamics simulations of work hardening
Sills, Ryan B.; Aghaei, Amin; Cai, Wei
2016-04-25
Efficient time integration is a necessity for dislocation dynamics simulations of work hardening to achieve experimentally relevant strains. In this work, an efficient time integration scheme using a high order explicit method with time step subcycling and a newly-developed collision detection algorithm are evaluated. First, time integrator performance is examined for an annihilating Frank–Read source, showing the effects of dislocation line collision. The integrator with subcycling is found to significantly out-perform other integration schemes. The performance of the time integration and collision detection algorithms is then tested in a work hardening simulation. The new algorithms show a 100-fold speed-up relativemore » to traditional schemes. As a result, subcycling is shown to improve efficiency significantly while maintaining an accurate solution, and the new collision algorithm allows an arbitrarily large time step size without missing collisions.« less
Mean ionic activity coefficients in aqueous NaCl solutions from molecular dynamics simulations
Mester, Zoltan; Panagiotopoulos, Athanassios Z.
2015-01-28
The mean ionic activity coefficients of aqueous NaCl solutions of varying concentrations at 298.15 K and 1 bar have been obtained from molecular dynamics simulations by gradually turning on the interactions of an ion pair inserted into the solution. Several common non-polarizable water and ion models have been used in the simulations. Gibbs-Duhem equation calculations of the thermodynamic activity of water are used to confirm the thermodynamic consistency of the mean ionic activity coefficients. While the majority of model combinations predict the correct trends in mean ionic activity coefficients, they overestimate their values at high salt concentrations. The solubility predictions also suffer from inaccuracies, with all models underpredicting the experimental values, some by large factors. These results point to the need for further ion and water model development.
Dumpala, Santoshrupa; Broderick, Scott R.; Rajan, Krishna; Khalilov, Umedjon; Neyts, Erik C.; Duin, Adri C. T. van; Provine, J; Howe, Roger T.
2015-01-05
In this paper, we quantitatively investigate with atom probe tomography, the effect of temperature on the interfacial transition layer suboxide species due to the thermal oxidation of silicon. The chemistry at the interface was measured with atomic scale resolution, and the changes in chemistry and intermixing at the interface were identified on a nanometer scale. We find an increase of suboxide (SiOx) concentration relative to SiO{sub 2} and increased oxygen ingress with elevated temperatures. Our experimental findings are in agreement with reactive force field molecular dynamics simulations. This work demonstrates the direct comparison between atom probe derived chemical profiles and atomistic-scale simulations for transitional interfacial layer of suboxides as a function of temperature.
Molecular dynamics simulations of organic SIMS with Cu{sub n} (n=1-3) clusters
Townes, J. A.; White, A. K.; Krantzman, K. D.; Garrison, B. J.
1999-06-10
Molecular dynamics simulations have been performed to study the effect of cluster size on the emission yield and damage cross section in organic SIMS. A model system composed of a monolayer of biphenyl molecules on a Cu(001) substrate was bombarded with Cu{sub n} (n=1-3) projectiles at kinetic energies of 0.100 keV per atom. The yield increases with cluster size, but a nonlinear enhancement in yield is not observed. The yield-to-damage ratio, on the other hand, increases with the use of clusters, indicating that clusters have the potential to improve the sensitivity of SIMS.
Molecular Dynamics Simulations of Displacement Cascades in Single and Polycrystalline Zirconia
Du Jincheng
2009-03-10
Displacement cascades in zirconia have been studied using classical molecular dynamics simulations. Polycrystalline zirconia with nano-meter grains were created using Voronoi polyhedra construction and studied in comparison with single crystalline zirconia. The results show that displacement cascades with similar kinetic energy generated larger number of displaced atoms in polycrystalline than in the single crystal structure. The fraction of atoms with coordination number change was also higher in polycrystalline zirconia that was explained to be due to the diffusion of oxygen and relaxation at grain boundaries.
Molecular dynamics simulations of grain boundaries in thin nanocrystalline silicon films
Berman, G.P.; Doolen, G.D.; Mainieri, R.; Campbell, D.K.; Luchnikov, V.A. |
1997-10-01
Using molecular dynamics simulations, the grain boundaries in thin polycrystalline silicon films (considered as promising material for future nanoelectronic devices) are investigated. It is shown that in polysilicon film with randomly oriented grains the majority of grain boundaries are disordered. However, some grains with small mutual orientation differences can form extended crystalline patterns. The structure of the grain boundaries satisfies the thermodynamical criterion. The majority of atoms in the grain boundaries are tetrahedrally coordinated with the nearest neighbors, even though the grain boundaries are disordered. The grain boundary matter is characterized as an amorphous phase with a characteristic tetragonality value.
Bjorgaard, J. A.; Nelson, T.; Kalinin, K.; Kuzmenko, V.; Velizhanin, K. A.; Tretiak, S.
2015-04-28
In this study, an efficient method of treating solvent effects in excited state molecular dynamics (ESMD) is implemented and tested by exploring the solvatochromic effects in substituted p-phenylene vinylene oligomers. A continuum solvent model is used which has very little computational overhead. This allows simulations of ESMD with solvent effects on the scale of hundreds of picoseconds for systems of up to hundreds of atoms. At these time scales, solvatochromic shifts in fluoresence spectra can be described. Solvatochromic shifts in absorption and fluorescence spectra from ESMD are compared with time-dependent density functional theory calculations and experiments.
Shimojo, Fuyuki; Hattori, Shinnosuke; Department of Physics, Kumamoto University, Kumamoto 860-8555 ; Kalia, Rajiv K.; Mou, Weiwei; Nakano, Aiichiro; Nomura, Ken-ichi; Rajak, Pankaj; Vashishta, Priya; Kunaseth, Manaschai; National Nanotechnology Center, Pathumthani 12120 ; Ohmura, Satoshi; Department of Physics, Kumamoto University, Kumamoto 860-8555; Department of Physics, Kyoto University, Kyoto 606-8502 ; Shimamura, Kohei; Department of Physics, Kumamoto University, Kumamoto 860-8555; Department of Applied Quantum Physics and Nuclear Engineering, Kyushu University, Fukuoka 819-0395
2014-05-14
We introduce an extension of the divide-and-conquer (DC) algorithmic paradigm called divide-conquer-recombine (DCR) to perform large quantum molecular dynamics (QMD) simulations on massively parallel supercomputers, in which interatomic forces are computed quantum mechanically in the framework of density functional theory (DFT). In DCR, the DC phase constructs globally informed, overlapping local-domain solutions, which in the recombine phase are synthesized into a global solution encompassing large spatiotemporal scales. For the DC phase, we design a lean divide-and-conquer (LDC) DFT algorithm, which significantly reduces the prefactor of the O(N) computational cost for N electrons by applying a density-adaptive boundary condition at the peripheries of the DC domains. Our globally scalable and locally efficient solver is based on a hybrid real-reciprocal space approach that combines: (1) a highly scalable real-space multigrid to represent the global charge density; and (2) a numerically efficient plane-wave basis for local electronic wave functions and charge density within each domain. Hybrid space-band decomposition is used to implement the LDC-DFT algorithm on parallel computers. A benchmark test on an IBM Blue Gene/Q computer exhibits an isogranular parallel efficiency of 0.984 on 786 432 cores for a 50.3 × 10{sup 6}-atom SiC system. As a test of production runs, LDC-DFT-based QMD simulation involving 16 661 atoms is performed on the Blue Gene/Q to study on-demand production of hydrogen gas from water using LiAl alloy particles. As an example of the recombine phase, LDC-DFT electronic structures are used as a basis set to describe global photoexcitation dynamics with nonadiabatic QMD (NAQMD) and kinetic Monte Carlo (KMC) methods. The NAQMD simulations are based on the linear response time-dependent density functional theory to describe electronic excited states and a surface-hopping approach to describe transitions between the excited states. A series of
Use of Aria to simulate laser weld pool dynamics for neutron generator production.
Noble, David R.; Notz, Patrick K.; Martinez, Mario J.; Kraynik, Andrew Michael
2007-09-01
This report documents the results for the FY07 ASC Integrated Codes Level 2 Milestone number 2354. The description for this milestone is, 'Demonstrate level set free surface tracking capabilities in ARIA to simulate the dynamics of the formation and time evolution of a weld pool in laser welding applications for neutron generator production'. The specialized boundary conditions and material properties for the laser welding application were implemented and verified by comparison with existing, two-dimensional applications. Analyses of stationary spot welds and traveling line welds were performed and the accuracy of the three-dimensional (3D) level set algorithm is assessed by comparison with 3D moving mesh calculations.
Trueba, Alondra Torres; Kroon, Maaike C.; Peters, Cor J.; Moudrakovski, Igor L.; Ratcliffe, Christopher I.; Ripmeester, John A.; Alavi, Saman
2014-06-07
Prospective industrial applications of clathrate hydrates as materials for gas separation require further knowledge of cavity distortion, cavity selectivity, and defects induction by guest-host interactions. The results presented in this contribution show that under certain temperature conditions the guest combination of CH{sub 3}F and a large polar molecule induces defects on the clathrate hydrate framework that allow intercage guest dynamics. {sup 13}C NMR chemical shifts of a CH{sub 3}F/CH{sub 4}/TBME sH hydrate and a temperature analysis of the {sup 2}H NMR powder lineshapes of a CD{sub 3}F/THF sII and CD{sub 3}F/TBME sH hydrate, displayed evidence that the populations of CH{sub 4} and CH{sub 3}F in the D and D{sup ?} cages were in a state of rapid exchange. A hydrogen bonding analysis using molecular dynamics simulations on the TBME/CH{sub 3}F and TBME/CH{sub 4} sH hydrates showed that the presence of CH{sub 3}F enhances the hydrogen bonding probability of the TBME molecule with the water molecules of the cavity. Similar results were obtained for THF/CH{sub 3}F and THF/CH{sub 4} sII hydrates. The enhanced hydrogen bond formation leads to the formation of defects in the water hydrogen bonding lattice and this can enhance the migration of CH{sub 3}F molecules between adjacent small cages.
CFD Combustion Modeling with Conditional Moment Closure using...
Office of Energy Efficiency and Renewable Energy (EERE) (indexed site)
Combustion Modeling with Conditional Moment Closure using Tabulated Chemistry CFD Combustion Modeling with Conditional Moment Closure using Tabulated Chemistry A method is ...
CFD Analysis of Particle Deposition During DPF Filtration Processes...
Office of Energy Efficiency and Renewable Energy (EERE) (indexed site)
Analysis of Particle Deposition During DPF Filtration Processes CFD Analysis of Particle Deposition During DPF Filtration Processes A 3-D DPF model is developed to predict ...
Advanced CFD Models for High Efficiency Compression Ignition Engines
Advanced CFD models for high efficiency compression-ignition engines can be used to show how turbulence-chemistry interactions influence autoignition and combustion.
Simulation and dynamics of entropy-driven, molecular self-assembly processes
Mayer, B.; Kohler, G.,; Rasmussen, S.,
1997-04-01
Molecular self-assembly is frequently found to generate higher-order functional structures in biochemical systems. One such example is the self-assembly of lipids in aqueous solution forming membranes, micelles, and vesicles; another is the dynamic formation and rearrangement of the cytoskeleton. These processes are often driven by local, short-range forces and therefore the dynamics is solely based on local interactions. In this paper, we introduce a cellular automata based simulation, the lattice molecular automaton, in which data structures, representing different molecular entities such as water and hydrophilic and hydrophobic monomers, share locally propagated force information on a hexagonal, two-dimensional lattice. The purpose of this level of description is the simulation of entropic and enthalpic flows in a microcanonical, molecular ensemble to gain insight about entropy-driven processes in molecular many-particle systems. Three applications are shown, i.e., modeling structural features of a polar solvent, cluster formation of hydrophobic monomers in a polar environment, and the self-assembly of polymers. Processes leading to phase separation on a molecular level are discussed. A thorough discussion of the computational details, advantages, and limitations of the lattice molecular automaton approach is given elsewhere [B. Mayer and S. Rasmussen (unpublished)]. {copyright} {ital 1997} {ital The American Physical Society}
A model of lipid-free Apolipoprotein A-I revealed by iterative molecular dynamics simulation
Zhang, Xing; Lei, Dongsheng; Zhang, Lei; Rames, Matthew; Zhang, Shengli
2015-03-20
Apolipoprotein A-I (apo A-I), the major protein component of high-density lipoprotein, has been proven inversely correlated to cardiovascular risk in past decades. The lipid-free state of apo A-I is the initial stage which binds to lipids forming high-density lipoprotein. Molecular models of lipid-free apo A-I have been reported by methods like X-ray crystallography and chemical cross-linking/mass spectrometry (CCL/MS). Through structural analysis we found that those current models had limited consistency with other experimental results, such as those from hydrogen exchange with mass spectrometry. Through molecular dynamics simulations, we also found those models could not reach a stable equilibrium state. Therefore, by integrating various experimental results, we proposed a new structural model for lipidfree apo A-I, which contains a bundled four-helix N-terminal domain (1–192) that forms a variable hydrophobic groove and a mobile short hairpin C-terminal domain (193–243). This model exhibits an equilibrium state through molecular dynamics simulation and is consistent with most of the experimental results known from CCL/MS on lysine pairs, fluorescence resonance energy transfer and hydrogen exchange. This solution-state lipid-free apo A-I model may elucidate the possible conformational transitions of apo A-I binding with lipids in high-density lipoprotein formation.
A model of lipid-free Apolipoprotein A-I revealed by iterative molecular dynamics simulation
Zhang, Xing; Lei, Dongsheng; Zhang, Lei; Rames, Matthew; Zhang, Shengli
2015-03-20
Apolipoprotein A-I (apo A-I), the major protein component of high-density lipoprotein, has been proven inversely correlated to cardiovascular risk in past decades. The lipid-free state of apo A-I is the initial stage which binds to lipids forming high-density lipoprotein. Molecular models of lipid-free apo A-I have been reported by methods like X-ray crystallography and chemical cross-linking/mass spectrometry (CCL/MS). Through structural analysis we found that those current models had limited consistency with other experimental results, such as those from hydrogen exchange with mass spectrometry. Through molecular dynamics simulations, we also found those models could not reach a stable equilibrium state. Therefore,more » by integrating various experimental results, we proposed a new structural model for lipidfree apo A-I, which contains a bundled four-helix N-terminal domain (1–192) that forms a variable hydrophobic groove and a mobile short hairpin C-terminal domain (193–243). This model exhibits an equilibrium state through molecular dynamics simulation and is consistent with most of the experimental results known from CCL/MS on lysine pairs, fluorescence resonance energy transfer and hydrogen exchange. This solution-state lipid-free apo A-I model may elucidate the possible conformational transitions of apo A-I binding with lipids in high-density lipoprotein formation.« less
Liu, M. [Institute of Engineering Thermophysics, Chinese Academy of Sciences, Beijing100190 (China); Department of Physics, University of Chinese Academy of Sciences, Beijing 100049 (China); Qiu, L., E-mail: qiulin111@sina.com, E-mail: jzzhengxinghua@163.com; Zheng, X. H., E-mail: qiulin111@sina.com, E-mail: jzzhengxinghua@163.com; Zhu, J.; Tang, D. W. [Institute of Engineering Thermophysics, Chinese Academy of Sciences, Beijing100190 (China)
2014-09-07
In this article, molecular dynamics simulation was performed to study the heat transport in secondary particles chain of silica aerogel. The two adjacent particles as the basic heat transport unit were modelled to characterize the heat transfer through the calculation of thermal resistance and vibrational density of states (VDOS). The total thermal resistance of two contact particles was predicted by non-equilibrium molecular dynamics simulations (NEMD). The defects were formed by deleting atoms in the system randomly first and performing heating and quenching process afterwards to achieve the DLCA (diffusive limited cluster-cluster aggregation) process. This kind of treatment showed a very reasonable prediction of thermal conductivity for the silica aerogels compared with the experimental values. The heat transport was great suppressed as the contact length increased or defect concentration increased. The constrain effect of heat transport was much significant when contact length fraction was in the small range (<0.5) or the defect concentration is in the high range (>0.5). Also, as the contact length increased, the role of joint thermal resistance played in the constraint of heat transport was increasing. However, the defect concentration did not affect the share of joint thermal resistance as the contact length did. VDOS of the system was calculated by numerical method to characterize the heat transport from atomic vibration view. The smaller contact length and greater defect concentration primarily affected the longitudinal acoustic modes, which ultimately influenced the heat transport between the adjacent particles.
Donna Post Guillen; Daniel S. Wendt; Steven P. Antal; Michael Z. Podowski
2007-11-01
The purpose of this paper is to document the review of several open-literature sources of both experimental capabilities and published hydrodynamic data to aid in the validation of a Computational Fluid Dynamics (CFD) based model of a slurry bubble column (SBC). The review included searching the Web of Science, ISI Proceedings, and Inspec databases, internet searches as well as other open literature sources. The goal of this study was to identify available experimental facilities and relevant data. Integral (i.e., pertaining to the SBC system), as well as fundamental (i.e., separate effects are considered), data are included in the scope of this effort. The fundamental data is needed to validate the individual mechanistic models or closure laws used in a Computational Multiphase Fluid Dynamics (CMFD) simulation of a SBC. The fundamental data is generally focused on simple geometries (i.e., flow between parallel plates or cylindrical pipes) or custom-designed tests to focus on selected interfacial phenomena. Integral data covers the operation of a SBC as a system with coupled effects. This work highlights selected experimental capabilities and data for the purpose of SBC model validation, and is not meant to be an exhaustive summary.
Donna Post Guillen; Daniel S. Wendt
2007-11-01
The purpose of this paper is to document the review of several open-literature sources of both experimental capabilities and published hydrodynamic data to aid in the validation of a Computational Fluid Dynamics (CFD) based model of a slurry bubble column (SBC). The review included searching the Web of Science, ISI Proceedings, and Inspec databases, internet searches as well as other open literature sources. The goal of this study was to identify available experimental facilities and relevant data. Integral (i.e., pertaining to the SBC system), as well as fundamental (i.e., separate effects are considered), data are included in the scope of this effort. The fundamental data is needed to validate the individual mechanistic models or closure laws used in a Computational Multiphase Fluid Dynamics (CMFD) simulation of a SBC. The fundamental data is generally focused on simple geometries (i.e., flow between parallel plates or cylindrical pipes) or custom-designed tests to focus on selected interfacial phenomena. Integral data covers the operation of a SBC as a system with coupled effects. This work highlights selected experimental capabilities and data for the purpose of SBC model validation, and is not meant to be an exhaustive summary.
High Resolution Simulation of Beam Dynamics in Electron Linacs for Free Electron Lasers
Ryne, R.D.; Venturini, M.; Zholents, A.A.; Qiang, J.
2009-01-05
In this paper we report on large scale multi-physics simulation of beam dynamics in electron linacs for next generation free electron lasers (FELs). We describe key features of a parallel macroparticle simulation code including three-dimensional (3D) space-charge effects, short-range structure wake fields, longitudinal coherent synchrotron radiation (CSR) wake fields, and treatment of radiofrequency (RF) accelerating cavities using maps obtained from axial field profiles. A macroparticle up-sampling scheme is described that reduces the shot noise from an initial distribution with a smaller number of macroparticles while maintaining the global properties of the original distribution. We present a study of the microbunching instability which is a critical issue for future FELs due to its impact on beam quality at the end of the linac. Using parameters of a planned FEL linac at Lawrence Berkeley National Laboratory (LBNL), we show that a large number of macroparticles (beyond 100 million) is needed to control numerical shot noise that drives the microbunching instability. We also explore the effect of the longitudinal grid on simulation results. We show that acceptable results are obtained with around 2048 longitudinal grid points, and we discuss this in view of the spectral growth rate predicted from linear theory. As an application, we present results from simulations using one billion macroparticles of the FEL linac under design at LBNL. We show that the final uncorrelated energy spread of the beam depends not only on the initial uncorrelated energy spread but also depends strongly on the shape of the initial current profile. By using a parabolic initial current profile, 5 keV initial uncorrelated energy spread at 40 MeV injection energy, and improved linac design, those simulations demonstrate that a reasonable beam quality can be achieved at the end of the linac, with the final distribution having about 100 keV energy spread, 2.4 GeV energy, and 1.2 kA peak
Phase-Contrast MRI and CFD Modeling of Apparent 3He Gas Flow in Rat Pulmonary Airways
Minard, Kevin R.; Kuprat, Andrew P.; Kabilan, Senthil; Jacob, Rick E.; Einstein, Daniel R.; Carson, James P.; Corley, Richard A.
2012-08-01
Phase-contrast (PC) magnetic resonance imaging (MRI) with hyperpolarized 3He is potentially useful for developing and testing patient-specific models of pulmonary airflow. One challenge, however, is that PC-MRI provides apparent values of local 3He velocity that not only depend on actual airflow but also on gas diffusion. This not only blurs laminar flow patterns in narrow airways but also introduces anomalous airflow structure that reflects gas-wall interactions. Here, both effects are predicted in a live rat using computational fluid dynamics (CFD), and for the first time, simulated patterns of apparent 3He gas velocity are compared with in-vivo PC-MRI. Results show (1) that correlations (R2) between measured and simulated airflow patterns increase from 0.23 to 0.79 simply by accounting for apparent 3He transport, and that (2) remaining differences are mainly due to uncertain airway segmentation and partial volume effects stemming from relatively coarse MRI resolution. Higher-fidelity testing of pulmonary airflow predictions should therefore be possible with future imaging improvements.
Modified Baryonic Dynamics: two-component cosmological simulations with light sterile neutrinos
Angus, G.W.; Gentile, G.; Diaferio, A.; Famaey, B.; Heyden, K.J. van der E-mail: diaferio@ph.unito.it E-mail: gianfranco.gentile@ugent.be
2014-10-01
In this article we continue to test cosmological models centred on Modified Newtonian Dynamics (MOND) with light sterile neutrinos, which could in principle be a way to solve the fine-tuning problems of the standard model on galaxy scales while preserving successful predictions on larger scales. Due to previous failures of the simple MOND cosmological model, here we test a speculative model where the modified gravitational field is produced only by the baryons and the sterile neutrinos produce a purely Newtonian field (hence Modified Baryonic Dynamics). We use two-component cosmological simulations to separate the baryonic N-body particles from the sterile neutrino ones. The premise is to attenuate the over-production of massive galaxy cluster halos which were prevalent in the original MOND plus light sterile neutrinos scenario. Theoretical issues with such a formulation notwithstanding, the Modified Baryonic Dynamics model fails to produce the correct amplitude for the galaxy cluster mass function for any reasonable value of the primordial power spectrum normalisation.
Modifications to WRFs dynamical core to improve the treatment of moisture for large-eddy simulations
Xiao, Heng; Endo, Satoshi; Wong, May; Skamarock, William C.; Klemp, Joseph B.; Fast, Jerome D.; Gustafson, Jr., William I.; Vogelmann, Andrew; Wang, Hailong; Liu, Yangang; Lin, Wuyin
2015-10-29
Yamaguchi and Feingold (2012) note that the cloud fields in their large-eddy simulations (LESs) of marine stratocumulus using the Weather Research and Forecasting (WRF) model exhibit a strong sensitivity to time stepping choices. In this study, we reproduce and analyze this sensitivity issue using two stratocumulus cases, one marine and one continental. Results show that (1) the sensitivity is associated with spurious motions near the moisture jump between the boundary layer and the free atmosphere, and (2) these spurious motions appear to arise from neglecting small variations in water vapor mixing ratio (qv) in the pressure gradient calculation in the acoustic sub-stepping portion of the integration procedure. We show that this issue is remedied in the WRF dynamical core by replacing the prognostic equation for the potential temperature θ with one for the moist potential temperature θm=θ(1+1.61qv), which allows consistent treatment of moisture in the calculation of pressure during the acoustic sub-steps. With this modification, the spurious motions and the sensitivity to the time stepping settings (i.e., the dynamic time step length and number of acoustic sub-steps) are eliminated in both of the example stratocumulus cases. In conclusion, this modification improves the applicability of WRF for LES applications, and possibly other models using similar dynamical core formulations, and also permits the use of longer time steps than in the original code.
Modifications to WRFs dynamical core to improve the treatment of moisture for large-eddy simulations
Xiao, Heng; Endo, Satoshi; Wong, May; Skamarock, William C.; Klemp, Joseph B.; Fast, Jerome D.; Gustafson, Jr., William I.; Vogelmann, Andrew; Wang, Hailong; Liu, Yangang; et al
2015-10-29
Yamaguchi and Feingold (2012) note that the cloud fields in their large-eddy simulations (LESs) of marine stratocumulus using the Weather Research and Forecasting (WRF) model exhibit a strong sensitivity to time stepping choices. In this study, we reproduce and analyze this sensitivity issue using two stratocumulus cases, one marine and one continental. Results show that (1) the sensitivity is associated with spurious motions near the moisture jump between the boundary layer and the free atmosphere, and (2) these spurious motions appear to arise from neglecting small variations in water vapor mixing ratio (qv) in the pressure gradient calculation in themore » acoustic sub-stepping portion of the integration procedure. We show that this issue is remedied in the WRF dynamical core by replacing the prognostic equation for the potential temperature θ with one for the moist potential temperature θm=θ(1+1.61qv), which allows consistent treatment of moisture in the calculation of pressure during the acoustic sub-steps. With this modification, the spurious motions and the sensitivity to the time stepping settings (i.e., the dynamic time step length and number of acoustic sub-steps) are eliminated in both of the example stratocumulus cases. In conclusion, this modification improves the applicability of WRF for LES applications, and possibly other models using similar dynamical core formulations, and also permits the use of longer time steps than in the original code.« less
Jin, Jiaqi; Miller, Jan D.; Dang, Liem X.
2014-04-10
In this paper, we report on a molecular dynamics simulation (MDS) study of the behavior of interfacial water at selected sulfide mineral surfaces under anaerobic conditions. The study revealed the interfacial water structure and wetting characteristics of the pyrite (100) surface, galena (100) surface, chalcopyrite (012) surface, sphalerite (110) surface, and molybdenite surfaces (i.e., the face, armchair-edge, and zigzag-edge surfaces), including simulated contact angles, relative number density profiles, water dipole orientations, hydrogen-bonding, and residence times. For force fields of the metal and sulfur atoms in selected sulfide minerals used in the MDS, we used the universal force field (UFF) and another set of force fields optimized by quantum chemical calculations for interactions with interfacial water molecules at selected sulfide mineral surfaces. Simulation results for the structural and dynamic properties of interfacial water molecules indicate the natural hydrophobic character for the selected sulfide mineral surfaces under anaerobic conditions as well as the relatively weak hydrophobicity for the sphalerite (110) surface and two molybdenite edge surfaces. Part of the financial support for this study was provided by the U.S. Department of Energy (DOE) under Basic Science Grant No. DE-FG-03-93ER14315. The Division of Chemical Sciences, Geosciences, and Biosciences, Office of Basic Energy Sciences (BES), of the DOE, funded work performed by Liem X. Dang. Battelle operates Pacific Northwest National Laboratory for DOE. The calculations were carried out using computer resources provided by BES. The authors are grateful to Professor Tsun-Mei Chang for valuable discussions.
Rudd, R E
2009-02-05
Recent advances in the ability to generate extremes of pressure and temperature in dynamic experiments and to probe the response of materials has motivated the need for special materials optimized for those conditions as well as a need for a much deeper understanding of the behavior of materials subjected to high pressure and/or temperature. Of particular importance is the understanding of rate effects at the extremely high rates encountered in those experiments, especially with the next generation of laser drives such as at the National Ignition Facility. Here we use large-scale molecular dynamics (MD) simulations of the high-rate deformation of nanocrystalline tantalum to investigate the processes associated with plastic deformation for strains up to 100%. We use initial atomic configurations that were produced through simulations of solidification in the work of Streitz et al [Phys. Rev. Lett. 96, (2006) 225701]. These 3D polycrystalline systems have typical grain sizes of 10-20 nm. We also study a rapidly quenched liquid (amorphous solid) tantalum. We apply a constant volume (isochoric), constant temperature (isothermal) shear deformation over a range of strain rates, and compute the resulting stress-strain curves to large strains for both uniaxial and biaxial compression. We study the rate dependence and identify plastic deformation mechanisms. The identification of the mechanisms is facilitated through a novel technique that computes the local grain orientation, returning it as a quaternion for each atom. This analysis technique is robust and fast, and has been used to compute the orientations on the fly during our parallel MD simulations on supercomputers. We find both dislocation and twinning processes are important, and they interact in the weak strain hardening in these extremely fine-grained microstructures.
Sarkar, Avik; Sun, Xin; Sundaresan, Sankaran
2012-12-01
A post-combustion carbon-capture system utilizing a bubbling fluidized bed of sorbent particles is currently being developed as a part of the Carbon Capture and Simulation Initiative (CCSI) efforts. Adsorption of carbon dioxide (CO2) by these amine based sorbent particles is exothermic and arrays of immersed cylindrical heat transfer tubes are often utilized to maintain the lower temperatures favorable for CO2 capture. In multiphase computational fluid dynamics (CFD) simulations of the full-scale devices, which can be up to 10 m in size, approximately 103 cells are required in each dimension to accurately resolve the cylindrical tubes, which are only a few centimeters in diameter. Since the tubes cannot be resolved explicitly in CFD simulations, alternate methods to account for the influence of these immersed objects need to be developed.
Dynamic simulations of geologic materials using combined FEM/DEM/SPH analysis
Morris, J P; Johnson, S M
2008-03-26
An overview of the Lawrence Discrete Element Code (LDEC) is presented, and results from a study investigating the effect of explosive and impact loading on geologic materials using the Livermore Distinct Element Code (LDEC) are detailed. LDEC was initially developed to simulate tunnels and other structures in jointed rock masses using large numbers of polyhedral blocks. Many geophysical applications, such as projectile penetration into rock, concrete targets, and boulder fields, require a combination of continuum and discrete methods in order to predict the formation and interaction of the fragments produced. In an effort to model this class of problems, LDEC now includes implementations of Cosserat point theory and cohesive elements. This approach directly simulates the transition from continuum to discontinuum behavior, thereby allowing for dynamic fracture within a combined finite element/discrete element framework. In addition, there are many application involving geologic materials where fluid-structure interaction is important. To facilitate solution of this class of problems a Smooth Particle Hydrodynamics (SPH) capability has been incorporated into LDEC to simulate fully coupled systems involving geologic materials and a saturating fluid. We will present results from a study of a broad range of geomechanical problems that exercise the various components of LDEC in isolation and in tandem.
Development of an object-oriented dynamics simulator for a LFR DEMO
Ponciroli, R.; Bortot, S.; Lorenzi, S.; Cammi, A.
2012-07-01
A control-oriented dynamics simulator for a Generation IV Lead-cooled Fast Reactor (LFR) demonstrator (DEMO) has been developed aimed at providing a flexible, simple and fast-running tool allowing to perform design-basis transient and stability analyses, and to lay the foundations for the study of the system control strategy. For such purposes, a model representing a compromise between accuracy and straightforwardness has been necessarily sought, and in this view an object-oriented approach based on the Modelica language has been adopted. The reactor primary and secondary systems have been implemented by assembling both component models already available in a specific thermal-hydraulic library, and ad hoc developed nuclear component models suitably modified according to the specific DEMO configuration. The resulting overall plant simulator, incorporating also the balance of plant, consists in the following essential parts: core, integrated steam generator/primary pump block, cold and hot legs, primary coolant cold pool, turbine, heat sink, secondary coolant pump. Afterwards, the reactor response to typical transient initiators has been investigated: feedwater mass flow rate and temperature enhancement, turbine admission valve coefficient variation, increase of primary coolant mass flow rate, and transient of overpower have been simulated; results have been compared with the outcomes of analogous analyses performed by employing a lumped-parameter DEMO plant model. (authors)
Simulating Collisions for Hydrokinetic Turbines
Richmond, Marshall C.; Romero Gomez, Pedro DJ; Rakowski, Cynthia L.
2013-10-01
Evaluations of blade-strike on an axial-flow Marine Hydrokinetic turbine were conducted using a conventional methodology as well as an alternative modeling approach proposed in the present document. The proposed methodology integrates the following components into a Computa- tional Fluid Dynamics (CFD) model: (i) advanced eddy-resolving flow simulations, (ii) ambient turbulence based on field data, (iii) moving turbine blades in highly transient flows, and (iv) Lagrangian particles to mimic the potential fish pathways. The sensitivity of blade-strike prob- ability to the following conditions was also evaluated: (i) to the turbulent environment, (ii) to fish size and (iii) to mean stream flow velocity. The proposed methodology provided fraction of collisions and offered the capability of analyzing the causal relationships between the flow envi- ronment and resulting strikes on rotating blades. Overall, the conventional methodology largely overestimates the probability of strike, and lacks the ability to produce potential fish and aquatic biota trajectories as they interact with the rotating turbine. By using a set of experimental corre- lations of exposure-response of living fish colliding on moving blades, the occurrence, frequency and intensity of the particle collisions was next used to calculate the survival rate of fish crossing the MHK turbine. This step indicated survival rates always greater than 98%. Although the proposed CFD framework is computationally more expensive, it provides the advantage of evaluating multiple mechanisms of stress and injury of hydrokinetic turbine devices on fish.
Schiffmann, Florian; VandeVondele, Joost
2015-06-28
We present an improved preconditioning scheme for electronic structure calculations based on the orbital transformation method. First, a preconditioner is developed which includes information from the full Kohn-Sham matrix but avoids computationally demanding diagonalisation steps in its construction. This reduces the computational cost of its construction, eliminating a bottleneck in large scale simulations, while maintaining rapid convergence. In addition, a modified form of Hotelling’s iterative inversion is introduced to replace the exact inversion of the preconditioner matrix. This method is highly effective during molecular dynamics (MD), as the solution obtained in earlier MD steps is a suitable initial guess. Filtering small elements during sparse matrix multiplication leads to linear scaling inversion, while retaining robustness, already for relatively small systems. For system sizes ranging from a few hundred to a few thousand atoms, which are typical for many practical applications, the improvements to the algorithm lead to a 2-5 fold speedup per MD step.
Molecular dynamics simulations of 30 and 2 keV Ga in Si
Giannuzzi, Lucille A.; Garrison, Barbara J.
2007-09-15
Focused Ga{sup +} ion beams are routinely used at high incident angles for specimen preparation. Molecular dynamics simulations of 2 and 30 keV Ga bombardment of Si(011) at a grazing angle of 88 deg. were conducted to assess sputtering characteristics and damage depth. The bombardment of atomically flat surfaces and surfaces with vacancies shows little energy transfer yielding ion reflection. The bombardment of surfaces with adatoms allows for the coupling of the energy of motion parallel to the surface into the substrate resulting in sputtering. The adatom and one other Si atom eject, and motion in the substrate occurs down to a depth of 13 A. Experimental evidence shows that sputtering is a reality, suggesting that an atomically flat surface is never achieved.
Melting behaviour of gold-platinum nanoalloy clusters by molecular dynamics simulations
Ong, Yee Pin; Yoon, Tiem Leong; Lim, Thong Leng
2015-04-24
The melting behavior of bimetallic gold-platinum nanoclusters is studied by applying Brownian-type isothermal molecular dynamics (MD) simulation, a program modified from the cubic coupling scheme (CCS). The process begins with the ground-state structures obtained from global minimum search algorithm and proceeds with the investigation of the effect of temperature on the thermal properties of gold-platinum nanoalloy clusters. N-body Gupta potential has been employed in order to account for the interactions between gold and platinum atoms. The ground states of the nanoalloy clusters, which are core-shell segregated, are heated until they become thermally segregated. The detailed melting mechanism of the nanoalloy clusters is studied via this approach to provide insight into the thermal stability of the nanoalloy clusters.
Dynamically consistent method for mixed quantum-classical simulations: A semiclassical approach
Antipov, Sergey V.; Ye, Ziyu; Ananth, Nandini
2015-05-14
We introduce a new semiclassical (SC) framework, the Mixed Quantum-Classical Initial Value Representation (MQC-IVR), that can be tuned to reproduce existing quantum-limit and classical-limit SC approximations to quantum real-time correlation functions. Applying a modified Filinov transformation to a quantum-limit SC formulation leads to the association of a Filinov parameter with each degree of freedom in the system; varying this parameter from zero to infinity controls the extent of quantization of the corresponding mode. The resulting MQC-IVR expression provides a consistent dynamic framework for mixed quantum-classical simulations and we demonstrate its numerical accuracy in the calculation of real-time correlation functions for a model 1D system and a model 2D system over the full range of quantum- to classical-limit behaviors.
Noe, F [University of Heidelberg; Daidone, Isabella [University of Heidelberg; Smith, Jeremy C [ORNL; DiNola, Alfredo [University of Rome; Amadei, Andrea [University of Rome 'Tor Vergata', Rome, Italy
2008-08-01
A quantitative understanding of the complex relationship between microscopic structure and the thermodynamics driving peptide and protein folding is a major goal of biophysical chemistry. Here, we present a methodology comprising the use of an extended quasi-Gaussian entropy theory parametrized using molecular dynamics simulation that provides a complete description of the thermodynamics of peptide conformational states. The strategy is applied to analyze the conformational thermodynamics of MR121-GSGSW, a peptide well characterized in experimental studies. The results demonstrate that the extended state of the peptide possesses the lowest partial molar entropy. The origin of this entropy decrease is found to be in the increase of the density and orientational order of the hydration water molecules around the peptide, induced by the 'unfolding'. While such a reduction of the configurational entropy is usually associated with the hydrophobic effect, it is here found to be mainly due to the interaction of the solute charges with the solvent, that is, electrostriction.
Noe, F [University of Heidelberg; Daidone, Isabella [University of Heidelberg; Smith, Jeremy C [ORNL; DiNola, Alfredo [University of Rome; Amadei, Andrea [University of Rome 'Tor Vergata', Rome, Italy
2008-06-01
A quantitative understanding of the complex relationship between microscopic structure and the thermodynamics driving peptide and protein folding is a major goal of biophysical chemistry. Here, we present a methodology comprising the use of an extended quasi-Gaussian entropy theory parametrized using molecular dynamics simulation that provides a complete description of the thermodynamics of peptide conformational states. The strategy is applied to analyze the conformational thermodynamics of MR121-GSGSW, a peptide well characterized in experimental studies. The results demonstrate that the extended state of the peptide possesses the lowest partial molar entropy. The origin of this entropy decrease is found to be in the increase of the density and orientational order of the hydration water molecules around the peptide, induced by the 'unfolding'. While such a reduction of the configurational entropy is usually associated with the hydrophobic effect, it is here found to be mainly due to the interaction of the solute charges with the solvent, that is, electrostriction.
