CFD Simulation of Dynamic Thrust and Radial Forces on a Vertical Axis Wind Turbine Blade
Tullis, Stephen
CFD Simulation of Dynamic Thrust and Radial Forces on a Vertical Axis Wind Turbine Blade K. Mc vibration source of a small scale vertical axis wind turbine. The dynamic loading on the blades detail. 1. INTRODUCTION A prototype of a small scale vertical axis wind turbine is currently being field
The Effects of Geometry on Flexible Duct CFD Simulations
Ugursal, A.; Culp, C.
2008-01-01T23:59:59.000Z
dynamics (CFD) simulations allow variable configurations and are emerging as an alternative to laboratory measurements. Issues with the CFD simulations of flexible ducts have been modeling the complex geometry and the computational requirements to complete...
Solution characters of iterative coupling between energy simulation and CFD programs
Chen, Qingyan "Yan"
1 Solution characters of iterative coupling between energy simulation and CFD programs Zhiqiang Energy simulation (ES) and computational fluid dynamics (CFD) provide important and complementary information for building energy and indoor environment designs. A coupled ES and CFD simulation can eliminate
Chen, Qingyan "Yan"
and Computational Fluid Dynamics (CFD) have been widely used in simulations of building airflow distribution takes several minutes to perform an hour-by-hour dynamic simulation of a whole building for one year. "Validation of a coupled multizone and CFD program for building airflow and contaminant transport simulations
Thanh D.B. Nguyen; Young-Il Lim; Seong-Joon Kim; Won-Hyeon Eom; Kyung-Seun Yoo [Hankyong National University, Jungangno (Republic of Korea). Laboratory of Functional Analysis of Complex Systems (FACS)
2008-11-15T23:59:59.000Z
A turbulent reacting flow computational fluid dynamics (CFD) model involving a droplet size distribution function in the discrete droplet phase is first built for selective noncatalytic reduction (SNCR) processes using urea solution as a NOx removal reagent. The model is validated with the experimental data obtained from a pilot-scale urea-based SNCR reactor installed with a 150 kW gas burner. New kinetic parameters of seven chemical reactions for the urea-based NOx reduction are identified and incorporated into the three-dimensional turbulent flow CFD model. The two-phase droplet model with the non-uniform droplet size is also combined with the CFD model to predict the trajectory of the droplets and to examine the mixing between the flue gas and reagents. The maximum NO reduction efficiency of about 80%, experimentally measured at the reactor outlet, is obtained at 940{degree}C and a normalized stoichiometric ratio (NSR) = 2.0 under the conditions of 11% excess air and low CO concentration (10-15 ppm). At the reaction temperature of 940{degree}C, the difference of a maximum of 10% between experiments and simulations of the NO reduction percentage is observed for NSR = 1.0, 1.5, and 2.0. The ammonia slip is overestimated in CFD simulation at low temperatures, especially lower than 900{degree}C. However, the CFD simulation results above 900{degree}C show a reasonable agreement with the experimental data of NOx reduction and ammonia slip as a function of the NSR. 31 refs., 3 figs., 6 tabs.
CFD Simulations of Joint Urban Atmospheric Dispersion Field Study
Lee, R; Humphreys III, T; Chan, S
2004-06-17T23:59:59.000Z
The application of Computational Fluid Dynamics (CFD) to the understanding of urban wind flow and dispersion processes has gained increasing attention over recent years. While many of the simpler dispersion models are based on a set of prescribed meteorology to calculate dispersion, the CFD approach has the ability of coupling the wind field to dispersion processes. This has distinct advantages when very detailed results are required, such as for the case where the releases occur around buildings and within urban areas. CFD also has great flexibility as a testbed for turbulence models, which has important implications for atmospheric dispersion problems. In the spring of 2003, a series of dispersion field experiments (Joint Urban 2003) were conducted at Oklahoma City (Allwine, et. al, 2004). These experiments were complimentary to the URBAN 2000 field studies at Salt Lake City (Shinn, et. al, 2000) in that they will provide a second set of comprehensive field data for evaluation of CFD as well as for other dispersion models. In contrast to the URBAN 2000 experiments that were conducted entirely at night, these new field studies took place during both daytime and nighttime thus including the possibility of convective as well as stable atmospheric conditions. Initially several CFD modeling studies were performed to provide guidance for the experimental team in the selection of release sites and in the deployment of wind and concentration sensors. Also, while meteorological and concentration measurements were taken over the greater Oklahoma City urban area, our CFD calculations were focused on the near field of the release point. The proximity of the source to a large commercial building and to the neighboring buildings several of which have multistories, present a significant challenge even for CFD calculations involving grid resolutions as fine as 1 meter. A total of 10 Intensive Observations Periods (IOP's) were conducted within the 2003 field experiments. SF6 releases in the form of puffs or continuous sources were disseminated over 6 daytime and 4 nighttime episodes. Many wind and concentration sensors were used to provide wind and SF6 data over both long and short time-averaging periods. In addition to the usual near surface measurements, data depicting vertical profiles of wind and concentrations adjacent to the outside walls of several buildings were also taken. Also of interest were observations of the trajectory of balloons that were deployed close to the tracer release area. Many of the balloons released exhibit extremely quick ascents up from ground level to the top of buildings, thus implying highly convective conditions. In this paper we will present some simulations that were performed during the planning of the field experiments. The calculations were based on two possible release sites at the intersections of Sheridan and Robinson, and Broadway and Sheridan. These results provided initial information on flow and dispersion patterns, which could be used to guide optimal placement of sensors at appropriate locations. We will also discuss results of more recent simulations for several releases in which reliable data is available. These simulations will be compared with the near field data taken from the wind sensors as well as the time-averaged data from the concentration sensors. Among the other topics discussed are initial and boundary conditions used in the simulations, adaptation of building GIS data for CFD modeling and analysis of field data.
Performance of coupled building energy and CFD simulations Zhiqiang John Zhaia,*, Qingyan Yan Chenb
Zhai, John Z.
a coupled energy simulation and computational fluid dynamics program with different coupling methods/cooling energy required and building envelope thermal information, such as surface temperature and heat fluxPerformance of coupled building energy and CFD simulations Zhiqiang John Zhaia,*, Qingyan Yan Chenb
Computational Fluid Dynamics (CFD) Modelling on Soot Yield for Fire
Computational Fluid Dynamics (CFD) Modelling on Soot Yield for Fire Engineering Assessment Yong S (CFD) Modelling is now widely used by fire safety engineers throughout the world as a tool of the smoke control design as part of the performance based fire safety design in the current industry
Multiscale CFD simulations of entrained flow gasification
Kumar, Mayank, Ph. D. Massachusetts Institute of Technology
2011-01-01T23:59:59.000Z
The design of entrained flow gasifiers and their operation has largely been an experience based enterprise. Most, if not all, industrial scale gasifiers were designed before it was practical to apply CFD models. Moreover, ...
V European Conference on Computational Fluid Dynamics ECCOMAS CFD 2010
Berning, Torsten
V European Conference on Computational Fluid Dynamics ECCOMAS CFD 2010 J. C. F. Pereira and A, increase the mixing of fuel and oxidant, control formation of harmful emissions, and increase the life
Validation of CFD Simulations for Natural Ventilation , Camille Allocca1
Chen, Qingyan "Yan"
ventilation is a very typical unsteady flow problem, the study of natural ventilation by RANS may need1 Validation of CFD Simulations for Natural Ventilation Yi Jiang1 , Camille Allocca1 , and Qingyan ventilation, which may provide occupants with good indoor air quality and a high level of thermal comfort
Dr. Chenn Zhou
2008-10-15T23:59:59.000Z
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.
Thermal hydraulic simulations, error estimation and parameter sensitivity studies in Drekar::CFD
Smith, Thomas Michael [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Shadid, John N. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Pawlowski, Roger P. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Cyr, Eric C. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Wildey, Timothy Michael [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
2014-01-01T23:59:59.000Z
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.
In, Wang-Kee; Chun, Tae-Hyun; Shin, Chang-Hwan; Oh, Dong-Seok [Korea Atomic Energy Research Institute, 1045 Daedeokdaero, Yuseong-Gu, Daejeon, Korea 305-353 (Korea, Republic of)
2007-07-01T23:59:59.000Z
A computational fluid dynamics (CFD) analysis has been performed to investigate a flow-mixing and heat-transfer enhancement caused by a mixing-vane spacer in a LWR fuel assembly which is a rod bundle. This paper presents the CFD simulations of a flow mixing and heat transfer in a fully heated 5x5 array of a rod bundle with a split-vane and hybrid-vane spacer. The CFD prediction at a low Reynolds number of 42,000 showed a reasonably good agreement of the initial heat transfer enhancement with the measured one for a partially heated experiment using a similar spacer structure. The CFD simulation also predicted the decay rate of a normalized Nusselt number downstream of the split-vane spacer which agrees fairly well with those of the experiment and the correlation. The CFD calculations for the split vane and hybrid vane at the LWR operating conditions(Re = 500,000) predicted hot fuel spots in a streaky structure downstream of the spacer, which occurs due to the secondary flow occurring in an opposite direction near the fuel rod. However, the split-vane and hybrid-vane spacers are predicted to significantly enhance the overall heat transfer of a LWR nuclear fuel assembly. (authors)
Deng, T.; Zhang, Q.; Zhang, G.; Yuan, H.