Zhang, Meng; Charles, River; Tong, Huimin; Zhang, Lei; Patel, Mili; Wang, Francis; Rames, Matthew J.; Ren, Amy; Rye, Kerry-Anne; Qiu, Xiayang; Johns, Douglas G.; Charles, M. Arthur; Ren, Gang
2015-03-04
Cholesteryl ester transfer protein (CETP) mediates the transfer of cholesterol esters (CE) from atheroprotective high-density lipoproteins (HDL) to atherogenic low-density lipoproteins (LDL). CETP inhibition has been regarded as a promising strategy for increasing HDL levels and subsequently reducing the risk of cardiovascular diseases (CVD). Although the crystal structure of CETP is known, little is known regarding how CETP binds to HDL. Here, we investigated how various HDL-like particles interact with CETP by electron microscopy and molecular dynamics simulations. Results showed that CETP binds to HDL via hydrophobic interactions rather than protein-protein interactions. The HDL surface lipid curvature generates a hydrophobic environment, leading to CETP hydrophobic distal end interaction. This interaction is independent of other HDL components, such as apolipoproteins, cholesteryl esters and triglycerides. Thus, disrupting these hydrophobic interactions could be a new therapeutic strategy for attenuating the interaction of CETP with HDL.
Zhang, Meng; Charles, River; Tong, Huimin; Zhang, Lei; Patel, Mili; Wang, Francis; Rames, Matthew J.; Ren, Amy; Rye, Kerry-Anne; Qiu, Xiayang; et al
2015-03-04
Cholesteryl ester transfer protein (CETP) mediates the transfer of cholesterol esters (CE) from atheroprotective high-density lipoproteins (HDL) to atherogenic low-density lipoproteins (LDL). CETP inhibition has been regarded as a promising strategy for increasing HDL levels and subsequently reducing the risk of cardiovascular diseases (CVD). Although the crystal structure of CETP is known, little is known regarding how CETP binds to HDL. Here, we investigated how various HDL-like particles interact with CETP by electron microscopy and molecular dynamics simulations. Results showed that CETP binds to HDL via hydrophobic interactions rather than protein-protein interactions. The HDL surface lipid curvature generates a hydrophobicmore » environment, leading to CETP hydrophobic distal end interaction. This interaction is independent of other HDL components, such as apolipoproteins, cholesteryl esters and triglycerides. Thus, disrupting these hydrophobic interactions could be a new therapeutic strategy for attenuating the interaction of CETP with HDL.« less
Plant-wide dynamic simulation of an IGCC plant with CO2 capture
Bhattacharyya, D.; Turton, R.; Zitney, S.
2009-01-01
To eliminate the harmful effects of greenhouse gases, especially that of CO2, future coalfired power plants need to consider the option for CO2 capture. The loss in efficiency for CO2 capture is less in an Integrated Gasification Combined Cycle (IGCC) plant compared to other conventional coal combustion processes. However, no IGCC plant with CO2 capture currently exists in the world. Therefore, it is important to consider the operability and controllability issues of such a plant before it is commercially built. With this objective in mind, a detailed plant-wide dynamic simulation of an IGCC plant with CO2 capture has been developed. The plant considers a General Electric Energy (GEE)-type downflow radiant-only gasifier followed by a quench section. A two-stage water gas shift (WGS) reaction is considered for conversion of about 96 mol% of CO to CO2. A two-stage acid gas removal (AGR) process based on a physical solvent is simulated for selective capture of H2S and CO2. The clean syngas is sent to a gas turbine (GT) followed by a heat recovery steam generator (HRSG). The steady state results are validated with data from a commercial gasifier. A 5 % ramp increase in the flowrate of coal is introduced to study the system dynamics. To control the conversion of CO at a desired level in the WGS reactors, the steam/CO ratio is manipulated. This strategy is found to be efficient for this operating condition. In the absence of an efficient control strategy in the AGR process, the environmental emissions exceeded the limits by a great extent.
Chen, Sow-Hsin; Lagi, Marco; Chu, Xiang-qiang; Zhang, Yang; Kim, Chansoo; Faraone, Antonio; Fratini, Emiliano; Baglioni, Piero
2010-01-01
This review article describes our neutron scattering experiments made in the past four years for the understanding of the single-particle (hydrogen atom) dynamics of a protein and its hydration water and the strong coupling between them. We found that the key to this strong coupling is the existence of a fragile-to-strong dynamic crossover (FSC) phenomenon occurring at around T L = 225±5 K in the hydration water. On lowering of the temperature toward FSC, the structure of hydration water makes a transition from predominantly the high density form (HDL), a more fluid state, to predominantly the low density formmore » (LDL), a less fluid state, derived from the existence of a liquid–liquid critical point at an elevated pressure. We show experimentally that this sudden switch in the mobility of hydration water on Lysozyme, B-DNA and RNA triggers the dynamic transition, at a temperature T D = 220 K, for these biopolymers. In the glassy state, below T D , the biopolymers lose their vital conformational flexibility resulting in a substantial diminishing of their biological functions. We also performed molecular dynamics (MD) simulations on a realistic model of hydrated lysozyme powder, which confirms the existence of the FSC and the hydration level dependence of the FSC temperature. Furthermore, we show a striking feature in the short time relaxation ( β -relaxation) of protein dynamics, which is the logarithmic decay spanning 3 decades (from ps to ns). The long time α -relaxation shows instead a diffusive behavior, which supports the liquid-like motions of protein constituents. We then discuss our recent high-resolution X-ray inelastic scattering studies of globular proteins, Lysozyme and Bovine Serum Albumin. We were able to measure the dispersion relations of collective, intra-protein phonon-like excitations in these proteins for the first time. We found that the phonon energies show a marked softening and at the same time their population increases
Dynamic Simulation of Shipping Package Subjected to Torque Load and Sequential Impacts
Wu, T
2006-04-17
A numerical technique has been developed to simulate the structural responses of radioactive material packaging components requiring closure-tightening torque to the scenarios of the hypothetical accident conditions (HAC) defined in the Code of Federal Regulations Title 10 part 71 (10CFR 71). A rigorous solution to this type of problem poses a considerable mathematical challenge. Conventional methods for evaluating the residue stresses due to the torque load are either inaccurate or not applicable to dynamic analyses. In addition, the HAC events occur sequentially and the cumulative damage to the package needs to be evaluated. Commonly, individual HAC events are analyzed separately and the cumulative damage is not addressed. As a result, strict compliance of the package with the requirements specified in 10CFR 71 is usually demonstrated by physical testing. The proposed technique utilizes the combination of kinematic constraints, rigid-body motions and structural deformations to overcome some of the difficulties encountered in modeling the effect of cumulative damage in numerical solutions. The analyses demonstrating use of this technique were performed to determine the cumulative damage of torque preload, a 30-foot drop, a 30-foot dynamic crush and a 40-inch free fall onto a mild steel pipe.
Theoretical studies of zirconium and carbon clusters with molecular dynamics simulations
Zhang, B.
1993-08-01
In this dissertation, we will present a systematic study of structures of fullerenes ranging from C{sub 20} to C{sub 100} by introducing a novel scheme. Using our new scheme, we not only reproduce all known fullerene structures but also successfully predicted several other fullerene structures which were confirmed by experiments. By utilizing the tight-binding molecular-dynamic (TBMD) simulation, we also studied the dynamical behavior of fullerenes: Vibrations, thermal disintegration of individual clusters as well as collisions between fullerenes. If the beauty of carbon fullerene is not enough, people found that carbon can also form tubules and even speculated that they can form three-dimensional graphite-like networks. By extending our fullerene structure searching scheme, we performed a search for the ground-state structure of three dimensional carbon network. We found the most stable structure people ever proposed for simple cubic based networks. From the difference of this new form of carbon and graphite in the electronic and vibrational properties, we propose an experimental probe to identify these novel three-dimensional carbon networks.
Cygan, Randall T.; Daemen, Luke L.; Ilgen, Anastasia G.; Krumhansl, James L.; Nenoff, Tina M.
2015-11-16
The study of mineral–water interfaces is of great importance to a variety of applications including oil and gas extraction, gas subsurface storage, environmental contaminant treatment, and nuclear waste repositories. Understanding the fundamentals of that interface is key to the success of those applications. Confinement of water in the interlayer of smectite clay minerals provides a unique environment to examine the interactions among water molecules, interlayer cations, and clay mineral surfaces. Smectite minerals are characterized by a relatively low layer charge that allows the clay to swell with increasing water content. Montmorillonite and beidellite varieties of smectite were investigated to comparemore » the impact of the location of layer charge on the interlayer structure and dynamics. Inelastic neutron scattering of hydrated and dehydrated cation-exchanged smectites was used to probe the dynamics of the interlayer water (200–900 cm–1 spectral region) and identify the shift in the librational edge as a function of the interlayer cation. Molecular dynamics simulations of equivalent phases and power spectra, derived from the resulting molecular trajectories, indicate a general shift in the librational behavior with interlayer cation that is generally consistent with the neutron scattering results for the monolayer hydrates. Both neutron scattering and power spectra exhibit librational structures affected by the location of layer charge and by the charge of the interlayer cation. Furthermore, divalent cations (Ba2+ and Mg2+) characterized by large hydration enthalpies typically exhibit multiple broad librational peaks compared to monovalent cations (Cs+ and Na+), which have relatively small hydration enthalpies.« less
Cygan, Randall T.; Daemen, Luke L.; Ilgen, Anastasia G.; Krumhansl, James L.; Nenoff, Tina M.
2015-11-16
The study of mineral–water interfaces is of great importance to a variety of applications including oil and gas extraction, gas subsurface storage, environmental contaminant treatment, and nuclear waste repositories. Understanding the fundamentals of that interface is key to the success of those applications. Confinement of water in the interlayer of smectite clay minerals provides a unique environment to examine the interactions among water molecules, interlayer cations, and clay mineral surfaces. Smectite minerals are characterized by a relatively low layer charge that allows the clay to swell with increasing water content. Montmorillonite and beidellite varieties of smectite were investigated to compare the impact of the location of layer charge on the interlayer structure and dynamics. Inelastic neutron scattering of hydrated and dehydrated cation-exchanged smectites was used to probe the dynamics of the interlayer water (200–900 cm^{–1} spectral region) and identify the shift in the librational edge as a function of the interlayer cation. Molecular dynamics simulations of equivalent phases and power spectra, derived from the resulting molecular trajectories, indicate a general shift in the librational behavior with interlayer cation that is generally consistent with the neutron scattering results for the monolayer hydrates. Both neutron scattering and power spectra exhibit librational structures affected by the location of layer charge and by the charge of the interlayer cation. Furthermore, divalent cations (Ba^{2+} and Mg^{2+}) characterized by large hydration enthalpies typically exhibit multiple broad librational peaks compared to monovalent cations (Cs^{+} and Na^{+}), which have relatively small hydration enthalpies.
Ab initio molecular dynamics simulation of pressure-induced phase transformation of BeO
Xiao, H. Y.; Duan, G.; Zu, X. T.; Weber, W. J.
2011-05-05
Ab initio molecular dynamics (MD) method has been used to study high pressure-induced phase transformation in BeO based on the local density approximation (LDA) and the generalized gradient approximation (GGA). Both methods show that the wurtzite (WZ) and zinc blende (ZB) BeO transforms to the rocksalt (RS) structure smoothly at high pressure. The transition pressures obtained from the LDA method are about 40 GPa larger than the GGA result for both WZ ? RS and ZB ? RS phase transformations, and the phase transformation mechanisms revealed by the LDA and GGA methods are different. For WZ ? RS phase transformations both mechanisms obtained from the LDA and GGA methods are not comparable to the previous ab initio MD simulations of WZ BeO at 700 GPa based on the GGA method. It is suggested that the phase transformation mechanisms of BeO revealed by the ab initio MD simulations are affected remarkably by the exchangecorrelation functional employed and the way of applying pressure.
Frhlich, Markus G. E-mail: ThompsonDon@missouri.edu; Sewell, Thomas D. Thompson, Donald L. E-mail: ThompsonDon@missouri.edu
2014-01-14
The mechanical and structural responses of hydroxyl-terminated cis-1,4-polybutadiene melts to shock waves were investigated by means of all-atom non-reactive molecular dynamics simulations. The simulations were performed using the OPLS-AA force field but with the standard 12-6 Lennard-Jones potential replaced by the Buckingham exponential-6 potential to better represent the interactions at high compression. Monodisperse systems containing 64, 128, and 256 backbone carbon atoms were studied. Supported shock waves were generated by impacting the samples onto stationary pistons at impact velocities of 1.0, 1.5, 2.0, and 2.5 km s{sup ?1}, yielding shock pressures between approximately 2.8 GPa and 12.5 GPa. Single-molecule structural properties (squared radii of gyration, asphericity parameters, and orientational order parameters) and mechanical properties (density, shock pressure, shock temperature, and shear stress) were analyzed using a geometric binning scheme to obtain spatio-temporal resolution in the reference frame centered on the shock front. Our results indicate that while shear stress behind the shock front is relieved on a ?0.5 ps time scale, a shock-induced transition to a glass-like state occurs with a concomitant increase of structural relaxation times by several orders of magnitude.
Makwana, K. D. Cattaneo, F.; Zhdankin, V.; Li, H.; Daughton, W.
2015-04-15
Simulations of decaying magnetohydrodynamic (MHD) turbulence are performed with a fluid and a kinetic code. The initial condition is an ensemble of long-wavelength, counter-propagating, shear-Alfvén waves, which interact and rapidly generate strong MHD turbulence. The total energy is conserved and the rate of turbulent energy decay is very similar in both codes, although the fluid code has numerical dissipation, whereas the kinetic code has kinetic dissipation. The inertial range power spectrum index is similar in both the codes. The fluid code shows a perpendicular wavenumber spectral slope of k{sub ⊥}{sup −1.3}. The kinetic code shows a spectral slope of k{sub ⊥}{sup −1.5} for smaller simulation domain, and k{sub ⊥}{sup −1.3} for larger domain. We estimate that collisionless damping mechanisms in the kinetic code can account for the dissipation of the observed nonlinear energy cascade. Current sheets are geometrically characterized. Their lengths and widths are in good agreement between the two codes. The length scales linearly with the driving scale of the turbulence. In the fluid code, their thickness is determined by the grid resolution as there is no explicit diffusivity. In the kinetic code, their thickness is very close to the skin-depth, irrespective of the grid resolution. This work shows that kinetic codes can reproduce the MHD inertial range dynamics at large scales, while at the same time capturing important kinetic physics at small scales.
Barrows, Wesley; Dingreville, Rémi; Spearot, Douglas
2015-10-19
A statistical approach combined with molecular dynamics simulations is used to study the influence of hydrogen on intergranular decohesion. This methodology is applied to a Ni Σ3(112)[11¯0] symmetric tilt grain boundary. Hydrogenated grain boundaries with different H concentrations are constructed using an energy minimization technique with initial H atom positions guided by Monte Carlo simulation results. Decohesion behavior is assessed through extraction of a traction–separation relationship during steady-state crack propagation in a statistically meaningful approach, building upon prior work employing atomistic cohesive zone volume elements (CZVEs). A sensitivity analysis is performed on the numerical approach used to extract the traction–separationmore » relationships, clarifying the role of CZVE size, threshold parameters necessary to differentiate elastic and decohesion responses, and the numerical averaging technique. Results show that increasing H coverage at the Ni Σ3(112)[11¯0] grain boundary asymmetrically influences the crack tip velocity during propagation, leads to a general decrease in the work of separation required for crack propagation, and provides a reduction in the peak stress in the extracted traction–separation relationship. Furthermore the present framework offers a meaningful vehicle to pass atomistically derived interfacial behavior to higher length scale formulations for intergranular fracture.« less
Bai, Xian-Ming; Zhang, Yongfeng; Tonks, Michael R.
2015-02-01
Strong thermal gradients in low-thermal-conductivity ceramics may drive extended defects, such as grain boundaries and voids, to migrate in preferential directions. In this work, molecular dynamics simulations are conducted to study thermal gradient driven grain boundary migration and to verify a previously proposed thermal gradient driving force equation, using uranium dioxide as a model system. It is found that a thermal gradient drives grain boundaries to migrate up the gradient and the migration velocity increases under a constant gradient owing to the increase in mobility with temperature. Different grain boundaries migrate at very different rates due to their different intrinsic mobilities. The extracted mobilities from the thermal gradient driven simulations are compared with those calculated from two other well-established methods and good agreement between the three different methods is found, demonstrating that the theoretical equation of the thermal gradient driving force is valid, although a correction of one input parameter should be made. The discrepancy in the grain boundary mobilities between modeling and experiments is also discussed.
Numerical simulation of the compressor coil of the plasma dynamic accelerator
Thomas, P.
1997-01-01
The plasma dynamic accelerator accelerates a plasma to very high velocities in a coaxial accelerator and then compresses it in a compressor coil, achieving high densities. The axial component of the current distribution, extending from the tip of the coaxial accelerator`s center electrode to the coil turns, causes compressing forces, the radial component yields accelerating forces. The rapid change of the coil current induces azimuthal eddy currents in the plasma that interact with the coil`s magnetic field, again yielding Lorentz forces. Aerodynamic compression may also be an important effect. A new two-dimensional magnetohydrodynamics code is used to investigate which of these effects are really important for the compression. The code allows one to simulate all effects mentioned separately and in combination. In a first step only aerodynamic compression is considered. Then each electromagnetic effect is imposed on the system. Finally, a complete simulation of the compressor coil is performed. The analysis of the results provides new insights in the way the coil operates. This paper presents important aspects of the mathematical model and of the numerical implementation and reports results.
Greathouse, Jeffery A.; Cygan, Randall T.; Fredrich, Joanne T.; Jerauld, Gary R.
2016-01-20
In this study, the diffusion of water and ions in the interlayer region of smectite clay minerals represents a direct probe of the type and strength of clay–fluid interactions. Interlayer diffusion also represents an important link between molecular simulation and macroscopic experiments. Here we use molecular dynamics simulation to investigate trends in cation and water diffusion in montmorillonite interlayers, looking specifically at the effects of layer charge, interlayer cation and cation charge (sodium or calcium), water content, and temperature. For Na-montmorillonite, the largest increase in ion and water diffusion coefficients occurs between the one-layer and two-layer hydrates, corresponding to themore » transition from inner-sphere to outer-sphere surface complexes. Calculated activation energies for ion and water diffusion in Na-montmorillonite are similar to each other and to the water hydrogen bond energy, suggesting the breaking of water–water and water–clay hydrogen bonds as a likely mechanism for interlayer diffusion. A comparison of interlayer diffusion with that of bulk electrolyte solutions reveals a clear trend of decreasing diffusion coefficient with increasing electrolyte concentration, and in most cases the interlayer diffusion results are nearly coincident with the corresponding bulk solutions. Trends in electrical conductivities computed from the ion diffusion coefficients are also compared.« less
Barrows, Wesley; Dingreville, Rmi; Spearot, Douglas
2015-10-19
A statistical approach combined with molecular dynamics simulations is used to study the influence of hydrogen on intergranular decohesion. This methodology is applied to a Ni ?3(112)[110] symmetric tilt grain boundary. Hydrogenated grain boundaries with different H concentrations are constructed using an energy minimization technique with initial H atom positions guided by Monte Carlo simulation results. Decohesion behavior is assessed through extraction of a tractionseparation relationship during steady-state crack propagation in a statistically meaningful approach, building upon prior work employing atomistic cohesive zone volume elements (CZVEs). A sensitivity analysis is performed on the numerical approach used to extract the tractionseparation relationships, clarifying the role of CZVE size, threshold parameters necessary to differentiate elastic and decohesion responses, and the numerical averaging technique. Results show that increasing H coverage at the Ni ?3(112)[110] grain boundary asymmetrically influences the crack tip velocity during propagation, leads to a general decrease in the work of separation required for crack propagation, and provides a reduction in the peak stress in the extracted tractionseparation relationship. Furthermore the present framework offers a meaningful vehicle to pass atomistically derived interfacial behavior to higher length scale formulations for intergranular fracture.
Quantify Water Extraction by TBP/Dodecane via Molecular Dynamics Simulations
Khomami, Bamin; Cui, Shengting; de Almeida, Valmor F.; Felker, Kevin
2013-05-16
The purpose of this project is to quantify the interfacial transport of water into the most prevalent nuclear reprocessing solvent extractant mixture, namely tri-butyl- phosphate (TBP) and dodecane, via massively parallel molecular dynamics simulations on the most powerful machines available for open research. Specifically, we will accomplish this objective by evolving the water/TBP/dodecane system up to 1 ms elapsed time, and validate the simulation results by direct comparison with experimentally measured water solubility in the organic phase. The significance of this effort is to demonstrate for the first time that the combination of emerging simulation tools and state-of-the-art supercomputers can provide quantitative information on par to experimental measurements for solvent extraction systems of relevance to the nuclear fuel cycle. Results: Initially, the isolated single component, and single phase systems were studied followed by the two-phase, multicomponent counterpart. Specifically, the systems we studied were: pure TBP; pure n-dodecane; TBP/n-dodecane mixture; and the complete extraction system: water-TBP/n-dodecane two phase system to gain deep insight into the water extraction process. We have completely achieved our goal of simulating the molecular extraction of water molecules into the TBP/n-dodecane mixture up to the saturation point, and obtained favorable comparison with experimental data. Many insights into fundamental molecular level processes and physics were obtained from the process. Most importantly, we found that the dipole moment of the extracting agent is crucially important in affecting the interface roughness and the extraction rate of water molecules into the organic phase. In addition, we have identified shortcomings in the existing OPLS-AA force field potential for long-chain alkanes. The significance of this force field is that it is supposed to be optimized for molecular liquid simulations. We found that it failed for dodecane and
Kim, Junghan; Iype, Eldhose; Frijns, Arjan J.H.; Nedea, Silvia V.; Steenhoven, Anton A. van
2014-07-01
Molecular dynamics simulations of heat transfer in gases are computationally expensive when the wall molecules are explicitly modeled. To save computational time, an implicit boundary function is often used. Steele's potential has been used in studies of fluidsolid interface for a long time. In this work, the conceptual idea of Steele's potential was extended in order to simulate watersilicon and watersilica interfaces. A new wall potential model is developed by using the electronegativity-equalization method (EEM), a ReaxFF empirical force field and a non-reactive molecular dynamics package PumMa. Contact angle simulations were performed in order to validate the wall potential model. Contact angle simulations with the resulting tabulated wall potentials gave a siliconwater contact angle of 129, a quartzwater contact angle of 0, and a cristobalitewater contact angle of 40, which are in reasonable agreement with experimental values.
Computational Fluid Dynamic Analysis of the VHTR Lower Plenum Standard Problem
Richard W. Johnson; Richard R. Schultz
2009-07-01
The United States Department of Energy is promoting the resurgence of nuclear power in the U. S. for both electrical power generation and production of process heat required for industrial processes such as the manufacture of hydrogen for use as a fuel in automobiles. The DOE project is called the next generation nuclear plant (NGNP) and is based on a Generation IV reactor concept called the very high temperature reactor (VHTR), which will use helium as the coolant at temperatures ranging from 450 ºC to perhaps 1000 ºC. While computational fluid dynamics (CFD) has not been used for past safety analysis for nuclear reactors in the U. S., it is being considered for safety analysis for existing and future reactors. It is fully recognized that CFD simulation codes will have to be validated for flow physics reasonably close to actual fluid dynamic conditions expected in normal and accident operational situations. To this end, experimental data have been obtained in a scaled model of a narrow slice of the lower plenum of a prismatic VHTR. The present report presents results of CFD examinations of these data to explore potential issues with the geometry, the initial conditions, the flow dynamics and the data needed to fully specify the inlet and boundary conditions; results for several turbulence models are examined. Issues are addressed and recommendations about the data are made.
Towards the Integration of APECS and VE-Suite for Virtual Power Plant Co-Simulation
Zitney, S.E.; McCorkle, D.; Yang, C.; Jordan, T.; Swensen, D.; Bryden, M.
2007-05-01
Process modeling and simulation tools are widely used for the design and operation of advanced power generation systems. These tools enable engineers to solve the critical process systems engineering problems that arise throughout the lifecycle of a power plant, such as designing a new process, troubleshooting a process unit or optimizing operations of the full process. To analyze the impact of complex thermal and fluid flow phenomena on overall power plant performance, the Department of Energy’s (DOE) National Energy Technology Laboratory (NETL) has developed the Advanced Process Engineering Co-Simulator (APECS). The APECS system is an integrated software suite that combines process simulation (e.g., Aspen Plus) and high-fidelity equipment simulations such as those based on computational fluid dynamics (CFD), together with advanced analysis capabilities including case studies, sensitivity analysis, stochastic simulation for risk/uncertainty analysis, and multi-objective optimization. In this paper we discuss the initial phases of the integration of the APECS system with the immersive and interactive virtual engineering software, VE-Suite, developed at Iowa State University and Ames Laboratory. VE-Suite uses the ActiveX (OLE Automation) controls in the Aspen Plus process simulator wrapped by the CASI library developed by Reaction Engineering International to run process/CFD co-simulations and query for results. This integration represents a necessary step in the development of virtual power plant co-simulations that will ultimately reduce the time, cost, and technical risk of developing advanced power generation systems.
Development of a Prototype Lattice Boltzmann Code for CFD of Fusion Systems.
Pattison, Martin J; Premnath, Kannan N; Banerjee, Sanjoy; Dwivedi, Vinay
2007-02-26
Designs of proposed fusion reactors, such as the ITER project, typically involve the use of liquid metals as coolants in components such as heat exchangers, which are generally subjected to strong magnetic fields. These fields induce electric currents in the fluids, resulting in magnetohydrodynamic (MHD) forces which have important effects on the flow. The objective of this SBIR project was to develop computational techniques based on recently developed lattice Boltzmann techniques for the simulation of these MHD flows and implement them in a computational fluid dynamics (CFD) code for the study of fluid flow systems encountered in fusion engineering. The code developed during this project, solves the lattice Boltzmann equation, which is a kinetic equation whose behaviour represents fluid motion. This is in contrast to most CFD codes which are based on finite difference/finite volume based solvers. The lattice Boltzmann method (LBM) is a relatively new approach which has a number of advantages compared with more conventional methods such as the SIMPLE or projection method algorithms that involve direct solution of the Navier-Stokes equations. These are that the LBM is very well suited to parallel processing, with almost linear scaling even for very large numbers of processors. Unlike other methods, the LBM does not require solution of a Poisson pressure equation leading to a relatively fast execution time. A particularly attractive property of the LBM is that it can handle flows in complex geometries very easily. It can use simple rectangular grids throughout the computational domain -- generation of a body-fitted grid is not required. A recent advance in the LBM is the introduction of the multiple relaxation time (MRT) model; the implementation of this model greatly enhanced the numerical stability when used in lieu of the single relaxation time model, with only a small increase in computer time. Parallel processing was implemented using MPI and demonstrated the
A CFD-based wind solver for a fast response transport and dispersion model
Gowardhan, Akshay A; Brown, Michael J; Pardyjak, Eric R; Senocak, Inanc
2010-01-01
In many cities, ambient air quality is deteriorating leading to concerns about the health of city inhabitants. In urban areas with narrow streets surrounded by clusters of tall buildings, called street canyons, air pollution from traffic emissions and other sources is difficult to disperse and may accumulate resulting in high pollutant concentrations. For various situations, including the evacuation of populated areas in the event of an accidental or deliberate release of chemical, biological and radiological agents, it is important that models should be developed that produce urban flow fields quickly. For these reasons it has become important to predict the flow field in urban street canyons. Various computational techniques have been used to calculate these flow fields, but these techniques are often computationally intensive. Most fast response models currently in use are at a disadvantage in these cases as they are unable to correlate highly heterogeneous urban structures with the diagnostic parameterizations on which they are based. In this paper, a fast and reasonably accurate computational fluid dynamics (CFD) technique that solves the Navier-Stokes equations for complex urban areas has been developed called QUIC-CFD (Q-CFD). This technique represents an intermediate balance between fast (on the order of minutes for a several block problem) and reasonably accurate solutions. The paper details the solution procedure and validates this model for various simple and complex urban geometries.
Lundquist, J K; Chan, S T
2005-11-30
The validity of omitting stability considerations when simulating transport and dispersion in the urban environment is explored using observations from the Joint URBAN 2003 field experiment and computational fluid dynamics simulations of that experiment. Four releases of sulfur hexafluoride, during two daytime and two nighttime intensive observing periods, are simulated using the building-resolving computational fluid dynamics model, FEM3MP to solve the Reynolds Averaged Navier-Stokes equations with two options of turbulence parameterizations. One option omits stability effects but has a superior turbulence parameterization using a non-linear eddy viscosity (NEV) approach, while the other considers buoyancy effects with a simple linear eddy viscosity (LEV) approach for turbulence parameterization. Model performance metrics are calculated by comparison with observed winds and tracer data in the downtown area, and with observed winds and turbulence kinetic energy (TKE) profiles at a location immediately downwind of the central business district (CBD) in the area we label as the urban shadow. Model predictions of winds, concentrations, profiles of wind speed, wind direction, and friction velocity are generally consistent with and compare reasonably well with the field observations. Simulations using the NEV turbulence parameterization generally exhibit better agreement with observations. To further explore this assumption of a neutrally-stable atmosphere within the urban area, TKE budget profiles slightly downwind of the urban wake region in the 'urban shadow' are examined. Dissipation and shear production are the largest terms which may be calculated directly. The advection of TKE is calculated as a residual; as would be expected downwind of an urban area, the advection of TKE produced within the urban area is a very large term. Buoyancy effects may be neglected in favor of advection, shear production, and dissipation. For three of the IOPs, buoyancy production may
Carbon Capture Simulation Initiative: A Case Study in Multi-Scale Modeling and New Challenges
Miller, David; Syamlal, Madhava; Mebane, David; Storlie, Curtis; Bhattacharyya, Debangsu; Sahinidis, Nikolaos V.; Agarwal, Deborah A.; Tong, Charles; Zitney, Stephen E.; Sarkar, Avik; Sun, Xin; Sundaresan, Sankaran; Ryan, Emily M.; Engel, David W.; Dale, Crystal
2014-04-01
Advanced multi-scale modeling and simulation has the potential to dramatically reduce development time, resulting in considerable cost savings. The Carbon Capture Simulation Initiative is a partnership among national laboratories, industry and universities that is developing and deploying a suite of multi-scale modeling and simulation tools including basic data submodels, steady-state and dynamic process models, process optimization and uncertainty quantification tools, an advanced dynamic process control framework, high-resolution filtered computational-fluid-dynamic (CFD) submodels, validated high-fidelity device-scale CFD models with quantified uncertainty, and a risk analysis framework. These tools and models enable basic data submodels, including thermodynamics and kinetics, to be used within detailed process models to synthesize and optimize a process. The resulting process informs the development of process control systems and more detailed simulations of potential equipment to improve the design and reduce scale-up risk. Quantification and propagation of uncertainty across scales is an essential part of these tools and models.
Carbon Capture Simulation Initiative: A Case Study in Multi-Scale Modeling and New Challenges
Miller, David C; Syamlal, Madhava; Zitney, Stephen E.
2014-06-07
Abstract: Advanced multi-scale modeling and simulation has the potential to dramatically reduce development time, resulting in considerable cost savings. The Carbon Capture Simulation Initiative is a partnership among national laboratories, industry and universities that is developing and deploying a suite of multi-scale modeling and simulation tools including basic data submodels, steady-state and dynamic process models, process optimization and uncertainty quantification tools, an advanced dynamic process control framework, high-resolution filtered computational-fluid-dynamic (CFD) submodels, validated high-fidelity device-scale CFD models with quantified uncertainty, and a risk analysis framework. These tools and models enable basic data submodels, including thermodynamics and kinetics, to be used within detailed process models to synthesize and optimize a process. The resulting process informs the development of process control systems and more detailed simulations of potential equipment to improve the design and reduce scale-up risk. Quantification and propagation of uncertainty across scales is an essential part of these tools and models.
Three dimensional analysis of turbulent steam jets in enclosed structures : a CFD approach.
Ishii, M.; NguyenLe, Q.
1999-04-20
This paper compares the three-dimensional numerical simulation with the experimental data of a steam blowdown event in a light water reactor containment building. The temperature and pressure data of a steam blowdown event was measured at the Purdue University Multi-Dimensional Integrated Test Assembly (PUMA), a scaled model of the General Electric simplified Boiling Water Reactor. A three step approach was used to analyze the steam jet behavior. First, a 1-Dimensional, system level RELAP5/Mod3.2 model of the steam blowdown event was created and the results used to set the initial conditions for the PUMA blowdown experiments. Second, 2-Dimensional CFD models of the discharged steam jets were computed using PHOENICS, a commercially available CFD package. Finally, 3-Dimensional model of the PUMA drywell was created with the boundary conditions based on experimental measurements. The results of the 1-D and 2-D models were reported in the previous meeting. This paper discusses in detail the formulation and the results of the 3-Dimensional PHOENICS model of the PUMA drywell. It is found that the 3-D CFD solutions compared extremely well with the measured data.
Dresser, Thomas J.; Dotson, Curtis L.; Fisher, Richard K.; Graf, Michael J.; Richmond, Marshall C.; Rakowski, Cynthia L.; Carlson, Thomas J.; Mathur, Dilip; Heisey, Paul G.
2007-10-10
This paper, the second part of a 2 part paper, discusses the use of Computational Fluid Dynamics (CFD) to gain further insight into the results of fish release testing conducted to evaluate the modifications made to upgrade Unit 8 at Wanapum Dam. Part 1 discusses the testing procedures and fish passage survival. Grant PUD is working with Voith Siemens Hydro (VSH) and the Pacific Northwest National Laboratory (PNNL) of DOE and Normandeau Associates in this evaluation. VSH has prepared the geometry for the CFD analysis corresponding to the four operating conditions tested with Unit 9, and the 5 operating conditions tested with Unit 8. Both VSH and PNNL have conducting CFD simulations of the turbine intakes, stay vanes, wicket gates, turbine blades and draft tube of the units. Primary objectives of the analyses were: determine estimates of where the inserted fish passed the turbine components determine the characteristics of the flow field along the paths calculated for pressure, velocity gradients and acceleration associated with fish sized bodies determine the velocity gradients at the structures where fish to structure interaction is predicted. correlate the estimated fish location of passage with observed injuries correlate the calculated pressure and acceleration with the information recorded with the sensor fish utilize the results of the analysis to further interpret the results of the testing. This paper discusses the results of the CFD analyses made to assist the interpretation of the fish test results.
computational-fluid-dynamics-student-thesis
U.S. Department of Energy (DOE) all webpages (Extended Search)
Fluid Dynamics Student Thesis Abstract DEVELOPMENT OF A THREE-DIMENSIONAL SCOURING METHODOLOGY AND ITS IMPLEMENTATION IN A COMMERCIAL CFD CODE FOR OPEN CHANNEL FLOW OVER A FLOODED BRIDGE DECK The Computational Fluid Dynamics staff at TRACC is supporting three students from Northern Illinois University who are working for a Masters degree. The CFD staff is directing the thesis research and working with them on three projects: (1) a three-dimensional scour computation methodology for pressure flow
PArallel Reacting Multiphase FLOw Computational Fluid Dynamic Analysis
Energy Science and Technology Software Center (OSTI)
2002-06-01
PARMFLO is a parallel multiphase reacting flow computational fluid dynamics (CFD) code. It can perform steady or unsteady simulations in three space dimensions. It is intended for use in engineering CFD analysis of industrial flow system components. Its parallel processing capabilities allow it to be applied to problems that use at least an order of magnitude more computational cells than the number that can be used on a typical single processor workstation (about 106 cellsmore » in parallel processing mode versus about io cells in serial processing mode). Alternately, by spreading the work of a CFD problem that could be run on a single workstation over a group of computers on a network, it can bring the runtime down by an order of magnitude or more (typically from many days to less than one day). The software was implemented using the industry standard Message-Passing Interface (MPI) and domain decomposition in one spatial direction. The phases of a flow problem may include an ideal gas mixture with an arbitrary number of chemical species, and dispersed droplet and particle phases. Regions of porous media may also be included within the domain. The porous media may be packed beds, foams, or monolith catalyst supports. With these features, the code is especially suited to analysis of mixing of reactants in the inlet chamber of catalytic reactors coupled to computation of product yields that result from the flow of the mixture through the catalyst coaled support structure.« less
Final technical report [ACCELERATED MOLECULAR DYNAMICS SIMULATIONS OF REACTIVE HYDROCARBON SYSTEMS
Stuart, Steven J.
2014-02-25
The research activities in this project consisted of four different sub-projects. Three different accelerated dynamics techniques (parallel replica dynamics, hyperdynamics, and temperature-accelerated dynamics) were applied to the modeling of pyrolysis of hydrocarbons. In addition, parallel replica dynamics was applied to modeling of polymerization.
Meeks, E.; Chou, C. -P.; Garratt, T.