2006-01-01T23:59:59.000Z
The Hunan International Exhibition Center (HIEC) is a large space building. A stratified air-conditioning system on the second floor of the building has been adopted. Due to some problems with the air supply jet diffuser, CFD simulations were...
Deng, T.; Zhang, Q.; Zhang, G.; Yuan, H.
2006-01-01T23:59:59.000Z
The Hunan International Exhibition Center (HIEC) is a large space building. A stratified air-conditioning system on the second floor of the building has been adopted. Due to some problems with the air supply jet diffuser, CFD simulations were...
Coupled full core neutron transport/CFD simulations of pressurized water reactors
Kochunas, B.; Stimpson, S.; Collins, B.; Downar, T. [Dept. of Nuclear Engineering and Radiological Sciences, Univ. of Michigan, 2200 Bonisteel Blvd, Ann Arbor, MI 48104 (United States); Brewster, R.; Baglietto, E. [CD-adapco, 60 Broadhollow Road, Melville, NY 11747 (United States); Yan, J. [Westinghouse Electric Company LLC, Columbia, SC (United States)
2012-07-01T23:59:59.000Z
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)
Chen, Qingyan "Yan"
BUILDING ENERGY AND CFD SIMULATION Zhiqiang Zhai* Department of Civil, Environmental and Architectural, IN 47907-2088, USA ABSTRACT The integration of building Energy Simulation (ES) and Computational Fluid, Energy Simulation, CFD, Coupling INTRODUCTION A building energy simulation (ES) program predicts building
SENSITIVITY ANALYSIS AND APPLICATION GUIDES FOR INTEGRATED BUILDING ENERGY AND CFD SIMULATION
Chen, Qingyan "Yan"
1 SENSITIVITY ANALYSIS AND APPLICATION GUIDES FOR INTEGRATED BUILDING ENERGY AND CFD SIMULATION Engineering Purdue University 585 Purdue Mall, West Lafayette, IN 47907-2088, USA Abstract Building energy suggestions on appropriate usage of the coupling simulation are provided. 1. Introduction Building energy
Solution characters of iterative coupling between energy simulation and CFD programs
Zhai, John Z.
States, building services consume more than one third of the primary energy consumption and twoSolution characters of iterative coupling between energy simulation and CFD programs Zhiqiang Zhaia Massachusetts Avenue, Cambridge, MA 02139-4307, USA b School of Mechanical Engineering, Purdue University, 1288
3-D Time-Accurate CFD Simulations of Wind Turbine Rotor Flow Fields
3-D Time-Accurate CFD Simulations of Wind Turbine Rotor Flow Fields Nilay Sezer-Uzol and Lyle N around the National Renewable Energy Laboratory (NREL) Phase VI horizontal axis wind turbine rotor. The 3 turbulent flow that generates the noise, in the context of the wind turbine application. I. Introduction
Performance Evaluation and CFD Simulation of Multiphase Twin-Screw Pumps
Patil, Abhay
2013-05-16T23:59:59.000Z
and velocity profile agreed well with previous studies. Results are validated using an analytical approach as well as experimental data. A two-phase CFD simulation was performed for 50% GVF. An Eulerian approach was employed to evaluate multiphase flow behavior...
Kochevsky, A N
2005-01-01T23:59:59.000Z
The paper describes capabilities of numerical simulation of liquid flows with solid and/or gas admixtures in centrifugal pumps using modern commercial CFD software packages, with the purpose to predict performance curves of the pumps treating such media. In particular, the approaches and multiphase flow models available in the package CFX-5 are described; their advantages and disadvantages are analyzed.
Comparative Study: CFD ?P Versus Measured ?P for 30% Flexible Ducts
Ugursal, A.; Culp, C.
2006-01-01T23:59:59.000Z
Systems Lab Texas A&M University College Station, TX ABSTRACT This study modeled air flow and pressure drops in non-metallic flexible ducts using Computational Fluid Dynamic (CFD) analysis. CFD simulation results showed very close comparison... on both ends. A CFD model was built and simulations were run under different volumetric air flows. The static pressure drop for those conditions were analyzed and displayed. The final CFD model is tuned until the closest results to the experimental...
Zhai, Zhiqiang, 1971-
2003-01-01T23:59:59.000Z
Building energy simulation (ES) and computational fluid dynamics (CFD) can play important roles in building design by providing essential information to help design energy-efficient, thermally comfortable and healthy ...
Dynamic Positioning Simulator Dynamic Positioning Simulator
Vuik, Kees
to the ocean floor, without using anchors accomplished by two or more propulsive devices controlled by inputs Dynamic Positioning: No tugboats needed; Offshore set-up is quick; Power saving; Precision situations more Simulator 11 / 24 #12;Dynamic Positioning Simulator Hydrodynamics Forces on Ship: Wave Force Fwd = CXwd (wd
Broader source: Energy.gov [DOE]
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...
Chen, Qingyan "Yan"
.0 for simulating airflow and contaminant transport in and around buildings," Accepted by HVAC&R Research. #121 Using CFD Capabilities of CONTAM 3.0 for Simulating Airflow and Contaminant Transport In and Around Buildings Liangzhu (Leon) Wang, W. Stuart Dols1 Qingyan Chen2 1 Indoor Air Quality and Ventilation
V European Conference on Computational Fluid Dynamics ECCOMAS CFD 2010
Nicoud, Franck
for the optimisation of the energy consumption (heating or cooling); it is then necessary to develop accurate LES. Sequeira (Eds) Lisbon, Portugal,14-17 June 2010 IS THE DYNAMIC PROCEDURE APPROPRIATE FOR ALL SGS MODELS ? H, Subgrid- scale model Abstract. The rapid growth of supercomputers will probably make the use of Large eddy
CFD Simulation of 3D Flow field in a Gas Centrifuge
Dongjun Jiang; Shi Zeng [Tsinghua University, Beijing, 100084 (China)
2006-07-01T23:59:59.000Z
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)
JACKSON VL
2011-08-31T23:59:59.000Z
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.
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.
2012-10-07T23:59:59.000Z
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 significantly from the average.
Comparative Study: CFD ?P Versus Measured ?P for 30% Flexible Ducts
Ugursal, A.; Culp, C.
2006-01-01T23:59:59.000Z
COMPARATIVE STUDY: CFD ?P VERSUS MEASURED ?P FOR 30% FLEXIBLE DUCTS Ahmet U?ursal Ph.D. Student, Department of Architecture Texas A&M University College Station, TX Charles Culp, Ph.D., P.E. Associate Professor, Department of Architecture... & Associate Director, Energy Systems Lab Texas A&M University College Station, TX ABSTRACT This study modeled air flow and pressure drops in non-metallic flexible ducts using Computational Fluid Dynamic (CFD) analysis. CFD simulation results showed...
FPGA Acceleration of Discrete Molecular Dynamics Simulation
Herbordt, Martin
' & $ % FPGA Acceleration of Discrete Molecular Dynamics Simulation Joshua Model Thesis submitted UNIVERSITY COLLEGE OF ENGINEERING Thesis FPGA Acceleration of Discrete Molecular Dynamics Simulation Acceleration of Discrete Molecular Dynamics Simulation Joshua Model ABSTRACT Molecular dynamics simulation
Babic, Miroslav; Kljenak, Ivo; Mavko, Borut [Reactor Engineering Division, Jozef Stefan Institute, Jamova 39, Ljubljana (Slovenia)
2006-07-01T23:59:59.000Z
The CFD code CFX4.4 was used to simulate an experiment in the ThAI facility, which was designed for investigation of thermal-hydraulic processes during a severe accident inside a Light Water Reactor containment. In the considered experiment, air was initially present in the vessel, and helium and steam were injected during different phases of the experiment at various mass flow rates and at different locations. The main purpose of the proposed work was to assess the capabilities of the CFD code to reproduce the atmosphere structure with a three-dimensional model, coupled with condensation models proposed by the authors. A three-dimensional model of the ThAI vessel for the CFX4.4 code was developed. The flow in the simulation domain was modeled as single-phase. Steam condensation on vessel walls was modeled as a sink of mass and energy using a correlation that was originally developed for an integral approach. A simple model of bulk phase change was also included. Calculated time-dependent variables together with temperature and volume fraction distributions at the end of different experiment phases are compared to experimental results. (authors)
Molecular dynamics simulation of threshold displacement energies...
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
simulation of threshold displacement energies in zircon. Molecular dynamics simulation of threshold displacement energies in zircon. Abstract: Molecular-dynamics simulations were...
Development of CFD-Based Simulation Tools for In-Situ Thermal Processing of
Office of Scientific and Technical Information (OSTI)
AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE:1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level:5 TablesExports to3,1,50022,3,,0,,6,1,Separation 23Tribal EnergyCatalyticPreparation and propertiessystemDOSFAC2 user`s guideState of the ArtandCFD-Based
FPGA ACCELERATION OF MOLECULAR DYNAMICS SIMULATIONS
Herbordt, Martin
' & $ % FPGA ACCELERATION OF MOLECULAR DYNAMICS SIMULATIONS YONGFENG GU Dissertation submitted;BOSTON UNIVERSITY COLLEGE OF ENGINEERING Dissertation FPGA ACCELERATION OF MOLECULAR DYNAMICS SIMULATIONS DYNAMICS SIMULATIONS (Order No. ) YONGFENG GU Boston University, College of Engineering, 2008 Major
Dynamic simulation of voltage collapses
Deuse, J.; Stubbe, M. (Tractebel, Brussels (Belgium))
1993-08-01T23:59:59.000Z
Most of the time the voltage collapse phenomena are studied by means of computer programs designed for the calculation of steady state conditions. But in the real world, the simultaneous occurrences of losses of synchronism, of AVR dynamics or of transformer tap changes call for a full dynamic simulation of voltage phenomena. The present paper shows some examples of dynamic simulations of voltage phenomena using a new general purpose stability program (EUROSTAG), covering in a continuous way the classical fields of transient, mid-term and long-term stability, and also the quasi steady state conditions of a power system.
Performance of Coupled Building Energy and CFD Simulations Zhiqiang (John) Zhai
Chen, Qingyan "Yan"
, West Lafayette, IN 47907-2088, USA Abstract The integration of building energy simulation (ES efficiency, and energy consumption. Based on the information, a building designer is able to modify his and accurate convective heat transfers that help ES to calculate more accurately total energy consumption
Simulations with dynamical HISQ quarks
A. Bazavov; C. Bernard; C. DeTar; W. Freeman; Steven Gottlieb; U. M. Heller; J. E. Hetrick; J. Laiho; L. Levkova; M. Oktay; J. Osborn; R. L. Sugar; D. Toussaint; R. S. Van de Water
2010-12-06T23:59:59.000Z
We report on the status of a program of generating and using configurations with four flavors of dynamical quarks, using the HISQ action. We study the lattice spacing dependence of physical quantities in these simulations, using runs at several lattice spacings, but with the light quark mass held fixed at two tenths of the strange quark mass. We find that the lattice artifacts in the HISQ simulations are much smaller than those in the asqtad simulations at the same lattice spacings and quark masses. We also discuss methods for setting the scale, or assigning a lattice spacing to ensembles run at unphysical parameters.
The Dalles Dam, Columbia River: Spillway Improvement CFD Study
Cook, Chris B.; Richmond, Marshall C.; Serkowski, John A.
2006-06-01T23:59:59.000Z
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 was then applied to address specific SIS design questions. Specifically, the CFD models were used to evaluate flow deflectors, baffle block removal and the effects of spillwalls. The CFD models were also used to evaluate downstream differences at other locations, such as at the Highway 197 bridge piers and Oregon shore islands, due to alterations in spill pattern. CFD model results were analyzed to quantitatively compare impacts of the spillwall that has subsequently been constructed between bays 6 and 7. CFD model results provided detailed information about how the spillwall would impact downstream flow patterns that complemented results from the 1:80 scale physical model. The CFD model was also used to examine relative differences between the juvenile spill pattern used in previous years and the anticipated spill pattern that will be applied once the wall is complete. In addition, the CFD model examined velocity magnitudes over the downstream basalt shelf to investigate potential for erosion under high flow conditions (e.g., 21 kcfs/bay for bays 1 through 6) with the spillwall in place. Several appendices follow the results and discussion sections of this report. These appendices document the large number of CFD simulations that have been performed by PNNL; both spillway improvement study (SIS) related and those performed for related biological tests.
Thermoacoustic engine simulations with lattice Boltzmann CFD. Tasks 3, 4 and 5 progress report
NONE
1995-02-06T23:59:59.000Z
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.
Radiation in molecular dynamic simulations
Glosli, J; Graziani, F; More, R; Murillo, M; Streitz, F; Surh, M
2008-10-13T23:59:59.000Z
Hot dense radiative (HDR) plasmas common to Inertial Confinement Fusion (ICF) and stellar interiors have high temperature (a few hundred eV to tens of keV), high density (tens to hundreds of g/cc) and high pressure (hundreds of Megabars to thousands of Gigabars). Typically, such plasmas undergo collisional, radiative, atomic and possibly thermonuclear processes. In order to describe HDR plasmas, computational physicists in ICF and astrophysics use atomic-scale microphysical models implemented in various simulation codes. Experimental validation of the models used to describe HDR plasmas are difficult to perform. Direct Numerical Simulation (DNS) of the many-body interactions of plasmas is a promising approach to model validation but, previous work either relies on the collisionless approximation or ignores radiation. We present a new numerical simulation technique to address a currently unsolved problem: the extension of molecular dynamics to collisional plasmas including emission and absorption of radiation. The new technique passes a key test: it relaxes to a blackbody spectrum for a plasma in local thermodynamic equilibrium. This new tool also provides a method for assessing the accuracy of energy and momentum exchange models in hot dense plasmas. As an example, we simulate the evolution of non-equilibrium electron, ion, and radiation temperatures for a hydrogen plasma using the new molecular dynamics simulation capability.
Accelerated dynamics simulations of nanotubes.
Uberuaga, B. P. (Blas Pedro); Stuart, S. J. (Steve J.); Voter, A. F.
2002-01-01T23:59:59.000Z
We report on the application of accelerated dynamics techniques to the study of carbon nanotubes. We have used the parallel replica method and temperature accelerated dynamics simulations are currently in progress. In the parallel replica study, we have stretched tubes at a rate significantly lower than that used in previous studies. In these preliminary results, we find that there are qualitative differences in the rupture of the nanotubes at different temperatures. We plan on extending this investigation to include nanotubes of various chiralities. We also plan on exploring unique geometries of nanotubes.
Molecular dynamics simulation studies of electrolytes andelectrolyte...
Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site
studies of electrolytes and electrolyteelectrode interfaces Molecular dynamics simulation studies of electrolytes and electrolyteelectrode interfaces 2009 DOE Hydrogen Program...
CFD analysis of laminar oscillating flows
Booten, C. W. Charles W.); Konecni, S. (Snezana); Smith, B. L. (Barton L.); Martin, R. A. (Richard A.)
2001-01-01T23:59:59.000Z
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.
Xu, Chuanfu, E-mail: xuchuanfu@nudt.edu.cn [College of Computer Science, National University of Defense Technology, Changsha 410073 (China); Deng, Xiaogang; Zhang, Lilun [College of Computer Science, National University of Defense Technology, Changsha 410073 (China); Fang, Jianbin [Parallel and Distributed Systems Group, Delft University of Technology, Delft 2628CD (Netherlands); Wang, Guangxue; Jiang, Yi [State Key Laboratory of Aerodynamics, P.O. Box 211, Mianyang 621000 (China); Cao, Wei; Che, Yonggang; Wang, Yongxian; Wang, Zhenghua; Liu, Wei; Cheng, Xinghua [College of Computer Science, National University of Defense Technology, Changsha 410073 (China)
2014-12-01T23:59:59.000Z
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 solve realistic CFD problems with both complex configurations and high-order schemes.
Ship hull resistance calculations using CFD methods
Voxakis, Petros
2012-01-01T23:59:59.000Z
In past years, the computational power and run-time required by Computational Fluid Dynamics (CFD) codes restricted their use in ship design space exploration. Increases in computational power available to designers, in ...
Molecular Dynamics Simulation of the AgCl/Electrolyte Interfacial...
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Simulation of the AgClElectrolyte Interfacial Capacity. Molecular Dynamics Simulation of the AgClElectrolyte Interfacial Capacity. Abstract: Molecular dynamics simulation of the...
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:...
Parallel Implementation of Power System Dynamic Simulation
Jin, Shuangshuang; Huang, Zhenyu; Diao, Ruisheng; Wu, Di; Chen, Yousu
2013-07-21T23:59:59.000Z
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.
A Molecular Dynamics Simulation of the Turbulent Couette Minimal Flow Unit
Smith, E R
2015-01-01T23:59:59.000Z
A molecular dynamics (MD) simulation of planar Couette flow is presented for the minimal channel in which turbulence structures can be sustained. Evolution over a single breakdown and regeneration cycle is compared to computational fluid dynamics (CFD) simulations. Qualitative similar structures are observed and turbulent statistics show excellent quantitative agreement. The molecular scale law of the wall is presented in which stick-slip molecular wall-fluid interactions replace the no-slip conditions. The impact of grid resolution is explored and the observed structures are seen to be dependant on averaging time and length scales. The kinetic energy spectra show a range of scales are present in the molecular system and that spectral content is dependent on the grid resolution employed. The subgrid velocity of the molecules is compared to spatial averaged velocity using joint probability density functions. Molecular trajectories, diffusions and Lagrangian statistics are presented. The importance of sub-grid ...
Atomic detail brownian dynamics simulations of concentrated protein...
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detail brownian dynamics simulations of concentrated protein solutions with a mean field treatment of hydrodynamic Atomic detail brownian dynamics simulations of concentrated...