2013-03-31
Engineering simulations of coal gasifiers are typically performed using computational fluid dynamics (CFD) software, where a 3-D representation of the gasifier equipment is used to model the fluid flow in the gasifier and source terms from the coal gasification process are captured using discrete-phase model source terms. Simulations using this approach can be very time consuming, making it difficult to imbed such models into overall system simulations for plant design and optimization. For such system-level designs, process flowsheet software is typically used, such as Aspen Plus® [1], where each component where each component is modeled using a reduced-order model. For advanced power-generation systems, such as integrated gasifier/gas-turbine combined-cycle systems (IGCC), the critical components determining overall process efficiency and emissions are usually the gasifier and combustor. Providing more accurate and more computationally efficient reduced-order models for these components, then, enables much more effective plant-level design optimization and design for control. Based on the CHEMKIN-PRO and ENERGICO software, we have developed an automated methodology for generating an advanced form of reduced-order model for gasifiers and combustors. The reducedorder model offers representation of key unit operations in flowsheet simulations, while allowing simulation that is fast enough to be used in iterative flowsheet calculations. Using high-fidelity fluiddynamics models as input, Reaction Design’s ENERGICO® [2] software can automatically extract equivalent reactor networks (ERNs) from a CFD solution. For the advanced reduced-order concept, we introduce into the ERN a much more detailed kinetics model than can be included practically in the CFD simulation. The state-of-the-art chemistry solver technology within CHEMKIN-PRO allows that to be accomplished while still maintaining a very fast model turn-around time. In this way, the ERN becomes the basis for
A surface ice module for wind turbine dynamic response simulation using FAST
Yu, Bingbin; Karr, Dale G.; Song, Huimin; Sirnivas, Senu
2016-06-03
It is a fact that developing offshore wind energy has become more and more serious worldwide in recent years. Many of the promising offshore wind farm locations are in cold regions that may have ice cover during wintertime. The challenge of possible ice loads on offshore wind turbines raises the demand of modeling capacity of dynamic wind turbine response under the joint action of ice, wind, wave, and current. The simulation software FAST is an open source computer-aided engineering (CAE) package maintained by the National Renewable Energy Laboratory. In this paper, a new module of FAST for assessing the dynamicmore » response of offshore wind turbines subjected to ice forcing is presented. In the ice module, several models are presented which involve both prescribed forcing and coupled response. For conditions in which the ice forcing is essentially decoupled from the structural response, ice forces are established from existing models for brittle and ductile ice failure. For conditions in which the ice failure and the structural response are coupled, such as lock-in conditions, a rate-dependent ice model is described, which is developed in conjunction with a new modularization framework for FAST. In this paper, analytical ice mechanics models are presented that incorporate ice floe forcing, deformation, and failure. For lower speeds, forces slowly build until the ice strength is reached and ice fails resulting in a quasi-static condition. For intermediate speeds, the ice failure can be coupled with the structural response and resulting in coinciding periods of the ice failure and the structural response. A third regime occurs at high speeds of encounter in which brittle fracturing of the ice feature occurs in a random pattern, which results in a random vibration excitation of the structure. An example wind turbine response is simulated under ice loading of each of the presented models. This module adds to FAST the capabilities for analyzing the response of wind
Molecular dynamics simulation for arrangement of nickel atoms filled in carbon nanotubes
Bai, Liu Zhenyu, Zhao; Lirui, Liu
2014-08-28
Carbon Nanotubes (CNTs) filled with metals can be used in capacitors, sensors, rechargeable batteries, and so on. Atomic arrangement of the metals has an important role in the function of the composites. The tips of CNTs were opened, and then nickel was filled by means of hydrothermal oxidation/ultrasonic vibration method. The tests of TEM, HREM, and EDX (energy-dispersive X-ray spectroscopy) analysis showed that Ni was filled in CNTs successfully. The atomic arrangement of nickel filled into single wall carbon nanotubes was investigated by molecular dynamics simulation. The radial distribution function and bond orientation order were established to analyze the atomic arrangement of nickel filled in carbon nanotubes during the cooling process. The results show that nickel atoms became in order gradually and preferably crystallized on the inner wall of carbon nanotubes when the temperature decreased from 1600?K. After it cooled to 100?K, the arrangement of nickel atoms in outermost circle was regular and dense, but there were many defects far from the wall of CNTs. According to the calculation of bond orientation order parameters Q{sub 6} and its visualization, the structure of nickel is Face-centered cube (f.c.c). (1,1,1){sub Ni} was close on the inner surface of carbon nanotubes. Radial direction of CNTs was [1,1,1] crystal orientation. Axial direction of CNTs, namely, filling direction, was [1{sup }, 1{sup },2] crystal orientation.
Molecular dynamics simulations of uranyl adsorption and structure on the basal surface of muscovite
Teich-McGoldrick, Stephanie L.; Greathouse, Jeffery A.; Cygan, Randall T.
2014-02-05
Anthropogenic activities have led to an increased concentration of uranium on the Earth’s surface and potentially in the subsurface with the development of nuclear waste repositories. Uranium is soluble in groundwater, and its mobility is strongly affected by the presence of clay minerals in soils and in subsurface sediments. We use molecular dynamics simulations to probe the adsorption of aqueous uranyl (UO22+) ions onto the basal surface of muscovite, a suitable proxy for typically ultrafine-grained clay phases. Model systems include the competitive adsorption between potassium counterions and aqueous ions (0.1 M and 1.0 M UO2Cl2 , 0.1 M NaCl). Wemore » find that for systems with potassium and uranyl ions present, potassium ions dominate the adsorption phenomenon. Potassium ions adsorb entirely as inner-sphere complexes associated with the ditrigonal cavity of the basal surface. Uranyl ions adsorb in two configurations when it is the only ion species present, and in a single configuration in the presence of potassium. Finally, the majority of adsorbed uranyl ions are tilted less than 45° relative to the muscovite surface, and are associated with the Si4Al2 rings near aluminum substitution sites.« less
Effect of point defects on the thermal conductivity of UO2: molecular dynamics simulations
Liu, Xiang-Yang; Stanek, Christopher Richard; Andersson, Anders David Ragnar
2015-07-21
The thermal conductivity of uranium dioxide (UO_{2}) fuel is an important materials property that affects fuel performance since it is a key parameter determining the temperature distribution in the fuel, thus governing, e.g., dimensional changes due to thermal expansion, fission gas release rates, etc. [1] The thermal conductivity of UO_{2} nuclear fuel is also affected by fission gas, fission products, defects, and microstructural features such as grain boundaries. Here, molecular dynamics (MD) simulations are carried out to determine quantitatively, the effect of irradiation induced point defects on the thermal conductivity of UO_{2}, as a function of defect concentrations, for a range of temperatures, 300 – 1500 K. The results will be used to develop enhanced continuum thermal conductivity models for MARMOT and BISON by INL. These models express the thermal conductivity as a function of microstructure state-variables, thus enabling thermal conductivity models with closer connection to the physical state of the fuel [2].
Lamonte, K.; Gomez Gualdron, D.; Scanlon, L. G.; Sandi, G.; Feld, W.; Balbuena, P. B.; Chemical Sciences and Engineering Division; Texas A&M Univ.; Wright-Patterson Air Force Base; Wright State Univ.
2008-11-01
Tetramethyl ammonium lithium phthalocyanine is explored as a potential material for storage of molecular hydrogen. Density functional theory calculations are used to investigate the molecular structure and the dimer conformation. Additional scans performed to determine the interactions of a H{sub 2} molecule located at various distances from the molecular sites are used to generate a simple force field including dipole-induced-dipole interactions. This force field is employed in molecular dynamics simulations to calculate adsorption isotherms at various pressures. The regions of strongest adsorption are quantified as functions of temperature, pressure, and separation between molecules in the adsorbent phase, and compared to the regions of strongest binding energy as given by the proposed force field. It is found that the total adsorption could not be predicted only from the spatial distribution of the strongest binding energies; the available volume is the other contributing factor even if the volume includes regions of much lower binding energy. The results suggest that the complex anion is primarily involved in the adsorption process with molecular hydrogen, whereas the cation serves to provide access for hydrogen adsorption in both sides of the anion molecular plane, and spacing between the planes.
Insight into the molecular switch mechanism of human Rab5a from molecular dynamics simulations
Wang, Jing-Fang; Shanghai Center for Bioinformation Technology, 100 Qinzhou Road, Shanghai 200235; Gordon Life Science Institute, 13784 Torrey Del Mar Drive, San Diego, CA 92130 ; Chou, Kuo-Chen
2009-12-18
Rab5a is currently a most interesting target because it is responsible for regulating the early endosome fusion in endocytosis and possibly the budding process. We utilized longtime-scale molecular dynamics simulations to investigate the internal motion of the wild-type Rab5a and its A30P mutant. It was observed that, after binding with GTP, the global flexibility of the two proteins is increasing, while the local flexibility in their sensitive sites (P-loop, switch I and II regions) is decreasing. Also, the mutation of Ala30 to Pro30 can cause notable flexibility variations in the sensitive sites. However, this kind of variations is dramatically reduced after binding with GTP. Such a remarkable feature is mainly caused by the water network rearrangements in the sensitive sites. These findings might be of use for revealing the profound mechanism of the displacements of Rab5a switch regions, as well as the mechanism of the GDP dissociation and GTP association.
Molecular dynamics simulations of the melting curve of NiAl alloy under pressure
Zhang, Wenjin; Peng, Yufeng; Liu, Zhongli
2014-05-15
The melting curve of B2-NiAl alloy under pressure has been investigated using molecular dynamics technique and the embedded atom method (EAM) potential. The melting temperatures were determined with two approaches, the one-phase and the two-phase methods. The first one simulates a homogeneous melting, while the second one involves a heterogeneous melting of materials. Both approaches reduce the superheating effectively and their results are close to each other at the applied pressures. By fitting the well-known Simon equation to our melting data, we yielded the melting curves for NiAl: 1783(1 + P/9.801){sup 0.298} (one-phase approach), 1850(1 + P/12.806){sup 0.357} (two-phase approach). The good agreement of the resulting equation of states and the zero-pressure melting point (calc., 1850 25 K, exp., 1911 K) with experiment proved the correctness of these results. These melting data complemented the absence of experimental high-pressure melting of NiAl. To check the transferability of this EAM potential, we have also predicted the melting curves of pure nickel and pure aluminum. Results show the calculated melting point of Nickel agrees well with experiment at zero pressure, while the melting point of aluminum is slightly higher than experiment.
Structure of rigid polymers confined to nanoparticles: Molecular dynamics simulations insight
Maskey, Sabina; Lane, J. Matthew D.; Perahia, Dvora; Grest, Gary S.
2016-02-04
Nanoparticles (NPs) grafted with organic layers form hybrids able to retain their unique properties through integration into the mesoscopic scale. The organic layer structure and response often determine the functionality of the hybrids on the mesoscopic length scale. Using molecular dynamics (MD) simulations, we probe the conformation of luminescent rigid polymers, dialkyl poly(p-phenylene ethynylene)s (PPE), end-grafted onto a silica nanoparticle in different solvents as the molecular weights and polymer coverages are varied. We find that, in contrast to NP-grafted flexible polymers, the chains are fully extended independent of the solvent. In toluene and decane, which are good solvents, the graftedmore » PPEs chains assume a similar conformation to that observed in dilute solutions. In water, which is a poor solvent for the PPEs, the polymer chains form one large cluster but remain extended. The radial distribution of the chains around the core of the nanoparticle is homogeneous in good solvents, whereas in poor solvents clusters are formed independent of molecular weights and coverages. As a result, the clustering is distinctively different from the response of grafted flexible and semiflexible polymers.« less
Molecular dynamics simulations of uranyl adsorption and structure on the basal surface of muscovite
Teich-McGoldrick, Stephanie L.; Greathouse, Jeffery A.; Cygan, Randall T.
2014-02-05
Anthropogenic activities have led to an increased concentration of uranium on the Earth’s surface and potentially in the subsurface with the development of nuclear waste repositories. Uranium is soluble in groundwater, and its mobility is strongly affected by the presence of clay minerals in soils and in subsurface sediments. We use molecular dynamics simulations to probe the adsorption of aqueous uranyl (UO_{2}^{2+}) ions onto the basal surface of muscovite, a suitable proxy for typically ultrafine-grained clay phases. Model systems include the competitive adsorption between potassium counterions and aqueous ions (0.1 M and 1.0 M UO_{2}Cl_{2} , 0.1 M NaCl). We find that for systems with potassium and uranyl ions present, potassium ions dominate the adsorption phenomenon. Potassium ions adsorb entirely as inner-sphere complexes associated with the ditrigonal cavity of the basal surface. Uranyl ions adsorb in two configurations when it is the only ion species present, and in a single configuration in the presence of potassium. Finally, the majority of adsorbed uranyl ions are tilted less than 45° relative to the muscovite surface, and are associated with the Si_{4}Al_{2} rings near aluminum substitution sites.
Advanced CFD Models for High Efficiency Compression Ignition...
Advanced CFD models for high efficiency compression-ignition engines can be used to show how turbulence-chemistry interactions influence autoignition and combustion. p-19raja.pdf ...
Sandia Energy - CFD-Populated Empirical Turbine Wake Model
U.S. Department of Energy (DOE) all webpages (Extended Search)
parameters that effect tidal turbine wakes, such as yaw angle to incident flow and vertical blockage ratio, may be incorporated as part of future revisions of the CFD populated...
Whitley, Heather D.; Scullard, Christian R.; Benedict, Lorin X.; Castor, John I.; Randles, Amanda; Glosli, James N.; Richards, David F.; Desjarlais, Michael P.; Graziani, Frank R.
2015-12-04
Here, we present a discussion of kinetic theory treatments of linear electrical and thermal transport in hydrogen plasmas, for a regime of interest to inertial confinement fusion applications. In order to assess the accuracy of one of the more involved of these approaches, classical Lenard-Balescu theory, we perform classical molecular dynamics simulations of hydrogen plasmas using 2-body quantum statistical potentials and compute both electrical and thermal conductivity from out particle trajectories using the Kubo approach. Our classical Lenard-Balescu results employing the identical statistical potentials agree well with the simulations.
Hyeon-Deuk, Kim; Ando, Koji
2014-05-07
Liquid para-hydrogen (p-H{sub 2}) is a typical quantum liquid which exhibits strong nuclear quantum effects (NQEs) and thus anomalous static and dynamic properties. We propose a real-time simulation method of wave packet (WP) molecular dynamics (MD) based on non-empirical intra- and inter-molecular interactions of non-spherical hydrogen molecules, and apply it to condensed-phase p-H{sub 2}. The NQEs, such as WP delocalization and zero-point energy, are taken into account without perturbative expansion of prepared model potential functions but with explicit interactions between nuclear and electron WPs. The developed MD simulation for 100 ps with 1200 hydrogen molecules is realized at feasible computational cost, by which basic experimental properties of p-H{sub 2} liquid such as radial distribution functions, self-diffusion coefficients, and shear viscosities are all well reproduced.
A coke/soot formation model for multiphase reacting flow simulation
Chang, S.L.; Lottes, S.A.; Petrick, M.; Zhou, C.Q. |
1997-03-01
Coke is a by-product in petroleum fluid catalytic cracking (FCC) processes. The concentration of coke in an FCC riser reactor is a critical parameter used to evaluate the riser performance. A coke formation and transport model was developed. It was incorporated into a computational fluid dynamic (CFD) computer code, ICRKFLO, to simulate the coke formation processes in an FCC riser reactor. Based on a similar process, a soot formation model can be derived from the coke formation model and used for diesel combustion processes, where soot is emitted as one of the primary pollutants.
Schryver, Jack; Nutaro, James; Shankar, Mallikarjun
2015-10-30
An agent-based simulation model hierarchy emulating disease states and behaviors critical to progression of diabetes type 2 was designed and implemented in the DEVS framework. The models are translations of basic elements of an established system dynamics model of diabetes. In this model hierarchy, which mimics diabetes progression over an aggregated U.S. population, was dis-aggregated and reconstructed bottom-up at the individual (agent) level. Four levels of model complexity were defined in order to systematically evaluate which parameters are needed to mimic outputs of the system dynamics model. Moreover, the four estimated models attempted to replicate stock counts representing disease statesmore » in the system dynamics model, while estimating impacts of an elderliness factor, obesity factor and health-related behavioral parameters. Health-related behavior was modeled as a simple realization of the Theory of Planned Behavior, a joint function of individual attitude and diffusion of social norms that spread over each agent s social network. Although the most complex agent-based simulation model contained 31 adjustable parameters, all models were considerably less complex than the system dynamics model which required numerous time series inputs to make its predictions. In all three elaborations of the baseline model provided significantly improved fits to the output of the system dynamics model. The performances of the baseline agent-based model and its extensions illustrate a promising approach to translate complex system dynamics models into agent-based model alternatives that are both conceptually simpler and capable of capturing main effects of complex local agent-agent interactions.« less
Investigations of the Application of CFD to Flow Expected in the Lower Plenum of the Prismatic VHTR
Richard W.Johnson; Tara Gallaway; Donna P. Guillen
2006-09-01
The Generation IV (Gen IV) very high temperature reactor (VHTR) will either be a prismatic (block) or pebble bed design. However, a prismatic VHTR reference design, based on the General Atomics Gas Turbine-Modular Helium Reactor (GT-MHR) [General Atomics, 1996] has been developed for preliminary analysis purposes [MacDonald, et al., 2003]. Numerical simulation studies reported herein are based on this reference design. In the lower plenum of the prismatic reference design, the flow will be introduced by dozens of turbulent jets from the core above. The jet flow will encounter rows of columns that support the core. The flow from the core will have to turn ninety degrees and flow toward the exit duct as it passed through the forest of support columns. Due to the radial variation of the power density in the core, the jets will be at various temperatures at the inlet to the lower plenum. This presents some concerns, including that local hot spots may occur in the lower plenum. This may have a deleterious effect on the materials present as well as cause a variation in temperature to be present as the flow enters the power conversion system machinery, which could cause problems with the operation of the machinery. In the past, systems analysis codes have been used to model flow in nuclear reactor systems. It is recognized, however, that such codes are not capable of modeling the local physics of the flow to be able to analyze for local mixing and temperature variations. This has led to the determination that computational fluid dynamic (CFD) codes be used, which are generally regarded as having the capability of accurately simulating local flow physics. Accurate flow modeling involves determining appropriate modeling strategies needed to obtain accurate analyses. These include determining the fineness of the grid needed, the required iterative convergence tolerance, which numerical discretization method to use, and which turbulence model and wall treatment should be
Leishear, R.; Poirier, M.; Lee, S.; Fowley, M.
2012-06-26
diameters and different horizontal orientations of the jets were investigated with respect to blending. Two types of blending tests were performed. The first set of eighty-one tests blended small quantities of tracer fluids into solution. Data from these tests were statistically evaluated to determine blending times for the addition of tracer solution to tanks, and blending times were successfully compared to Computational Fluid Dynamics (CFD) models. The second set of four tests blended bulk quantities of solutions of different density and viscosity. For example, in one test a quarter tank of water was added to a three quarters of a tank of a more viscous salt solution. In this case, the blending process was noted to significantly change due to stratification of fluids, and blending times increased substantially. However, CFD models for stratification and the variability of blending times for different density fluids was not pursued, and further research is recommended in the area of blending bulk quantities of fluids. All in all, testing showed that CFD models can be effectively applied if statistically validated through experimental testing, but in the absence of experimental validation CFD model scan be extremely misleading as a basis for design and operation decisions.
User Guide for PV Dynamic Model Simulation Written on PSCAD Platform
Muljadi, E.; Singh, M.; Gevorgian, V.
2014-11-01
This document describes the dynamic photovoltaic model developed by the National Renewable Energy Laboratory and is intended as a guide for users of these models.
Browning, J. R.; Jonkman, J.; Robertson, A.; Goupee, A. J.
2012-11-01
In 2007, the FAST wind turbine simulation tool, developed and maintained by the U.S. Department of Energy's (DOE's) National Renewable Energy Laboratory (NREL), was expanded to include capabilities that are suitable for modeling floating offshore wind turbines. In an effort to validate FAST and other offshore wind energy modeling tools, DOE funded the DeepCwind project that tested three prototype floating wind turbines at 1/50th scale in a wave basin, including a semisubmersible, a tension-leg platform, and a spar buoy. This paper describes the use of the results of the spar wave basin tests to calibrate and validate the FAST offshore floating simulation tool, and presents some initial results of simulated dynamic responses of the spar to several combinations of wind and sea states.
Li, Zhongyu; Shao, Lin; Chen, Di; Wang, Jing
2014-04-14
Strong electronic stopping power of swift ions in a semiconducting or insulating substrate can lead to localized electron stripping. The subsequent repulsive interactions among charged target atoms can cause Coulomb explosion. Using molecular dynamics simulation, we simulate Coulomb explosion in silicon by introducing an ionization pulse lasting for different periods, and at different substrate temperatures. We find that the longer the pulse period, the larger the melting radius. The observation can be explained by a critical energy density model assuming that melting required thermal energy density is a constant value and the total thermal energy gained from Coulomb explosion is linearly proportional to the ionization period. Our studies also show that melting radius is larger at higher substrate temperatures. The temperature effect is explained due to a longer structural relaxation above the melting temperature at original ionization boundary due to lower heat dissipation rates. Furthermore, simulations show the formation of shock waves, created due to the compression from the melting core.
Molecular dynamics simulations of D{sub 2}O ice photodesorption
Arasa, C.; Andersson, S.; Cuppen, H. M.; Dishoeck, E. F. van; Kroes, G. J.
2011-04-28
Molecular dynamics (MD) calculations have been performed to study the ultraviolet (UV) photodissociation of D{sub 2}O in an amorphous D{sub 2}O ice surface at 10, 20, 60, and 90 K, in order to investigate the influence of isotope effects on the photodesorption processes. As for H{sub 2}O, the main processes after UV photodissociation are trapping and desorption of either fragments or D{sub 2}O molecules. Trapping mainly takes place in the deeper monolayers of the ice, whereas desorption occurs in the uppermost layers. There are three desorption processes: D atom, OD radical, and D{sub 2}O molecule photodesorption. D{sub 2}O desorption takes places either by direct desorption of a recombined D{sub 2}O molecule, or when an energetic D atom produced by photodissociation kicks a surrounding D{sub 2}O molecule out of the surface by transferring part of its momentum. Desorption probabilities are calculated for photoexcitation of D{sub 2}O in the top four monolayers and are compared quantitatively with those for H{sub 2}O obtained from previous MD simulations of UV photodissociation of amorphous water ice at different ice temperatures [Arasa et al., J. Chem. Phys. 132, 184510 (2010)]. The main conclusions are the same, but the average D atom photodesorption probability is smaller than that of the H atom (by about a factor of 0.9) because D has lower kinetic energy than H, whereas the average OD radical photodesorption probability is larger than that of OH (by about a factor of 2.5-2.9 depending on ice temperature) because OD has higher translational energy than OH for every ice temperature studied. The average D{sub 2}O photodesorption probability is larger than that of H{sub 2}O (by about a factor of 1.4-2.3 depending on ice temperature), and this is entirely due to a larger contribution of the D{sub 2}O kick-out mechanism. This is an isotope effect: the kick-out mechanism is more efficient for D{sub 2}O ice, because the D atom formed after D{sub 2}O photodissociation
Lan, Tian; Li, Chen; Niedziela, Jennifer L; Smith, Hillary; Abernathy, Douglas L; Rossman, George; Fultz, B.
2014-01-01
Inelastic neutron scattering measurements on silver oxide (Ag2O) with the cuprite structure were performed at temperatures from 40 to 400 K, and Fourier transform far-infrared spectra were measured from 100 to 300 K. The measured phonon densities of states and the infrared spectra showed unusually large energy shifts with temperature, and large linewidth broadenings. First principles molecular dynamics (MD) calculations were performed at various temperatures, successfully accounting for the negative thermal expansion (NTE) and local dynamics. Using the Fourier-transformed velocity autocorrelation method, the MD calculations reproduced the large anharmonic effects of Ag2O, and were in excellent agreement with the neutron scattering data. The quasiharmonic approximation (QHA) was less successful in accounting for much of the phonon behavior. The QHA could account for some of the NTE below 250 K, although not at higher temperatures. Strong anharmonic effects were found for both phonons and for the NTE. The lifetime broadenings of Ag2O were explained by anharmonic perturbation theory, which showed rich interactions between the Ag-dominated modes and the O-dominated modes in both up- and down-conversion processes.
Large-Scale Condensed Matter and Fluid Dynamics Simulations in Three
U.S. Department of Energy (DOE) all webpages (Extended Search)
Diverse Areas: Whole Brain Blood Flow Simulations | Argonne Leadership Computing Facility A snapshot of blood flow simulated and visualized within a digitally reconstructed patient-specific middle cerebral artery aneurysm. The figure depicts a snapshot of blood flow simulated and visualized using the parallel LB code HemeLB within a digitally reconstructed patient-specific middle cerebral artery aneurysm. The top-left and top-right images show the volume rendering of the velocity field and
CAPE-OPEN Integration for Advanced Process Engineering Co-Simulation
Zitney, S.E.
2006-11-01
This paper highlights the use of the CAPE-OPEN (CO) standard interfaces in the Advanced Process Engineering Co-Simulator (APECS) developed at the National Energy Technology Laboratory (NETL). The APECS system uses the CO unit operation, thermodynamic, and reaction interfaces to provide its plug-and-play co-simulation capabilities, including the integration of process simulation with computational fluid dynamics (CFD) simulation. APECS also relies heavily on the use of a CO COM/CORBA bridge for running process/CFD co-simulations on multiple operating systems. For process optimization in the face of multiple and some time conflicting objectives, APECS offers stochastic modeling and multi-objective optimization capabilities developed to comply with the CO software standard. At NETL, system analysts are applying APECS to a wide variety of advanced power generation systems, ranging from small fuel cell systems to commercial-scale power plants including the coal-fired, gasification-based FutureGen power and hydrogen production plant.
Lee, Mal Soon; McGrail, B. Peter; Rousseau, Roger J.; Glezakou, Vassiliki Alexandra
2015-10-12
The interface between a solid and a complex multi-component liquid forms a unique reaction environment whose structure and composition can significantly deviate from either bulk or liquid phase and is poorly understood due the innate difficulty to obtain molecular level information. Feldspar minerals, as typified by the Ca-end member Anorthite, serve as prototypical model systems to assess the reactivity and ion mobility at solid/water-bearing supercritical fluid (WBSF) interfaces due to recent X-ray based measurements that provide information on water-film formation, and cation vacancies at these surfaces. Using density functional theory based molecular dynamics, which allows the evaluation of reactivity and condensed phase dynamics on equal footing, we report on the structure and dynamics of water nucleation and surface aggregation, carbonation and Ca mobilization under geologic carbon sequestration scenarios (T=323 K and P=90 bar). We find that water has a strong enthalpic preference for aggregation on a Ca-rich, O-terminated anorthite (001) surface, but entropy strongly hinders the film formation at very low water concentrations. Carbonation reactions readily occur at electron-rich terminal Oxygen sites adjacent to cation vacancies, when in contact with supercritical CO2. Cation vacancies of this type can form readily in the presence of a water layer that allows for facile and enthalpicly favorable Ca2+ extraction and solvation. Apart from providing unprecedented molecular level detail of a complex three component (mineral, water and scCO2) system), this work highlights the ability of modern capabilities of AIMD methods to begin to qualitatively and quantitatively address structure and reactivity at solid-liquid interfaces of high chemical complexity. This work was supported by the US Department of Energy, Office of Fossil Energy (M.-S. L., B. P. M. and V.-A. G.) and the Office of Basic Energy Science, Division of Chemical Sciences, Geosciences and Biosciences
An Eulerian CFD model and X-ray radiography for coupled nozzle...
U.S. Department of Energy (DOE) all webpages (Extended Search)
An Eulerian CFD model and X-ray radiography for coupled nozzle flow and spray in internal combustion engines Title An Eulerian CFD model and X-ray radiography for coupled nozzle...
L3: THM.CFD.P9.06 Enhanced Turbulence
U.S. Department of Energy (DOE) all webpages (Extended Search)
THM.CFD.P9.06 Enhanced Turbulence Model Capabilities in Hydra-TH Thomas Smith and Mark ... (L3 Milestone THM.CFD.P9.06) Thomas M. Smith Multiphysics Applications Sandia National ...
PIV Uncertainty Methodologies for CFD Code Validation at the MIR Facility
Piyush Sabharwall; Richard Skifton; Carl Stoots; Eung Soo Kim; Thomas Conder
2013-12-01
Currently, computational fluid dynamics (CFD) is widely used in the nuclear thermal hydraulics field for design and safety analyses. To validate CFD codes, high quality multi dimensional flow field data are essential. The Matched Index of Refraction (MIR) Flow Facility at Idaho National Laboratory has a unique capability to contribute to the development of validated CFD codes through the use of Particle Image Velocimetry (PIV). The significance of the MIR facility is that it permits non intrusive velocity measurement techniques, such as PIV, through complex models without requiring probes and other instrumentation that disturb the flow. At the heart of any PIV calculation is the cross-correlation, which is used to estimate the displacement of particles in some small part of the image over the time span between two images. This image displacement is indicated by the location of the largest peak. In the MIR facility, uncertainty quantification is a challenging task due to the use of optical measurement techniques. Currently, this study is developing a reliable method to analyze uncertainty and sensitivity of the measured data and develop a computer code to automatically analyze the uncertainty/sensitivity of the measured data. The main objective of this study is to develop a well established uncertainty quantification method for the MIR Flow Facility, which consists of many complicated uncertainty factors. In this study, the uncertainty sources are resolved in depth by categorizing them into uncertainties from the MIR flow loop and PIV system (including particle motion, image distortion, and data processing). Then, each uncertainty source is mathematically modeled or adequately defined. Finally, this study will provide a method and procedure to quantify the experimental uncertainty in the MIR Flow Facility with sample test results.
COMPARISON OF EXPERIMENTAL RESULTS TO CFD MODELS FOR BLENDING IN A TANK USING DUAL OPPOSING JETS
Leishear, R.
2011-08-07
Research has been completed in a pilot scale, eight foot diameter tank to investigate blending, using a pump with dual opposing jets. The jets re-circulate fluids in the tank to promote blending when fluids are added to the tank. Different jet diameters and different horizontal and vertical orientations of the jets were investigated. In all, eighty five tests were performed both in a tank without internal obstructions and a tank with vertical obstructions similar to a tube bank in a heat exchanger. These obstructions provided scale models of several miles of two inch diameter, serpentine, vertical cooling coils below the liquid surface for a full scale, 1.3 million gallon, liquid radioactive waste storage tank. Two types of tests were performed. One type of test used a tracer fluid, which was homogeneously blended into solution. Data were statistically evaluated to determine blending times for solutions of different density and viscosity, and the blending times were successfully compared to computational fluid dynamics (CFD) models. The other type of test blended solutions of different viscosity. For example, in one test a half tank of water was added to a half tank of a more viscous, concentrated salt solution. In this case, the fluid mechanics of the blending process was noted to significantly change due to stratification of fluids. CFD models for stratification were not investigated. This paper is the fourth in a series of papers resulting from this research (Leishear, et.al. [1- 4]), and this paper documents final test results, statistical analysis of the data, a comparison of experimental results to CFD models, and scale-up of the results to a full scale tank.
Jakobtorweihen, S. Ingram, T.; Gerlach, T.; Smirnova, I.; Zuniga, A. Chaides; Keil, F. J.
2014-07-28
Quantitative predictions of biomembrane/water partition coefficients are important, as they are a key property in pharmaceutical applications and toxicological studies. Molecular dynamics (MD) simulations are used to calculate free energy profiles for different solutes in lipid bilayers. How to calculate partition coefficients from these profiles is discussed in detail and different definitions of partition coefficients are compared. Importantly, it is shown that the calculated coefficients are in quantitative agreement with experimental results. Furthermore, we compare free energy profiles from MD simulations to profiles obtained by the recent method COSMOmic, which is an extension of the conductor-like screening model for realistic solvation to micelles and biomembranes. The free energy profiles from these molecular methods are in good agreement. Additionally, solute orientations calculated with MD and COSMOmic are compared and again a good agreement is found. Four different solutes are investigated in detail: 4-ethylphenol, propanol, 5-phenylvaleric acid, and dibenz[a,h]anthracene, whereby the latter belongs to the class of polycyclic aromatic hydrocarbons. The convergence of the free energy profiles from biased MD simulations is discussed and the results are shown to be comparable to equilibrium MD simulations. For 5-phenylvaleric acid the influence of the carboxyl group dihedral angle on free energy profiles is analyzed with MD simulations.
A new shared-memory programming paradigm for molecular dynamics simulations on the Intel Paragon
D`Azevedo, E.F.; Romine, C.H.
1994-12-01
This report describes the use of shared memory emulation with DOLIB (Distributed Object Library) to simplify parallel programming on the Intel Paragon. A molecular dynamics application is used as an example to illustrate the use of the DOLIB shared memory library. SOTON-PAR, a parallel molecular dynamics code with explicit message-passing using a Lennard-Jones 6-12 potential, is rewritten using DOLIB primitives. The resulting code has no explicit message primitives and resembles a serial code. The new code can perform dynamic load balancing and achieves better performance than the original parallel code with explicit message-passing.
Buitrago, C. Francisco; Bolintineanu, Dan; Seitz, Michelle E.; Opper, Kathleen L.; Wagener, Kenneth B.; Stevens, Mark J.; Frischknecht, Amalie Lucile; Winey, Karen I.
2015-02-09
Designing acid- and ion-containing polymers for optimal proton, ion, or water transport would benefit profoundly from predictive models or theories that relate polymer structures with ionomer morphologies. Recently, atomistic molecular dynamics (MD) simulations were performed to study the morphologies of precise poly(ethylene-co-acrylic acid) copolymer and ionomer melts. Here, we present the first direct comparisons between scattering profiles, I(q), calculated from these atomistic MD simulations and experimental X-ray data for 11 materials. This set of precise polymers has spacers of exactly 9, 15, or 21 carbons between acid groups and has been partially neutralized with Li, Na, Cs, or Zn. Inmore » these polymers, the simulations at 120 °C reveal ionic aggregates with a range of morphologies, from compact, isolated aggregates (type 1) to branched, stringy aggregates (type 2) to branched, stringy aggregates that percolate through the simulation box (type 3). Excellent agreement is found between the simulated and experimental scattering peak positions across all polymer types and aggregate morphologies. The shape of the amorphous halo in the simulated I(q) profile is in excellent agreement with experimental I(q). We found that the modified hard-sphere scattering model fits both the simulation and experimental I(q) data for type 1 aggregate morphologies, and the aggregate sizes and separations are in agreement. Given the stringy structure in types 2 and 3, we develop a scattering model based on cylindrical aggregates. Both the spherical and cylindrical scattering models fit I(q) data from the polymers with type 2 and 3 aggregates equally well, and the extracted aggregate radii and inter- and intra-aggregate spacings are in agreement between simulation and experiment. Furthermore, these dimensions are consistent with real-space analyses of the atomistic MD simulations. By combining simulations and experiments, the ionomer scattering peak can be associated with the
Browning, J. R.; Jonkman, J.; Robertson, A.; Goupee, A. J.
2014-01-01
In this study, high-quality computer simulations are required when designing floating wind turbines because of the complex dynamic responses that are inherent with a high number of degrees of freedom and variable metocean conditions. In 2007, the FAST wind turbine simulation tool, developed and maintained by the U.S. Department of Energy's (DOE's) National Renewable Energy Laboratory (NREL), was expanded to include capabilities that are suitable for modeling floating offshore wind turbines. In an effort to validate FAST and other offshore wind energy modeling tools, DOE funded the DeepCwind project that tested three prototype floating wind turbines at 1/50th scale inmore » a wave basin, including a semisubmersible, a tension-leg platform, and a spar buoy. This paper describes the use of the results of the spar wave basin tests to calibrate and validate the FAST offshore floating simulation tool, and presents some initial results of simulated dynamic responses of the spar to several combinations of wind and sea states. Wave basin tests with the spar attached to a scale model of the NREL 5-megawatt reference wind turbine were performed at the Maritime Research Institute Netherlands under the DeepCwind project. This project included free-decay tests, tests with steady or turbulent wind and still water (both periodic and irregular waves with no wind), and combined wind/wave tests. The resulting data from the 1/50th model was scaled using Froude scaling to full size and used to calibrate and validate a full-size simulated model in FAST. Results of the model calibration and validation include successes, subtleties, and limitations of both wave basin testing and FAST modeling capabilities.« less
Browning, J. R.; Jonkman, J.; Robertson, A.; Goupee, A. J.
2014-01-01
In this study, high-quality computer simulations are required when designing floating wind turbines because of the complex dynamic responses that are inherent with a high number of degrees of freedom and variable metocean conditions. In 2007, the FAST wind turbine simulation tool, developed and maintained by the U.S. Department of Energy's (DOE's) National Renewable Energy Laboratory (NREL), was expanded to include capabilities that are suitable for modeling floating offshore wind turbines. In an effort to validate FAST and other offshore wind energy modeling tools, DOE funded the DeepCwind project that tested three prototype floating wind turbines at 1/50^{th} scale in a wave basin, including a semisubmersible, a tension-leg platform, and a spar buoy. This paper describes the use of the results of the spar wave basin tests to calibrate and validate the FAST offshore floating simulation tool, and presents some initial results of simulated dynamic responses of the spar to several combinations of wind and sea states. Wave basin tests with the spar attached to a scale model of the NREL 5-megawatt reference wind turbine were performed at the Maritime Research Institute Netherlands under the DeepCwind project. This project included free-decay tests, tests with steady or turbulent wind and still water (both periodic and irregular waves with no wind), and combined wind/wave tests. The resulting data from the 1/50th model was scaled using Froude scaling to full size and used to calibrate and validate a full-size simulated model in FAST. Results of the model calibration and validation include successes, subtleties, and limitations of both wave basin testing and FAST modeling capabilities.
Chen, Y.; Lundqvist, Per; Pridasawas, Wimolsiri
2010-07-15
Carbon dioxide is an environmental benign natural working fluid and has been proposed as a working media for a solar-driven power system. In the current work, the dynamic performance of a small scale solar-driven carbon dioxide power system is analyzed by dynamic simulation tool TRNSYS 16 and Engineering Equation Solver (EES) using co-solving technique. Both daily performance and yearly performance of the proposed system have been simulated. Different system operating parameters, which will influence the system performance, have been discussed. Under the Swedish climatic condition, the maximum daily power production is about 12 kW h and the maximum monthly power production is about 215 kW h with the proposed system working conditions. Besides the power being produced, the system can also produce about 10 times much thermal energy, which can be used for space heating, domestic hot water supply or driving absorption chillers. The simulation results show that the proposed system is a promising and environmental benign alternative for conventional low-grade heat source utilization system. (author)
Jin, Jiaqi; Miller, Jan D.; Dang, Liem X.; Wick, Collin D.
2015-12-10
In the first part of this paper, an experimental contact angle study of the fresh and Cu2+ activated sphalerite-ZnS surface as well as the covellite-CuS (001) surface is reported describing the increased hydrophobic character of the surface during Cu2+ activation. In addition to these experimental results, the fresh sphalerite-ZnS (110), copper-zinc sulfide-CuZnS2 (110), villamaninite- CuS2 (100), and covellite-CuS (001) surfaces were examined using Molecular Dynamics Simulation (MDS). Our MDS results on the behavior of interfacial water at the fresh sphalerite-ZnS (110), copper-zinc sulfide-CuZnS2 (110), villamaninite-CuS2 (100), and covellite-CuS (001) surfaces include simulated contact angles, water number density distribution, water dipole orientation, water residence time, and hydrogen-bonding considerations. The copper content at the Cu2+ activated sphalerite surface seems to account for the increased hydrophobicity as revealed by both experimental and MD simulated contact angle measurements. The relatively greater hydrophobic character developed at the Cu2+ activated sphalerite surface and at the copper-zinc sulfide surface has been described by MDS, based on the structure of interfacial water and its dynamic properties. L.X.D. acknowledges funding from the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences.
Quantifying Uncertainty in Computer Predictions | netl.doe.gov
U.S. Department of Energy (DOE) all webpages (Extended Search)
multiphase computational fluid dynamics (CFD) models that underpin the simulation of ... Multiphase CFD models, for example, have the ability to predict the performance of ...
U.S. Department of Energy (DOE) all webpages (Extended Search)
This paper describes the development of a computational fluid dynamics (CFD) methodology ... blade geometry and steady CFD simulations were used to perform a grid resolution study. ...
Bonneville Powerhouse 2 Fish Guidance Efficiency Studies: CFD Model of the Forebay
Rakowski, Cynthia L.; Serkowski, John A.; Richmond, Marshall C.
2012-07-01
In ongoing work, U.S. Army Corps of Engineers, Portland District (CENWP) is seeking to better understand and improve the conditions within the Bonneville Powerhouse 2 (B2) turbine intakes to improve survival of downstream migrant salmonid smolt. In this study, the existing B2 forebay computational fluid dynamics (CFD) model was modified to include a more detailed representation of all B2 turbine intakes. The modified model was validated to existing field-measured forebay ADCP velocities. The initial CFD model scenarios tested a single project operation and the impact of adding the Behavior Guidance System (BGS) or Corner Collector. These structures had impacts on forebay flows. Most notable was that the addition of the BGS and Corner Collector reduced the lateral extent of the recirculation areas on the Washington shore and Cascade Island and reduced the flow velocity parallel to the powerhouse in front of Units 11 and 12. For these same cases, at the turbine intakes across the powerhouse, there was very little difference in the flow volume into the gatewell for the clean forebay, and the forebay with the BGS in place and/or the Corner Collector operating. The largest differences were at Units 11 to 13. The CFD model cases testing the impact of the gatewell slot fillers showed no impact to the forebay flows, but large differences within the gatewells. With the slot fillers, the flow above the standard traveling screen and into the gatewell increased (about 100 cfs at each turbine intake) and the gap flow decreased across the powerhouse for all cases. The increased flow up the gatewell was further enhanced with only half the units operating. The flow into the gatewell slot was increased about 35 cfs for each bay of each intake across the powerhouse; this change was uniform across the powerhouse. The flows in the gatewell of Unit 12, the most impacted unit for the scenarios, was evaluated. In front of the vertical barrier screen, the CFD model with slot fillers
Radiation damage in cubic ZrO2 and yttria-stabilized zirconia from molecular dynamics simulations
Aidhy, Dilpuneet S.; Zhang, Yanwen; Weber, William J.
2014-11-20
Here, we perform molecular dynamics simulation on cubic ZrO2 and yttria-stabilized zirconia (YSZ) to elucidate defect cluster formation resulting from radiation damage, and evaluate the impact of Y-dopants. Interstitial clusters composed of split-interstitial building blocks, i.e., Zr-Zr or Y-Zr are formed. Moreover, oxygen vacancies control cation defect migration; in their presence, Zr interstitials aggregate to form split-interstitials whereas in their absence Zr interstitials remain immobile, as isolated single-interstitials. Y-doping prevents interstitial cluster formation due to sequestration of oxygen vacancies.
Radiation damage in cubic-ZrO2 and yttria-stabilized zirconia from molecular dynamics simulations
Aidhy, Dilpuneet S; Zhang, Yanwen; Weber, William J
2015-01-01
We perform molecular dynamics simulation on cubic ZrO2 and yttria-stabilized zirconia (YSZ) to elucidate defect cluster formation resulting from radiation damage, and evaluate the impact of Y-dopants. Interstitial clusters composed of split-interstitial building blocks, i.e., Zr-Zr or Y-Zr are formed. Oxygen vacancies control cation defect migration; in their presence, Zr interstitials aggregate to form split-interstitials whereas in their absence Zr interstitials remain immobile, as isolated single-interstitials. Y-doping prevents interstitial cluster formation due to sequestration of oxygen vacancies.
Yuri, Yosuke
2015-06-29
Three-dimensional (3D) ordering of a charged-particle beams circulating in a storage ring is systematically studied with a molecular-dynamics simulation code. An ion beam can exhibit a 3D ordered configuration at ultralow temperature as a result of powerful 3D laser cooling. Various unique characteristics of the ordered beams, different from those of crystalline beams, are revealed in detail, such as the single-particle motion in the transverse and longitudinal directions, and the dependence of the tune depression and the Coulomb coupling constant on the operating points.
Experimental investigation and CFD analysis on cross flow in the core of PMR200
Lee, Jeong -Hun; Yoon, Su -Jong; Cho, Hyoung -Kyu; Jae, Moosung; Park, Goon -Cherl
2015-04-16
The Prismatic Modular Reactor (PMR) is one of the major Very High Temperature Reactor (VHTR) concepts, which consists of hexagonal prismatic fuel blocks and reflector blocks made of nuclear gradegraphite. However, the shape of the graphite blocks could be easily changed by neutron damage duringthe reactor operation and the shape change can create gaps between the blocks inducing the bypass flow.In the VHTR core, two types of gaps, a vertical gap and a horizontal gap which are called bypass gap and cross gap, respectively, can be formed. The cross gap complicates the flow field in the reactor core by connectingmore » the coolant channel to the bypass gap and it could lead to a loss of effective coolant flow in the fuel blocks. Thus, a cross flow experimental facility was constructed to investigate the cross flow phenomena in the core of the VHTR and a series of experiments were carried out under varying flow rates and gap sizes. The results of the experiments were compared with CFD (Computational Fluid Dynamics) analysis results in order to verify its prediction capability for the cross flow phenomena. Fairly good agreement was seen between experimental results and CFD predictions and the local characteristics of the cross flow was discussed in detail. Based on the calculation results, pressure loss coefficient across the cross gap was evaluated, which is necessary for the thermo-fluid analysis of the VHTR core using a lumped parameter code.« less
EVALUATION OF AN EXPERIMENTAL DATA SET TO BE VALIDATION DATA FOR CFD FOR A VHTR
Richard W. Johnson
2010-09-01
The very high temperature reactor (VHTR) has been chosen as the concept for the next generation nuclear plant (NGNP), supported by the U. S. Department of Energy. There are two basic designs for the VHTR: a prismatic design and a pebble-bed design. In the prismatic design, the coolant (helium) exits the core into a lower plenum as jets. The helium then turns 90° and flows toward the exit duct around cylindrical support posts. Safety analysis by computational fluid dynamics (CFD) is desired to determine the level of mixing of the jets and check for hot spots. Experimental data were taken in a scaled model of a slice of the lower plenum of a prismatic VHTR. Numerical investigations have been made using CFD to determine if the data are suitable for validation. This paper provides the findings of the investigations including results for a modified version of the flow field. The investigations include a determination of the extent of the computational domain needed, the best outlet boundary condition to use, the accuracy of the inlet data, application of several turbulence models and the search for the cause of an instability that causes large random excursions of flow variables. It is found that the inlet data measured by PIV are not sufficiently accurate and that the instability is apparently caused by the presence of the first inlet jet which impinges on a recirculation zone.
Grant Hawkes; James O'Brien
2012-06-01
Various three dimensional computational fluid dynamics (CFD) models of solid oxide electrolyzers have been created and analyzed at the Idaho National Laboratory since the inception of the Nuclear Hydrogen Initiative in 2004. Three models presented herein include: a 60 cell planar cross flow with inlet and outlet plenums, 10 cell integrated planar cross flow, and internally manifolded five cell planar cross flow. Mass, momentum, energy, and species conservation and transport are provided via the core features of the commercial CFD code FLUENT. A solid-oxide fuel cell (SOFC) module adds the electrochemical reactions and loss mechanisms and computation of the electric field throughout the cell. The FLUENT SOFC user-defined subroutine was modified for this work to allow for operation in the SOEC mode. Model results provide detailed profiles of temperature, Nernst potential, operating potential, activation over-potential, anode-side gas composition, cathode-side gas composition, current density and hydrogen production over a range of stack operating conditions. Predicted mean outlet hydrogen and steam concentrations vary linearly with current density, as expected. Contour plots of local electrolyte temperature, current density, and Nernst potential indicated the effects of heat transfer, endothermic reaction, Ohmic heating, and change in local gas composition. Results are discussed for using these models in the electrolysis mode. Discussion of thermal neutral voltage, enthalpy of reaction, hydrogen production is reported herein. Contour plots and discussion show areas of likely cell degradation, flow distribution in inlet plenum, and flow distribution across and along the flow channels of the current collectors
Experimental investigation and CFD analysis on cross flow in the core of PMR200
Lee, Jeong -Hun; Yoon, Su -Jong; Cho, Hyoung -Kyu; Jae, Moosung; Park, Goon -Cherl
2015-04-16
The Prismatic Modular Reactor (PMR) is one of the major Very High Temperature Reactor (VHTR) concepts, which consists of hexagonal prismatic fuel blocks and reflector blocks made of nuclear gradegraphite. However, the shape of the graphite blocks could be easily changed by neutron damage duringthe reactor operation and the shape change can create gaps between the blocks inducing the bypass flow.In the VHTR core, two types of gaps, a vertical gap and a horizontal gap which are called bypass gap and cross gap, respectively, can be formed. The cross gap complicates the flow field in the reactor core by connecting the coolant channel to the bypass gap and it could lead to a loss of effective coolant flow in the fuel blocks. Thus, a cross flow experimental facility was constructed to investigate the cross flow phenomena in the core of the VHTR and a series of experiments were carried out under varying flow rates and gap sizes. The results of the experiments were compared with CFD (Computational Fluid Dynamics) analysis results in order to verify its prediction capability for the cross flow phenomena. Fairly good agreement was seen between experimental results and CFD predictions and the local characteristics of the cross flow was discussed in detail. Based on the calculation results, pressure loss coefficient across the cross gap was evaluated, which is necessary for the thermo-fluid analysis of the VHTR core using a lumped parameter code.
Ghobadi, Ahmadreza F.; Elliott, J. Richard
2013-12-21
In this work, we aim to develop a version of the Statistical Associating Fluid Theory (SAFT)-? equation of state (EOS) that is compatible with united-atom force fields, rather than experimental data. We rely on the accuracy of the force fields to provide the relation to experimental data. Although, our objective is a transferable theory of interfacial properties for soft and fused heteronuclear chains, we first clarify the details of the SAFT-? approach in terms of site-based simulations for homogeneous fluids. We show that a direct comparison of Helmholtz free energy to molecular simulation, in the framework of a third order Weeks-Chandler-Andersen perturbation theory, leads to an EOS that takes force field parameters as input and reproduces simulation results for Vapor-Liquid Equilibria (VLE) calculations. For example, saturated liquid density and vapor pressure of n-alkanes ranging from methane to dodecane deviate from those of the Transferable Potential for Phase Equilibria (TraPPE) force field by about 0.8% and 4%, respectively. Similar agreement between simulation and theory is obtained for critical properties and second virial coefficient. The EOS also reproduces simulation data of mixtures with about 5% deviation in bubble point pressure. Extension to inhomogeneous systems and united-atom site types beyond those used in description of n-alkanes will be addressed in succeeding papers.
Fully 3D Multiple Beam Dynamics Processes Simulation for the Fermilab Tevatron
Stern, E.; Amundson, J.; Spentzouris, P; Valishev, A.; /Fermilab
2010-06-01
The Fermilab Tevatron has been, until 2010, the premier high-energy physics collider in the world. The data collected over the last decade by high-energy physics experiments running at the Tevatron have been analyzed to make important measurements in fundamental areas such as B meson masses and flavor oscillation, searches for the Higgs boson, and supersymmetry. Collecting these data at the limits of detectability has required the Tevatron to operate reliably at high beam intensities to maximize the number of collisions to analyze. This impressive achievement has been assisted by the use of HPC resources and software provided through the SciDAC program. This paper describes the enhancements to the BeamBeam3d code to realistically simulate the Tevatron, the validation of these simulations, and the improvement in equipment reliability and personal safety achieved with the aid of simulations.
Smith, P. E.
2003-07-16
The specific aims of the project were: to provide an atomic level description of the interactions between benzene, water and ions in solutions. To determine the degree of association between two benzene molecules in aqueous and salt solutions. To investigate the structure and dynamics of the interface between benzene and water or salt solution.
Hansen, C.; Marklin, G.; Victor, B.; Akcay, C.; Jarboe, T.
2015-04-15
We present simulations of inductive helicity injection in the Helicity Injected Torus with Steady Inductive helicity injection (HIT-SI) device that treats the entire plasma volume in a single dynamic MHD model. A new fully 3D numerical tool, the PSI-center TETrahedral mesh code, was developed that provides the geometric flexibility required for this investigation. Implementation of a zero-? Hall MHD model using PSI-TET will be presented including formulation of a new self-consistent magnetic boundary condition for the wall of the HIT-SI device. Results from simulations of HIT-SI are presented focusing on injector dynamics that are investigated numerically for the first time. Asymmetries in the plasma loading between the two helicity injectors and progression of field reversal in each injector are observed. Analysis indicates cross-coupling between injectors through confinement volume structures. Injector impedance is found to scale with toroidal current at fixed density, consistent with experimental observation. Comparison to experimental data with an injector drive frequency of 14.5 kHz shows good agreement with magnetic diagnostics. Global mode structures from Bi-Orthogonal decomposition agree well with experimental data for the first four modes.
Particle simulation of collision dynamics for ion beam injection into a rarefied gas
Giuliano, Paul N.; Boyd, Iain D.
2013-03-15
This study details a comparison of ion beam simulations with experimental data from a simplified plasma test cell in order to study and validate numerical models and environments representative of electric propulsion devices and their plumes. The simulations employ a combination of the direct simulation Monte Carlo and particle-in-cell methods representing xenon ions and atoms as macroparticles. An anisotropic collision model is implemented for momentum exchange and charge exchange interactions between atoms and ions in order to validate the post-collision scattering behaviors of dominant collision mechanisms. Cases are simulated in which the environment is either collisionless or non-electrostatic in order to prove that the collision models are the dominant source of low- and high-angle particle scattering and current collection within this environment. Additionally, isotropic cases are run in order to show the importance of anisotropy in these collision models. An analysis of beam divergence leads to better characterization of the ion beam, a parameter that requires careful analysis. Finally, suggestions based on numerical results are made to help guide the experimental design in order to better characterize the ion environment.
Jin, Jiaqi; Miller, Jan D.; Dang, Liem X.; Wick, Collin D.
2015-06-01
In the first part of this paper, a Scanning Electron Microscopy and contact angle study of a pyrite surface (100) is reported describing the relationship between surface oxidation and the hydrophilic surface state. In addition to these experimental results, the following simulated surface states were examined using Molecular Dynamics Simulation (MDS): fresh unoxidized (100) surface; polysulfide at the (100) surface; elemental sulfur at the (100) surface. Crystal structures for the polysulfide and elemental sulfur at the (100) surface were simulated using Density Functional Theory (DFT) quantum chemical calculations. The well known oxidation mechanism which involves formation of a metal deficient layer was also described with DFT. Our MDS results of the behavior of interfacial water at the fresh and oxidized pyrite (100) surfaces without/with the presence of ferric hydroxide include simulated contact angles, number density distribution for water, water dipole orientation, water residence time, and hydrogen-bonding considerations. The significance of the formation of ferric hydroxide islands in accounting for the corresponding hydrophilic surface state is revealed not only from experimental contact angle measurements but also from simulated contact angle measurements using MDS. The hydrophilic surface state developed at oxidized pyrite surfaces has been described by MDS, on which basis the surface state is explained based on interfacial water structure. The Division of Chemical Sciences, Geosciences, and Biosciences, Office of Basic Energy Sciences (BES), of the DOE funded work performed by Liem X. Dang. Battelle operates the Pacific Northwest National Laboratory for DOE. The calculations were carried out using computer resources provided by BES.
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Lisal, Martin; Izak, Pavel
2013-07-07
Molecular dynamics simulations of n-hexane adsorbed onto the interface of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([bmim][Tf{sub 2}N]) are performed at three n-hexane surface densities, ranged from 0.7 to 2.3 {mu}mol/m{sup 2} at 300 K. For [bmim][Tf{sub 2}N] room-temperature ionic liquid, we use a non-polarizable all-atom force field with the partial atomic charges based on ab initio calculations for the isolated ion pair. The net charges of the ions are {+-}0.89e, which mimics the anion to cation charge transfer and polarization effects. The OPLS-AA force field is employed for modeling of n-hexane. The surface tension is computed using the mechanical route and its value decreases with increase of the n-hexane surface density. The [bmim][Tf{sub 2}N]/n-hexane interface is analyzed using the intrinsic method, and the structural and dynamic properties of the interfacial, sub-interfacial, and central layers are computed. We determine the surface roughness, global and intrinsic density profiles, and orientation ordering of the molecules to describe the structure of the interface. We further compute the survival probability, normal and lateral self-diffusion coefficients, and re-orientation correlation functions to elucidate the effects of n-hexane on dynamics of the cations and anions in the layers.
Mass transport properties of Pu/DT mixtures from orbital free molecular dynamics simulations
Kress, Joel David; Ticknor, Christopher; Collins, Lee A.
2015-09-16
Mass transport properties (shear viscosity and diffusion coefficients) for Pu/DT mixtures were calculated with Orbital Free Molecular Dynamics (OFMD). The results were fitted to simple functions of mass density (for ρ=10.4 to 62.4 g/cm^{3}) and temperature (for T=100 up to 3,000 eV) for Pu/DT mixtures consisting of 100/0, 25/75, 50/50, and 75/25 by number.
Predictive Simulation and Design of Materials by Quasicontinuum and Accelerated Dynamics Methods
Luskin, Mitchell; James, Richard; Tadmor, Ellad
2014-03-30
This project developed the hyper-QC multiscale method to make possible the computation of previously inaccessible space and time scales for materials with thermally activated defects. The hyper-QC method combines the spatial coarse-graining feature of a finite temperature extension of the quasicontinuum (QC) method (aka “hot-QC”) with the accelerated dynamics feature of hyperdynamics. The hyper-QC method was developed, optimized, and tested from a rigorous mathematical foundation.
Fanourgakis, Georgios S.; Tipparaju, Vinod; Nieplocha, Jarek; Xantheas, Sotiris S.
2007-01-01
An efficient parallelization scheme for classical Molecular Dynamics simulations with flexible polarizable empirical potentials is presented. It is based on the standard Ewald summation technique to handle the long-range electrostatic and induction interactions. The algorithm for this parallelization scheme is designed for systems containing several thousands of polarizable sites in the simulation box. Its performance is evaluated during Molecular Dynamics simulations under periodic boundary conditions with unit cell sizes ranging from 128-512 water molecules employing two exible, polarizable water models [POL1(F) and TTM2-F] containing 1 and 3 polarizable sites respectively. The efficiency of the algorithm, is evaluated against a flexible, pairwise-additive water model (TIP4F). The benchmarks were performed on both shared and distributed memory platforms. As a result of the efficient calculations of the induced dipole moments, a superlinear scaling as a function of the number of the processors is observed in several cases. To the best of our knowledge, this is the first attempt for a parallel implementation of a polarizable potential under periodic boundary conditions. Guidelines for adapting the algorithm for larger systems are also discussed. This research was performed in part using the Molecular Science Computing Facility (MSCF) in the William R. Wiley Environmental Molecular Sciences laboratory, a national scientific user facility sponsored by the U.S. Department of Energys Office of Biological and Environmental Research located at the Pacific Northwest National Laboratory. The Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy under contract DE-AC05-76RL01830.
1D GAS-DYNAMIC SIMULATION OF SHOCK-WAVE PROCESSES VIA INTERNET
Khishchenko, K. V.; Levashov, P. R.; Povarnitsyn, M. E.; Zakharenkov, A. S.
2009-12-28
We present a Web-interface for 1D simulation of different shock-wave experiments. The choosing of initial parameters, the modeling itself and output data treatment can be made directly via the Internet. The interface is based upon the expert system on shock-wave data and equations of state and contains both the Eulerian and Lagrangian Godunov hydrocodes. The availability of equations of state for a broad set of substances makes this system a useful tool for planning and interpretation of shock-wave experiments. As an example of simulation with the system, results of modeling of multistep shock loading of potassium between polytetrafluoroethylene and stainless steel plates are presented in comparison with experimental data from Shakhray et al.(2005).
Stadler, Michael; Kranzl, Lukas; Huber, Claus; Haas, Reinhard; Tsioliaridou, Elena
2006-05-01
The European Union has established a number of targetsregarding energy efficiency, Renewable Energy Sources (RES) and CO2reductions as the 'GREEN PAPER on Energy Efficiency', the Directive for'promotion of the use of bio-fuels or other renewable fuels fortransport' or 'Directive of the European Parliament of the Council on thepromotion of cogeneration based on a useful heat demand in the internalenergy market'. A lot of the according RES and RUE measures are notattractive for investors from an economic point of view. Thereforegovernmentsall over the world have to spend public money to promotethese technologies/measures to bring them into market. These expenditureshave to be adjusted to budget concerns and should be spent mostefficiently. Therefore, the spent money has to be dedicated totechnologies and efficiency measures with the best yield in CO2 reductionwithout wasting money. The core question: "How can public money - forpromoting sustainable energy systems - be spent most efficiently toreduce GHG-emissions?" has been well investigated by the European projectInvert. In course of this project a simulation tool has been designed toanswer this core question. This paper describes the modelling with theInvert simulation tool and shows the key features necessary forsimulating the energy system. A definition of 'Promotion SchemeEfficiency' is given which allows estimating the most cost effectivetechnologies and/or efficiency measures to reduce CO2 emissions.Investigations performed with the Invert simulation tool deliver anoptimum portfolio mix of technologies and efficiency measures for eachselected region. Within Invert seven European regions were simulated andfor the Austrian case study the detailed portfolio mix is shown andpolitical conclusions are derived.
Zhuchenko, S. V.
2014-11-12
This report presents a PC-based program for solution gas dynamics and heat exchange mathematical tasks in fuel assemblies of the fast-neutron nuclear reactors. A fuel assembly consisting of bulk heat-generating elements, which are integrated together by the system of supply and pressure manifolds, is examined. Spherical heat-generating microelements, which contain nuclear fuel, are pulled into the heat-generating elements. Gaseous coolant proceed from supply manifolds to heat-generating elements, where it withdraws the nuclear reaction heat and assembles in pressure manifolds.
L3:THM.CFD.P6.02 Hydra-TH Milestone Report Yidong Xia and Hong Luo
U.S. Department of Energy (DOE) all webpages (Extended Search)
Milestone Report Yidong Xia and Hong Luo North Carolina State University March 31, 2013 CASL-8-2013-0324-000 CASL-U-2013-0324-000 Hydra-TH Milestone Report (L3:THM.CFD.P6.02) Yidong Xia and Hong Luo Computational Fluid Dynamics Laboratory Department of Mechanical and Aerospace Engineering North Carolina State University Engineering Bldg 3, Campus Box 7910 Raleigh, NC 27695-7910 Jozsef Bakosi, Mark A. Christon and Lori Pritchett-Sheats Computational Physics and Methods, CCS-2 Los Alamos National
L3:THM.CFD.P7.02 Hydra-TH Milestone Report Yidong Xia, Hong Luo,
U.S. Department of Energy (DOE) all webpages (Extended Search)
2 Hydra-TH Milestone Report Yidong Xia, Hong Luo, Jozsef Bakosi, Mark Christon, Lori Pritchett-Sheats NCSU, LANL September 30, 2013 CASL-8-2013-0198-000 Hydra-TH Milestone Report (L3:THM.CFD.P7.02) Yidong Xia and Hong Luo Computational Fluid Dynamics Laboratory Department of Mechanical and Aerospace Engineering North Carolina State University Engineering Bldg 3, Campus Box 7910 Raleigh, NC 27695-7910 Jozsef Bakosi, Mark A. Christon and Lori Pritchett-Sheats Computational Physics and Methods,
Simulative research on the anode plasma dynamics in the high-power electron beam diode
Cai, Dan; Liu, Lie; Ju, Jin-Chuan; Zhang, Tian-Yang; Zhao, Xue-Long; Zhou, Hong-Yu
2015-07-15
Anode plasma generated by electron beams could limit the electrical pulse-length, modify the impedance and stability of diode, and affect the generator to diode power coupling. In this paper, a particle-in-cell code is used to study the dynamics of anode plasma in the high-power electron beam diode. The effect of gas type, dynamic characteristic of ions on the diode operation with bipolar flow model are presented. With anode plasma appearing, the amplitude of diode current is increased due to charge neutralizations of electron flow. The lever of neutralization can be expressed using saturation factor. At same pressure of the anode gas layer, the saturation factor of CO{sub 2} is bigger than the H{sub 2}O vapor, namely, the generation rate of C{sup +} ions is larger than the H{sup +} ions at the same pressure. The transition time of ions in the anode-cathode gap could be used to estimate the time of diode current maximum.
Simulation study of dynamic aperture with head-on beam-beam compensation in the RHIC
Luo, Y.; Fischer, W.
2010-08-01
In this note we summarize the calculated 10{sup 6} turn dynamic apertures with the proposed head-on beam-beam compensation in the Relativistic Heavy Ion Collider (RHIC). To compensate the head-on beam-beam effect in the RHIC 250 GeV polarized proton run, we are planning to introduce a DC electron beam with the same transverse profile as the proton beam to collide with the proton beam. Such a device to provide the electron beam is called an electron lens (e-lens). In this note we first present the optics and beam parameters and the tracking setup. Then we compare the calculated dynamic apertures without and with head-on beam-beam compensation. The effects of adjusted phase advances between IP8 and the center of e-lens and second order chromaticity correction are checked. In the end we will scan the proton and electron beam parameters with head-on beam-beam compensation.
Using a dynamic point-source percolation model to simulate bubble growth.
Zimmerman, Jonathan A.; Zeigler, David A.; Cowgill, Donald F.
2004-05-01
Accurate modeling of nucleation, growth and clustering of helium bubbles within metal tritide alloys is of high scientific and technological importance. Of interest is the ability to predict both the distribution of these bubbles and the manner in which these bubbles interact at a critical concentration of helium-to-metal atoms to produce an accelerated release of helium gas. One technique that has been used in the past to model these materials, and again revisited in this research, is percolation theory. Previous efforts have used classical percolation theory to qualitatively and quantitatively model the behavior of interstitial helium atoms in a metal tritide lattice; however, higher fidelity models are needed to predict the distribution of helium bubbles and include features that capture the underlying physical mechanisms present in these materials. In this work, we enhance classical percolation theory by developing the dynamic point-source percolation model. This model alters the traditionally binary character of site occupation probabilities by enabling them to vary depending on proximity to existing occupied sites, i.e. nucleated bubbles. This revised model produces characteristics for one and two dimensional systems that are extremely comparable with measurements from three dimensional physical samples. Future directions for continued development of the dynamic model are also outlined.
Numerical simulation of cathode plasma dynamics in magnetically insulated vacuum transmission lines
Thoma, C.; Genoni, T. C.; Welch, D. R.; Rose, D. V.; Clark, R. E.; Miller, C. L.; Stygar, W. A.; Kiefer, M. L.
2015-03-15
A novel algorithm for the simulation of cathode plasmas in particle-in-cell codes is described and applied to investigate cathode plasma evolution in magnetically insulated transmission lines (MITLs). The MITL electron sheath is modeled by a fully kinetic electron species. Electron and ion macroparticles, both modeled as fluid species, form a dense plasma which is initially localized at the cathode surface. Energetic plasma electron particles can be converted to kinetic electrons to resupply the electron flux at the plasma edge (the “effective” cathode). Using this model, we compare results for the time evolution of the cathode plasma and MITL electron flow with a simplified (isothermal) diffusion model. Simulations in 1D show a slow diffusive expansion of the plasma from the cathode surface. But in multiple dimensions, the plasma can expand much more rapidly due to anomalous diffusion caused by an instability due to the strong coupling of a transverse magnetic mode in the electron sheath with the expanding resistive plasma layer.
Koizumi, Kenichi; Nobusada, Katsuyuki; Boero, Mauro
2015-12-31
Ab initio molecular dynamics simulations have been used to inspect the adsorption of O{sub 2} to a small gold-copper alloy cluster supported on graphene. The exposed Cu atom in this cluster acts as a crucial attractive site for the approaching of O{sub 2} and consequently widens the reaction channel for the adsorption process. Conversely, a pure Au cluster on the same graphene support is inactive for the O{sub 2} adsorption because the corresponding reaction channel for the adsorption is very narrow. These results clearly indicate that doping a different metal to the Au cluster is a way to enhance the oxygen adsorption and to promote catalytic reactions.
Dislocation Dynamics Simulations of Junctions in Hexagonal Close-Packed Crystals
Wu, C; Aubry, S; Chung, P; Arsenlis, A
2011-12-05
The formation and strength of dislocations in the hexagonal closed packed material beryllium are studied through dislocation junctions and the critical stress required to break them. Dislocation dynamics calculations (using the code ParaDiS) of junction maps are compared to an analytical line tension approximation in order to validate our model. Results show that the two models agree very well. Also the critical shear stress necessary to break 30{sup o} - 30{sup o} and 30{sup o} - 90{sup o} dislocation junctions is computed numerically. Yield surfaces are mapped out for these junctions to describe their stability regions as function of resolved shear stresses on the glide planes. The example of two non-coplanar binary dislocation junctions with slip planes [2-1-10] (01-10) and [-12-10] (0001) corresponding to a prismatic and basal slip respectively is chosen to verify and validate our implementation.
Considering value of information when using CFD in design
Misra, John Satprim
2009-12-19
This thesis presents an approach to find lower resolution CFD models that can accurately lead a designer to a correct decision at a lower computational cost. High-fidelity CFD models often contain too much information and come at a higher computational cost, limiting the designs a designer can test and how much optimization can be performed on the design. Lower model resolution is commonly used to reduce computational time. However there are no clear guidelines on how much model accuracy is required. Instead experience and intuition are used to select an appropriate lower resolution model. This thesis presents an alternative to this ad hoc method by considering the added value of the addition information provided by increasing accurate and more computationally expensive models.
Bai, Xue-Ning
2015-01-10
We perform three-dimensional stratified shearing-box magnetohydrodynamic (MHD) simulations on the gas dynamics of protoplanetary disks with a net vertical magnetic flux of B {sub z0}. All three nonideal MHD effects, Ohmic resistivity, the Hall effect, and ambipolar diffusion, are included in a self-consistent manner based on equilibrium chemistry. We focus on regions toward outer disk radii, from 5 to 60 AU, where Ohmic resistivity tends to become negligible, ambipolar diffusion dominates over an extended region across the disk height, and the Hall effect largely controls the dynamics near the disk midplane. We find that at around R = 5 AU the system launches a laminar or weakly turbulent magnetocentrifugal wind when the net vertical field B {sub z0} is not too weak. Moreover, the wind is able to achieve and maintain a configuration with reflection symmetry at the disk midplane. The case with anti-aligned field polarity (Ω⋅B{sub z0}<0) is more susceptible to the magnetorotational instability (MRI) when B {sub z0} decreases, leading to an outflow oscillating in radial directions and very inefficient angular momentum transport. At the outer disk around and beyond R = 30 AU, the system shows vigorous MRI turbulence in the surface layer due to far-UV ionization, which efficiently drives disk accretion. The Hall effect affects the stability of the midplane region to the MRI, leading to strong/weak Maxwell stress for aligned/anti-aligned field polarities. Nevertheless, the midplane region is only very weakly turbulent in both cases. Overall, the basic picture is analogous to the conventional layered accretion scenario applied to the outer disk. In addition, we find that the vertical magnetic flux is strongly concentrated into thin, azimuthally extended shells in most of our simulations beyond 15 AU, leading to enhanced radial density variations know as zonal flows. Theoretical implications and observational consequences are briefly discussed.
Fu, Yao E-mail: jhsong@cec.sc.edu; Song, Jeong-Hoon E-mail: jhsong@cec.sc.edu
2014-08-07
Hardy stress definition has been restricted to pair potentials and embedded-atom method potentials due to the basic assumptions in the derivation of a symmetric microscopic stress tensor. Force decomposition required in the Hardy stress expression becomes obscure for multi-body potentials. In this work, we demonstrate the invariance of the Hardy stress expression for a polymer system modeled with multi-body interatomic potentials including up to four atoms interaction, by applying central force decomposition of the atomic force. The balance of momentum has been demonstrated to be valid theoretically and tested under various numerical simulation conditions. The validity of momentum conservation justifies the extension of Hardy stress expression to multi-body potential systems. Computed Hardy stress has been observed to converge to the virial stress of the system with increasing spatial averaging volume. This work provides a feasible and reliable linkage between the atomistic and continuum scales for multi-body potential systems.
Test Cases for Wind Power Plant Dynamic Models on Real-Time Digital Simulator: Preprint
Singh, M.; Muljadi, E.; Gevorgian, V.
2012-06-01
The objective of this paper is to present test cases for wind turbine generator and wind power plant models commonly used during commissioning of wind power plants to ensure grid integration compatibility. In this paper, different types of wind power plant models based on the Western Electricity Coordinating Council Wind Generator Modeling Group's standardization efforts are implemented on a real-time digital simulator, and different test cases are used to gauge their grid integration capability. The low-voltage ride through and reactive power support capability and limitations of wind turbine generators under different grid conditions are explored. Several types of transient events (e.g., symmetrical and unsymmetrical faults, frequency dips) are included in the test cases. The differences in responses from different types of wind turbine are discussed in detail.
A Scalable O(N) Algorithm for Large-Scale Parallel First-Principles Molecular Dynamics Simulations
Osei-Kuffuor, Daniel; Fattebert, Jean-Luc
2014-01-01
Traditional algorithms for first-principles molecular dynamics (FPMD) simulations only gain a modest capability increase from current petascale computers, due to their O(N^{3}) complexity and their heavy use of global communications. To address this issue, we are developing a truly scalable O(N) complexity FPMD algorithm, based on density functional theory (DFT), which avoids global communications. The computational model uses a general nonorthogonal orbital formulation for the DFT energy functional, which requires knowledge of selected elements of the inverse of the associated overlap matrix. We present a scalable algorithm for approximately computing selected entries of the inverse of the overlap matrix, based on an approximate inverse technique, by inverting local blocks corresponding to principal submatrices of the global overlap matrix. The new FPMD algorithm exploits sparsity and uses nearest neighbor communication to provide a computational scheme capable of extreme scalability. Accuracy is controlled by the mesh spacing of the finite difference discretization, the size of the localization regions in which the electronic orbitals are confined, and a cutoff beyond which the entries of the overlap matrix can be omitted when computing selected entries of its inverse. We demonstrate the algorithm's excellent parallel scaling for up to O(100K) atoms on O(100K) processors, with a wall-clock time of O(1) minute per molecular dynamics time step.
Colvin, J D; Minich, R W; Kalantar, D H
2007-03-29
The recent diagnostic capability of the Omega laser to study solid-solid phase transitions at pressures greater than 10 GPa and at strain rates exceeding 10{sup 7} s{sup -1} has also provided valuable information on the dynamic elastic-plastic behavior of materials. We have found, for example, that plasticity kinetics modifies the effective loading and thermodynamic paths of the material. In this paper we derive a kinetics equation for the time-dependent plastic response of the material to dynamic loading, and describe the model's implementation in a radiation-hydrodynamics computer code. This model for plasticity kinetics incorporates the Gilman model for dislocation multiplication and saturation. We discuss the application of this model to the simulation of experimental velocity interferometry data for experiments on Omega in which Fe was shock compressed to pressures beyond the {alpha}-to-{var_epsilon} phase transition pressure. The kinetics model is shown to fit the data reasonably well in this high strain rate regime and further allows quantification of the relative contributions of dislocation multiplication and drag. The sensitivity of the observed signatures to the kinetics model parameters is presented.
Lísal, Martin
2013-12-07
We present molecular-level insight into the liquid/gas interface of two chiral room-temperature ionic liquids (RTILs) derived from 1-n-butyl-3-methylimidazolium bromide ([bmim][Br]); namely, (R)-1-butyl-3-(3-hydroxy-2-methylpropyl)imidazolium bromide (hydroxypropyl) and 1-butyl-3-[(1R)-nopyl]imidazolium bromide (nopyl). We use our currently developed force field which was validated against the experimental bulk density, heat of vaporization, and surface tension of [bmim][Br]. The force field for the RTILs adopts the Chemistry at Harvard Molecular Mechanics (CHARMM) parameters for the intramolecular and repulsion-dispersion interactions along with the reduced partial atomic charges based on ab initio calculations. The net charges of the ions are around ±0.8e, which mimic the anion to cation charge transfer and many-body effects. Molecular dynamics simulations in the slab geometry combined with the intrinsic interface analysis are employed to provide a detailed description of the RTIL/gas interface in terms of the structural and dynamic properties of the interfacial, sub-interfacial, and central layers at a temperature of 300 K. The focus is on the comparison of the liquid/gas interface for the chiral RTILs with the interface for parent [bmim][Br]. The structure of the interface is elucidated by evaluating the surface roughness, intrinsic atomic density profiles, and orientation ordering of the cations. The dynamics of the ions at the interfacial region is characterized by computing the survival probability, and normal and lateral self-diffusion coefficients in the layers.