Molecular Dynamics Simulation Studies of Electrolytes andElectrolyte...
Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site
Dynamics Simulation Studies of Electrolytes and ElectrolyteElectrode Interfaces Molecular Dynamics Simulation Studies of Electrolytes and ElectrolyteElectrode Interfaces 2010 DOE...
Hajdukiewicz, M.; Keane, M.; O'Flynn, B.; O'Grady, W.
2010-01-01T23:59:59.000Z
Computational Fluid Dynamics (CFD) is a robust tool for modeling interactions within and between fluids and solids. CFD can help understand and predict phenomena that are difficult to test experimentally leading to cleaner, ...
Simulation of Complex Fluids using Dissipative Particle Dynamics
Title: Simulation of Complex Fluids using Dissipative Particle Dynamics Abstract: Dissipative Particle Dynamics (DPD) is a relatively new mesoscopic method ...
Dynamic simulations of arrays of Josephson junctions
Eikmans, H.; van Himbergen, J.E. (Institute for Theoretical Physics, University of Utrecht, P.O. Box 80.006, 3508 TA Utrecht, The Netherlands (NL))
1990-05-01T23:59:59.000Z
First we introduce a very efficient algorithm for dynamic simulations of a wide class of arrays of Josephson junctions with realistic boundaries. With this algorithm one can also represent current-biased arrays with periodic boundaries. Next we present results of extensive simulations of ladder arrays. We evaluate the resistance as a function of magnetic field and find striking differences between different geometries.
Dynamic Simulation of Nuclear Hydrogen Production Systems
Dynamic Simulation of Nuclear Hydrogen Production Systems by Patricio D. Ram´irez Mu~noz Submitted Simulation of Nuclear Hydrogen Production Systems by Patricio D. Ram´irez Mu~noz Submitted to the Department of Doctor of Philosophy in Chemical Engineering Abstract Nuclear hydrogen production processes have been
Efficient dynamic synchronous machine simulation with harmonics
Haskew, T.A.; Stern, H.P.; Chen, Z. [Univ. of Alabama, Tuscaloosa, AL (United States). Dept. of Electrical Engineering] [Univ. of Alabama, Tuscaloosa, AL (United States). Dept. of Electrical Engineering
1996-06-01T23:59:59.000Z
Within this paper, an efficient procedure for the dynamic simulation of faulted synchronous machines operating in the presence of harmonics is presented. The algorithm employs steady-state frequency domain techniques for simulation of the transmission system sequence networks and time domain methods for the synchronous machines represented in the odq frame of reference. The procedure affords greater accuracy than conventional fault analysis techniques based strictly on steady-state methods, yet requires far less computational time than full system dynamic simulations such as those using the EMTP.
DYNAMIC SIMULATION OF PERFORMANCE DEVELOPMENT
Perl, JÃ¼rgen
for scheduling optimal training planes. (a) offline analysis (b) online prediction load profile original) online prediction load profile original performance profile simulated performance profile predicted performance profile Figure 1: Offline load-performance-analysis (a) compared to online performance
Computational fluid dynamics (CFD) simulations of aerosol in a u-shaped steam generator tube
Longmire, Pamela
2009-05-15T23:59:59.000Z
velocity is equal to the mean velocity which is known (for instance from turbulence model predictions) plus a fluctuation, which is unknown. The fluctuating velocity component transports particles away from the mean flow and is responsible for particle...
Computational fluid dynamics (CFD) simulations of aerosol in a u-shaped steam generator tube
Longmire, Pamela
2009-05-15T23:59:59.000Z
To quantify primary side aerosol retention, an Eulerian/Lagrangian approach was used to investigate aerosol transport in a compressible, turbulent, adiabatic, internal, wall-bounded flow. The ARTIST experimental project (Phase I) served...
Lee, S.
2011-05-05T23:59:59.000Z
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 elevation of transfer pump for minimum sludge disturbance. (2) An empirical equation for a tank with no cooling coils agrees reasonably with the current modeling results for the dual jet. (3) From the sensitivity study of the cooling coils, it was found that the tank mixing time for the coiled tank was about two times longer than that of the tank fluid with no coils under the 1/10th scale, while the coiled tank required only 50% longer than the one without coils under the full scale Tank 50H. In addition, the time difference is reduced when the pumping U{sub o}d{sub o} value is increased for a given tank. (4) The blending time for T-shape dual jet pump is about 20% longer than that of 15{sup o} upward V-shape pump under the 1/10th pilot-scale tank, while the time difference between the two pumps is about 12% for the full-scale Tank 50H. These results are consistent with the literature information. (5) A transfer pump with a solid-plate suction screen operating at 130 gpm can be located 9.5 inches above settled sludge for 2 in screen height in a 85 ft waste tank without disturbing any sludge. Detailed results are summarized in Table 13. Final pump performance calculations were made by using the established CW pump design, and operating conditions to satisfy the two requirements of minimum sludge disturbance, and adequate blending of tank contents. The final calculation results show that the blending times for the coiled and uncoiled tanks coupled with the CW pump design are 159 and 83 minutes, respectively. All the results are provided in Table 16.
Helton, Donald McLean
2002-01-01T23:59:59.000Z
The premise of the work presented here is to use a common analytical tool, Computational Fluid Dynamics (CFD), along with a prevalent turbulence model, Large Eddy Simulation (LES), to study the flow past rectangular cylinders. In an attempt to use...
CFD modeling of entrained-flow coal gasifiers with improved physical and chemical sub-models
Ma, J.; Zitney, S.
2012-01-01T23:59:59.000Z
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.
ENERGY SERIES "CFD Modeling and its Application in Steam Condenser
Bergman, Keren
SEMINAR: ENERGY SERIES "CFD Modeling and its Application in Steam Condenser Performance Improvement will discuss the application of CFD to steam condensers, an area where both of the above mentioned limitations of computational fluid dynamics, having applied these techniques extensively in the design large heat exchangers
Dynamic procedure for filtered gyrokinetic simulations
Morel, P.; Banon Navarro, A.; Albrecht-Marc, M.; Carati, D. [Statistical and Plasma Physics Laboratory, Universite Libre de Bruxelles, Bruxelles 1050 (Belgium); Merz, F.; Goerler, T.; Jenko, F. [Max-Planck-Institut fuer Plasmaphysik, EURATOM Association, D-85748 Garching (Germany)
2012-01-15T23:59:59.000Z
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.
Spin dynamics simulations at AGS
Huang, H.; MacKay, W.W.; Meot, F.; Roser, T.
2010-05-23T23:59:59.000Z
To preserve proton polarization through acceleration, it is important to have a correct model of the process. It has been known that with the insertion of the two helical partial Siberian snakes in the Alternating Gradient Synchrotron (AGS), the MAD model of AGS can not deal with a field map with offset orbit. The stepwise ray-tracing code Zgoubi provides a tool to represent the real electromagnetic fields in the modeling of the optics and spin dynamics for the AGS. Numerical experiments of resonance crossing, including spin dynamics in presence of the snakes and Q-jump, have been performed in AGS lattice models, using Zgoubi. This contribution reports on various results so obtained.
Head Loss Evaluation in a PWR Reactor Vessel Using CFD Analysis
Ji Hwan Jeong; Jong Pil Park [School of Mechanical Engineering, Pusan National University, Enesys Jangjeon-dong, Geumjeong-gu, Busan (Korea, Republic of); Byoung-Sub Han [Jangdae-dong, Yusong-gu, Daejeon (Korea, Republic of)
2006-07-01T23:59:59.000Z
Nuclear vendors and utilities perform lots of simulations and analyses in order to ensure the safe operation of nuclear power plants (NPPs). In general, the simulations are carried out using vendor-specific design codes and best-estimate system analysis codes and most of them were developed based on 1-dimensional lumped parameter models. During the past decade, however, computers, parallel computation methods, and 3-dimensional computational fluid dynamics (CFD) codes have been dramatically enhanced. It is believed to be beneficial to take advantage of advanced commercial CFD codes in safety analysis and design of NPPs. The present work aims to analyze the flow distribution in downcomer and lower plenum of Korean standard nuclear power plants (KSNPs) using STAR-CD. The lower plenum geometry of a PWR is very complicated since there are so many reactor internals, which hinders in CFD analysis for real reactor geometry up to now. The present work takes advantage of 3D CAD model so that real geometry of lower plenum is used. The results give a clear figure about flow fields in the reactor vessel, which is one of major safety concerns. The calculated pressure drop across downcomer and lower plenum appears to be in good agreement with the data in engineering calculation note. A algorithm which can evaluate head loss coefficient which is necessary for thermal-hydraulic system code running was suggested based on this CFD analysis results. (authors)
Bonneville Project: CFD of the Spillway Tailrace
Rakowski, Cynthia L.; Serkowski, John A.; Richmond, Marshall C.; Romero Gomez, Pedro DJ
2012-11-19T23:59:59.000Z
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.
Atomistic Simulation of Nafion Membrane: 2. Dynamics of Water...