Oladosu, Gbadebo A; Kline, Keith L
2013-01-01
The global indirect land use change (ILUC) implications of biofuel use in the United States of America (USA) from 2001 to 2010 are evaluated with a dynamic general equilibrium model. The effects of biofuels production on agricultural land area vary by year; from a net expansion of 0.17 ha per 1000 gallons produced (2002) to a net contraction of 0.13 ha per 1000 gallons (2018) in Case 1 of our simulation. In accordance with the general narrative about the implications of biofuel policy, agricultural land area increased in many regions of the world. However, oil-export dependent economies experienced agricultural land contraction because of reductions in their revenues. Reducing crude oil imports is a major goal of biofuel policy, but the land use change implications have received little attention in the literature. Simulations evaluating the effects of doubling supply elasticities for land and fossil resources show that these parameters can significantly influence the land use change estimates. Therefore, research that provides empirically-based and spatially-detailed agricultural land-supply curves and capability to project future fossil energy prices is critical for improving estimates of the effects of biofuel policy on land use.
de Almeida, Valmor F; Cui, Shengting; Khomami, Bamin
2014-01-01
Molecular dynamics simulations of tri-n-butyl-phosphate (TBP)/n-dodecane mixture in the liquid phase have been carried out using two recently developed TBP force field models (J. Phys. Chem. B 2012, 116, 305) in combination with the all-atom optimized potentials for liquid simulations (OPLS-AA) force field model for n-dodecane. Specifically, the electric dipole moment of TBP, mass density of the mixture, and the excess volume of mixing were computed with TBP mole fraction ranging from 0 to 1. It is found that the aforementioned force field models accurately predict the mass density of the mixture in the entire mole fraction range. Commensurate with experimental measurements, the electric dipole moment of the TBP was found to slightly increase with the mole fraction of TBP in the mixture. Also, in accord with experimental data, the excess volume of mixing is positive in the entire mole fraction range, peaking at TBP mole fraction range 0.3 0.5. Finally, a close examination of the spatial pair correlation functions between TBP molecules, and between TBP and n-dodecane molecules, revealed formation of TBP dimers through self-association at close distance, a phenomenon with ample experimental evidence.
Mabuchi, Takuya; Tokumasu, Takashi
2014-09-14
We have performed a detailed analysis of the structural properties of the sulfonate groups in terms of isolated and overlapped solvation shells in the nanostructure of hydrated Nafion membrane using classical molecular dynamics simulations. Our simulations have demonstrated the correlation between the two different areas in bound water region, i.e., the first solvation shell, and the vehicular transport of hydronium ions at different water contents. We have employed a model of the Nafion membrane using the improved force field, which is newly modified and validated by comparing the density and water diffusivity with those obtained experimentally. The first solvation shells were classified into the two types, the isolated area and the overlapped area. The mean residence times of solvent molecules explicitly showed the different behaviors in each of those areas in terms of the vehicular transport of protons: the diffusivity of classical hydronium ions in the overlapped area dominates their total diffusion at lower water contents while that in the isolated area dominates for their diffusion at higher water contents. The results provided insights into the importance role of those areas in the solvation shells for the diffusivity of vehicular transport of hydronium ions in hydrated Nafion membrane.
Parkes, Marie V.; Demir, Hakan; Teich-McGoldrick, Stephanie L.; Sholl, David S.; Greathouse, Jeffery A.; Allendorf, Mark D.
2014-03-28
Molecular dynamics simulations were used to investigate trends in noble gas (Ar, Kr, Xe) diffusion in the metal-organic frameworks HKUST-1 and ZIF-8. Diffusion occurs primarily through inter-cage jump events, with much greater diffusion of guest atoms in HKUST-1 compared to ZIF-8 due to the larger cage and window sizes in the former. We compare diffusion coefficients calculated for both rigid and flexible frameworks. For rigid framework simulations, in which the framework atoms were held at their crystallographic or geometry optimized coordinates, sometimes dramatic differences in guest diffusion were seen depending on the initial framework structure or the choice of framework force field parameters. When framework flexibility effects were included, argon and krypton diffusion increased significantly compared to rigid-framework simulations using general force field parameters. Additionally, for argon and krypton in ZIF-8, guest diffusion increased with loading, demonstrating that guest-guest interactions between cages enhance inter-cage diffusion. No inter-cage jump events were seen for xenon atoms in ZIF-8 regardless of force field or initial structure, and the loading dependence of xenon diffusion in HKUST-1 is different for rigid and flexible frameworks. Diffusion of krypton and xenon in HKUST-1 depends on two competing effects: the steric effect that decreases diffusion as loading increases, and the “small cage effect” that increases diffusion as loading increases. Finally, a detailed analysis of the window size in ZIF-8 reveals that the window increases beyond its normal size to permit passage of a (nominally) larger krypton atom.
Parkes, Marie V.; Demir, Hakan; Teich-McGoldrick, Stephanie L.; Sholl, David S.; Greathouse, Jeffery A.; Allendorf, Mark D.
2014-03-28
Molecular dynamics simulations were used to investigate trends in noble gas (Ar, Kr, Xe) diffusion in the metal-organic frameworks HKUST-1 and ZIF-8. Diffusion occurs primarily through inter-cage jump events, with much greater diffusion of guest atoms in HKUST-1 compared to ZIF-8 due to the larger cage and window sizes in the former. We compare diffusion coefficients calculated for both rigid and flexible frameworks. For rigid framework simulations, in which the framework atoms were held at their crystallographic or geometry optimized coordinates, sometimes dramatic differences in guest diffusion were seen depending on the initial framework structure or the choice of frameworkmore » force field parameters. When framework flexibility effects were included, argon and krypton diffusion increased significantly compared to rigid-framework simulations using general force field parameters. Additionally, for argon and krypton in ZIF-8, guest diffusion increased with loading, demonstrating that guest-guest interactions between cages enhance inter-cage diffusion. No inter-cage jump events were seen for xenon atoms in ZIF-8 regardless of force field or initial structure, and the loading dependence of xenon diffusion in HKUST-1 is different for rigid and flexible frameworks. Diffusion of krypton and xenon in HKUST-1 depends on two competing effects: the steric effect that decreases diffusion as loading increases, and the “small cage effect” that increases diffusion as loading increases. Finally, a detailed analysis of the window size in ZIF-8 reveals that the window increases beyond its normal size to permit passage of a (nominally) larger krypton atom.« less
Swaminarayan, Sriram; Germann, Timothy C; Kadau, Kai; Fossum, Gordon C
2008-01-01
The authors present timing and performance numbers for a short-range parallel molecular dynamics (MD) code, SPaSM, that has been rewritten for the heterogeneous Roadrunner supercomputer. Each Roadrunner compute node consists of two AMD Opteron dual-core microprocessors and four PowerXCell 8i enhanced Cell microprocessors, so that there are four MPI ranks per node, each with one Opteron and one Cell. The interatomic forces are computed on the Cells (each with one PPU and eight SPU cores), while the Opterons are used to direct inter-rank communication and perform I/O-heavy periodic analysis, visualization, and checkpointing tasks. The performance measured for our initial implementation of a standard Lennard-Jones pair potential benchmark reached a peak of 369 Tflop/s double-precision floating-point performance on the full Roadrunner system (27.7% of peak), corresponding to 124 MFlop/Watt/s at a price of approximately 3.69 MFlops/dollar. They demonstrate an initial target application, the jetting and ejection of material from a shocked surface.
3D CFD Model of High Temperature H2O/CO2 Co-electrolysis
Grant Hawkes; James O'Brien; Carl Stoots; Stephen Herring; Joe Hartvigsen
2007-06-01
3D CFD Model of High Temperature H2O/CO2 Co-Electrolysis Grant Hawkes1, James O’Brien1, Carl Stoots1, Stephen Herring1 Joe Hartvigsen2 1 Idaho National Laboratory, Idaho Falls, Idaho, grant.hawkes@inl.gov 2 Ceramatec Inc, Salt Lake City, Utah INTRODUCTION A three-dimensional computational fluid dynamics (CFD) model has been created to model high temperature co-electrolysis of steam and carbon dioxide in a planar solid oxide electrolyzer (SOE) using solid oxide fuel cell technology. A research program is under way at the Idaho National Laboratory (INL) to simultaneously address the research and scale-up issues associated with the implementation of planar solid-oxide electrolysis cell technology for syn-gas production from CO2 and steam. Various runs have been performed under different run conditions to help assess the performance of the SOE. This paper presents CFD results of this model compared with experimental results. The Idaho National Laboratory (INL), in conjunction with Ceramatec Inc. (Salt Lake City, USA) has been researching for several years the use of solid-oxide fuel cell technology to electrolyze steam for large-scale nuclear-powered hydrogen production. Now, an experimental research project is underway at the INL to produce syngas by simultaneously electrolyzing at high-temperature steam and carbon dioxide (CO2) using solid oxide fuel cell technology. A strong interest exists in the large-scale production of syn-gas from CO2 and steam to be reformed into a usable transportation fuel. If biomass is used as the carbon source, the overall process is climate neutral. Consequently, there is a high level of interest in production of syn-gas from CO2 and steam electrolysis. With the price of oil currently around $60 / barrel, synthetically-derived hydrocarbon fuels (synfuels) have become economical. Synfuels are typically produced from syngas – hydrogen (H2) and carbon monoxide (CO) -- using the Fischer-Tropsch process, discovered by Germany before World
Use of a dynamic simulation model to understand nitrogen cycling in the middle Rio Grande, NM.
Meixner, Tom; Tidwell, Vincent Carroll; Oelsner, Gretchen; Brooks, Paul; Roach, Jesse D.
2008-08-01
Water quality often limits the potential uses of scarce water resources in semiarid and arid regions. To best manage water quality one must understand the sources and sinks of both solutes and water to the river system. Nutrient concentration patterns can identify source and sink locations, but cannot always determine biotic processes that affect nutrient concentrations. Modeling tools can provide insight into these large-scale processes. To address questions about large-scale nitrogen removal in the Middle Rio Grande, NM, we created a system dynamics nitrate model using an existing integrated surface water--groundwater model of the region to evaluate our conceptual models of uptake and denitrification as potential nitrate removal mechanisms. We modeled denitrification in groundwater as a first-order process dependent only on concentration and used a 5% denitrification rate. Uptake was assumed to be proportional to transpiration and was modeled as a percentage of the evapotranspiration calculated within the model multiplied by the nitrate concentration in the water being transpired. We modeled riparian uptake as 90% and agricultural uptake as 50% of the respective evapotranspiration rates. Using these removal rates, our model results suggest that riparian uptake, agricultural uptake and denitrification in groundwater are all needed to produce the observed nitrate concentrations in the groundwater, conveyance channels, and river as well as the seasonal concentration patterns. The model results indicate that a total of 497 metric tons of nitrate-N are removed from the Middle Rio Grande annually. Where river nitrate concentrations are low and there are no large nitrate sources, nitrate behaves nearly conservatively and riparian and agricultural uptake are the most important removal mechanisms. Downstream of a large wastewater nitrate source, denitrification and agricultural uptake were responsible for approximately 90% of the nitrogen removal.
Fluid dynamic studies for a simulated Melton Valley Storage Tank slurry
Hylton, T.D.; Youngblood, E.L.; Cummins, R.L.
1994-07-01
The Melton Valley Storage Tanks (MVSTs), are used for the collection and storage of remote-handled radioactive liquid wastes. These wastes, which were typically acidic when generated, were neutralized with the addition of sodium hydroxide to protect the storage tanks from corrosion, but this caused the transuranic and heavy metals to precipitate. These wastes will eventually need to be removed from the tanks for ultimate disposal. The objective of the research activities discussed in this report is to support the design of a pipeline transport system between the MVSTs and a treatment facility. Since the wastes in the MVSTs are highly radioactive, a surrogate slurry was developed for this study. Rheological properties of the simulated slurry were determined in a test loop in which the slurry was circulated through three pipeline viscometers of different diameters. Pressure drop data at varying flow rates were used to obtain shear stress and shear rate data. The data were analyzed, and the slurry rheological properties were analyzed by the Power Law model and the Bingham plastic model. The plastic viscosity and yield stress data obtained from the rheological tests were used as inputs for a piping design software package, and the pressure drops predicted by the software compared well with the pressure drop data obtained from the test loop. The minimum transport velocity was determine for the slurry by adding known nominal sizes of glass spheres to the slurry. However, it was shown that the surrogate slurry exhibited hindered settling, which may substantially decrease the minimum transport velocity. Therefore, it may be desired to perform additional tests with a surrogate with a lower concentration of suspended solids to determine the minimum transport velocity.
Grant L. Hawkes; James E. O'Brien; Greg Tao
2011-11-01
A three-dimensional computational fluid dynamics (CFD) electrochemical model has been created to model high-temperature electrolysis cell performance and steam electrolysis in an internally manifolded planar solid oxide electrolysis cell (SOEC) stack. This design is being evaluated at the Idaho National Laboratory for hydrogen production from nuclear power and process heat. Mass, momentum, energy, and species conservation and transport are provided via the core features of the commercial CFD code FLUENT. A solid-oxide fuel cell (SOFC) model adds the electrochemical reactions and loss mechanisms and computation of the electric field throughout the cell. The FLUENT SOFC user-defined subroutine was modified for this work to allow for operation in the SOEC mode. Model results provide detailed profiles of temperature, operating potential, steam-electrode gas composition, oxygen-electrode gas composition, current density and hydrogen production over a range of stack operating conditions. Single-cell and five-cell results will be presented. Flow distribution through both models is discussed. Flow enters from the bottom, distributes through the inlet plenum, flows across the cells, gathers in the outlet plenum and flows downward making an upside-down ''U'' shaped flow pattern. Flow and concentration variations exist downstream of the inlet holes. Predicted mean outlet hydrogen and steam concentrations vary linearly with current density, as expected. Effects of variations in operating temperature, gas flow rate, oxygen-electrode and steam-electrode current density, and contact resistance from the base case are presented. Contour plots of local electrolyte temperature, current density, and Nernst potential indicate the effects of heat transfer, reaction cooling/heating, and change in local gas composition. Results are discussed for using this design in the electrolysis mode. Discussion of thermal neutral voltage, enthalpy of reaction, hydrogen production, cell thermal
Simulation of FCC riser flow with multiphase heat transfer and cracking reactions.
Chang, S. L.; Zhou, C. Q.; Energy Systems
2003-08-01
A validated Computational Fluid Dynamics (CFD) code ICRKFLO was developed for simulations of three-dimensional three-phase reacting flows in Fluid Catalytic Cracking (FCC) riser reactors. It calculates the product yields based on local flow properties by solving the fundamental conservation principles of mass, momentum, and energy for the flow properties associated with the gas, liquid, and solid phases. Unique phenomenological models and numerical techniques were developed specifically for the FCC flow simulation. The models include a spray vaporization model, a particle-solid interaction model, and an interfacial heat transfer model. The numerical techniques include a time-integral approach to overcome numerical stiffness problems in chemical kinetics rate calculations and a hybrid hydrodynamic-kinetic treatment to facilitate detailed kinetics calculations of cracking reactions. ICRKFLO has been validated with extensive test data from two pilot and one commercial FCC units. It is proven to be useful for advanced development of FCC riser reactors.
Bennion, Brian J.; Essiz, Sebnem G.; Lau, Edmond Y.; Fattebert, Jean -Luc; Emigh, Aiyana; Lightstone, Felice C.; Salsbury , Jr, Freddie
2015-04-13
Irreversible inactivation of human acetylcholinesterase (hAChE) by organophosphorous pesticides (OPs) and chemical weapon agents (CWA) has severe morbidity and mortality consequences. We present data from quantum mechanics/molecular mechanics (QM/MM) and 80 classical molecular dynamics (MD) simulations of the apo and soman-adducted forms of hAChE to investigate the effects on the dynamics and protein structure when the catalytic Serine 203 is phosphonylated. We find that the soman phosphonylation of the active site Ser203 follows a water assisted addition-elimination mechanism with the elimination of the fluoride ion being the highest energy barrier at 6.5 kcal/mole. We observe soman-dependent changes in backbone and sidechain motions compared to the apo form of the protein. These alterations restrict the soman-adducted hAChE to a structural state that is primed for the soman adduct to be cleaved and removed from the active site. The altered motions and resulting structures provide alternative pathways into and out of the hAChE active site. In the soman-adducted protein both side and back door pathways are viable for soman adduct access. Correlation analysis of the apo and soman adducted MD trajectories shows that the correlation of gorge entrance and back door motion is disrupted when hAChE is adducted. This supports the hypothesis that substrate and product can use two different pathways as entry and exit sites in the apo form of the protein. These alternative pathways have important implications for the rational design of medical countermeasures.
Bennion, Brian J.; Essiz, Sebnem G.; Lau, Edmond Y.; Fattebert, Jean -Luc; Emigh, Aiyana; Lightstone, Felice C.; Salsbury , Jr, Freddie
2015-04-13
Irreversible inactivation of human acetylcholinesterase (hAChE) by organophosphorous pesticides (OPs) and chemical weapon agents (CWA) has severe morbidity and mortality consequences. We present data from quantum mechanics/molecular mechanics (QM/MM) and 80 classical molecular dynamics (MD) simulations of the apo and soman-adducted forms of hAChE to investigate the effects on the dynamics and protein structure when the catalytic Serine 203 is phosphonylated. We find that the soman phosphonylation of the active site Ser203 follows a water assisted addition-elimination mechanism with the elimination of the fluoride ion being the highest energy barrier at 6.5 kcal/mole. We observe soman-dependent changes in backbone andmore » sidechain motions compared to the apo form of the protein. These alterations restrict the soman-adducted hAChE to a structural state that is primed for the soman adduct to be cleaved and removed from the active site. The altered motions and resulting structures provide alternative pathways into and out of the hAChE active site. In the soman-adducted protein both side and back door pathways are viable for soman adduct access. Correlation analysis of the apo and soman adducted MD trajectories shows that the correlation of gorge entrance and back door motion is disrupted when hAChE is adducted. This supports the hypothesis that substrate and product can use two different pathways as entry and exit sites in the apo form of the protein. These alternative pathways have important implications for the rational design of medical countermeasures.« less
Wang, Jinyang; Zhong, Haimin; Qiu, Wenda; Chen, Liuping; Feng, Huajie
2014-03-14
The binary infinite dilute diffusion coefficients, D{sub 12}{sup ?}, of some alkylbenzenes (Ph-C{sub n}, from Ph-H to Ph-C{sub 12}) from 313 K to 333 K at 15 MPa in supercritical carbon dioxide (scCO{sub 2}) have been studied by molecular dynamics (MD) simulation. The MD values agree well with the experimental ones, which indicate MD simulation technique is a powerful way to predict and obtain diffusion coefficients of solutes in supercritical fluids. Besides, the local structures of Ph-C{sub n}/CO{sub 2} fluids are further investigated by calculating radial distribution functions and coordination numbers. It qualitatively convinces that the first solvation shell of Ph-C{sub n} in scCO{sub 2} is significantly influenced by the structure of Ph-C{sub n} solute. Meanwhile, the mean end-to-end distance, the mean radius of gyration and dihedral angle distribution are calculated to gain an insight into the structural properties of Ph-C{sub n} in scCO{sub 2}. The abnormal trends of radial distribution functions and coordination numbers can be reasonably explained in term of molecular flexibility. Moreover, the computed results of dihedral angle clarify that flexibility of long-chain Ph-C{sub n} is the result of internal rotation of C-C single bond (?{sub c-c}) in alkyl chain. It is interesting that compared with n-alkane, because of the existence of benzene ring, the flexibility of alkyl chain in Ph-C{sub n} with same carbon atom number is significantly reduced, as a result, the carbon chain dependence of diffusion behaviors for long-chain n-alkane (n ? 5) and long-chain Ph-C{sub n} (n ? 4) in scCO{sub 2} are different.
de Almeida, Valmor F.; Liu, Hongjun; Herwig, Kenneth W.; Kidder, Michelle
2016-01-01
That incoherent scattering from protiated molecular liquids adds a constant background to the measured scattering intensity is well known, but less appreciated is the fact that coherent scattering is also induced by the presence of hydrogen in a deuterated liquid. In fact, the scattering intensity can be very sensitive, in the small-q region, with respect to the amounts and distribution of residual H in the system. We used 1,4-dioxane liquid to demonstrate that the partial structure factors of the HD and DD atom pairs contribute significantly to inter-molecular scattering and that uncertainty in the extent of deuteration account for discrepancies between simulations and measurements. Both contributions to uncertainty have similar magnitudes: scattering interference of the hydrogen-deuterium pair, and complementary interference from the deuterium-deuterium pair by virtue of chemical inhomogeneity. This situation arises in practice since deuteration of liquids is often 99% or less. A combined experimental and extensive computational study of static thermal neutron scattering of 1,4-dioxane demonstrates the foregoing. We show, through simulations, that the reason for the differences is the content of protiated dioxane (vendors quote 1%). We estimate that up to 5% (at 298K and at 343K) protiated mole fraction may be involved in generating the scattering differences. Finally, we find that the particular distribution of hydrogen in the protiated molecules affects the results significantly; here we considered molecules to be either fully protiated or fully deuterated. This scenario best reconciles the computational and experimental results, and leads us to speculate that the deuteration synthesis process tends to leave a molecule either fully deuterated or fully protiated. Although we have used 1,4-dioxane as a model liquid, the effects described in this study extend to similar liquids and similar systematic experimental/computational studies can be performed to either
Liu, Hongjun; Herwig, Kenneth W.; Kidder, Michelle K.; de Almeida, Valmor F.
2016-06-08
That incoherent scattering from protiated molecular liquids adds a constant background to the measured scattering intensity is well-known, but less appreciated is the fact that coherent scattering is also induced by the presence of hydrogen in a deuterated liquid. In fact, the scattering intensity can be very sensitive, in the small-q region, with respect to the amounts and distribution of residual H in the system. We used 1,4-dioxane liquid to demonstrate that the partial structure factors of the HD and DD atom pairs contribute significantly to intermolecular scattering and that uncertainty in the extent of deuteration account for discrepancies betweenmore » simulations and measurements. Both contributions to uncertainty have similar magnitudes: scattering interference of the hydrogen–deuterium pair, and complementary interference from the deuterium–deuterium pair by virtue of chemical inhomogeneity. This situation arises in practice since deuteration of liquids is often 99% or less. A combined experimental and extensive computational study of static thermal neutron scattering of 1,4-dioxane demonstrates the foregoing. We show, through simulations, that the reason for the differences is the content of protiated dioxane (vendors quote 1%). We estimate that up to 5% (at 298 K and at 343 K) protiated molar fraction may be involved in generating the scattering differences. Finally, we find that the particular distribution of hydrogen in the protiated molecules affects the results significantly; here, we considered molecules to be either fully protiated or fully deuterated. This scenario best reconciles the computational and experimental results, and leads us to speculate that the deuteration synthesis process tends to leave a molecule either fully deuterated or fully protiated. As a result, we have used 1,4-dioxane as a model liquid, the effects described in this study extend to similar liquids, and similar systematic experimental/computational studies can be
Sato, Hiroyuki; Kubo, Shinji; Sakaba, Nariaki; Ohashi, Hirofumi; Sano, Naoki; Nishihara, Tetsuo; Kunitomi, Kazuhiko
2007-07-01
The objective of this study is to confirm the availability of proposed mitigation methodology against thermal load increase events initiated by the thermochemical water splitting IS process hydrogen production system (IS process) coupling with the High temperature Engineering Test Reactor (HTTR). Japan Atomic Energy Agency (JAEA) has been performing the development of dynamic simulation code which can evaluate complex phenomena in the HTTR-IS system all at one once to achieve the requirement. The notable feature of the developed code is the Advanced Process Heat Exchanger (APHX) module which enables to estimate the IS process thermal load variation considering phase change and chemical reaction behavior assumed in the APHX. In this paper, two cases of dynamic calculation for the thermal load increase events were performed using the newly developed APHX module. The results of the analytical studies clearly show the availability of the developed model for dynamic simulation of the HTTR-IS system and the thermal load increase mitigation methodology. (authors)
Virtual Simulation of Vision 21 Energy Plants
Syamlal, Madhava; Felix, Paul E.; Osawe, Maxwell O.; Fiveland, Woodrow A.; Sloan, David G.; Zitney, Stephen E.; Joop, Frank; Cleetus, Joseph; Lapshin, Igor B.
2001-11-06
The Vision 21 Energy plants will be designed by combining several individual power, chemical, and fuel-conversion technologies. These independently developed technologies or technology modules can be interchanged and combined to form the complete Vision 21 plant that achieves the needed level of efficiency and environmental performance at affordable costs. The knowledge about each technology module must be captured in computer models so that the models can be linked together to simulate the entire Vision 21 power plant in a Virtual Simulation environment. Eventually the Virtual Simulation will find application in conceptual design, final design, plant operation and control, and operator training. In this project we take the first step towards developing such a Vision 21 Simulator. There are two main knowledge domains of a plant--the process domain (what is in the pipes), and the physical domain (the pipes and equipment that make up the plant). Over the past few decades, commercial software tools have been developed for each of these functions. However, there are three main problems that inhibit the design and operation of power plants: (1) Many of these tools, largely developed for chemicals and refining, have not been widely adopted in the power industry. (2) Tools are not integrated across functions. For example, the knowledge represented by computational fluid dynamics (CFD) models of equipment is not used in process-level simulations. (3) No tool exists for readily integrating the design and behavioral knowledge about components. These problems must be overcome to develop the Vision 21 Simulator. In this project our major objective is to achieve a seamless integration of equipment-level and process-level models and apply the integrated software to power plant simulations. Specifically we are developing user-friendly tools for linking process models (Aspen Plus) with detailed equipment models (FLUENT CFD and other proprietary models). Such integration will
Graphite Oxidation Simulation in HTR Accident Conditions
El-Genk, Mohamed
2012-10-19
Massive air and water ingress, following a pipe break or leak in steam-generator tubes, is a design-basis accident for high-temperature reactors (HTRs). Analysis of these accidents in both prismatic and pebble bed HTRs requires state-of-the-art capability for predictions of: 1) oxidation kinetics, 2) air helium gas mixture stratification and diffusion into the core following the depressurization, 3) transport of multi-species gas mixture, and 4) graphite corrosion. This project will develop a multi-dimensional, comprehensive oxidation kinetics model of graphite in HTRs, with diverse capabilities for handling different flow regimes. The chemical kinetics/multi-species transport model for graphite burning and oxidation will account for temperature-related changes in the properties of graphite, oxidants (O2, H2O, CO), reaction products (CO, CO2, H2, CH4) and other gases in the mixture (He and N2). The model will treat the oxidation and corrosion of graphite in geometries representative of HTR core component at temperatures of 900°C or higher. The developed chemical reaction kinetics model will be user-friendly for coupling to full core analysis codes such as MELCOR and RELAP, as well as computational fluid dynamics (CFD) codes such as CD-adapco. The research team will solve governing equations for the multi-dimensional flow and the chemical reactions and kinetics using Simulink, an extension of the MATLAB solver, and will validate and benchmark the model's predictions using reported experimental data. Researchers will develop an interface to couple the validated model to a commercially available CFD fluid flow and thermal-hydraulic model of the reactor , and will perform a simulation of a pipe break in a prismatic core HTR, with the potential for future application to a pebble-bed type HTR.
Gabl, Sonja; Schröder, Christian; Braun, Daniel; Steinhauser, Othmar; Weingärtner, Hermann
2014-05-14
Combining simulation and model theories, this paper analyses the impact of pair dynamics on the intermolecular nuclear Overhauser effect (NOE) in liquids. For the first time, we give a distance resolved NOE. When applied to the ionic liquid 1-ethyl-3-methyl-imidazolium tetrafluoroborate the NOE turns out to be of long-range nature. This behaviour translates to the experimentally measured cross- and longitudinal relaxation rates. We were able to calculate the heteronuclear NOE from simulation data, despite the high computational effort. Model theories are computationally less demanding and cover the complete frequency range of the respective spectral density function, they are usually based on a very simple pair distribution function and the solution of the diffusion equation. In order to model the simulated data sufficiently, these simplifications in structure and dynamics have to be generalised considerably.
Markutsya, Sergiy; Lamm, Monica H.
2014-11-07
We report on a new approach for deriving coarse-grained intermolecular forces that retains the frictional contribution that is often discarded by conventional coarse-graining methods. The approach is tested for water and an aqueous glucose solution, and the results from the new implementation for coarse-grained molecular dynamics simulation show remarkable agreement with the dynamics obtained from reference all-atom simulations. The agreement between the structural properties observed in the coarse-grained and all-atom simulations is also preserved. We discuss how this approach may be applied broadly to any existing coarse-graining method where the coarse-grained models are rigorously derived from all-atom reference systems.
Xu, W.; Lan, Z.; Peng, B. L.; Wen, R. F.; Ma, X. H.
2015-02-07
Heterogeneous nucleation of water droplet on surfaces with different solid-liquid interaction intensities is investigated by molecular dynamics simulation. The interaction potentials between surface atoms and vapor molecules are adjusted to obtain various surface free energies, and the nucleation process and wetting state of nuclei on surfaces are investigated. The results indicate that near-constant contact angles are already established for nano-scale nuclei on various surfaces, with the contact angle decreasing with solid-liquid interaction intensities linearly. Meanwhile, noticeable fluctuation of vapor-liquid interfaces can be observed for the nuclei that deposited on surfaces, which is caused by the asymmetric forces from vapor molecules. The formation and growth rate of nuclei are increasing with the solid-liquid interaction intensities. For low energy surface, the attraction of surface atoms to water molecules is comparably weak, and the pre-existing clusters can depart from the surface and enter into the bulk vapor phase. The distribution of clusters within the bulk vapor phase becomes competitive as compared with that absorbed on surface. For moderate energy surfaces, heterogeneous nucleation predominates and the formation of clusters within bulk vapor phase is suppressed. The effect of high energy particles that embedded in low energy surface is also discussed under the same simulation system. The nucleation preferably initiates on the high energy particles, and the clusters that formed on the heterogeneous particles are trapped around their original positions instead of migrating around as that observed on smooth surfaces. This feature makes it possible for the heterogeneous particles to act as fixed nucleation sites, and simulation results also suggest that the number of nuclei increases monotonously with the number of high energy particles. The growth of nuclei on high energy particles can be divided into three sub-stages, beginning with the formation
Intercomparison of 3D pore-scale flow and solute transport simulation methods
Mehmani, Yashar; Schoenherr, Martin; Pasquali, Andrea; Perkins, William A.; Kim, Kyungjoo; Perego, Mauro; Parks, Michael L.; Balhoff, Matthew T.; Richmond, Marshall C.; Geier, Martin; Krafczyk, Manfred; Luo, Li -Shi; Tartakovsky, Alexandre M.; Yang, Xiaofan; Scheibe, Timothy D.; Trask, Nathaniel
2015-09-28
Multiple numerical approaches have been developed to simulate porous media fluid flow and solute transport at the pore scale. These include 1) methods that explicitly model the three-dimensional geometry of pore spaces and 2) methods that conceptualize the pore space as a topologically consistent set of stylized pore bodies and pore throats. In previous work we validated a model of the first type, using computational fluid dynamics (CFD) codes employing a standard finite volume method (FVM), against magnetic resonance velocimetry (MRV) measurements of pore-scale velocities. Here we expand that validation to include additional models of the first type based on the lattice Boltzmann method (LBM) and smoothed particle hydrodynamics (SPH), as well as a model of the second type, a pore-network model (PNM). The PNM approach used in the current study was recently improved and demonstrated to accurately simulate solute transport in a two-dimensional experiment. While the PNM approach is computationally much less demanding than direct numerical simulation methods, the effect of conceptualizing complex three-dimensional pore geometries on solute transport in the manner of PNMs has not been fully determined. We apply all four approaches (FVM-based CFD, LBM, SPH and PNM) to simulate pore-scale velocity distributions and (for capable codes) nonreactive solute transport, and intercompare the model results. Comparisons are drawn both in terms of macroscopic variables (e.g., permeability, solute breakthrough curves) and microscopic variables (e.g., local velocities and concentrations). Generally good agreement was achieved among the various approaches, but some differences were observed depending on the model context. The intercomparison work was challenging because of variable capabilities of the codes, and inspired some code enhancements to allow consistent comparison of flow and transport simulations across the full suite of methods. This paper provides support for confidence
Intercomparison of 3D pore-scale flow and solute transport simulation methods
Mehmani, Yashar; Schoenherr, Martin; Pasquali, Andrea; Perkins, William A.; Kim, Kyungjoo; Perego, Mauro; Parks, Michael L.; Balhoff, Matthew T.; Richmond, Marshall C.; Geier, Martin; et al
2015-09-28
Multiple numerical approaches have been developed to simulate porous media fluid flow and solute transport at the pore scale. These include 1) methods that explicitly model the three-dimensional geometry of pore spaces and 2) methods that conceptualize the pore space as a topologically consistent set of stylized pore bodies and pore throats. In previous work we validated a model of the first type, using computational fluid dynamics (CFD) codes employing a standard finite volume method (FVM), against magnetic resonance velocimetry (MRV) measurements of pore-scale velocities. Here we expand that validation to include additional models of the first type based onmore » the lattice Boltzmann method (LBM) and smoothed particle hydrodynamics (SPH), as well as a model of the second type, a pore-network model (PNM). The PNM approach used in the current study was recently improved and demonstrated to accurately simulate solute transport in a two-dimensional experiment. While the PNM approach is computationally much less demanding than direct numerical simulation methods, the effect of conceptualizing complex three-dimensional pore geometries on solute transport in the manner of PNMs has not been fully determined. We apply all four approaches (FVM-based CFD, LBM, SPH and PNM) to simulate pore-scale velocity distributions and (for capable codes) nonreactive solute transport, and intercompare the model results. Comparisons are drawn both in terms of macroscopic variables (e.g., permeability, solute breakthrough curves) and microscopic variables (e.g., local velocities and concentrations). Generally good agreement was achieved among the various approaches, but some differences were observed depending on the model context. The intercomparison work was challenging because of variable capabilities of the codes, and inspired some code enhancements to allow consistent comparison of flow and transport simulations across the full suite of methods. This paper provides support for
Simulation of macromolecule self-assembly in solution: A multiscale approach
Lavino, Alessio D. Barresi, Antonello A. Marchisio, Daniele L.; Pasquale, Nicodemo di; Carbone, Paola
2015-12-17
One of the most common processes to produce polymer nanoparticles is to induce self-assembly by using the solvent-displacement method, in which the polymer is dissolved in a “good” solvent and the solution is then mixed with an “anti-solvent”. The polymer ability to self-assemble in solution is therefore determined by its structural and transport properties in solutions of the pure solvents and at the intermediate compositions. In this work, we focus on poly-ε-caprolactone (PCL) which is a biocompatible polymer that finds widespread application in the pharmaceutical and biomedical fields, performing simulation at three different scales using three different computational tools: full atomistic molecular dynamics (MD), population balance modeling (PBM) and computational fluid dynamics (CFD). Simulations consider PCL chains of different molecular weight in solution of pure acetone (good solvent), of pure water (anti-solvent) and their mixtures, and mixing at different rates and initial concentrations in a confined impinging jets mixer (CIJM). Our MD simulations reveal that the nano-structuring of one of the solvents in the mixture leads to an unexpected identical polymer structure irrespectively of the concentration of the two solvents. In particular, although in pure solvents the behavior of the polymer is, as expected, very different, at intermediate compositions, the PCL chain shows properties very similar to those found in pure acetone as a result of the clustering of the acetone molecules in the vicinity of the polymer chain. We derive an analytical expression to predict the polymer structural properties in solution at different solvent compositions and use it to formulate an aggregation kernel to describe the self-assembly in the CIJM via PBM and CFD. Simulations are eventually validated against experiments.
Feng, J.; Liu, L.; Chen, J.; Du, Y.; Zhou, R.; Xiao, B.
2010-06-15
The aging behaviors of Cu-Cr alloys in the early stage at different temperatures are investigated by molecular dynamics simulations. First principles potentials are used for the interactions between Cu and Cr atoms. The initial behavior of precipitation is characterized by transmission electron microscope and electron energy disperse spectroscopy. The results showed that Cu-Cr supersaturated solid solution is thermodynamically unstable. The mean-square displacements of the atoms are used to describe the diffusivity. At room temperature, the atoms only show harmonic vibrations near the equilibrium positions. The mutual diffusion at 873 K is different from the unidirectional diffusion in low temperatures. The calculation shows that aging process is accelerated with increasing temperature, which is not only due to the lower diffusion activation energy of Cr at higher temperature, but also because Cu atoms are also participated in the aging process. When ''aging'' at 1073 K, the precipitation of Cr element is dissolved again into Cu matrix, which is an ''over-aging'' state of Cu-Cr alloy at high temperature.
Wilson, S. R.; Mendelev, M. I.
2015-01-08
Solid–liquid interface (SLI) properties of the Ni–Zr B33 phase were determined from molecular dynamics simulations. In order to perform these measurements, a new semi-empirical potential for Ni–Zr alloy was developed that well reproduces the material properties required to model SLIs in the Ni50.0Zr50.0 alloy. In particular, the developed potential is shown to provide that the solid phase emerging from the liquid Ni50.0Zr50.0alloy is B33 (apart from a small fraction of point defects), in agreement with the experimental phase diagram. The SLI properties obtained using the developed potential exhibit an extraordinary degree of anisotropy. It is observed that anisotropies in bothmore » the interfacial free energy and mobility are an order of magnitude larger than those measured to date in any other metallic compound. Moreover, the [0 1 0] interface is shown to play a significant role in the observed anisotropy. Our data suggest that the [0 1 0] interface simultaneously corresponds to the lowest mobility, the lowest free energy and the highest stiffness of all inclinations in B33 Ni–Zr. This finding can be understood by taking into account a rather complicated crystal structure in this crystallographic direction.« less
Fan, Haidong; Aubry, Sylvie; Arsenlis, Athanasios; El-Awady, Jaafar A.
2015-04-13
The mechanical response of micro-twinned polycrystalline magnesium was studied through three-dimensional discrete dislocation dynamics (DDD). A systematic interaction model between dislocations and (1012) tension twin boundaries (TBs) was proposed and introduced into the DDD framework. In addition, a nominal grain boundary (GB) model agreeing with experimental results was also introduced to mimic the GB’s barrier effect. The current simulation results show that TBs act as a strong obstacle to gliding dislocations, which contributes significantly to the hardening behavior of magnesium. On the other hand, the deformation accommodated by twinning plays a softening role. Therefore, the concave shape of the Mgmore » stress-strain curve results from the competition between dislocation-TB induced hardening and twinning deformation induced softening. At low strain levels, twinning deformation induced softening dominates and a decreasing hardening rate is observed in Stage-I. In Stage-II, both the hardening and softening effects decline, but twinning deformation induced softening declines faster, which leads to an increasing hardening rate.« less
Zhang, Yongfeng; Bai, Xian-Ming; Yu, Jianguo; Tonks, Michael R.; Noordhoek, Mark J.; Phillpot, Simon R.
2016-06-01
A formation path for homogeneous γ hydride formation in hcp α-Zr, from solid solution to the ζ and then the γ hydride, was demonstrated using molecular static calculations and molecular dynamic simulations with the charge-optimized many-body (COMB) potential. Hydrogen has limited solubility in α-Zr. Once the solubility limit is exceeded, the stability of solid solution gives way to that of coherent hydride phases such as the ζ hydride by planar precipitation of hydrogen. At finite temperatures, the ζ hydride goes through a partial hcp-fcc transformation via 1/3 <1¯100> slip on the basal plane, and transforms into a mixture of γmore » hydride and α-Zr. In the ζ hydride, slip on the basal plane is favored thermodynamically with negligible barrier, and is therefore feasible at finite temperatures without mechanical loading. The transformation process involves slips of three equivalent shear partials, in contrast to that proposed in the literature where only a single shear partial was involved. The adoption of multiple slip partials minimizes the macroscopic shape change of embedded hydride clusters and the shear strain accumulation in the matrix, and thus reduces the overall barrier needed for homogeneous γ hydride formation. In conclusion, this formation path requires finite temperatures for hydrogen diffusion without mechanical loading. Therefore, it should be effective at the cladding operating conditions.« less
Yang, Yihan; Zhao, Hongwei; Zhang, Lin; Shao, Mingkun; Liu, Hongda; Huang, Hu
2013-10-15
Understanding the behaviors of the material removal mechanism of ultra-precision polishing process has been a critical issue of generating well-formed surface. In order to make clear the abrasive self-rotation effects on material removal at the atomic level, a three-dimensional molecular dynamics (MD) model is conducted to study the mechanics of ultra-precision polishing on single-crystal copper with a diamond abrasive and the effects of abrasive self-rotation velocity and direction. Morse potential energy function and EAM potential energy function are applied to model the copper/diamond and copper/copper interactions, respectively. The simulation results show that the deformation mechanism of single-crystal copper is due to the formation and movement of dislocations in the specimen. In addition, with the increasing of abrasive self-rotation velocity, the deformation mechanism falls from cutting to plowing regimes. The abrasive self-rotation velocity and direction have effects on the morphology and quality of the specimen surface, distribution and evolution of defects under the surface of the specimen. Also, the interatomic force between abrasive and specimen is studied to account for the effects of different polishing conditions.
Mayer, Brian P.; Kennedy, Daniel J.; Lau, Edmond Y.; Valdez, Carlos A.
2016-02-04
Cyclodextrins (CDs) are investigated for their ability to form inclusion complexes with the analgesic fentanyl and three similar molecules: acetylfentanyl, thiofentanyl, and acetylthiofentanyl. Stoichiometry, binding strength, and complex structure are revealed through nuclear magnetic resonance (NMR) techniques and discussed in terms of molecular dynamics (MD) simulations. It was found that β-cyclodextrin is generally capable of forming the strongest complexes with the fentanyl panel. Two-dimensional NMR data and computational chemical calculations are used to derive solution-state structures of the complexes. Binding of the fentanyls to the CDs occurs at the amide phenyl ring, leaving the majority of the molecule solvated bymore » water, an observation common to all four fentanyls. This finding suggests a universal binding behavior, as the vast majority of previously synthesized fentanyl analogues contain this structural moiety. Furthermore, this baseline study serves as the most complete work on CD:fentanyl complexes to date and provides the insights into strategies for producing future generations of designer cyclodextrins capable of stronger and more selective complexation of fentanyl and its analogues.« less
Rao, R. Prasada; Reddy, M.V.; Adams, S.; Chowdari, B.V.R.
2015-06-15
Highlights: • LiFePO{sub 4} compound was prepared by carbothermal reduction method. • In-situ XRD studies were carried out on LiFePO{sub 4} at various temperatures. • Dedicated imperial potentials used to explain the variation of lattice constants. • It exhibited reversible capacity of 140 (±5) mAh g{sup −1}, stable up to 400 cycles. - Abstract: LiFePO{sub 4} was prepared using carbothermal reduction method. In-situ temperature dependent structural studies were carried using X-ray diffraction. Molecular dynamics simulations were conducted for the LiFePO{sub 4} using empirical potentials developed using bond valence approach to investigate the structural variations. Electrochemical behaviour of LiFePO{sub 4} was evaluated using cyclic voltammetry and galvanostatic cycling studies at room temperature. Charge–discharge cycling studies showed a reversible capacities 140 (±5) mAh g{sup −1} at the end of 50th cycle and these capacity values were stable up to 400 cycles and almost nil capacity fade between 50 and 400 cycles, showing excellent capacity retention, low capacity fading. The cyclic voltammetry studies showed a main cathodic and anodic redox peaks at 3.34 and 3.5 V vs. Li, respectively.
D. M. McEligot; K.G. Condie; G. E. Mc Creery; H. M. Mc Ilroy
2005-09-01
The objective of the present report is to document the design of our first experiment to measure generic flow phenomena expected to occur in the lower plenum of a typical prismatic VHTR (Very High Temperature Reactor) concept. In the process, fabrication sketches are provided for the use of CFD (computational fluid dynamics) analysts wishing to employ the data for assessment of their proposed codes. The general approach of the project is to develop new benchmark experiments for assessment in parallel with CFD and coupled CFD/systems code calculations for the same geometry. One aspect of the complex flow in a prismatic VHTR is being addressed: flow and thermal mixing in the lower plenum ("hot streaking" issue). Current prismatic VHTR concepts were examined to identify their proposed flow conditions and geometries over the range from normal operation to decay heat removal in a pressurized cooldown. Approximate analyses were applied to determine key non-dimensional parameters and their magnitudes over this operating range. The flow in the lower plenum can locally be considered to be a situation of multiple jets into a confined crossflow -- with obstructions. Flow is expected to be turbulent with momentum-dominated turbulent jets entering; buoyancy influences are estimated to be negligible in normal full power operation. Experiments are needed for the combined features of the lower plenum flows. Missing from the typical jet experiments available are interactions with nearby circular posts and with vertical posts in the vicinity of vertical walls - with near stagnant surroundings at one extreme and significant crossflow at the other.
CASL - PWR Reactor Vessel Multi-Physics CFD Model
U.S. Department of Energy (DOE) all webpages (Extended Search)
PWR Reactor Vessel Multi-Physics CFD Model Jin Yan*1, Yiban Xu1, Andrew Petrarca1, Zeses Karoutas1, Emre Tatli1, Emilio Baglietto2, Jess Gehin3 1Westinghouse Electric Company LLC 2Massachusetts Institute of Technology 3Oak Ridge National Lab *Correspondence to: yan3j@westinghouse.com A complete 3D SolidWorks CAD model of Watts Bar Unit 1 was constructed based on drawings. A single fuel assembly CAD model including all geometrical details was created based on the Westinghouse V5H 17x17 fuel
Breault, Ronald W,; Huckaby, Ernest D.; Shadle, Lawrence J; Spenik, James L.
2013-01-01
The National Energy Technology Laboratory is investigating a new process for CO{sub 2} capture from large sources such as utility power generation facilities as an alternative to liquid amine based absorption processes. Many, but not all of these advanced dry processes are based upon sorbents composed of supported polyamines. In this analysis, experiments have been conducted in a small facility at different temperatures and compared to CFD reactor predictions using kinetics obtained from TGA tests. This particular investigation compares the predicted performance and the experimental performance of one of these new class of sorbents in a fluidized bed reactor. In the experiment, the sorbent absorbs CO{sub 2} from simulated flue gas in a riser reactor, separates the carbonated particles from the de-carbonated flue gas in a cyclone and then regenerates the sorbent, creating a concentrated stream of pure CO{sub 2} for sequestration. In this work, experimental measurements of adsorption are compared to predictions from a 3-dimensional non-isothermal reacting multiphase flow model. The effects of the gas flow rate and reactor temperature are explored. It is shown that the time duration for CO{sub 2} adsorption decreased for an increase in the gas flow. The details of the experimental facility and the model as well as the comparative analysis between the data and the simulation results are discussed.
Mirfathi, S. M.; Pahlavani, M. R.
2008-12-15
The dynamical model based on the asymmetric mass division has been applied to calculate pre-scission neutron multiplicity from heavy-ion induced fusion-fission reactions. Links between the pre-scission neutron multiplicity, excitation energy, and asymmetric mass distribution are clarified based on the Monte Carlo simulation and Langevin dynamics. The pre-scission neutron multiplicity is calculated and compared with the respective experimental data over a wide range of excitation energy and nonconstant viscosity. The analysis indicates a different effect for the application of asymmetric mass division in different energy regions of such processes.
Madaan, Nitesh; Bao, Jie; Nandasiri, Manjula I.; Xu, Zhijie; Thevuthasan, Suntharampillai; Devaraj, Arun
2015-08-31
The experimental atom probe tomography results from two different specimen orientations (top-down and side-ways) of a high oxygen ion conducting Samaria-doped-ceria/Scandia-stabilized-zirconia multilayer thin film solid oxide fuel cell electrolyte was correlated with level-set method based field evaporation simulations for the same specimen orientations. This experiment-theory correlation explains the dynamic specimen shape evolution and ion trajectory aberrations that can induce density artifacts in final reconstruction leading to inaccurate estimation of interfacial intermixing. This study highlights the need and importance of correlating experimental results with field evaporation simulations when using atom probe tomography for studying oxide heterostructure interfaces.
Bisikalo, D.; Kaygorodov, P.; Ionov, D.; Shematovich, V.; Lammer, H.; Fossati, L.
2013-02-10
Hubble Space Telescope transit observations in the near-UV performed in 2009 made WASP-12b one of the most 'mysterious' exoplanets; the system presents an early ingress, which can be explained by the presence of optically thick matter located ahead of the planet at a distance of {approx}4-5 planet radii. This work follows previous attempts to explain this asymmetry with an exospheric outflow or a bow shock, induced by a planetary magnetic field, and provides a numerical solution of the early ingress, though we did not perform any radiative transfer calculation. We performed pure 3D gas dynamic simulations of the plasma interaction between WASP-12b and its host star and describe the flow pattern in the system. In particular, we show that the overfilling of the planet's Roche lobe leads to a noticeable outflow from the upper atmosphere in the direction of the L{sub 1} and L{sub 2} points. Due to the conservation of the angular momentum, the flow to the L{sub 1} point is deflected in the direction of the planet's orbital motion, while the flow toward L{sub 2} is deflected in the opposite direction, resulting in a non-axisymmetric envelope, surrounding the planet. The supersonic motion of the planet inside the stellar wind leads to the formation of a bow shock with a complex shape. The existence of the bow shock slows down the outflow through the L{sub 1} and L{sub 2} points, allowing us to consider a long-living flow structure that is in the steady state.
Bluff Body Flow Simulation Using a Vortex Element Method
Anthony Leonard; Phillippe Chatelain; Michael Rebel
2004-09-30
Heavy ground vehicles, especially those involved in long-haul freight transportation, consume a significant part of our nation's energy supply. it is therefore of utmost importance to improve their efficiency, both to reduce emissions and to decrease reliance on imported oil. At highway speeds, more than half of the power consumed by a typical semi truck goes into overcoming aerodynamic drag, a fraction which increases with speed and crosswind. Thanks to better tools and increased awareness, recent years have seen substantial aerodynamic improvements by the truck industry, such as tractor/trailer height matching, radiator area reduction, and swept fairings. However, there remains substantial room for improvement as understanding of turbulent fluid dynamics grows. The group's research effort focused on vortex particle methods, a novel approach for computational fluid dynamics (CFD). Where common CFD methods solve or model the Navier-Stokes equations on a grid which stretches from the truck surface outward, vortex particle methods solve the vorticity equation on a Lagrangian basis of smooth particles and do not require a grid. They worked to advance the state of the art in vortex particle methods, improving their ability to handle the complicated, high Reynolds number flow around heavy vehicles. Specific challenges that they have addressed include finding strategies to accurate capture vorticity generation and resultant forces at the truck wall, handling the aerodynamics of spinning bodies such as tires, application of the method to the GTS model, computation time reduction through improved integration methods, a closest point transform for particle method in complex geometrics, and work on large eddy simulation (LES) turbulence modeling.
Simulation of Thermal Stratification in BWR Suppression Pools with One Dimensional Modeling Method
Haihua Zhao; Ling Zou; Hongbin Zhang
2014-01-01
The suppression pool in a boiling water reactor (BWR) plant not only is the major heat sink within the containment system, but also provides the major emergency cooling water for the reactor core. In several accident scenarios, such as a loss-of-coolant accident and extended station blackout, thermal stratification tends to form in the pool after the initial rapid venting stage. Accurately predicting the pool stratification phenomenon is important because it affects the peak containment pressure; the pool temperature distribution also affects the NPSHa (available net positive suction head) and therefore the performance of the Emergency Core Cooling System and Reactor Core Isolation Cooling System pumps that draw cooling water back to the core. Current safety analysis codes use zero dimensional (0-D) lumped parameter models to calculate the energy and mass balance in the pool; therefore, they have large uncertainties in the prediction of scenarios in which stratification and mixing are important. While three-dimensional (3-D) computational fluid dynamics (CFD) methods can be used to analyze realistic 3-D configurations, these methods normally require very fine grid resolution to resolve thin substructures such as jets and wall boundaries, resulting in a long simulation time. For mixing in stably stratified large enclosures, the BMIX++ code (Berkeley mechanistic MIXing code in C++) has been developed to implement a highly efficient analysis method for stratification where the ambient fluid volume is represented by one-dimensional (1-D) transient partial differential equations and substructures (such as free or wall jets) are modeled with 1-D integral models. This allows very large reductions in computational effort compared to multi-dimensional CFD modeling. One heat-up experiment performed at the Finland POOLEX facility, which was designed to study phenomena relevant to Nordic design BWR suppression pool including thermal stratification and mixing, is used for
U.S. Department of Energy (DOE) all webpages (Extended Search)
COER HYDRODYNAMIC MODELING COMPETITION: MODELING THE DYNAMIC RESPONSE OF A FLOATING BODY USING THE WEC-SIM AND FAST SIMULATION TOOLS Michael Lawson Braulio Barahona Garzon Fabian Wendt Yi-Hsiang Yu National Renewable Energy Laboratory Golden, Colorado, USA Carlos Michelen Sandia National Laboratories Albuquerque, New Mexico, USA ABSTRACT The Center for Ocean Energy Research (COER) at the University of Maynooth in Ireland organized a hydrodynamic modeling competition in conjunction with OMAE2015.
U.S. Department of Energy (DOE) all webpages (Extended Search)
COER Hydrodynamic Modeling Competition: Modeling the Dynamic Response of a Floating Body Using the WEC-Sim and FAST Simulation Tools Preprint M. Lawson, B. Barahona Garzon, F. Wendt, and Y-H. Yu National Renewable Energy Laboratory C. Michelen Sandia National Laboratories To be presented at the 34 th International Conference on Ocean, Offshore, and Arctic Engineering (OMAE 2015) St. John's, Newfoundland, Canada May 31-June 5, 2015 Conference Paper NREL/CP-5000-63594 March 2015 NOTICE The
Das, Anuradha; Das, Suman; Biswas, Ranjit
2015-01-21
Temperature dependent relaxation dynamics, particle motion characteristics, and heterogeneity aspects of deep eutectic solvents (DESs) made of acetamide (CH{sub 3}CONH{sub 2}) and urea (NH{sub 2}CONH{sub 2}) have been investigated by employing time-resolved fluorescence measurements and all-atom molecular dynamics simulations. Three different compositions (f) for the mixture [fCH{sub 3}CONH{sub 2} + (1 − f)NH{sub 2}CONH{sub 2}] have been studied in a temperature range of 328-353 K which is ∼120-145 K above the measured glass transition temperatures (∼207 K) of these DESs but much lower than the individual melting temperature of either of the constituents. Steady state fluorescence emission measurements using probe solutes with sharply different lifetimes do not indicate any dependence on excitation wavelength in these metastable molten systems. Time-resolved fluorescence anisotropy measurements reveal near-hydrodynamic coupling between medium viscosity and rotation of a dissolved dipolar solute. Stokes shift dynamics have been found to be too fast to be detected by the time-resolution (∼70 ps) employed, suggesting extremely rapid medium polarization relaxation. All-atom simulations reveal Gaussian distribution for particle displacements and van Hove correlations, and significant overlap between non-Gaussian (α{sub 2}) and new non-Gaussian (γ) heterogeneity parameters. In addition, no stretched exponential relaxations have been detected in the simulated wavenumber dependent acetamide dynamic structure factors. All these results are in sharp contrast to earlier observations for ionic deep eutectics with acetamide [Guchhait et al., J. Chem. Phys. 140, 104514 (2014)] and suggest a fundamental difference in interaction and dynamics between ionic and non-ionic deep eutectic solvent systems.
Churchfield, M. J.; Moriarty, P. J.; Hao, Y.; Lackner, M. A.; Barthelmie, R.; Lundquist, J.; Oxley, G. S.
2014-12-01
The focus of this work is the comparison of the dynamic wake meandering model and large-eddy simulation with field data from the Egmond aan Zee offshore wind plant composed of 36 3-MW turbines. The field data includes meteorological mast measurements, SCADA information from all turbines, and strain-gauge data from two turbines. The dynamic wake meandering model and large-eddy simulation are means of computing unsteady wind plant aerodynamics, including the important unsteady meandering of wakes as they convect downstream and interact with other turbines and wakes. Both of these models are coupled to a turbine model such that power and mechanical loads of each turbine in the wind plant are computed. We are interested in how accurately different types of waking (e.g., direct versus partial waking), can be modeled, and how background turbulence level affects these loads. We show that both the dynamic wake meandering model and large-eddy simulation appear to underpredict power and overpredict fatigue loads because of wake effects, but it is unclear that they are really in error. This discrepancy may be caused by wind-direction uncertainty in the field data, which tends to make wake effects appear less pronounced.
Xie, Binbin; Liu, Lihong; Cui, Ganglong; Fang, Wei-Hai; Cao, Jun; Feng, Wei; Li, Xin-qi
2015-11-21
In this work, the recently introduced quantum trajectory mean-field (QTMF) approach is implemented and employed to explore photodissociation dynamics of diazirinone (N{sub 2}CO), which are based on the high-level ab initio calculation. For comparison, the photodissociation process has been simulated as well with the fewest-switches surface hopping (FSSH) and the ab initio multiple spawning (AIMS) methods. Overall, the dynamical behavior predicted by the three methods is consistent. The N{sub 2}CO photodissociation at λ > 335 nm is an ultrafast process and the two C—N bonds are broken in a stepwise way, giving birth to CO and N{sub 2} as the final products in the ground state. Meanwhile, some noticeable differences were found in the QTMF, FSSH, and AIMS simulated time constants for fission of the C—N bonds, excited-state lifetime, and nonadiabatic transition ratios in different intersection regions. These have been discussed in detail. The present study provides a clear evidence that direct ab initio QTMF approach is one of the reliable tools for simulating nonadiabatic dynamics processes.
FINAL SIMULATION RESULTS FOR DEMONSTRATION CASE 1 AND 2
David Sloan; Woodrow Fiveland
2003-10-15
The goal of this DOE Vision-21 project work scope was to develop an integrated suite of software tools that could be used to simulate and visualize advanced plant concepts. Existing process simulation software did not meet the DOE's objective of ''virtual simulation'' which was needed to evaluate complex cycles. The overall intent of the DOE was to improve predictive tools for cycle analysis, and to improve the component models that are used in turn to simulate equipment in the cycle. Advanced component models are available; however, a generic coupling capability that would link the advanced component models to the cycle simulation software remained to be developed. In the current project, the coupling of the cycle analysis and cycle component simulation software was based on an existing suite of programs. The challenge was to develop a general-purpose software and communications link between the cycle analysis software Aspen Plus{reg_sign} (marketed by Aspen Technology, Inc.), and specialized component modeling packages, as exemplified by industrial proprietary codes (utilized by ALSTOM Power Inc.) and the FLUENT{reg_sign} computational fluid dynamics (CFD) code (provided by Fluent Inc). A software interface and controller, based on an open CAPE-OPEN standard, has been developed and extensively tested. Various test runs and demonstration cases have been utilized to confirm the viability and reliability of the software. ALSTOM Power was tasked with the responsibility to select and run two demonstration cases to test the software--(1) a conventional steam cycle (designated as Demonstration Case 1), and (2) a combined cycle test case (designated as Demonstration Case 2). Demonstration Case 1 is a 30 MWe coal-fired power plant for municipal electricity generation, while Demonstration Case 2 is a 270 MWe, natural gas-fired, combined cycle power plant. Sufficient data was available from the operation of both power plants to complete the cycle configurations. Three runs
Multiphase flow simulations of a moving fluidized bed regenerator in a carbon capture unit
Sarkar, Avik; Pan, Wenxiao; Suh, Dong-Myung; Huckaby, E. D.; Sun, Xin
2014-10-01
To accelerate the commercialization and deployment of carbon capture technologies, computational fluid dynamics (CFD)-based tools may be used to model and analyze the performance of carbon capture devices. This work presents multiphase CFD-based flow simulations for the regeneration device responsible for extracting CO_{2} from CO_{2}-loaded sorbent particles before the particles are recycled. The use of solid particle sorbents in this design is a departure from previously reported systems, where aqueous sorbents are employed. Another new feature is the inclusion of a series of perforated plates along the regenerator height. The influence of these plates on sorbent distribution is examined for varying sorbent holdup, fluidizing gas velocity, and particle size. The residence time distribution of sorbents is also measured to classify the low regime as plug flow or well-mixed flow. The purpose of this work is to better understand the sorbent flow characteristics before reaction kinetics of CO_{2} desorption can be implemented.
Preliminary results for a two-dimensional simulation of the working process of a Stirling engine
Makhkamov, K.K.; Ingham, D.B.
1998-07-01
Stirling engines have several potential advantages over existing types of engines, in particular they can use renewable energy sources for power production and their performance meets the demands on the environmental security. In order to design Stirling Engines properly, and to put into effect their potential performance, it is important to more accurately mathematically simulate its working process. At present, a series of very important mathematical models are used for describing the working process of Stirling Engines and these are, in general, classified as models of three levels. All the models consider one-dimensional schemes for the engine and assume a uniform fluid velocity, temperature and pressure profiles at each plane of the internal gas circuit of the engine. The use of two-dimensional CFD models can significantly extend the capabilities for the detailed analysis of the complex heat transfer and gas dynamic processes which occur in the internal gas circuit, as well as in the external circuit of the engine. In this paper a two-dimensional simplified frame (no construction walls) calculation scheme for the Stirling Engine has been assumed and the standard {kappa}-{var{underscore}epsilon} turbulence model has been used for the analysis of the engine working process. The results obtained show that the use of two-dimensional CFD models gives the possibility of gaining a much greater insight into the fluid flow and heat transfer processes which occur in Stirling Engines.
Pre-test CFD Calculations for a Bypass Flow Standard Problem
Rich Johnson
2011-11-01
The bypass flow in a prismatic high temperature gas-cooled reactor (HTGR) is the flow that occurs between adjacent graphite blocks. Gaps exist between blocks due to variances in their manufacture and installation and because of the expansion and shrinkage of the blocks from heating and irradiation. Although the temperature of fuel compacts and graphite is sensitive to the presence of bypass flow, there is great uncertainty in the level and effects of the bypass flow. The Next Generation Nuclear Plant (NGNP) program at the Idaho National Laboratory has undertaken to produce experimental data of isothermal bypass flow between three adjacent graphite blocks. These data are intended to provide validation for computational fluid dynamic (CFD) analyses of the bypass flow. Such validation data sets are called Standard Problems in the nuclear safety analysis field. Details of the experimental apparatus as well as several pre-test calculations of the bypass flow are provided. Pre-test calculations are useful in examining the nature of the flow and to see if there are any problems associated with the flow and its measurement. The apparatus is designed to be able to provide three different gap widths in the vertical direction (the direction of the normal coolant flow) and two gap widths in the horizontal direction. It is expected that the vertical bypass flow will range from laminar to transitional to turbulent flow for the different gap widths that will be available.
Real-time POD-CFD Wind-Load Calculator for PV Systems
Huayamave, Victor; Divo, Eduardo; Ceballos, Andres; Barriento, Carolina; Stephen, Barkaszi; Hubert, Seigneur
2014-03-21
The primary objective of this project is to create an accurate web-based real-time wind-load calculator. This is of paramount importance for (1) the rapid and accurate assessments of the uplift and downforce loads on a PV mounting system, (2) identifying viable solutions from available mounting systems, and therefore helping reduce the cost of mounting hardware and installation. Wind loading calculations for structures are currently performed according to the American Society of Civil Engineers/ Structural Engineering Institute Standard ASCE/SEI 7; the values in this standard were calculated from simplified models that do not necessarily take into account relevant characteristics such as those from full 3D effects, end effects, turbulence generation and dissipation, as well as minor effects derived from shear forces on installation brackets and other accessories. This standard does not include provisions that address the special requirements of rooftop PV systems, and attempts to apply this standard may lead to significant design errors as wind loads are incorrectly estimated. Therefore, an accurate calculator would be of paramount importance for the preliminary assessments of the uplift and downforce loads on a PV mounting system, identifying viable solutions from available mounting systems, and therefore helping reduce the cost of the mounting system and installation. The challenge is that although a full-fledged three-dimensional computational fluid dynamics (CFD) analysis would properly and accurately capture the complete physical effects of air flow over PV systems, it would be impractical for this tool, which is intended to be a real-time web-based calculator. CFD routinely requires enormous computation times to arrive at solutions that can be deemed accurate and grid-independent even in powerful and massively parallel computer platforms. This work is expected not only to accelerate solar deployment nationwide, but also help reach the SunShot Initiative goals
An Eulerian CFD Model and X-ray Radiography for Coupled Nozzle...
U.S. Department of Energy (DOE) all webpages (Extended Search)
Model and X-ray Radiography for Coupled Nozzle Flow and Spray in Internal Combustion Engines Title An Eulerian CFD Model and X-ray Radiography for Coupled Nozzle Flow and Spray in...
Jeffrey C. Joe; Diego Mandelli; Ronald L. Boring; Curtis L. Smith; Rachel B. Shirley
2015-07-01
The United States Department of Energy is sponsoring the Light Water Reactor Sustainability program, which has the overall objective of supporting the near-term and the extended operation of commercial nuclear power plants. One key research and development (R&D) area in this program is the Risk-Informed Safety Margin Characterization pathway, which combines probabilistic risk simulation with thermohydraulic simulation codes to define and manage safety margins. The R&D efforts to date, however, have not included robust simulations of human operators, and how the reliability of human performance or lack thereof (i.e., human errors) can affect risk-margins and plant performance. This paper describes current and planned research efforts to address the absence of robust human reliability simulations and thereby increase the fidelity of simulated accident scenarios.
A New CFD Model for understanding and Managing Diesel Particulate Filter
Office of Energy Efficiency and Renewable Energy (EERE) (indexed site)
Regeneration | Department of Energy CFD Model for understanding and Managing Diesel Particulate Filter Regeneration A New CFD Model for understanding and Managing Diesel Particulate Filter Regeneration 2004_deer_hou.pdf (1.4 MB) More Documents & Publications Substrate Studies of an Electrically-Assisted Diesel Particulate Filter Diesel Particulate Filter: A Success for Faurecia Exhaust Systems Vehicle Evaluation of Downsized Dow ACM DPF
Petascale, Adaptive CFD (ALCF ESP Technical Report): ALCF-2 Early Science
Office of Scientific and Technical Information (OSTI)
Program Technical Report (Technical Report) | SciTech Connect Petascale, Adaptive CFD (ALCF ESP Technical Report): ALCF-2 Early Science Program Technical Report Citation Details In-Document Search Title: Petascale, Adaptive CFD (ALCF ESP Technical Report): ALCF-2 Early Science Program Technical Report Authors: Jansen, K.E. ; Rasquin, M. [1] ; University of Colorado Boulder) [2] + Show Author Affiliations (LCF) ( Publication Date: 2013-05-13 OSTI Identifier: 1079768 Report Number(s):
Skelton, Adam; Fenter, Paul; Kubicki, James D.; Wesolowski, David J; Cummings, Peter T
2011-01-01
Classical molecular dynamics (CMD) simulations of the (1011) surface of quartz interacting with bulk liquid water are performed using three different classical force fields, Lopes et al., ClayFF, and CHARMM water contact angle (CWCA), and compared to ab initio molecular dynamics (AIMD) and X-ray reflectivity (XR) results. The axial densities of the water and surface atoms normal to the surface are calculated and compared to previous XR experiments. Favorable agreement is shown for all the force fields with respect to the position of the water atoms. Analyses such as the radial distribution functions between water and hydroxyl atoms and the average cosine of the angle between the water dipole vector and the normal of the surface are also calculated for each force field. Significant differences are found between the different force fields from such analyses, indicating differing descriptions of the structured water in the near vicinity of the surface. AIMD simulations are also performed to obtain the water and hydroxyl structure for comparison among the predictions of the three classical force fields to better understand which force field is most accurate. It is shown that ClayFF exhibits the best agreement with the AIMD simulations for water hydroxyl radial distribution functions, suggesting that ClayFF treats the hydrogen bonding more accurately.
Dynamic response of CSM composite plates - simulation using material No. 58 in LS-DYNA3D
Bilkhu, S.S.; Founas, M.; Fong, W.; Agaram, V.
1997-12-31
The paper deals with finite element simulations of transverse impact response of plates made from continuous strand mat(CSM) glass/acrylic composite which is a potential candidate for making light weight automotive body panels. Two impact tests on the plates which result in two very different kinds of response, a drop tower test and a dart test, have been simulated using anisotropic material damage model No. 58 in LS-DYNA3D. In view of the results obtained in this study, the authors discuss the suitability of material model No. 58 for simulations of impact response in a bending environment.
Caratzoulas, Stavros; Courtney, Timothy; Vlachos, Dionisios G.
2011-01-01
We use the conversion of protonated glycerol to acrolein for a case study of the mechanism of acid-catalyzed dehydration of polyols in aqueous environments. We employ hybrid Quamtum Mechanics/Molecular Mechanics Molecular Dynamics (QM/MM MD) simulations with biased sampling and perform free energy calculations for the elementary steps of the reaction. We investigate the effects of solvent dynamics and in particular the role of quantum mechanical water in the dehydration mechanism. We present results supporting a mechanism that proceeds via water-mediated proton transfers and thus through an enol intermediate. We find that the first dehydration may take place by two, low-energy pathways requiring, respectively, 20.9 and 18.8 kcal/mol of activation free energy. The second dehydration requires 19.9 kcal/mol of activation free energy while for the overall reaction we compute a free energy change of -8 kcal/mol.
Wu, Xiaokun; Han, Min; Ming, Dengming
2015-10-07
Membrane proteins play critically important roles in many cellular activities such as ions and small molecule transportation, signal recognition, and transduction. In order to fulfill their functions, these proteins must be placed in different membrane environments and a variety of protein-lipid interactions may affect the behavior of these proteins. One of the key effects of protein-lipid interactions is their ability to change the dynamics status of membrane proteins, thus adjusting their functions. Here, we present a multi-scaled normal mode analysis (mNMA) method to study the dynamics perturbation to the membrane proteins imposed by lipid bi-layer membrane fluctuations. In mNMA, channel proteins are simulated at all-atom level while the membrane is described with a coarse-grained model. mNMA calculations clearly show that channel gating motion can tightly couple with a variety of membrane deformations, including bending and twisting. We then examined bi-channel systems where two channels were separated with different distances. From mNMA calculations, we observed both positive and negative gating correlations between two neighboring channels, and the correlation has a maximum as the channel center-to-center distance is close to 2.5 times of their diameter. This distance is larger than recently found maximum attraction distance between two proteins embedded in membrane which is 1.5 times of the protein size, indicating that membrane fluctuation might impose collective motions among proteins within a larger area. The hybrid resolution feature in mNMA provides atomic dynamics information for key components in the system without costing much computer resource. We expect it to be a conventional simulation tool for ordinary laboratories to study the dynamics of very complicated biological assemblies. The source code is available upon request to the authors.
Simulation of Coal Ash Particle Deposition Experiments (Copyright 2011, American Chemical Society)
Ai, Weiguo; Kuhlman, John M
2011-01-20
Existing experimental ash particle deposition measurements from the literature have been simulated using the computational fluid dynamics (CFD) discrete phase model (DPM) Lagrangian particle tracking method and an existing ash particle deposition model based on the Johnson−Kendall−Roberts (JKR) theory, in the Fluent commercial CFD code. The experimental heating tube was developed to simulate ash temperature histories in a gasifier; ash-heating temperatures ranged from 1873 to 1573 K, spanning the ash-melting temperature. The present simulations used the realizable k−ε turbulence model to compute the gas flow field and the heat transfer to a cooled steel particle impact probe and DPM particle tracking for the particle trajectories and temperatures. A user-defined function (UDF) was developed to describe particle sticking/rebounding and particle detachment on the impinged wall surface. Expressions for the ash particle Young’s modulus in the model, E, versus the particle temperature and diameter were developed by fitting to the E values that were required to match the experimental ash sticking efficiencies from several particle size cuts and ash-heating temperatures for a Japanese bituminous coal. A UDF that implemented the developed stiffness parameter equations was then used to predict the particle sticking efficiency, impact efficiency, and capture efficiency for the entire ash-heating temperature range. Frequency histogram comparisons of adhesion and rebound behavior by particle size between model and experiments showed good agreement for each of the four ash-heating temperatures. However, to apply the present particle deposition model to other coals, a similar validation process would be necessary to develop the effective Young’s modulus versus the particle diameter and temperature correlation for each new coal.
Thermal-hydraulic simulation of mercury target concepts for a pulsed spallation neutron source
Siman-Tov, M.; Wendel, M.; Haines, J.
1996-06-01
The Oak Ridge Spallation Neutron Source (ORSNS) is a high-power, accelerator-based pulsed spallation neutron source being designed by a multi-laboratory team led by Oak Ridge National Laboratory to achieve very high fluxes of neutrons for scientific experiments. The ORSNS is projected to have a 1 MW proton beam upgradable to 5 MW. About 60% of the beam power (1-5 MW, 17-83 kJ/pulse in 0.5 microsec at 60 cps) is deposited in the liquid metal (mercury) target having the dimensions of 65x30x10 cm (about 19.5 liter). Peak steady state power density is about 150 and 785 MW/m{sup 3} for 1 MW and 5 MW beam respectively, whereas peak pulsed power density is as high as 5.2 and 26.1 GW/m{sup 3}, respectively. The peak pulse temperature rise rate is 14 million C/s (for 5 MW beam) whereas the total pulse temperature rise is only 7 C. In addition to thermal shock and materials compatibility, key feasibility issues for the target are related to its thermal-hydraulic performance. This includes proper flow distribution, flow reversals, possible {open_quotes}hot spots{close_quotes} and the challenge of mitigating the effects of thermal shock through possible injection of helium bubbles throughout the mercury volume or other concepts. The general computational fluid dynamics (CFD) code CFDS-FLOW3D was used to simulate the thermal and flow distribution in three preliminary concepts of the mercury target. Very initial CFD simulation of He bubbles injection demonstrates some potential for simulating behavior of He bubbles in flowing mercury. Much study and development will be required to be able to `predict`, even in a crude way, such a complex phenomena. Future direction in both design and R&D is outlined.
Fish Passage though Hydropower Turbines: Simulating Blade Strike using the Discrete Element Method
Richmond, Marshall C.; Romero Gomez, Pedro DJ
2014-12-08
mong the hazardous hydraulic conditions affecting anadromous and resident fish during their passage though turbine flows, two are believed to cause considerable injury and mortality: collision on moving blades and decompression. Several methods are currently available to evaluate these stressors in installed turbines, i.e. using live fish or autonomous sensor devices, and in reduced-scale physical models, i.e. registering collisions from plastic beads. However, a priori estimates with computational modeling approaches applied early in the process of turbine design can facilitate the development of fish-friendly turbines. In the present study, we evaluated the frequency of blade strike and nadir pressure environment by modeling potential fish trajectories with the Discrete Element Method (DEM) applied to fish-like composite particles. In the DEM approach, particles are subjected to realistic hydraulic conditions simulated with computational fluid dynamics (CFD), and particle-structure interactions—representing fish collisions with turbine blades—are explicitly recorded and accounted for in the calculation of particle trajectories. We conducted transient CFD simulations by setting the runner in motion and allowing for better turbulence resolution, a modeling improvement over the conventional practice of simulating the system in steady state which was also done here. While both schemes yielded comparable bulk hydraulic performance, transient conditions exhibited a visual improvement in describing flow variability. We released streamtraces (steady flow solution) and DEM particles (transient solution) at the same location from where sensor fish (SF) have been released in field studies of the modeled turbine unit. The streamtrace-based results showed a better agreement with SF data than the DEM-based nadir pressures did because the former accounted for the turbulent dispersion at the intake but the latter did not. However, the DEM-based strike frequency is more
Zuo, Wangda; Chen, Qingyan
2011-06-01
To design a healthy indoor environment, it is important to study airborne particle distribution indoors. As an intermediate model between multizone models and computational fluid dynamics (CFD), a fast fluid dynamics (FFD) model can be used to provide temporal and spatial information of particle dispersion in real time. This study evaluated the accuracy of the FFD for predicting transportation of particles with low Stokes number in a duct and in a room with mixed convection. The evaluation was to compare the numerical results calculated by the FFD with the corresponding experimental data and the results obtained by the CFD. The comparison showed that the FFD could capture major pattern of particle dispersion, which is missed in models with well-mixed assumptions. Although the FFD was less accurate than the CFD partially due to its simplification in numeric schemes, it was 53 times faster than the CFD.
Computational Fluid Dynamics Analysis of Flexible Duct Junction Box Design
Beach, Robert; Prahl, Duncan; Lange, Rich
2013-12-01
IBACOS explored the relationships between pressure and physical configurations of flexible duct junction boxes by using computational fluid dynamics (CFD) simulations to predict individual box parameters and total system pressure, thereby ensuring improved HVAC performance. Current Air Conditioning Contractors of America (ACCA) guidance (Group 11, Appendix 3, ACCA Manual D, Rutkowski 2009) allows for unconstrained variation in the number of takeoffs, box sizes, and takeoff locations. The only variables currently used in selecting an equivalent length (EL) are velocity of air in the duct and friction rate, given the first takeoff is located at least twice its diameter away from the inlet. This condition does not account for other factors impacting pressure loss across these types of fittings. For each simulation, the IBACOS team converted pressure loss within a box to an EL to compare variation in ACCA Manual D guidance to the simulated variation. IBACOS chose cases to represent flows reasonably correlating to flows typically encountered in the field and analyzed differences in total pressure due to increases in number and location of takeoffs, box dimensions, and velocity of air, and whether an entrance fitting is included. The team also calculated additional balancing losses for all cases due to discrepancies between intended outlet flows and natural flow splits created by the fitting. In certain asymmetrical cases, the balancing losses were significantly higher than symmetrical cases where the natural splits were close to the targets. Thus, IBACOS has shown additional design constraints that can ensure better system performance.