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2. Dynamics of Water Molecules and Hydronium Ions. Atomistic Simulation of Nafion Membrane: 2. Dynamics of Water Molecules and Hydronium Ions. Abstract: We have performed a...
An efficient parallelization scheme for molecular dynamics simulations...
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efficient parallelization scheme for molecular dynamics simulations with many-body, flexible, polarizable empirical An efficient parallelization scheme for molecular dynamics...
Molecular dynamics simulations of ion range profiles for heavy...
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simulations of ion range profiles for heavy ions in light targets. Molecular dynamics simulations of ion range profiles for heavy ions in light targets. Abstract: The determination...
Discrete Event Simulation of Molecular Dynamics with Configurable Logic
Herbordt, Martin
: {jtmodel|herbordt}@bu.edu Abstract: Molecular dynamics simulation based on discrete event simulation (DMD. Herbordt Department of Electrical and Computer Engineering Boston University; Boston, MA 02215 EMail
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
2010-08-01T23:59:59.000Z
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.
FPGA-BASED MULTIGRID COMPUTATION FOR MOLECULAR DYNAMICS SIMULATIONS
Herbordt, Martin
FPGA-BASED MULTIGRID COMPUTATION FOR MOLECULAR DYNAMICS SIMULATIONS Yongfeng Gu Martin C. Herbordt serial code. 1. INTRODUCTION Molecular Dynamics simulations (MD) are a fundamental tool for gaining Computer Architecture and Automated Design Laboratory Department of Electrical and Computer Engineering
Physics results from dynamical overlap fermion simulations
Shoji Hashimoto
2008-11-08T23:59:59.000Z
I summarize the physics results obtained from large-scale dynamical overlap fermion simulations by the JLQCD and TWQCD collaborations. The numerical simulations are performed at a fixed global topological sector; the physics results in the theta-vacuum is reconstructed by correcting the finite volume effect, for which the measurement of the topological susceptibility is crucial. Physics applications we studied so far include a calculation of chiral condensate, pion mass, decay constant, form factors, as well as (vector and axial-vector) vacuum polarization functions and nucleon sigma term.
Lee, S.
2011-05-17T23:59:59.000Z
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-phase model. The modeling results show that the flow patterns driven by four pump operation satisfy the solid suspension requirement, and the average solid concentration at the plane of the transfer pump inlet is about 12% higher than the tank average concentrations for the 70 inch tank level and about the same as the tank average value for the 29 inch liquid level. When one of the four pumps is not operated, the flow patterns are satisfied with the minimum suspension velocity criterion. However, the solid concentration near the tank bottom is increased by about 30%, although the average solid concentrations near the transfer pump inlet have about the same value as the four-pump baseline results. The flow pattern results show that although the two-pump case satisfies the minimum velocity requirement to suspend the sludge particles, it provides the marginal mixing results for the heavier or larger insoluble materials such as MST and KTPB particles. The results demonstrated that when more than one jet are aiming at the same position of the mixing tank domain, inefficient flow patterns are provided due to the highly localized momentum dissipation, resulting in inactive suspension zone. Thus, after completion of the indexed solids suspension, pump rotations are recommended to avoid producing the nonuniform flow patterns. It is noted that when tank liquid level is reduced from the highest level of 70 inches to the minimum level of 29 inches for a given number of operating pumps, the solid mixing efficiency becomes better since the ratio of the pump power to the mixing volume becomes larger. These results are consistent with the literature results.
Molecular Dynamics Simulations on High-Performance Reconfigurable
Herbordt, Martin
23 Molecular Dynamics Simulations on High-Performance Reconfigurable Computing Systems MATT CHIU. 2010. Molecular dynamics simulations on high performance recon- figurable computing systems. ACM Trans://doi.acm.org/10.1145/1862648.1862653. 1. INTRODUCTION Molecular dynamics simulation (MD) is a
Dynamic Simulation of Electric Machines on FPGA Boards
Zambreno, Joseph A.
Dynamic Simulation of Electric Machines on FPGA Boards Hao Chen, Song Sun, Dionysios C. Aliprantis USA Abstract--This paper presents the implementation of an induc- tion machine dynamic simulation] devices. Herein, the goal is to implement an entire dynamic simulation of an induction machine on a single
IGCC Dynamic Simulator and Training Center
Zitney, S.E.; Erbes, M.R. (Enginomix, LLC)
2006-10-01T23:59:59.000Z
Integrated Gasification Combined Cycle (IGCC) is emerging as the technology of choice for providing clean, low-cost electricity for the next generation of coal-fired power plants and will play a central role in the development of high-efficiency, zero-emissions power plants such as FutureGen. Several major utilities and developers recently announced plans to build IGCC plants and other major utilities are evaluating IGCC’s suitability for base-load capacity additions. This recent surge of attention to IGCC power generation is creating a growing demand for experience with the analysis, operation, and control of commercial-scale IGCC plants. To meet this need, the National Energy Technology Laboratory (NETL) has launched a project to develop a generic, full-scope, IGCC dynamic plant simulator for use in establishing a state-of-the-art simulator training center at West Virginia University’s (WVU) National Research Center for Coal and Energy (NRCCE). The IGCC Dynamic Simulator & Training (DS&T) Center will be established under the auspices of the Collaboratory for Process & Dynamic Systems Modeling (“Collaboratory”) organized between NETL, WVU, the University of Pittsburgh, and Carnegie Mellon University.
Dynamics Within an Organisation: Temporal Specification, Simulation and Evaluation
Treur, Jan
- 1 - Dynamics Within an Organisation: Temporal Specification, Simulation and Evaluation Catholijn is its dynamics. In this paper different types of specifications of properties of the dynamics within an organisation are introduced. Supporting tools for specification, simulation and analysis of dynamics within
INCORPORATING DYNAMIC 3D SIMULATION INTO PRA
Steven R Prescott; Curtis Smith
2011-07-01T23:59:59.000Z
Through continued advancement in computational resources, development that was previously done by trial and error production is now performed through computer simulation. These virtual physical representations have the potential to provide accurate and valid modeling results and are being used in many different technical fields. Risk assessment now has the opportunity to use 3D simulation to improve analysis results and insights, especially for external event analysis. By using simulations, the modeler only has to determine the likelihood of an event without having to also predict the results of that event. The 3D simulation automatically determines not only the outcome of the event, but when those failures occur. How can we effectively incorporate 3D simulation into traditional PRA? Most PRA plant modeling is made up of components with different failure modes, probabilities, and rates. Typically, these components are grouped into various systems and then are modeled together (in different combinations) as a “system” with logic structures to form fault trees. Applicable fault trees are combined through scenarios, typically represented by event tree models. Though this method gives us failure results for a given model, it has limitations when it comes to time-based dependencies or dependencies that are coupled to physical processes which may themselves be space- or time-dependent. Since, failures from a 3D simulation are naturally time related, they should be used in that manner. In our simulation approach, traditional static models are converted into an equivalent state diagram representation with start states, probabilistic driven movements between states and terminal states. As the state model is run repeatedly, it converges to the same results as the PRA model in cases where time-related factors are not important. In cases where timing considerations are important (e.g., when events are dependent upon each other), then the simulation approach will typically provide superior results and insights. We also couple the state model with the dynamic 3D simulation analysis representing events (such as flooding) to determine which (if any) components fail. Not only does the simulation take into account any failed items from the state model, but any failures caused by the simulation are incorporated back into the state model and factored into the overall results. Using this method we incorporate accurate 3D simulation results, eliminate static-based PRA issues, and have time ordered failure information.
Huang, Zhiming
2012-07-16T23:59:59.000Z
Current Velocity at Riser 2nd End Umax Maximum Current Velocity VIV Vortex Induced Vibration ix TABLE OF CONTENTS Page ABSTRACT.../L=Constant ...................................................................... 63 Figure 31 Grid Details on Riser Surface and Overlapping Region........................... 63 Figure 32 Data Grids with Riser Deflection.............................................................. 64 Figure 33 Vortex Shedding Evolution...
Huang, Zhiming
2012-07-16T23:59:59.000Z
and gas exploration and developments have been moving fast toward increasingly deeper water depth, i.e. 3,000m in Gulf of Mexico. Majority of the subsea wells are tied back to a surface platform through long risers, including steel catenary risers..., flexible risers, free standing risers, bundled risers, or top tensioned risers (ASME B31.4, 2002, ASME B31.8a, 2001, API 1111, 1999). These risers provide fluid conduit for fluid transport between subsea wells and surface platform, and protect...
Brownian Dynamics Simulation of Protein Solutions: Structural and Dynamical Properties
Mereghetti, Paolo; Gabdoulline, Razif; Wade, Rebecca C.
2010-12-01T23:59:59.000Z
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.
CFD Analysis of a Novel High Speed Rotary On/Off Valve 283 Proc. of 6th
Li, Perry Y.
CFD Analysis of a Novel High Speed Rotary On/Off Valve 283 Proc. of 6th FPNI-PhD Symp. West Lafayette 2010, pp. 283-294 CFD ANALYSIS OFA NOVEL HIGH SPEED ROTARY ON/OFF VALVE Meng WANG1 , Haink TU a novel type of high speed rotary on/off valve is analyzed using CFD (Computational Fluid Dynamics
AI-Based Simulation: An Alternative to Numerical Simulation and Modeling
Mohaghegh, Shahab
: Numerical Modeling, Simulation, Artificial Intelligence, Data Min- ing, Reservoir Modeling, Reservoir data for brown fields. The run-time of AI-Based reservoir models that provide complete field responses Computational Fluid Dynamics (CFD) to Numer- ical Reservoir Simulation (NRS) most of the computational modeling
Scaling studies and conceptual experiment designs for NGNP CFD assessment
D. M. McEligot; G. E. McCreery
2004-11-01T23:59:59.000Z
The objective of this report is to document scaling studies and conceptual designs for flow and heat transfer experiments intended to assess CFD codes and their turbulence models proposed for application to prismatic NGNP concepts. 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. Two aspects of the complex flow in an NGNP are being addressed: (1) flow and thermal mixing in the lower plenum ("hot streaking" issue) and (2) turbulence and resulting temperature distributions in reactor cooling channels ("hot channel" issue). Current prismatic NGNP concepts are being 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 have been applied to determine key non-dimensional parameters and their magnitudes over this operating range. For normal operation, the flow in the coolant channels can be considered to be dominant turbulent forced convection with slight transverse property variation. In a pressurized cooldown (LOFA) simulation, the flow quickly becomes laminar with some possible buoyancy influences. The flow in the lower plenum can locally be considered to be a situation of multiple hot jets into a confined crossflow -- with obstructions. Flow is expected to be turbulent with momentumdominated 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. Two types of heat transfer experiments are being considered. One addresses the "hot channel" problem, if necessary. The second type will treat heated jets entering a model plenum. Unheated MIR (Matched-Index-of-Refraction) experiments are first steps when the geometry is complicated. One does not want to use a computational technique which will not even handle constant properties properly. The purpose of the fluid dynamics experiments is to develop benchmark databases for the assessment of CFD solutions of the momentum equations, scalar mixing and turbulence models for typical NGNP plenum geometries in the limiting case of negligible buoyancy and constant fluid properties. As indicated by the scaling studies, in normal full power operation of a typical NGNP conceptual design, buoyancy influences should be negligible in the lower plenum. The MIR experiment will simulate flow features of the paths of jets as they mix in flowing through the array of posts in a lower plenum en route to the single exit duct. Conceptual designs for such experiments are described.
Simulation of spray drying in superheated steam using computational fluid dynamics
Frydman, A.; Vasseur, J.; Ducept, F.; Sionneau, M.; Moureh, J.
1999-09-01T23:59:59.000Z
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.
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
2006-09-01T23:59:59.000Z
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 the flow and energy transport as applied to nuclear reactor safety. However, it is expected that these practices and procedures will require updating from time to time as research and development affect them or replace them with better procedures. The practices and procedures are categorized into five groups. These are: 1.Code Verification 2.Code and Calculation Documentation 3.Reduction of Numerical Error 4.Quantification of Numerical Uncertainty (Calculation Verification) 5.Calculation Validation. These five categories have been identified from procedures currently required of CFD simulations such as those required for publication of a paper in the ASME Journal of Fluids Engineering and from the literature such as Roache [1998]. Code verification refers to the demonstration that the equations of fluid and energy transport have been correctly coded in the CFD code. Code and calculation documentation simply means that the equations and their discretizations, etc., and boundary and initial conditions used to pose the fluid flow problem are fully described in available documentation. Reduction of numerical error refers to practices and procedures to lower numerical errors to negligible or very low levels as is reasonably possible (such as avoiding use of first-order discretizations). The quantification of numerical uncertainty is also known as calculation verification. This means that estimates are made of numerical error to allow the characterization of the numerical
Computational fluid dynamic simulations of chemical looping fuel reactors utilizing gaseous fuels
Mahalatkar, K.; Kuhlman, J.; Huckaby, E.D.; O'Brien, T.
2011-01-01T23:59:59.000Z
A computational fluid dynamic(CFD) model for the fuel reactor of chemical looping combustion technology has been developed,withspecialfocusonaccuratelyrepresentingtheheterogeneous chemicalreactions.Acontinuumtwo-fluidmodelwasusedtodescribeboththegasandsolidphases. Detailedsub-modelstoaccountforfluid–particleandparticle–particleinteractionforceswerealso incorporated.Twoexperimentalcaseswereanalyzedinthisstudy(Son andKim,2006; Mattisonetal., 2001). SimulationswerecarriedouttotestthecapabilityoftheCFDmodeltocapturechangesinoutletgas concentrationswithchangesinnumberofparameterssuchassuperficialvelocity,metaloxide concentration,reactortemperature,etc.Fortheexperimentsof Mattissonetal.(2001), detailedtime varyingoutletconcentrationvalueswerecompared,anditwasfoundthatCFDsimulationsprovideda reasonablematchwiththisdata.
A Quasi-Dynamic HVAC and Building Simulation Methodology
Davis, Clinton Paul
2012-07-16T23:59:59.000Z
This thesis introduces a quasi-dynamic building simulation methodology which complements existing building simulators by allowing transient models of HVAC (heating, ventilating and air-conditioning) systems to be created in an analogous way...
Simulating Hamiltonian Dynamics with a Truncated Taylor Series
Berry, Dominic W.
We describe a simple, efficient method for simulating Hamiltonian dynamics on a quantum computer by approximating the truncated Taylor series of the evolution operator. Our method can simulate the time evolution of a wide ...
Molecular Dynamics Simulations of Uranyl and Uranyl Carbonate...
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
of Uranyl and Uranyl Carbonate Adsorption at Alumino-silicate Surfaces. Molecular Dynamics Simulations of Uranyl and Uranyl Carbonate Adsorption at Alumino-silicate Surfaces....
Molecular dynamics simulation and ab intio studies of electrolytes...
Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site
Program, and Vehicle Technologies Program Annual Merit Review and Peer Evaluation es058smith2011o.pdf More Documents & Publications Molecular Dynamics Simulation Studies of...
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...
CFD modeling of commercial-scale entrained-flow coal gasifiers
Ma, J.; Zitney, S.
2012-01-01T23:59:59.000Z
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 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 system-wide design and optimization.
Ab Initio Molecular Dynamics Simulations of Low-Energy Recoil...
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
Initio Molecular Dynamics Simulations of Low-Energy Recoil Eventsin ThO2, CeO2, and ZrO2. Ab Initio Molecular Dynamics Simulations of Low-Energy Recoil Eventsin ThO2, CeO2, and...
Sensitivity, Approximation and Uncertainty in Power System Dynamic Simulation
1 Sensitivity, Approximation and Uncertainty in Power System Dynamic Simulation Ian A. Hiskens, Fellow, IEEE Jassim Alseddiqui Student Member, IEEE Abstract-- Parameters of power system models the influence of uncertainty in simulations of power system dynamic behaviour. It is shown that trajectory
Integrated Dynamic Simulation for Process Optimization and Control
Rubloff, Gary W.
Integrated Dynamic Simulation for Process Optimization and Control G. Brian Lu, Laura L. Tedder Film Deposition · Applications in Process Optimization for Manufacturing and the Environment Process efficient processes, equipment, sensor, and control systems #12;Dynamic Simulators for Sensor-Based Process
Chapter 7 Molecular Dynamics Simulations of Fluoro Polymers
Goddard III, William A.
131 Chapter 7 Molecular Dynamics Simulations of Fluoro Polymers: Prediction of Glass Transition for molecular dynamics simulation of the uoro polymers: Polytetra uoroethylene PTFE, Polyvinylidene uoride PVDF using a Build-Anneal-Quench procedure. For PTFE, PVDF, and ETFE uoro polymers, these results predict
Dynamic Simulation Model of a Consumer Foods Production Process !
Sun, Yu
schedule based on product list The SIMUL8 Component 1. Over 200 lines of simula0on code 2. ReadsDynamic Simulation Model of a Consumer Foods Production Process ! Goals · Create a dynamic simula0 Created par0ally automated Excel files to go handin hand with simula0on o Contains all SKUs and meat
2005-3-21 1 Dynamic Equipment and Process Simulation
Rubloff, Gary W.
· Equipment cost, reliability ESH · Reactant utilization · Energy · Emission Technology · Material Quality2005-3-21 1 Dynamic Equipment and Process Simulation for Atomic Layer Deposition Technology Wei Lei · Energy · Emissions Our work: Use dynamic simulation approach to study ALD equipment and process behavior
Modelling and simulation of multidisciplinary dynamic systems Lead: A. Fakri.