Smith, Kyle K.G.; Poulsen, Jens Aage; Nyman, Gunnar; Cunsolo, Alessandro; Rossky, Peter J.
2015-06-30
Here, we apply the Feynman-Kleinert Quasi-Classical Wigner (FK-QCW) method developed in our previous work [Smith et al., J. Chem. Phys. 142, 244112 (2015)] for the determination of the dynamic structure factor of liquid para-hydrogen and ortho-deuterium at state points of (T = 20.0 K, n = 21.24 nm-3) and (T = 23.0 K, n = 24.61 nm-3), respectively. When applied to this challenging system, it is shown that this new FK-QCW method consistently reproduces the experimental dynamic structure factor reported by Smith et al. [J. Chem. Phys. 140, 034501 (2014)] for all momentum transfers considered. Moreover, this shows that FK-QCWmore » provides a substantial improvement over the Feynman-Kleinert linearized path-integral method, in which purely classical dynamics are used. Furthermore, for small momentum transfers, it is shown that FK-QCW provides nearly the same results as ring-polymer molecular dynamics (RPMD), thus suggesting that FK-QCW provides a potentially more appealing algorithm than RPMD since it is not formally limited to correlation functions involving linear operators.« less
Grant Hawkes; James E. O'Brien
2008-10-01
A three-dimensional computational fluid dynamics (CFD) electrochemical model has been created to model high-temperature electrolysis cell performance and steam electrolysis in a new novel integrated planar porous-tube supported solid oxide electrolysis cell (SOEC). The model is of several integrated planar cells attached to a ceramic support tube. This design is being evaluated with modeling at the Idaho National Laboratory. Mass, momentum, energy, and species conservation and transport are provided via the core features of the commercial CFD code FLUENT. A solid-oxide fuel cell (SOFC) model adds the electrochemical reactions and loss mechanisms and computation of the electric field throughout the cell. The FLUENT SOFC user-defined subroutine was modified for this work to allow for operation in the SOEC mode. Model results provide detailed profiles of temperature, Nernst potential, operating potential, activation over-potential, anode-side gas composition, cathode-side gas composition, current density and hydrogen production over a range of stack operating conditions. Mean per-cell area-specific-resistance (ASR) values decrease with increasing current density. Predicted mean outlet hydrogen and steam concentrations vary linearly with current density, as expected. Effects of variations in operating temperature, gas flow rate, cathode and anode exchange current density, and contact resistance from the base case are presented. Contour plots of local electrolyte temperature, current density, and Nernst potential indicated the effects of heat transfer, reaction cooling/heating, and change in local gas composition. Results are discussed for using this design in the electrolysis mode. Discussion of thermal neutral voltage, enthalpy of reaction, hydrogen production, cell thermal efficiency, cell electrical efficiency, and Gibbs free energy are discussed and reported herein.
Xu, Zuwei; Zhao, Haibo Zheng, Chuguang
2015-01-15
This paper proposes a comprehensive framework for accelerating population balance-Monte Carlo (PBMC) simulation of particle coagulation dynamics. By combining Markov jump model, weighted majorant kernel and GPU (graphics processing unit) parallel computing, a significant gain in computational efficiency is achieved. The Markov jump model constructs a coagulation-rule matrix of differentially-weighted simulation particles, so as to capture the time evolution of particle size distribution with low statistical noise over the full size range and as far as possible to reduce the number of time loopings. Here three coagulation rules are highlighted and it is found that constructing appropriate coagulation rule provides a route to attain the compromise between accuracy and cost of PBMC methods. Further, in order to avoid double looping over all simulation particles when considering the two-particle events (typically, particle coagulation), the weighted majorant kernel is introduced to estimate the maximum coagulation rates being used for acceptance–rejection processes by single-looping over all particles, and meanwhile the mean time-step of coagulation event is estimated by summing the coagulation kernels of rejected and accepted particle pairs. The computational load of these fast differentially-weighted PBMC simulations (based on the Markov jump model) is reduced greatly to be proportional to the number of simulation particles in a zero-dimensional system (single cell). Finally, for a spatially inhomogeneous multi-dimensional (multi-cell) simulation, the proposed fast PBMC is performed in each cell, and multiple cells are parallel processed by multi-cores on a GPU that can implement the massively threaded data-parallel tasks to obtain remarkable speedup ratio (comparing with CPU computation, the speedup ratio of GPU parallel computing is as high as 200 in a case of 100 cells with 10 000 simulation particles per cell). These accelerating approaches of PBMC are
MODELING STRATEGIES TO COMPUTE NATURAL CIRCULATION USING CFD IN A VHTR AFTER A LOFA
Yu-Hsin Tung; Richard W. Johnson; Ching-Chang Chieng; Yuh-Ming Ferng
2012-11-01
A prismatic gas-cooled very high temperature reactor (VHTR) is being developed under the next generation nuclear plant program (NGNP) of the U.S. Department of Energy, Office of Nuclear Energy. In the design of the prismatic VHTR, hexagonal shaped graphite blocks are drilled to allow insertion of fuel pins, made of compacted TRISO fuel particles, and coolant channels for the helium coolant. One of the concerns for the reactor design is the effects of a loss of flow accident (LOFA) where the coolant circulators are lost for some reason, causing a loss of forced coolant flow through the core. In such an event, it is desired to know what happens to the (reduced) heat still being generated in the core and if it represents a problem for the fuel compacts, the graphite core or the reactor vessel (RV) walls. One of the mechanisms for the transport of heat out of the core is by the natural circulation of the coolant, which is still present. That is, how much heat may be transported by natural circulation through the core and upwards to the top of the upper plenum? It is beyond current capability for a computational fluid dynamic (CFD) analysis to perform a calculation on the whole RV with a sufficiently refined mesh to examine the full potential of natural circulation in the vessel. The present paper reports the investigation of several strategies to model the flow and heat transfer in the RV. It is found that it is necessary to employ representative geometries of the core to estimate the heat transfer. However, by taking advantage of global and local symmetries, a detailed estimate of the strength of the resulting natural circulation and the level of heat transfer to the top of the upper plenum is obtained.
Thermal transport in UO_{2} with defects and fission products by molecular dynamics simulations
Liu, Xiang-Yang; Cooper, Michael William Donald; Mcclellan, Kenneth James; Lashley, Jason Charles; Byler, Darrin David; Stanek, Christopher Richard; Andersson, Anders David Ragnar
2015-10-14
The importance of the thermal transport in nuclear fuel has motivated a wide range of experimental and modelling studies. In this report, the reduction of thermal transport in UO_{2} due to defects and fission products has been investigated using non-equilibrium MD simulations, with two sets of empirical potentials for studying the degregation of UO_{2} thermal conductivity including a Buckingham type interatomic potential and a recently developed EAM type interatomic potential. Additional parameters for U^{5+} and Zr^{4+} in UO_{2} have been developed for the EAM potential. The thermal conductivity results from MD simulations are then corrected for the spin-phonon scattering through Callaway model formulations. To validate the modelling results, comparison was made with experimental measurements on single crystal hyper-stoichiometric UO_{2+x} samples.
Heinrich, Jonathon R.; Cooke, David L.
2013-09-15
Electron trapping, electron heating, space-charge wings, wake eddies, and current collection by a positive probe in E×B drifting plasma were studied in three-dimensional electromagnetic particle-in-cell simulations. In these simulations, electrons and ions were magnetized with respect to the probe and the plasma was underdense (ω{sub pe}<ω{sub ce}). A large drift velocity (Mach 4.5 with respect to the ion acoustic speed) between the plasma and probe was created with background electric and magnetic fields. Four distinct regions developed in the presences of the positive probe: a quasi-trapped electron region, an electron-depletion wing, an ion-rich wing, and a wake region. We report on the observations of strong electron heating mechanisms, space-charge wings, ion cyclotron charge-density eddies in the wake, electron acceleration due to a magnetic presheath, and the current-voltage relationship.
Valone, S.M.; Hanson, D.E.; Kress, J.D.
1998-05-08
Simulations of Cl plasma etch of Si surfaces with MD techniques agree reasonably well with the available experimental information on yields and surface morphologies. This information has been supplied to a Monte Carlo etch profile resulting in substantial agreement with comparable inputs provided through controlled experiments. To the extent that more recent measurements of etch rates are more reliable than older ones, preliminary MD simulations using bond-order corrections to the atomic interactions between neighboring Si atoms on the surface improves agreement with experiment through an increase in etch rate and improved agreement with XPS measurements of surface stoichiometry. Thermochemical and geometric analysis of small Si-Br molecules is consistent with the current notions of the effects of including brominated species in etchant gases.
Booten, C.; Tabares-Velasco, P. C.
2012-08-01
This study demonstrates the ability of EnergyPlus to accurately model complex cooling strategies in a real home with a goal of shifting energy use off peak and realizing energy savings. The house was retrofitted through the Sacramento Municipal Utility District's (SMUD) deep energy retrofit demonstration program; field tests were operated by the National Renewable Energy Laboratory (NREL). The experimental data were collected as part of a larger study and are used here to validate simulation predictions.
Ghobadi, Ahmadreza F.; Elliott, J. Richard
2014-07-14
In this work, a new classical density functional theory is developed for group-contribution equations of state (EOS). Details of implementation are demonstrated for the recently-developed SAFT-? WCA EOS and selective applications are studied for confined fluids and vapor-liquid interfaces. The acronym WCA (Weeks-Chandler-Andersen) refers to the characterization of the reference part of the third-order thermodynamic perturbation theory applied in formulating the EOS. SAFT-? refers to the particular form of statistical associating fluid theory that is applied to the fused-sphere, heteronuclear, united-atom molecular models of interest. For the monomer term, the modified fundamental measure theory is extended to WCA-spheres. A new chain functional is also introduced for fused and soft heteronuclear chains. The attractive interactions are taken into account by considering the structure of the fluid, thus elevating the theory beyond the mean field approximation. The fluctuations of energy are also included via a non-local third-order perturbation theory. The theory includes resolution of the density profiles of individual groups such as CH{sub 2} and CH{sub 3} and satisfies stoichiometric constraints for the density profiles. New molecular simulations are conducted to demonstrate the accuracy of each Helmholtz free energy contribution in reproducing the microstructure of inhomogeneous systems at the united-atom level of coarse graining. At each stage, comparisons are made to assess where the present theory stands relative to the current state of the art for studying inhomogeneous fluids. Overall, it is shown that the characteristic features of real molecular fluids are captured both qualitatively and quantitatively. For example, the average pore density deviates ?2% from simulation data for attractive pentadecane in a 2-nm slit pore. Another example is the surface tension of ethane/heptane mixture, which deviates ?1% from simulation data while the theory reproduces
Karakulov, Valerii V.; Smolin, Igor Yu. E-mail: skrp@ftf.tsu.ru; Skripnyak, Vladimir A. E-mail: skrp@ftf.tsu.ru
2014-11-14
Mechanical behavior of stochastic metal-ceramic composites with the aluminum matrix under high-rate deformation at shock-wave loading is numerically simulated with consideration for structural evolution. Effective values of mechanical parameters of metal-ceramic composites Al
Keane, R.E.; Long, D.G.; Menakis, J.P.; Hann, W.J.; Bevins, C.D.
1996-10-01
The paper details the landscape succession model developed for the coarse-scale assessment called CRBSUM (Columbia River Basin SUccession Model) and presents some general results of the application of this model to the entire basin. CRBSUM was used to predict future landscape characteristics to evaluate management alternatives for both mid-and coarse-scale efforts. A test and sensitivity analysis of CRBSUM is also presented. This paper was written as a users guide for those who wish to run the model and interprete results, and its was also written as documentation for some results of the Interior Columbia River Basin simulation effort.
L3:THM.CFD.P5.03 Mark Christon LANL
U.S. Department of Energy (DOE) all webpages (Extended Search)
3 Mark Christon LANL Completed: 10/03/2012 CASL-U-2012-0163-000 Sensitivity, Verification, and Validation Studies of STAR-CD, STAR-CCM+, and Nphase CFD Boiling Models Isaac M. Asher ∗ , Timothy J. Drzewiecki † , Timothy P. Grunloh ‡ , Victor E. Petrov § , Krzysztof J. Fidkowski ¶ , Annalisa Manera , September 29, 2012 CASL Milestone L3-THM-CFD-P5-03 ∗ Graduate Student, Department of Aerospace Engineering, University of Michigan † Graduate Student, Department of Nuclear Engineering
Tran, H.; Domenech, J.-L.
2014-08-14
Spectral shapes of isolated lines of HCl perturbed by Ar are investigated for the first time using classical molecular dynamics simulations (CMDS). Using reliable intermolecular potentials taken from the literature, these CMDS provide the time evolution of the auto-correlation function of the dipole moment, whose Fourier-Laplace transform leads to the absorption spectrum. In order to test these calculations, room temperature spectra of various lines in the fundamental band of HCl diluted in Ar are measured, in a large pressure range, with a difference-frequency laser spectrometer. Comparisons between measured and calculated spectra show that the CMDS are able to predict the large Dicke narrowing effect on the shape of HCl lines and to satisfactorily reproduce the shapes of HCl spectra at different pressures and for various rotational quantum numbers.
Chen, P. H.; Avchachov, K.; Nordlund, K.; Pussi, K.
2013-06-21
Due to the peculiar nature of the atomic order in quasicrystals, examining phase transitions in this class of materials is of particular interest. Energetic particle irradiation can provide a way to modify the structure locally in a quasicrystal. To examine irradiation-induced phase transitions in quasicrystals on the atomic scale, we have carried out molecular dynamics simulations of collision cascades in CaCd{sub 6} quasicrystal cubic approximant with energies up to 10 keV at 0 and 300 K. The results show that the threshold energies depend surprisingly strongly on the local coordination environments. The energy dependence of stable defect formation exhibits a power-law dependence on cascade energy, and surviving defects are dominated by Cd interstitials and vacancies. Only a modest effect of temperature is observed on defect survival, while irradiation temperature increases lead to a slight increase in the average size of both vacancy clusters and interstitial clusters.
Development of CFD-Based Simulation Tools for In-Situ Thermal...
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Computational fluid dynamics modeling of proton exchange membrane fuel cells
UM,SUKKEE; WANG,C.Y.; CHEN,KEN S.
2000-02-11
A transient, multi-dimensional model has been developed to simulate proton exchange membrane (PEM) fuel cells. The model accounts simultaneously for electrochemical kinetics, current distribution, hydrodynamics and multi-component transport. A single set of conservation equations valid for flow channels, gas-diffusion electrodes, catalyst layers and the membrane region are developed and numerically solved using a finite-volume-based computational fluid dynamics (CFD) technique. The numerical model is validated against published experimental data with good agreement. Subsequently, the model is applied to explore hydrogen dilution effects in the anode feed. The predicted polarization cubes under hydrogen dilution conditions are found to be in qualitative agreement with recent experiments reported in the literature. The detailed two-dimensional electrochemical and flow/transport simulations further reveal that in the presence of hydrogen dilution in the fuel stream, hydrogen is depleted at the reaction surface resulting in substantial kinetic polarization and hence a lower current density that is limited by hydrogen transport from the fuel stream to the reaction site.
Rouleau, C. M. Puretzky, A. A.; Geohegan, D. B.; Shih, C.-Y.; Wu, C.; Zhigilei, L. V.
2014-05-12
The synthesis of metal nanoparticles by ultrafast laser ablation of nanometers-thick metal films has been studied experimentally and computationally. Near-threshold backside laser ablation of 2–20 nm-thick Pt films deposited on fused silica substrates was found to produce nanoparticles with size distributions that were bimodal for the thicker films, but collapsed into a single mode distribution for the thinnest film. Time-resolved imaging of blackbody emission from the Pt nanoparticles was used to reveal the nanoparticle propagation dynamics and estimate their temperatures. The observed nanoparticle plume was compact and highly forward-directed with a well-defined collective velocity that permitted multiple rebounds with substrates to be revealed. Large-scale molecular dynamics simulations were used to understand the evolution of compressive and tensile stresses in the thicker melted liquid films that lead to their breakup and ejection of two groups of nanoparticles with different velocity and size distributions. Ultrafast laser irradiation of ultrathin (few nm) metal films avoids the splitting of the film and appears to be a method well-suited to cleanly synthesize and deposit nanoparticles from semitransparent thin film targets in highly directed beams.
Kanevce, Ana; Kuciauskas, Darius; Levi, Dean H.; Johnston, Steven W.; Allende Motz, Alyssa M.
2015-07-28
We use two-dimensional numerical simulations to analyze high spatial resolution time-resolved spectroscopy data. This analysis is applied to two-photon excitation time-resolved photoluminescence (2PE-TRPL) but is broadly applicable to all microscopic time-resolved techniques. By solving time-dependent drift-diffusion equations, we gain insight into carrier dynamics and transport characteristics. Accurate understanding of measurement results establishes the limits and potential of the measurement and enhances its value as a characterization method. Diffusion of carriers outside of the collection volume can have a significant impact on the measured decay but can also provide an estimate of carrier mobility as well as lifetime. In addition to material parameters, the experimental conditions, such as spot size and injection level, can impact the measurement results. Although small spot size provides better resolution, it also increases the impact of diffusion on the decay; if the spot size is much smaller than the diffusion length, it impacts the entire decay. By reproducing experimental 2PE-TRPL decays, the simulations determine the bulk carrier lifetime from the data. The analysis is applied to single-crystal and heteroepitaxial CdTe, material important for solar cells, but it is also applicable to other semiconductors where carrier diffusion from the excitation volume could affect experimental measurements.
Lance, Blake W.; Smith, Barton L.
2016-06-23
Transient convection has been investigated experimentally for the purpose of providing Computational Fluid Dynamics (CFD) validation benchmark data. A specialized facility for validation benchmark experiments called the Rotatable Buoyancy Tunnel was used to acquire thermal and velocity measurements of flow over a smooth, vertical heated plate. The initial condition was forced convection downward with subsequent transition to mixed convection, ending with natural convection upward after a flow reversal. Data acquisition through the transient was repeated for ensemble-averaged results. With simple flow geometry, validation data were acquired at the benchmark level. All boundary conditions (BCs) were measured and their uncertainties quantified.more » Temperature profiles on all four walls and the inlet were measured, as well as as-built test section geometry. Inlet velocity profiles and turbulence levels were quantified using Particle Image Velocimetry. System Response Quantities (SRQs) were measured for comparison with CFD outputs and include velocity profiles, wall heat flux, and wall shear stress. Extra effort was invested in documenting and preserving the validation data. Details about the experimental facility, instrumentation, experimental procedure, materials, BCs, and SRQs are made available through this paper. As a result, the latter two are available for download and the other details are included in this work.« less
Pau, G. S. H.; Bisht, G.; Riley, W. J.
2014-04-04
Existing land surface models (LSMs) describe physical and biological processes that occur over a wide range of spatial and temporal scales. For example, biogeochemical and hydrological processes responsible for carbon (CO2, CH4) exchanges with the atmosphere range from molecular scale (pore-scale O2 consumption) to tens of kilometer scale (vegetation distribution, river networks). Additionally, many processes within LSMs are nonlinearly coupled (e.g., methane production and soil moisture dynamics), and therefore simple linear upscaling techniques can result in large prediction error. In this paper we applied a particular reduced-order modeling (ROM) technique known as "Proper Orthogonal Decomposition mapping method" that reconstructs temporally-resolvedmore » fine-resolution solutions based on coarse-resolution solutions. We applied this technique to four study sites in a polygonal tundra landscape near Barrow, Alaska. Coupled surface-subsurface isothermal simulations were performed for summer months (June–September) at fine (0.25 m) and coarse (8 m) horizontal resolutions. We used simulation results from three summer seasons (1998–2000) to build ROMs of the 4-D soil moisture field for the four study sites individually (single-site) and aggregated (multi-site). The results indicate that the ROM produced a significant computational speedup (> 103) with very small relative approximation error (< 0.1%) for two validation years not used in training the ROM. We also demonstrated that our approach: (1) efficiently corrects for coarse-resolution model bias and (2) can be used for polygonal tundra sites not included in the training dataset with relatively good accuracy (< 1.5% relative error), thereby allowing for the possibility of applying these ROMs across a much larger landscape. This method has the potential to efficiently increase the resolution of land models for coupled climate simulations, allowing LSMs to be used at spatial scales consistent with
Pokorna, Sarka; Jurkiewicz, Piotr; Hof, Martin; Vazdar, Mario; Cwiklik, Lukasz; Jungwirth, Pavel
2014-12-14
Time-dependent fluorescence shift (TDFS) of Laurdan embedded in phospholipid bilayers reports on hydration and mobility of the phospholipid acylgroups. Exchange of H{sub 2}O with D{sub 2}O prolongs the lifetime of lipid-water and lipid-water-lipid interactions, which is reflected in a significantly slower TDFS kinetics. Combining TDFS measurements in H{sub 2}O and D{sub 2}O hydrated bilayers with atomistic molecular dynamics (MD) simulations provides a unique tool for characterization of the hydrogen bonding at the acylgroup level of lipid bilayers. In this work, we use this approach to study the influence of fluoride anions on the properties of cationic bilayers composed of trimethylammonium-propane (DOTAP). The results obtained for DOTAP are confronted with those for neutral phosphatidylcholine (DOPC) bilayers. Both in DOTAP and DOPC H{sub 2}O/D{sub 2}O exchange prolongs hydrogen-bonding lifetime and does not disturb bilayer structure. These results are confirmed by MD simulations. TDFS experiments show, however, that for DOTAP this effect is cancelled in the presence of fluoride ions. We interpret these results as evidence that strongly hydrated fluoride is able to steal water molecules that bridge lipid carbonyls. Consequently, when attracted to DOTAP bilayer, fluoride disrupts the local hydrogen-bonding network, and the differences in TDFS kinetics between H{sub 2}O and D{sub 2}O hydrated bilayers are no longer observed. A distinct behavior of fluoride is also evidenced by MD simulations, which show different lipid-ion binding for Cl{sup −} and F{sup −}.
Pau, G. S. H.; Bisht, G.; Riley, W. J.
2014-09-17
Existing land surface models (LSMs) describe physical and biological processes that occur over a wide range of spatial and temporal scales. For example, biogeochemical and hydrological processes responsible for carbon (CO2, CH4) exchanges with the atmosphere range from the molecular scale (pore-scale O2 consumption) to tens of kilometers (vegetation distribution, river networks). Additionally, many processes within LSMs are nonlinearly coupled (e.g., methane production and soil moisture dynamics), and therefore simple linear upscaling techniques can result in large prediction error. In this paper we applied a reduced-order modeling (ROM) technique known as "proper orthogonal decomposition mapping method" that reconstructs temporally resolvedmore » fine-resolution solutions based on coarse-resolution solutions. We developed four different methods and applied them to four study sites in a polygonal tundra landscape near Barrow, Alaska. Coupled surface–subsurface isothermal simulations were performed for summer months (June–September) at fine (0.25 m) and coarse (8 m) horizontal resolutions. We used simulation results from three summer seasons (1998–2000) to build ROMs of the 4-D soil moisture field for the study sites individually (single-site) and aggregated (multi-site). The results indicate that the ROM produced a significant computational speedup (> 103) with very small relative approximation error (< 0.1%) for 2 validation years not used in training the ROM. We also demonstrate that our approach: (1) efficiently corrects for coarse-resolution model bias and (2) can be used for polygonal tundra sites not included in the training data set with relatively good accuracy (< 1.7% relative error), thereby allowing for the possibility of applying these ROMs across a much larger landscape. By coupling the ROMs constructed at different scales together hierarchically, this method has the potential to efficiently increase the resolution of land models for coupled
Bhattacharyya, D,; Turton, R.; Zitney, S.
2012-01-01
Load-following control of future integrated gasification combined cycle (IGCC) plants with pre-combustion CO{sub 2} capture is expected to be far more challenging as electricity produced by renewable energy is connected to the grid and strict environmental limits become mandatory requirements. To study control performance during load following, a plant-wide dynamic simulation of a coal-fed IGCC plant with CO{sub 2} capture has been developed. The slurry-fed gasifier is a single-stage, downward-fired, oxygen-blown, entrained-flow type with a radiant syngas cooler (RSC). The syngas from the outlet of the RSC goes to a scrubber followed by a two-stage sour shift process with inter-stage cooling. The acid gas removal (AGR) process is a dual-stage physical solvent-based process for selective removal of H{sub 2}S in the first stage and CO{sub 2} in the second stage. Sulfur is recovered using a Claus unit with tail gas recycle to the AGR. The recovered CO{sub 2} is compressed by a split-shaft multistage compressor and sent for sequestration after being treated in an absorber with triethylene glycol for dehydration. The clean syngas is sent to two advanced “F”-class gas turbines (GTs) partially integrated with an elevated-pressure air separation unit. A subcritical steam cycle is used for heat recovery steam generation. A treatment unit for the sour water strips off the acid gases for utilization in the Claus unit. The steady-state model developed in Aspen Plus® is converted to an Aspen Plus Dynamics® simulation and integrated with MATLAB® for control studies. The results from the plant-wide dynamic model are compared qualitatively with the data from a commercial plant having different configuration, operating condition, and feed quality than what has been considered in this work. For load-following control, the GT-lead with gasifier-follow control strategy is considered. A modified proportional–integral–derivative (PID) control is considered for the syngas
Code Verification of the HIGRAD Computational Fluid Dynamics Solver
Van Buren, Kendra L.; Canfield, Jesse M.; Hemez, Francois M.; Sauer, Jeremy A.
2012-05-04
The purpose of this report is to outline code and solution verification activities applied to HIGRAD, a Computational Fluid Dynamics (CFD) solver of the compressible Navier-Stokes equations developed at the Los Alamos National Laboratory, and used to simulate various phenomena such as the propagation of wildfires and atmospheric hydrodynamics. Code verification efforts, as described in this report, are an important first step to establish the credibility of numerical simulations. They provide evidence that the mathematical formulation is properly implemented without significant mistakes that would adversely impact the application of interest. Highly accurate analytical solutions are derived for four code verification test problems that exercise different aspects of the code. These test problems are referred to as: (i) the quiet start, (ii) the passive advection, (iii) the passive diffusion, and (iv) the piston-like problem. These problems are simulated using HIGRAD with different levels of mesh discretization and the numerical solutions are compared to their analytical counterparts. In addition, the rates of convergence are estimated to verify the numerical performance of the solver. The first three test problems produce numerical approximations as expected. The fourth test problem (piston-like) indicates the extent to which the code is able to simulate a 'mild' discontinuity, which is a condition that would typically be better handled by a Lagrangian formulation. The current investigation concludes that the numerical implementation of the solver performs as expected. The quality of solutions is sufficient to provide credible simulations of fluid flows around wind turbines. The main caveat associated to these findings is the low coverage provided by these four problems, and somewhat limited verification activities. A more comprehensive evaluation of HIGRAD may be beneficial for future studies.
Data Collection Methods for Validation of Advanced Multi-Resolution Fast Reactor Simulations
Tokuhiro, Akiro; Ruggles, Art; Pointer, David
2015-01-22
In pool-type Sodium Fast Reactors (SFR) the regions most susceptible to thermal striping are the upper instrumentation structure (UIS) and the intermediate heat exchanger (IHX). This project experimentally and computationally (CFD) investigated the thermal mixing in the region exiting the reactor core to the UIS. The thermal mixing phenomenon was simulated using two vertical jets at different velocities and temperatures as prototypic of two adjacent channels out of the core. Thermal jet mixing of anticipated flows at different temperatures and velocities were investigated. Velocity profiles are measured throughout the flow region using Ultrasonic Doppler Velocimetry (UDV), and temperatures along the geometric centerline between the jets were recorded using a thermocouple array. CFD simulations, using COMSOL, were used to initially understand the flow, then to design the experimental apparatus and finally to compare simulation results and measurements characterizing the flows. The experimental results and CFD simulations show that the flow field is characterized into three regions with respective transitions, namely, convective mixing, (flow direction) transitional, and post-mixing. Both experiments and CFD simulations support this observation. For the anticipated SFR conditions the flow is momentum dominated and thus thermal mixing is limited due to the short flow length associated from the exit of the core to the bottom of the UIS. This means that there will be thermal striping at any surface where poorly mixed streams impinge; rather unless lateral mixing is ‘actively promoted out of the core, thermal striping will prevail. Furthermore we note that CFD can be considered a ‘separate effects (computational) test’ and is recommended as part of any integral analysis. To this effect, poorly mixed streams then have potential impact on the rest of the SFR design and scaling, especially placement of internal components, such as the IHX that may see poorly mixed
MacDermaid, Christopher M. Klein, Michael L.; Fiorin, Giacomo; Kashyap, Hemant K.; DeVane, Russell H.; Shinoda, Wataru; Klauda, Jeffery B.
2015-12-28
The architecture of a biological membrane hinges upon the fundamental fact that its properties are determined by more than the sum of its individual components. Studies on model membranes have shown the need to characterize in molecular detail how properties such as thickness, fluidity, and macroscopic bending rigidity are regulated by the interactions between individual molecules in a non-trivial fashion. Simulation-based approaches are invaluable to this purpose but are typically limited to short sampling times and model systems that are often smaller than the required properties. To alleviate both limitations, the use of coarse-grained (CG) models is nowadays an established computational strategy. We here present a new CG force field for cholesterol, which was developed by using measured properties of small molecules, and can be used in combination with our previously developed force field for phospholipids. The new model performs with precision comparable to atomistic force fields in predicting the properties of cholesterol-rich phospholipid bilayers, including area per lipid, bilayer thickness, tail order parameter, increase in bending rigidity, and propensity to form liquid-ordered domains in ternary mixtures. We suggest the use of this model to quantify the impact of cholesterol on macroscopic properties and on microscopic phenomena involving localization and trafficking of lipids and proteins on cellular membranes.
Danish, Mohammad Suman, Sawan Srinivasan, Balaji
2014-12-15
The pressure Hessian tensor plays a key role in shaping the behavior of the velocity gradient tensor, and in turn, that of many incumbent non-linear processes in a turbulent flow field. In compressible flows, the role of pressure Hessian is even more important because it represents the level of fluid-thermodynamic coupling existing in the flow field. In this work, we first perform a direct numerical simulation-based study to clearly identify, isolate, and understand various important inviscid mechanisms that govern the evolution of the pressure Hessian tensor in compressible turbulence. The ensuing understanding is then employed to introduce major improvements to the existing Lagrangian model of the pressure Hessian tensor (the enhanced Homogenized Euler equation or EHEE) in terms of (i) non-symmetric, non-isentropic effects and (ii) improved representation of the anisotropic portion of the pressure Hessian tensor. Finally, we evaluate the new model extensively by comparing the new model results against known turbulence behavior over a range of Reynolds and Mach numbers. Indeed, the new model shows much improved performance as compared to the EHEE model.
Nawrocki, Grzegorz; Cieplak, Marek
2014-03-07
The growing usage of nanoparticles of zinc sulfide as quantum dots and biosensors calls for a theoretical assessment of interactions of ZnS with biomolecules. We employ the molecular-dynamics-based umbrella sampling method to determine potentials of mean force for 20 single amino acids near the ZnS (110) surface in aqueous solutions. We find that five amino acids do not bind at all and the binding energy of the remaining amino acids does not exceed 4.3 kJ/mol. Such energies are comparable to those found for ZnO (and to hydrogen bonds in proteins) but the nature of the specificity is different. Cysteine can bind with ZnS in a covalent way, e.g., by forming the disulfide bond with S in the solid. If this effect is included within a model incorporating the Morse potential, then the potential well becomes much deeperthe binding energy is close to 98 kJ/mol. We then consider tryptophan cage, a protein of 20 residues, and characterize its events of adsorption to ZnS. We demonstrate the relevance of interactions between the amino acids in the selection of optimal adsorbed conformations and recognize the key role of cysteine in generation of lasting adsorption. We show that ZnS is more hydrophobic than ZnO and that the density profile of water is quite different than that forming near ZnOit has only a minor articulation into layers. Furthermore, the first layer of water is disordered and mobile.
Brink, Jeandrew; Teukolsky, Saul A; Wasserman, Ira
2005-03-15
Two mechanisms for nonlinear mode saturation of the r mode in neutron stars have been suggested: the parametric instability mechanism involving a small number of modes and the formation of a nearly continuous Kolmogorov-type cascade. Using a network of oscillators constructed from the eigenmodes of a perfect fluid incompressible star, we investigate the transition between the two regimes numerically. Our network includes the 4995 inertial modes up to n{<=}30 with 146 998 direct couplings to the r mode and 1 306 999 couplings with detuning <0.002 (out of a total of approximately 10{sup 9} possible couplings). The lowest parametric instability thresholds for a range of temperatures are calculated and it is found that the r mode becomes unstable to modes with 13
Annual Report: Carbon Capture Simulation Initiative (CCSI) (30 September 2013)
Miller, David C.; Syamlal, Madhava; Cottrell, Roger; Kress, Joel D.; Sundaresan, S.; Sun, Xin; Storlie, C.; Bhattacharyya, D.; Tong, Charles; Zitney, Stephen E; Dale, Crystal; Engel, Dave; Agarwal, Deb; Calafiura, Paolo; Shinn, John
2014-03-05
Virginia University, Boston University and the University of Texas at Austin) bring unparalleled expertise in multiphase flow reactors, combustion, process synthesis and optimization, planning and scheduling, and process control techniques for energy processes. During Fiscal Year (FY) 13, CCSI announced the initial release of its first set of computational tools and models during the October 2012 meeting of its Industry Advisory Board. This initial release led to five companies licensing the CCSI Toolset under a Test and Evaluation Agreement this year. By the end of FY13, the CCSI Technical Team had completed development of an updated suite of computational tools and models. The list below summarizes the new and enhanced toolset components that were released following comprehensive testing during October 2013. 1. FOQUS. Framework for Optimization and Quantification of Uncertainty and Sensitivity. Package includes: FOQUS Graphic User Interface (GUI), simulation-based optimization engine, Turbine Client, and heat integration capabilities. There is also an updated simulation interface and new configuration GUI for connecting Aspen Plus or Aspen Custom Modeler (ACM) simulations to FOQUS and the Turbine Science Gateway. 2. A new MFIX-based Computational Fluid Dynamics (CFD) model to predict particle attrition. 3. A new dynamic reduced model (RM) builder, which generates computationally efficient RMs of the behavior of a dynamic system. 4. A completely re-written version of the algebraic surrogate model builder for optimization (ALAMO). The new version is several orders of magnitude faster than the initial release and eliminates the MATLAB dependency. 5. A new suite of high resolution filtered models for the hydrodynamics associated with horizontal cylindrical objects in a flow path. 6. The new Turbine Science Gateway (Cluster), which supports FOQUS for running multiple simulations for optimization or UQ using a local computer or cluster. 7. A new statistical tool (BSS
Prezhdo, Oleg V.
2012-03-22
provided a unified atomistic picture of the nature and dynamics of photoexcited states in semiconductor QDs. We also summarized our recent findings about the photoinduced electron dynamics at the chromophore-semiconductor interfaces from a time-domain ab initio perspective. The interface provides the foundation for a new, promising type of solar cell and presents a fundamentally important case study for several fields, including photo-, electro- and analytical chemistries, molecular electronics, and photography. Further, the interface offers a classic example of an interaction between an organic molecular species and an inorganic bulk material. Scientists employ different concepts and terminologies to describe molecular and solid states of matter, and these differences make it difficult to describe the interface with a single model. At the basic atomistic level of description, however, this challenge can be largely overcome. Recent advances in non-adiabatic molecular dynamics and time-domain density functional theory have created a unique opportunity for simulating the ultrafast, photoinduced processes on a computer very similar to the way that they occur in nature. These state-of-the-art theoretical tools offered a comprehensive picture of a variety of electron transfer processes that occur at the interface, including electron injection from the chromophore to the semiconductor, electron relaxation and delocalization inside the semiconductor, back-transfer of the electron to the chromophore and to the electrolyte, and regeneration of the neutral chromophore by the electrolyte. The ab initio time-domain modeling is particularly valuable for understanding these dynamic features of the ultrafast electron transfer processes, which cannot be represented by a simple rate description. We demonstrated using symmetry adapted cluster theory with configuration interaction (SAC-CI) that charging of small PbSe nanocrystals (NCs) greatly modifies their electronic states and optical
APPLICATIONS OF CFD METHOD TO GAS MIXING ANALYSIS IN A LARGE-SCALED TANK
Lee, S; Richard Dimenna, R
2007-03-19
The computational fluid dynamics (CFD) modeling technique was applied to the estimation of maximum benzene concentration for the vapor space inside a large-scaled and high-level radioactive waste tank at Savannah River site (SRS). The objective of the work was to perform the calculations for the benzene mixing behavior in the vapor space of Tank 48 and its impact on the local concentration of benzene. The calculations were used to evaluate the degree to which purge air mixes with benzene evolving from the liquid surface and its ability to prevent an unacceptable concentration of benzene from forming. The analysis was focused on changing the tank operating conditions to establish internal recirculation and changing the benzene evolution rate from the liquid surface. The model used a three-dimensional momentum coupled with multi-species transport. The calculations included potential operating conditions for air inlet and exhaust flows, recirculation flow rate, and benzene evolution rate with prototypic tank geometry. The flow conditions are assumed to be fully turbulent since Reynolds numbers for typical operating conditions are in the range of 20,000 to 70,000 based on the inlet conditions of the air purge system. A standard two-equation turbulence model was used. The modeling results for the typical gas mixing problems available in the literature were compared and verified through comparisons with the test results. The benchmarking results showed that the predictions are in good agreement with the analytical solutions and literature data. Additional sensitivity calculations included a reduced benzene evolution rate, reduced air inlet and exhaust flow, and forced internal recirculation. The modeling results showed that the vapor space was fairly well mixed and that benzene concentrations were relatively low when forced recirculation and 72 cfm ventilation air through the tank boundary were imposed. For the same 72 cfm air inlet flow but without forced recirculation
An Integrated RELAP5-3D and Multiphase CFD Code System Utilizing a Semi Implicit Coupling Technique
D.L. Aumiller; E.T. Tomlinson; W.L. Weaver
2001-06-21
An integrated code system consisting of RELAP5-3D and a multiphase CFD program has been created through the use of a generic semi-implicit coupling algorithm. Unlike previous CFD coupling work, this coupling scheme is numerically stable provided the material Courant limit is not violated in RELAP5-3D or at the coupling locations. The basis for the coupling scheme and details regarding the unique features associated with the application of this technique to a four-field CFD program are presented. Finally, the results of a verification problem are presented. The coupled code system is shown to yield accurate and numerically stable results.