Baudoin, GeneviÃ¨ve
Modelling and simulation of multidisciplinary dynamic systems Lead: A. Fakri. Permanent members: P. Integration of various engineering disciplines and the consideration of the dynamic control need a concurrent suited for the energy exchanges to study multidisciplinary dynamic engineering systems modelling. Our
Simulation of chemical reaction dynamics on an NMR quantum computer
Dawei Lu; Nanyang Xu; Ruixue Xu; Hongwei Chen; Jiangbin Gong; Xinhua Peng; Jiangfeng Du
2011-05-21T23:59:59.000Z
Quantum simulation can beat current classical computers with minimally a few tens of qubits and will likely become the first practical use of a quantum computer. One promising application of quantum simulation is to attack challenging quantum chemistry problems. Here we report an experimental demonstration that a small nuclear-magnetic-resonance (NMR) quantum computer is already able to simulate the dynamics of a prototype chemical reaction. The experimental results agree well with classical simulations. We conclude that the quantum simulation of chemical reaction dynamics not computable on current classical computers is feasible in the near future.
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. [Université de Nice Sophia Antipolis, CNRS, Observatoire de la Côte d'Azur, Nice (France)] [Université de Nice Sophia Antipolis, CNRS, Observatoire de la Côte 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)
2013-08-15T23:59:59.000Z
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.
Annual Report 1999 Environmental Dynamics and Simulation
NS Foster-Mills
2000-06-28T23:59:59.000Z
This annual report describes selected 1999 research accomplishments for the Environmental Dynamics and Simulation (ED and S) directorate, one of six research organizations in the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL). These accomplishments are representative of the different lines of research underway in the ED and S directorate. EMSL is one of US Department of Energy's (DOE) national scientific user facilities and is the centerpiece of DOE's commitment to providing world-class experimental, theoretical, and computational capabilities for solving the nation's environmental problems. Capabilities in the EMSL include over 100 major instrument systems for use by the resident research staff, their collaborators, and users of the EMSL. These capabilities are used to address the fundamental science that will be the basis for finding solutions to national environmental issues such as cleaning up contamianted areas at DOE sites across the country and developing green technologies that will reduce or eliminate future pollution production. The capabilities are also used to further the understanding of global climate change and environmental issues relevant to energy production and use and health effects resulting from exposure to contaminated environments.
Swing Check Valve Design Criteria and CFD Validation
Dallstream, Brian E.; Fricke, Brian A.; Becker, Bryan R. [University of Missouri-Kansas City (United States)
2006-07-01T23:59:59.000Z
This paper provides information on swing check valve selection criteria suitable for nuclear power plant applications. In this project, four swing check valves were analyzed to demonstrate the implementation and application of this information. In this example, swing check valves were selected according to 'ASME Boiler and Pressure Vessel Code, Section III' and 'ASME B16.34, Valves Flanged, Threaded, and Welding End'. This paper also discusses the utilization of Computational Fluid Dynamics Software (CFD) as a means to analyze valve design. The use of CFD is a relatively new approach for validation of valve design that is becoming invaluable due to the high cost of physical bench testing. The Instrument Society of America (ISA) Analysis Division and the American Society of Mechanical Engineers (ASME) Computational Fluid Dynamics Technical Committee have taken a proactive approach in setting standards and practices for the use of CFD in design and validation. (authors)
DYNAMIC SIMULATION OF THE TEMPORAL RESPONSE OF MICROSTRUCTURE FORMATION IN
DYNAMIC SIMULATION OF THE TEMPORAL RESPONSE OF MICROSTRUCTURE FORMATION IN MAGNETORHEOLOGICAL in that the dielectric response of an ER fluid is studied in response to an electrical stimulus. These studies of MR
Physics issues in simulations with dynamical overlap fermions
Thomas DeGrand; Stefan Schaefer
2004-12-01T23:59:59.000Z
We discuss the impact of various improvements on simulations of dynamical overlap fermions using the Hybrid Monte Carlo algorithm. We focus on the usage of fat links and multiple pseudo-fermion fields.
Molecular Dynamics Simulations of Heat Transfer In Nanoscale Liquid Films
Kim, Bo Hung
2010-07-14T23:59:59.000Z
Molecular Dynamics (MD) simulations of nano-scale flows typically utilize fixed lattice crystal interactions between the fluid and stationary wall molecules. This approach cannot properly model thermal interactions at the wall-fluid interface...
Brittle and ductile fracture of semiconductor nanowires --molecular dynamics simulations
Cai, Wei
Brittle and ductile fracture of semiconductor nanowires -- molecular dynamics simulations Keonwook November 9, 2006 Abstract Fracture of silicon and germanium nanowires in tension at room temperature potentials predict brittle fracture initiated by crack nucleation from the surface, most potentials predict
Simulation of the dynamic response of a damped taught string
Favennec, Hervé
2007-01-01T23:59:59.000Z
Marine pipeline are facing new issues involved by the increase of the depth of exploited oil and gas reservoirs. This thesis discusses the changes in the dynamic behavior of marine pipelines and proposes a simple simulation ...
Simulation Algorithms in Vehicle System Dynamics MARTIN ARNOLD
be considered as integration platform for simulation in vehicle system dynamics. In the present report we report the analysis of distributed physical phenomena like the elastic deformation of car components
Molecular Dynamics Simulation of Homogeneous Crystal Nucleation in Polyethylene
Yi, Peng
Using a realistic united-atom force field, molecular dynamics simulations were performed to study homogeneous nucleation of the crystal phase at about 30% supercooling from the melts of n-pentacontahectane (C150) and a ...
Large-Scale Hybrid Dynamic Simulation Employing Field Measurements
Huang, Zhenyu; Guttromson, Ross T.; Hauer, John F.
2004-06-30T23:59:59.000Z
Simulation and measurements are two primary ways for power engineers to gain understanding of system behaviors and thus accomplish tasks in system planning and operation. Many well-developed simulation tools are available in today's market. On the other hand, large amount of measured data can be obtained from traditional SCADA systems and currently fast growing phasor networks. However, simulation and measurement are still two separate worlds. There is a need to combine the advantages of simulation and measurements. In view of this, this paper proposes the concept of hybrid dynamic simulation which opens up traditional simulation by providing entries for measurements. A method is presented to implement hybrid simulation with PSLF/PSDS. Test studies show the validity of the proposed hybrid simulation method. Applications of such hybrid simulation include system event playback, model validation, and software validation.
Advanced CFD Models for High Efficiency Compression Ignition...
Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site
CFD Models for High Efficiency Compression Ignition Engines Advanced CFD Models for High Efficiency Compression Ignition Engines Advanced CFD models for high efficiency...
GTRF Calculations Using Hydra-TH (L3 Milestone THM.CFD.P5.05)
Bakosi, Jozsef [Los Alamos National Laboratory; Christon, Mark A. [Los Alamos National Laboratory; Francois, Marianne M. [Los Alamos National Laboratory; Lowrie, Robert B. [Los Alamos National Laboratory; Nourgaliev, Robert [Los Alamos National Laboratory
2012-09-05T23:59:59.000Z
This report describes the work carried out for completion of the Thermal Hydraulics Methods (THM) Level 3 Milestone THM.CFD.P5.05 for the Consortium for Advanced Simulation of Light Water Reactors (CASL). A series of body-fitted computational meshes have been generated by Numeca's Hexpress/Hybrid, a.k.a. 'Spider', meshing technology for the V5H 3 x 3 and 5 x 5 rod bundle geometries and subsequently used to compute the fluid dynamics of grid-to-rod fretting (GTRF). Spider is easy to use, fast, and automatically generates high-quality meshes for extremely complex geometries, required for the GTRF problem. Hydra-TH has been used to carry out large-eddy simulations on both 3 x 3 and 5 x 5 geometries, using different mesh resolutions. The results analyzed show good agreement with Star-CCM+ simulations and experimental data.
Modelling and Dynamic Simulation for Process Control
Skogestad, Sigurd
principles for model development are outlined, and these principles are applied to a simple ash tank (which. In this paper we consider dynamic process models obtained using fundamental principles (eg. based reactor, a simple trend analysis using temperature measurements may be suÆcient. Dynamic models
Reweighting QCD simulations with dynamical overlap fermions
Thomas DeGrand
2008-10-03T23:59:59.000Z
I apply a recently developed algorithm for reweighting simulations of lattice QCD from one quark mass to another to simulations performed with overlap fermions in the epsilon regime. I test it by computing the condensate from distributions of the low lying eigenvalues of the Dirac operator. Results seem favorable.
Fast Thermal Simulation for Architecture Level Dynamic Thermal Management
Tan, Sheldon X.-D.