Jake P. Gentle; Kurt S Myers; Tyler B Phillips; Inanc Senocak; Phil Anderson
2014-08-01
Dynamic Line Rating (DLR) is a smart grid technology that allows the rating of power line to be based on real-time conductor temperature dependent on local weather conditions. In current practice overhead power lines are generally given a conservative rating based on worst case weather conditions. Using historical weather data collected over a test bed area, we demonstrate there is often additional transmission capacity not being utilized with the current static rating practice. We investigate a new dynamic line rating methodology using computational fluid dynamics (CFD) to determine wind conditions along transmission lines at dense intervals. Simulated results are used to determine conductor temperature by calculating the transient thermal response of the conductor under variable environmental conditions. In calculating the conductor temperature, we use both a calculation with steady-state assumption and a transient calculation. Under low wind conditions, steady-state assumption predicts higher conductor temperatures that could lead to curtailments, whereas transient calculations produce conductor temperatures that are significantly lower, implying the availability of additional transmission capacity.
Hartmann, S., E-mail: steffen.hartmann@etit.tu-chemnitz.de; Blaudeck, T.; Hermann, S.; Wunderle, B. [Technische Universitt Chemnitz, Reichenhainer Str. 70, 09126 Chemnitz (Germany); Hlck, O. [Technische Universitt Chemnitz, Reichenhainer Str. 70, 09126 Chemnitz (Germany); Fraunhofer IZM Berlin, Gustav-Meyer-Allee 25, 13355 Berlin (Germany); Schulz, S. E.; Gessner, T. [Technische Universitt Chemnitz, Reichenhainer Str. 70, 09126 Chemnitz (Germany); Fraunhofer ENAS Chemnitz, Technologie-Campus 3, 09126 Chemnitz (Germany)
2014-04-14
In this paper, we present our results of experimental and numerical pull-out tests on carbon nanotubes (CNTs) embedded in palladium. We prepared simple specimens by employing standard silicon wafers, physical vapor deposition of palladium and deposition of CNTs with a simple drop coating technique. An AFM cantilever with known stiffness connected to a nanomanipulation system was utilized inside a scanning electron microscope (SEM) as a force sensor to determine forces acting on a CNT during the pull-out process. SEM-images of the cantilever attached to a CNT have been evaluated for subsequent displacement steps with greyscale correlation to determine the cantilever deflection. We compare the experimentally obtained pull-out forces with values of numerical investigations by means of molecular dynamics and give interpretations for deviations according to material impurities or defects and their influence on the pull-out data. We find a very good agreement of force data from simulation and experiment, which is 17 nN and in the range of 1061 nN, respectively. Our findings contribute to the ongoing research of the mechanical characterization of CNT-metal interfaces. This is of significant interest for the design of future mechanical sensors utilizing the intrinsic piezoresistive effect of CNTs or other future devices incorporating CNT-metal interfaces.
The thermal conductivity of mixed fuel U_{x}Pu_{1-x}O_{2}: molecular dynamics simulations
Liu, Xiang-Yang; Cooper, Michael William Donald; Stanek, Christopher Richard; Andersson, Anders David Ragnar
2015-10-16
Mixed oxides (MOX), in the context of nuclear fuels, are a mixture of the oxides of heavy actinide elements such as uranium, plutonium and thorium. The interest in the UO_{2}-PuO_{2} system arises from the fact that these oxides are used both in fast breeder reactors (FBRs) as well as in pressurized water reactors (PWRs). The thermal conductivity of UO_{2} fuel is an important material property that affects fuel performance since it is the key parameter determining the temperature distribution in the fuel, thus governing, e.g., dimensional changes due to thermal expansion, fission gas release rates, etc. For this reason it is important to understand the thermal conductivity of MOX fuel and how it differs from UO_{2}. Here, molecular dynamics (MD) simulations are carried out to determine quantitatively, the effect of mixing on the thermal conductivity of U_{x}Pu_{1-x}O_{2}, as a function of PuO_{2} concentrations, for a range of temperatures, 300 – 1500 K. The results will be used to develop enhanced continuum thermal conductivity models for MARMOT and BISON by INL. These models express the thermal conductivity as a function of microstructure state-variables, thus enabling thermal conductivity models with closer connection to the physical state of the fuel.
Larcher, G.; Tran, H. Schwell, M.; Chelin, P.; Landsheere, X.; Hartmann, J.-M.; Hu, S.-M.
2014-02-28
Room temperature absorption spectra of various transitions of pure CO{sub 2} have been measured in a broad pressure range using a tunable diode-laser and a cavity ring-down spectrometer, respectively, in the 1.6 μm and 0.8 μm regions. Their spectral shapes have been calculated by requantized classical molecular dynamics simulations. From the time-dependent auto-correlation function of the molecular dipole, including Doppler and collisional effects, spectral shapes are directly computed without the use of any adjusted parameter. Analysis of the spectra calculated using three different anisotropic intermolecular potentials shows that the shapes of pure CO{sub 2} lines, in terms of both the Lorentz widths and non-Voigt effects, slightly depend on the used potential. Comparisons between these ab initio calculations and the measured spectra show satisfactory agreement for all considered transitions (from J = 6 to J = 46). They also show that non-Voigt effects on the shape of CO{sub 2} transitions are almost independent of the rotational quantum number of the considered lines.
Huang, Yuxiang; Huang, Li; Wang, C. Z.; Kramer, M. J.; Ho, K. M.
2016-02-01
In this study, comparative analysis between Zr-rich Zr50Cu45Al5 and Cu-rich Cu50Zr45Al5 metallic glasses (MGs) is extensively performed to locate the key structural motifs accounting for their difference of glass forming ability. Here we adopt ab initio molecular dynamics simulations to investigate the local atomic structures of Zr50Cu45Al5 and Cu50Zr45Al5 MGs. A high content of icosahedral-related (full and distorted) orders was found in both samples, while in the Zr-rich MG full icosahedrons <0,0,12,0> is dominant, and in the Cu-rich one the distorted icosahedral orders, especially <0,2,8,2> and <0,2,8,1>, are prominent. And the <0,2,8,2> polyhedra in Cu50Zr45Al5 MG mainly originate from Al-centeredmore » clusters, while the <0,0,12,0> in Zr50Cu45Al5 derives from both Cu-centered clusters and Al-centered clusters. These difference may be ascribed to the atomic size difference and chemical property between Cu and Zr atoms. The relatively large size of Zr and large negative heat of mixing between Zr and Al atoms, enhancing the packing density and stability of metallic glass system, may be responsible for the higher glass forming ability of Zr50Cu45Al5.« less
Huang, Yuxiang; Huang, Li; Wang, C. Z.; Kramer, M. J.; Ho, K. M.
2016-02-01
Comparative analysis between Zr-rich Zr50Cu45Al5 and Cu-rich Cu50Zr45Al5 metallic glasses (MGs) is extensively performed to locate the key structural motifs accounting for their difference of glass forming ability. Here we adopt ab initio molecular dynamics simulations to investigate the local atomic structures of Zr50Cu45Al5 and Cu50Zr45Al5 MGs. A high content of icosahedral-related (full and distorted) orders was found in both samples, while in the Zr-rich MG full icosahedrons < 0,0,12,0 > is dominant, and in the Cu-rich one the distorted icosahedral orders, especially < 0,2,8,2 > and < 0,2,8,1 >, are prominent. And the < 0,2,8,2 > polyhedra in Cu50Zr45Al5more » MG mainly originate from Al-centered clusters, while the < 0,0,12,0 > in Zr50Cu45Al5 derives from both Cu-centered clusters and Al-centered clusters. These difference may be ascribed to the atomic size difference and chemical property between Cu and Zr atoms. Lastly, the relatively large size of Zr and large negative heat of mixing between Zr and Al atoms, enhancing the packing density and stability of metallic glass system, may be responsible for the higher glass forming ability of Zr50Cu45Al5.« less
Three-Dimensional CFD FLYGT Mixer Model and Results
Lee, S. Y.
2002-04-16
The main objectives of the present work are to examine detailed flow performance of the Tank 19 FLYGT mixer improved by the previous work, to conduct sensitivity analysis for a wide range of possible boundary conditions, and to investigate transient flow behavior and loading of the FLYGT mixer. For the present study, a flow simulation method is developed to calculate the flow around a marine-type propeller configuration of the FLYGT mixer.
L3:THM.CLS.P7.09 Advancements on Wall Boiling Modeling in CFD: Leveraging
U.S. Department of Energy (DOE) all webpages (Extended Search)
9 Advancements on Wall Boiling Modeling in CFD: Leveraging New Understanding from MIT Flow Boiling Facility Lindsey Gilman, Emilio Baglietto MIT Completed: August 30, 2013 CASL-8-2013-0185-000 ADVANCEMENTS ON WALL BOILING MODELING IN CFD: LEVERAGING NEW UNDERSTANDING FROM MIT FLOW BOILING FACILITY Lindsey Gilman, Emilio Baglietto August 30, 2013 (Rev. 0) Massachusetts Institute of Technology Cambridge, MA, USA August 2013 CASL-U-2013-0185-000 EXECUTIVE SUMMARY This milestone introduces advanced
Investigating Aeroelastic Performance of Multi-Mega Watt Wind Turbine Rotors Using CFD
U.S. Department of Energy (DOE) all webpages (Extended Search)
Investigating Aeroelastic Performance of Multi-MegaWatt Wind Turbine Rotors Using CFD David A. Corson 1 Altair Engineering, Inc., Clifton Park, NY, 12065 D. Todd Griffith 2 Sandia National Laboratories, Albuquerque, NM, 87185 Tom Ashwill 3 Sandia National Laboratories, Albuquerque, NM, 87185 Farzin Shakib 4 Altair Engineering, Inc., Mountain View, CA, 94043 Recent trends in wind power technology are focusing on increasing power output through an increase in rotor diameter. As the rotor diameter
Dehbi, A.; Badreddine, H.
2012-07-01
In CFD simulations of flow mixing in a steam generator (SG) during natural circulation, one is faced with the problem of representing the thousands of SG U-tubes. Typically simplifications are made to render the problem computationally tractable. In particular, one or a number of tubes are lumped in one volume which is treated as a single porous medium. This approach dramatically reduces the computational size of the problem and hence simulation time. In this work, we endeavor to investigate the adequacy of this approach by performing two separate simulations of flow in a mock-up with 262 U-tubes, i.e. one in which the porous media model is used for the tube bundle, and another in which the full geometry is represented. In both simulations, the Reynolds Stress (RMS) model of turbulence is used. We show that in steady state conditions, the porous media treatment yields results which are comparable to those of the full geometry representation (temperature distribution, recirculation ratio, hot plume spread, etc). Hence, the porous media approach can be extended with a good degree of confidence to the full scale SG. (authors)
A COMPUTATIONAL WORKBENCH ENVIRONMENT FOR VIRTUAL POWER PLANT SIMULATION
Mike Bockelie; Dave Swensen; Martin Denison; Connie Senior; Adel Sarofim; Bene Risio
2002-07-28
This is the seventh Quarterly Technical Report for DOE Cooperative Agreement No.: DE-FC26-00NT41047. The goal of the project is to develop and demonstrate a computational workbench for simulating the performance of Vision 21 Power Plant Systems. Within the last quarter, good progress has been made on the development of the IGCC workbench. A series of parametric CFD simulations for single stage and two stage generic gasifier configurations have been performed. An advanced flowing slag model has been implemented into the CFD based gasifier model. A literature review has been performed on published gasification kinetics. Reactor models have been developed and implemented into the workbench for the majority of the heat exchangers, gas clean up system and power generation system for the Vision 21 reference configuration. Modifications to the software infrastructure of the workbench have been commenced to allow interfacing to the workbench reactor models that utilize the CAPE{_}Open software interface protocol.
Garrison, Laura A.; Fisher, Jr., Richard K.; Sale, Michael J.; Cada, Glenn
2002-07-01
One of the contributing factors to fish injury in a turbine environment is shear stress. This paper presents the use of computational fluid dynamics (CFD) to display and quantify areas of elevated shear stress in the Wanapum Kaplan turbine operating at four different flow conditions over its operating range. CFD observations will be compared to field test observations at the same four flow conditions. Methods developed here could be used to facilitate the design of turbines and related water passages with lower risks of fish injury.
Harris, Jeff R.; Lance, Blake W.; Smith, Barton L.
2015-08-10
We present computational fluid dynamics (CFD) validation dataset for turbulent forced convection on a vertical plate. The design of the apparatus is based on recent validation literature and provides a means to simultaneously measure boundary conditions (BCs) and system response quantities (SRQs). Important inflow quantities for Reynolds-Averaged Navier-Stokes (RANS). CFD are also measured. Data are acquired at two heating conditions and cover the range 40,000 < Re_{x} < 300,000, 357 < Re_{δ2} < 813, and 0.02 < Gr/Re^{2} < 0.232.
Harris, Jeff R.; Lance, Blake W.; Smith, Barton L.
2015-08-10
We present computational fluid dynamics (CFD) validation dataset for turbulent forced convection on a vertical plate. The design of the apparatus is based on recent validation literature and provides a means to simultaneously measure boundary conditions (BCs) and system response quantities (SRQs). Important inflow quantities for Reynolds-Averaged Navier-Stokes (RANS). CFD are also measured. Data are acquired at two heating conditions and cover the range 40,000 < Rex < 300,000, 357 < Reδ2 < 813, and 0.02 < Gr/Re2 < 0.232.
On the application of computational fluid dynamics codes for liquefied natural gas dispersion.
Luketa-Hanlin, Anay Josephine; Koopman, Ronald P.; Ermak, Donald
2006-02-01
Computational fluid dynamics (CFD) codes are increasingly being used in the liquefied natural gas (LNG) industry to predict natural gas dispersion distances. This paper addresses several issues regarding the use of CFD for LNG dispersion such as specification of the domain, grid, boundary and initial conditions. A description of the k-{var_epsilon} model is presented, along with modifications required for atmospheric flows. Validation issues pertaining to the experimental data from the Burro, Coyote, and Falcon series of LNG dispersion experiments are also discussed. A description of the atmosphere is provided as well as discussion on the inclusion of the Coriolis force to model very large LNG spills.
Numerical Investigation of Vertical Plunging Jet Using a Hybrid Multifluid–VOF Multiphase CFD Solver
Shonibare, Olabanji Y.; Wardle, Kent E.
2015-01-01
A novel hybrid multiphase flow solver has been used to conduct simulations of a vertical plunging liquid jet. This solver combines a multifluid methodology with selective interface sharpening to enable simulation of both the initial jet impingement and the long-time entrained bubble plume phenomena. Models are implemented for variable bubble size capturing and dynamic switching of interface sharpened regions to capture transitions between the initially fully segregated flow types into the dispersed bubbly flow regime. It was found that the solver was able to capture the salient features of the flow phenomena under study and areas for quantitative improvement havemore » been explored and identified. In particular, a population balance approach is employed and detailed calibration of the underlying models with experimental data is required to enable quantitative prediction of bubble size and distribution to capture the transition between segregated and dispersed flow types with greater fidelity.« less
Parallel Atomistic Simulations
HEFFELFINGER,GRANT S.
2000-01-18
Algorithms developed to enable the use of atomistic molecular simulation methods with parallel computers are reviewed. Methods appropriate for bonded as well as non-bonded (and charged) interactions are included. While strategies for obtaining parallel molecular simulations have been developed for the full variety of atomistic simulation methods, molecular dynamics and Monte Carlo have received the most attention. Three main types of parallel molecular dynamics simulations have been developed, the replicated data decomposition, the spatial decomposition, and the force decomposition. For Monte Carlo simulations, parallel algorithms have been developed which can be divided into two categories, those which require a modified Markov chain and those which do not. Parallel algorithms developed for other simulation methods such as Gibbs ensemble Monte Carlo, grand canonical molecular dynamics, and Monte Carlo methods for protein structure determination are also reviewed and issues such as how to measure parallel efficiency, especially in the case of parallel Monte Carlo algorithms with modified Markov chains are discussed.
Enlisting CFD to fight hammer shock in jets
Miller, D.N.; Hamstra, J.W.
1997-03-01
This article describes how computational fluid dynamics can predict inlet hammer-shock loads for advanced tactical aircraft, a complex and costly task that has left existing methods grounded. The current strategy for tactical-aircraft development is directed toward reducing life-cycle cost with little or no compromise to aircraft performance. This strategy may be extended down to the component level, where the goal of future engine-inlet designs is to maintain aeroperformance and survivability while structural weight is reduced, thereby lowering costs. To address these goals, new design methods must evolve to minimize weight yet maintain necessary margins of structural safety. The ultimate loads for inlet structures are set by the peak pressures associated with hammer shocks induced by engine surge. Existing techniques for predicting peak pressure load are based on an empirical approach using flight-test data from F-111 jets, and have proven adequate for the F-016 normal-shock inlet (NSI). Current inlet designs differ significantly, however, featuring serpentine inlet ducts, swept aperture shapes, and composite structural materials. Consequently, a new approach is required to predict inlet hammer-shock loads for advanced inlets.
Othman, M. N. K. E-mail: zuradzman@unimap.edu.my E-mail: khairunizam@unimap.edu.my E-mail: s.yaacob@unimap.edu.my E-mail: abadal@unimap.edu.my; Zuradzman, M. Razlan E-mail: zuradzman@unimap.edu.my E-mail: khairunizam@unimap.edu.my E-mail: s.yaacob@unimap.edu.my E-mail: abadal@unimap.edu.my; Hazry, D. E-mail: zuradzman@unimap.edu.my E-mail: khairunizam@unimap.edu.my E-mail: s.yaacob@unimap.edu.my E-mail: abadal@unimap.edu.my; Khairunizam, Wan E-mail: zuradzman@unimap.edu.my E-mail: khairunizam@unimap.edu.my E-mail: s.yaacob@unimap.edu.my E-mail: abadal@unimap.edu.my; Shahriman, A. B. E-mail: zuradzman@unimap.edu.my E-mail: khairunizam@unimap.edu.my E-mail: s.yaacob@unimap.edu.my E-mail: abadal@unimap.edu.my; Yaacob, S. E-mail: zuradzman@unimap.edu.my E-mail: khairunizam@unimap.edu.my E-mail: s.yaacob@unimap.edu.my E-mail: abadal@unimap.edu.my; Ahmed, S. Faiz E-mail: zuradzman@unimap.edu.my E-mail: khairunizam@unimap.edu.my E-mail: s.yaacob@unimap.edu.my E-mail: abadal@unimap.edu.my; and others
2014-12-04
This paper explain the analysis of internal air flow velocity of a bladeless vertical takeoff and landing (VTOL) Micro Aerial Vehicle (MAV) hemisphere body. In mechanical design, before produce a prototype model, several analyses should be done to ensure the product's effectiveness and efficiency. There are two types of analysis method can be done in mechanical design; mathematical modeling and computational fluid dynamic. In this analysis, I used computational fluid dynamic (CFD) by using SolidWorks Flow Simulation software. The idea came through to overcome the problem of ordinary quadrotor UAV which has larger size due to using four rotors and the propellers are exposed to environment. The bladeless MAV body is designed to protect all electronic parts, which means it can be used in rainy condition. It also has been made to increase the thrust produced by the ducted propeller compare to exposed propeller. From the analysis result, the air flow velocity at the ducted area increased to twice the inlet air. This means that the duct contribute to the increasing of air velocity.
Simulator for Wind Farm Applications
Energy Science and Technology Software Center (OSTI)
2012-01-06
A modular tool for simulating wind plant aerodynamics with computational fluid dynamics and turbine structural and control response to the incoming flow.
Computational Pyrolysis Consortium
Office of Energy Efficiency and Renewable Energy (EERE) (indexed site)
reduce oxygen content, corrosivity, viscosity and increase stability) with vapor and ... and CFD Hemicellulose Cellulose Example dynamic simulation of biomass pyrolysis in a 0.1 ...
Agieienko, Vira N.; Kolesnik, Yaroslav V.; Kalugin, Oleg N.
2014-05-21
Molecular dynamics simulations of complexes of Mg{sup 2+}, Ca{sup 2+}, Sr{sup 2+}, and Ba{sup 2+} with 3-hydroxyflavone (flavonol, 3HF) and ClO {sub 4}{sup ?} in acetonitrile were performed. The united atoms force field model was proposed for the 3HF molecule using the results of DFT quantum chemical calculations. 3HF was interpreted as a rigid molecule with two internal degrees of freedom, i.e., rotation of the phenyl ring and of the OH group with respect to the chromone moiety. The interatomic radial distribution functions showed that interaction of the cations with flavonol occurs via the carbonyl group of 3HF and it is accompanied with substitution of one of the acetonitrile molecules in the cations first solvation shells. Formation of the cation3HF complexes does not have significant impact on the rotation of the phenyl ring with respect to the chromone moiety. However, the orientation of the flavonol's OH-group is more sensitive to the interaction with doubly charged cations. When complex with Mg{sup 2+} is formed, the OH-group turns out of the plane of the chromone moiety that leads to rupture of intramolecular H-bond in the ligand molecule. Complexation of Ca{sup 2+}, Sr{sup 2+}, and BaClO {sub 4}{sup +} with 3HF produces two structures with different OH-positions, as in the free flavonol with the intramolecular H-bond and as in the complex with Mg{sup 2+} with disrupted H-bonding. It was shown that additional stabilization of the [MgClO{sub 4}(3HF)]{sup +} and [BaClO{sub 4}(3HF)]{sup +} complexes is determined by strong affinity of perchlorate anion to interact with flavonol via intracomplex hydrogen bond between an oxygen atom of the anion and the hydrogen atom of the 3-hydroxyl group. Noticeable difference in the values of the self-diffusion coefficients for Kt{sup 2+} from one side and ClO {sub 4}{sup ?}, 3HF, and AN in the cations coordination shell from another side implies quite weak interaction between cation, anion, and ligands in the
Large-Eddy Simulation of Wind-Plant Aerodynamics: Preprint
Churchfield, M. J.; Lee, S.; Moriarty, P. J.; Martinez, L. A.; Leonardi, S.; Vijayakumar, G.; Brasseur, J. G.
2012-01-01
In this work, we present results of a large-eddy simulation of the 48 multi-megawatt turbines composing the Lillgrund wind plant. Turbulent inflow wind is created by performing an atmospheric boundary layer precursor simulation and turbines are modeled using a rotating, variable-speed actuator line representation. The motivation for this work is that few others have done wind plant large-eddy simulations with a substantial number of turbines, and the methods for carrying out the simulations are varied. We wish to draw upon the strengths of the existing simulations and our growing atmospheric large-eddy simulation capability to create a sound methodology for performing this type of simulation. We have used the OpenFOAM CFD toolbox to create our solver.
Numerical modeling of immiscible two-phase flow in micro-models using a commercial CFD code
Crandall, Dustin; Ahmadia, Goodarz; Smith, Duane H.
2009-01-01
Off-the-shelf CFD software is being used to analyze everything from flow over airplanes to lab-on-a-chip designs. So, how accurately can two-phase immiscible flow be modeled flowing through some small-scale models of porous media? We evaluate the capability of the CFD code FLUENT{trademark} to model immiscible flow in micro-scale, bench-top stereolithography models. By comparing the flow results to experimental models we show that accurate 3D modeling is possible.
General purpose steam table library : CASL L3:THM.CFD.P7.04 milestone report.
Carpenter, John H.; Belcourt, Noel; Nourgaliev, Robert
2013-08-01
Completion of the CASL L3 milestone THM.CFD.P7.04 provides a general purpose tabular interpolation library for material properties to support, in particular, standardized models for steam properties. The software consists of three parts, implementations of analytic steam models, a code to generate tables from those models, and an interpolation package to interface the tables to CFD codes such as Hydra-TH. Verification of the standard model is maintained through the entire train of routines. The performance of interpolation package exceeds that of freely available analytic implementation of the steam properties by over an order of magnitude.
Converting DYNAMO simulations to Powersim Studio simulations
Walker, La Tonya Nicole; Malczynski, Leonard A.
2014-02-01
DYNAMO is a computer program for building and running 'continuous' simulation models. It was developed by the Industrial Dynamics Group at the Massachusetts Institute of Technology for simulating dynamic feedback models of business, economic, and social systems. The history of the system dynamics method since 1957 includes many classic models built in DYANMO. It was not until the late 1980s that software was built to take advantage of the rise of personal computers and graphical user interfaces that DYNAMO was supplanted. There is much learning and insight to be gained from examining the DYANMO models and their accompanying research papers. We believe that it is a worthwhile exercise to convert DYNAMO models to more recent software packages. We have made an attempt to make it easier to turn these models into a more current system dynamics software language, Powersim Studio produced by Powersim AS^{2} of Bergen, Norway. This guide shows how to convert DYNAMO syntax into Studio syntax.
Guglielmetti, R.
2015-02-01
We will leverage new building performance and daylighting simulation tools to characterize the performance of a new electrochromic (EC) glazing as well as perform a field evaluation of the same product installed in a DoD facility. The in situ data will be used to validate and calibrate the simulation model, which will then be used to extrapolate the performance of the product across all US climate zones. The property as part of this agreement will be installed at MCAS Miramar, California.
CFD ANALYSES ON THE COOLING FOR SCQ MAGNETS IN BEPC II UPGRADE.
HE,Z.H.WANG,L.TANK,H.M.ZHANG,X.B.JIA,L.X.
2003-09-22
A pair of superconducting interaction region quadrupole magnets in Beijing Electron-Positron Collider Upgrade (BEPCII) are to be cooled by supercritical helium in order to eliminate the flow instabilities in the constrained cooling channels. The fluid flow is simulated by the commercial computational dynamics fluid software. The heat loads to the superconducting quadrupole (SCQ) magnets from the radiation shields at 80 K and from the thermal conduction of mechanical supports are considered. The temperature distribution of the fluid in the liquid helium cooling channels, and the heat transfer in the SCQ magnet and by its supports are presented. The influence of mass flow rate on pressure drop in the cooling passage is analyzed.
Lopez, A.R.; Hassan, B.; Oberkampf, W.L.; Neiser, R.A.; Roemer, T.J.
1996-09-01
The fluid and particle dynamics of a High-Velocity Oxygen-Fuel Thermal Spray torch are analyzed using computational and experimental techniques. Three-dimensional Computational Fluid Dynamics (CFD) results are presented for a curved aircap used for coating interior surfaces such as engine cylinder bores. The device analyzed is similar to the Metco Diamond Jet Rotating Wire (DJRW) torch. The feed gases are injected through an axisymmetric nozzle into the curved aircap. Premixed propylene and oxygen are introduced from an annulus in the nozzle, while cooling air is injected between the nozzle and the interior wall of the aircap. The combustion process is modeled using a single-step finite-rate chemistry model with a total of 9 gas species which includes dissociation of combustion products. A continually-fed steel wire passes through the center of the nozzle and melting occurs at a conical tip near the exit of the aircap. Wire melting is simulated computationally by injecting liquid steel particles into the flow field near the tip of the wire. Experimental particle velocity measurements during wire feed were also taken using a Laser Two-Focus (L2F) velocimeter system. Flow fields inside and outside the aircap are presented and particle velocity predictions are compared with experimental measurements outside of the aircap.
Accelerated Molecular Dynamics Methods
Office of Energy Efficiency and Renewable Energy (EERE) (indexed site)
... Los Alamos Parallel Replica Dynamics Procedure Start clock and run thermostatted MD on ... Sum the trajectory times over all M processors. Advance simulation clock by this t sum Los ...
Computational fluid dynamics modeling of two-phase flow in a BWR fuel assembly. Final CRADA Report.
Tentner, A.; Nuclear Engineering Division
2009-10-13
A direct numerical simulation capability for two-phase flows with heat transfer in complex geometries can considerably reduce the hardware development cycle, facilitate the optimization and reduce the costs of testing of various industrial facilities, such as nuclear power plants, steam generators, steam condensers, liquid cooling systems, heat exchangers, distillers, and boilers. Specifically, the phenomena occurring in a two-phase coolant flow in a BWR (Boiling Water Reactor) fuel assembly include coolant phase changes and multiple flow regimes which directly influence the coolant interaction with fuel assembly and, ultimately, the reactor performance. Traditionally, the best analysis tools for this purpose of two-phase flow phenomena inside the BWR fuel assembly have been the sub-channel codes. However, the resolution of these codes is too coarse for analyzing the detailed intra-assembly flow patterns, such as flow around a spacer element. Advanced CFD (Computational Fluid Dynamics) codes provide a potential for detailed 3D simulations of coolant flow inside a fuel assembly, including flow around a spacer element using more fundamental physical models of flow regimes and phase interactions than sub-channel codes. Such models can extend the code applicability to a wider range of situations, which is highly important for increasing the efficiency and to prevent accidents.
Ivanov, N. V.; Kakurin, A. M.
2014-10-15
Simulation of the magnetic island evolution under Resonant Magnetic Perturbation (RMP) in rotating T-10 tokamak plasma is presented with intent of TEAR code experimental validation. In the T-10 experiment chosen for simulation, the RMP consists of a stationary error field, a magnetic field of the eddy current in the resistive vacuum vessel and magnetic field of the externally applied controlled halo current in the plasma scrape-off layer (SOL). The halo-current loop consists of a rail limiter, plasma SOL, vacuum vessel, and external part of the circuit. Effects of plasma resistivity, viscosity, and RMP are taken into account in the TEAR code based on the two-fluid MHD approximation. Radial distribution of the magnetic flux perturbation is calculated with account of the externally applied RMP. A good agreement is obtained between the simulation results and experimental data for the cases of preprogrammed and feedback-controlled halo current in the plasma SOL.
Computational fluid dynamic modeling of fluidized-bed polymerization reactors
Rokkam, Ram
2012-01-01
Polyethylene is one of the most widely used plastics, and over 60 million tons are produced worldwide every year. Polyethylene is obtained by the catalytic polymerization of ethylene in gas and liquid phase reactors. The gas phase processes are more advantageous, and use fluidized-bed reactors for production of polyethylene. Since they operate so close to the melting point of the polymer, agglomeration is an operational concern in all slurry and gas polymerization processes. Electrostatics and hot spot formation are the main factors that contribute to agglomeration in gas-phase processes. Electrostatic charges in gas phase polymerization fluidized bed reactors are known to influence the bed hydrodynamics, particle elutriation, bubble size, bubble shape etc. Accumulation of electrostatic charges in the fluidized-bed can lead to operational issues. In this work a first-principles electrostatic model is developed and coupled with a multi-fluid computational fluid dynamic (CFD) model to understand the effect of electrostatics on the dynamics of a fluidized-bed. The multi-fluid CFD model for gas-particle flow is based on the kinetic theory of granular flows closures. The electrostatic model is developed based on a fixed, size-dependent charge for each type of particle (catalyst, polymer, polymer fines) phase. The combined CFD model is first verified using simple test cases, validated with experiments and applied to a pilot-scale polymerization fluidized-bed reactor. The CFD model reproduced qualitative trends in particle segregation and entrainment due to electrostatic charges observed in experiments. For the scale up of fluidized bed reactor, filtered models are developed and implemented on pilot scale reactor.
Thermal Hydraulic Simulations, Error Estimation and Parameter
U.S. Department of Energy (DOE) all webpages (Extended Search)
Studies in Drekar::CFD Thomas M. Smith, John N. Shadid, Roger P. Pawlowski, Eric ... Studies in Drekar::CFD Thomas M. Smith, John N. Shadid, Roger P. Pawlowski, Eric ...
Protein Dynamics and Biocatalysis
U.S. Department of Energy (DOE) all webpages (Extended Search)
Protein Dynamics and Biocatalysis Protein Dynamics and Biocatalysis 1998 Annual Report Grand Challenge Projects biocatalysis.gif A model of the Michaelis complex for the TEM-1/penicillin system from molecular dynamics simulations. Investigators: P. A. Bash, Northwestern University Medical School and M. Karplus, Harvard University Research Objectives A guiding principle of molecular biology is that the structure of a biomolecule defines its function. This principle is especially true in the case
Smith, Kyle K. G. Rossky, Peter J.; Poulsen, Jens Aage; Cunsolo, A.
2014-01-21
The dynamic structure factor of liquid para-hydrogen and ortho-deuterium in corresponding thermodynamic states (T = 20.0?K, n = 21.24?nm{sup ?3}) and (T = 23.0?K, n = 24.61?nm{sup ?3}), respectively, has been computed by both the Feynman-Kleinert linearized path-integral (FK-LPI) and Ring-Polymer Molecular Dynamics (RPMD) methods and compared with Inelastic X Ray Scattering spectra. The combined use of computational and experimental methods enabled us to reduce experimental uncertainties in the determination of the true sample spectrum. Furthermore, the refined experimental spectrum of para-hydrogen and ortho-deuterium is consistently reproduced by both FK-LPI and RPMD results at momentum transfers lower than 12.8?nm{sup ?1}. At larger momentum transfers the FK-LPI results agree with experiment much better for ortho-deuterium than for para-hydrogen. More specifically we found that for k ? 20.0 nm{sup ?1} para-hydrogen provides a test case for improved approximations to quantum dynamics.
Smoot, J.L.; Sagar, B.
1990-01-01
Approximately 2,000 m{sup 3} of liquid containing radioactive and chemical wastes leaked from the 241-T-106 single-shell tank at the Hanford Site. The leak discharged into the unsaturated, coarse-grained sediments of the Hanford formation which underlie the base of the tank. The PORFLO-3 computer code was used to study plume migration for {sup 106}Ru and {sup 137}Cs. The flow and transport properties of the soils through which the plume has migrated are critical input data for the model but are not available. Information from a catalogue of Hanford Site soil properties was used. The transient magnitudes and locations of the plume were simulated in three dimensions. Using the reduced vertical hydraulic conductivity, the migration of {sup 106}Ru and {sup 137}Cs was simulated for the time between 1973 and 1990. 24 refs., 33 figs., 3 tabs.
Substructured multibody molecular dynamics.
Grest, Gary Stephen; Stevens, Mark Jackson; Plimpton, Steven James; Woolf, Thomas B. (Johns Hopkins University, Baltimore, MD); Lehoucq, Richard B.; Crozier, Paul Stewart; Ismail, Ahmed E.; Mukherjee, Rudranarayan M. (Rensselaer Polytechnic Institute, Troy, NY); Draganescu, Andrei I.
2006-11-01
We have enhanced our parallel molecular dynamics (MD) simulation software LAMMPS (Large-scale Atomic/Molecular Massively Parallel Simulator, lammps.sandia.gov) to include many new features for accelerated simulation including articulated rigid body dynamics via coupling to the Rensselaer Polytechnic Institute code POEMS (Parallelizable Open-source Efficient Multibody Software). We use new features of the LAMMPS software package to investigate rhodopsin photoisomerization, and water model surface tension and capillary waves at the vapor-liquid interface. Finally, we motivate the recipes of MD for practitioners and researchers in numerical analysis and computational mechanics.
Progress on a New Integrated 3-D UCG Simulator and its Initial Application
Nitao, J J; Camp, D W; Buscheck, T A; White, J A; Burton, G C; Wagoner, J L; Chen, M
2011-09-22
A comprehensive simulator is being developed for underground coal gasification (UCG), with the capability to support site selection, design, hazard analyses, operations, and monitoring (Nitao et al., 2010). UCG is computationally challenging because it involves tightly-coupled multi-physical/chemical processes, with vastly different timescales. This new capability will predict cavity growth, product gas composition and rate, and the interaction with the host environment, accounting for site characteristics, injection gas composition and rate, and associated water-well extraction rates. Progress on the new simulator includes completion and system integration of a wall model, a rock spalling model, a cavity boundary tracking model, a one-dimensional cavity gas reactive transport model, a rudimentary rubble heat, mass, and reaction model, and coupling with a pre-existing hydrology simulator. An existing geomechanical simulator was enhanced to model cavity collapse and overburden subsidence. A commercial computational fluid dynamics (CFD) code is being evaluated to model cavity gas flow and combustion in two and three dimensions. Although the simulator is midway in its development, it was applied to modeling the Hoe Creek III field test (Stephens, 1981) conducted in the 1970s, in order to evaluate and demonstrate the simulator's basic capabilities, gain experience, and guide future development. Furthermore, it is consistent with our philosophy of incremental, spiral software development, which helps in identifying and resolving potential problems early in the process. The simulation accounts for two coal seams, two injection points, and air and oxygen phases. Approximate extent and shape of cavity growth showed reasonable agreement with interpreted field data. Product gas composition and carbon consumed could not be simultaneously matched for a given set of parameter values due to the rudimentary rubble model currently used, although they can be matched using separate
Pramanik, Tanmoy Roy, Urmimala; Register, Leonard F.; Banerjee, Sanjay K.; Tsoi, Maxim
2014-05-07
We studied spin-transfer-torque (STT) switching of a cross-shaped magnetic tunnel junction in a recent report [Roy et al., J. Appl. Phys. 113, 223904 (2013)]. In that structure, the free layer is designed to have four stable energy states using the shape anisotropy of a cross. STT switching showed different regions with increasing current density. Here, we employ the micromagnetic spectral mapping technique in an attempt to understand how the asymmetry of cross dimensions and spin polarization direction of the injected current affect the magnetization dynamics. We compute spatially averaged frequency-domain spectrum of the time-domain magnetization dynamics in the presence of the current-induced STT term. At low currents, the asymmetry of polarization direction and that of the arms are observed to cause a splitting of the excited frequency modes. Higher harmonics are also observed, presumably due to spin-wave wells caused by the regions of spatially non-uniform effective magnetic field. The results could be used towards designing a multi-bit-per-cell STT-based random access memory with an improved storage density.
Modifications to WRFs dynamical core to improve the treatment...
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Modifications to WRFs dynamical core to improve the treatment of moisture for large-eddy simulations Title: Modifications to WRFs dynamical core to improve the treatment of ...