Fast Thermal Simulation for Architecture Level Dynamic Thermal Management Pu Liu, Zhenyu Qi, Hang Li, Lingling Jin, Wei Wu, Sheldon X.-D. Tan, Jun Yang Department of Electrical Engineering temperature by dynamic thermal managements becomes necessary. This paper proposes a novel approach
A New Motorcycle Simulator Platform: Mechatronics Design, Dynamics Modeling
Paris-Sud XI, Université de
A New Motorcycle Simulator Platform: Mechatronics Design, Dynamics Modeling and Control L. Nehaoua and dynamics modeling will be presented. Some results are shown, validating the actutation requirements and platform control. 1. INTRODUCTION Road safety has become a major political and economical issue. While all
Learning Curve: A Simulation-based Approach to Dynamic Pricing
Greenwald, Amy
horizon. In this article, we refer to this type of changing of prices over time as dynamic pricing. Cost markets, the costs associated with making frequent, instantaneous price changes are greatly diminished [2Learning Curve: A Simulation-based Approach to Dynamic Pricing Joan Morris DiMicco, Amy Greenwald
Title of dissertation: MODELING, SIMULATING, AND CONTROLLING THE FLUID DYNAMICS
Shapiro, Benjamin
ABSTRACT Title of dissertation: MODELING, SIMULATING, AND CONTROLLING THE FLUID DYNAMICS OF ELECTRO an algorithm to steer indi- vidual particles inside the EWOD system by control of actuators already present number of actuators available in the EWOD system. #12;MODELING, SIMULATING, AND CONTROLLING THE FLUID
Dynamic Spherical Volumetric Simplex Splines with Applications in Biomedical Simulation
Hua, Jing
Dynamic Spherical Volumetric Simplex Splines with Applications in Biomedical Simulation Yunhao Tan computational framework based on dy- namic spherical volumetric simplex splines for simulation of genus- zero to reconstruct the high-fidelity digi- tal model of a real-world object with spherical volumetric simplex splines
NUMERICAL SIMULATION OF AIR POLLUTION DYNAMICS DUE TO
Olszewski Jr., Edward A.
NUMERICAL SIMULATION OF AIR POLLUTION DYNAMICS DUE TO POINT SOURCE EMISSIONS FROM AN INDUSTRIAL · Works Cited #12;Statement of the Problem · Numerical simulation of air pollution from a point source threat of air pollution Major health hazard to humans and ecosystem Billions effected, mainly
Dynamic wind turbine models in power system simulation tool
Dynamic wind turbine models in power system simulation tool DIgSILENT Anca D. Hansen, Florin Iov models in power system simulation tool DIgSILENT Department: Wind Energy Department Risø-R-1400(ed.2)(EN and at a system level. The report contains both the description of DIgSILENT built-in models for the electrical
Lawson, M. J.; Li, Y.; Sale, D. C.
2011-10-01T23:59:59.000Z
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.
Plasticity of metal wires in torsion: molecular dynamics and dislocation dynamics simulations
Cai, Wei
on plasticity of single crystal wires in torsion. In this paper, we examine the plasticity of single crystalPlasticity of metal wires in torsion: molecular dynamics and dislocation dynamics simulations-4040 Abstract The orientation dependent plasticity in metal nanowires is investigated using molecular dynamics
Plasticity of metal wires in torsion: Molecular dynamics and dislocation dynamics simulations
Cai, Wei
studies on plasticity of single crystal wires in torsion. In this paper, we examine the plasticityPlasticity of metal wires in torsion: Molecular dynamics and dislocation dynamics simulations t The orientation dependent plasticity in metal nanowires is investigated using molecular dynamics and dislocation
Simulation Methodologies for Satellite Solar Array Dynamics
Mohsenizadeh, Navid
2010-07-16T23:59:59.000Z
The purpose of the present thesis is to furnish diverse studies on the dynamic response of satellite solar arrays. The term flexible structure or, briefly, structure has different interpretations and definitions, depending on source...
Plasticity of metallic nanostructures : molecular dynamics simulations
Healy, Con
2014-11-27T23:59:59.000Z
During high speed cutting processes, metals are subject to high strains and strain rates. The dynamic nature of the deformation during high speed cutting makes it difficult to detect atomic scale deformation mechanisms ...
A visual simulation playground for engineering dynamics
Fong, Donald Brian
2008-10-10T23:59:59.000Z
. Interfaces . . . . . . . . . . . . . . . . . . . . . . . . . 11 a. IIntegratable . . . . . . . . . . . . . . . . . . . . 15 b. IForceable . . . . . . . . . . . . . . . . . . . . . . 15 3. The Simulation System . . . . . . . . . . . . . . . . . 16 B. The User... . . . . . . . . . . . . . . . . . . . . . . . . 25 1. Framework Flexibility . . . . . . . . . . . . . . . . . . 25 a. Spring-Mass System . . . . . . . . . . . . . . . . 26 b. Collision Detection and Response . . . . . . . . . 28 c. Friction . . . . . . . . . . . . . . . . . . . . . . . 30 2...
Reptational dynamics in dissipative particle dynamics simulations of polymer melts
P. Nikunen; I. Vattulainen; M. Karttunen
2005-12-12T23:59:59.000Z
Understanding the complex viscoelastic properties of polymeric liquids remains a challenge in materials science and soft matter physics. Here, we present a simple and computationally efficient criterion for the topological constraints in polymeric liquids using the Dissipative Particle Dynamics (DPD). The same approach is also applicable in other soft potential models. For short chains the model correctly reproduces Rouse-like dynamics whereas for longer chains the dynamics becomes reptational as the chain length is increased - something that is not attainable using standard DPD or other coarse-grained soft potential methods. Importantly, no new length scales or forces need to be added.
CFD Analysis of Nuclear Fuel Bundles and Spacer Grids for PWR Reactors
Capone, Luigi
2012-10-19T23:59:59.000Z
The analysis of the turbulent flows in nuclear fuel bundles is a very interesting task to optimize the efficiency of modern nuclear power plants. The proposed study utilizes Computational Fluid Dynamics (CFD) to characterize the flow pattern...
Villasmil Urdaneta, Larry Alfonso
2002-01-01T23:59:59.000Z
seals performance and leakage information indicating that friction factor increases as the seal clearance is increased, contradicting the theory predictions based on Moody's pipe-friction model. A Computational Fluid Dynamics (CFD) code is used...
Computational fluid dynamic applications
Chang, S.-L.; Lottes, S. A.; Zhou, C. Q.
2000-04-03T23:59:59.000Z
The rapid advancement of computational capability including speed and memory size has prompted the wide use of computational fluid dynamics (CFD) codes to simulate complex flow systems. CFD simulations are used to study the operating problems encountered in system, to evaluate the impacts of operation/design parameters on the performance of a system, and to investigate novel design concepts. CFD codes are generally developed based on the conservation laws of mass, momentum, and energy that govern the characteristics of a flow. The governing equations are simplified and discretized for a selected computational grid system. Numerical methods are selected to simplify and calculate approximate flow properties. For turbulent, reacting, and multiphase flow systems the complex processes relating to these aspects of the flow, i.e., turbulent diffusion, combustion kinetics, interfacial drag and heat and mass transfer, etc., are described in mathematical models, based on a combination of fundamental physics and empirical data, that are incorporated into the code. CFD simulation has been applied to a large variety of practical and industrial scale flow systems.
Standard Problems for CFD Validation for NGNP - Status Report
Richard W. Johnson; Richard R. Schultz
2010-08-01T23:59:59.000Z
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 optics used for data gathering. Particle image velocimetry (PIV) is used to take the data. The first standard problem represents several flow physics expected to be present in the lower plenum of the prismatic VHTR. In the lower plenum, heated helium coolant in the form of jets issues downward into the plenum and is then forced to turn ninety degrees and flow toward the exit duct. The lower plenum is filled with cylindrical graphite posts that hold up the core. Figure S-1 provides a plan view of the lower plenum. The red circles represent support posts holding up columns of heated blocks. Grey circles represent support posts under columns of reflector blocks. Helium enters the lower plenum at the junctions of the hexagonal blocks.
Use dynamic simulation to model HPU reactor depressuring
Ernest, J.B.; Depew, C.A. (Fluor Daniel, Inc., Irvine, CA (United States))
1995-01-01T23:59:59.000Z
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.
California at Irvine, University of
CVSys: A Coordination Framework for Dynamic and Fully Distributed Cardiovascular Modeling and dynamic simulation control. This coordination framework uniquely incorporates attributes of open indigenous and a more integrated system representation. Dynamic simulation control serves to interject new
SimSect Hybrid Dynamical Simulation Environment
Saranlý, Uluç
) runner and a compliant hexapod. The former example illustrates the basic elements of programming models. It was mainly built to simulate a hexapod robot with compliant legs. It can. however, be used to define with the SpringLoaded Inverted Pendulum(SLIP) and the Compliant Hexapod Model definitions. 1.3 Overview Sim
SimSect Hybrid Dynamical Simulation Environment
Saranlý, Uluç
) runner and a compliant hexapod. The former example illustrates the basic elements of programming models. It was mainly built to simulate a hexapod robot with compliant legs. It can. however, be used to define with the Spring-Loaded Inverted Pendulum(SLIP) and the Compliant Hexapod Model definitions. 1.3 Overview Sim
Programmable quantum simulation by dynamic Hamiltonian engineering
David L. Hayes; Steven T. Flammia; Michael J. Biercuk
2014-06-18T23:59:59.000Z
Quantum simulation is a promising near term application for mesoscale quantum information processors, with the potential to solve computationally intractable problems at the scale of just a few dozen interacting quantum systems. Recent experiments in a range of technical platforms have demonstrated the basic functionality of quantum simulation applied to quantum magnetism, quantum phase transitions, and relativistic quantum mechanics. In all cases, the underlying hardware platforms restrict the achievable inter-particle interaction, forming a serious constraint on the ability to realize a versatile, programmable quantum simulator. In this work, we address this problem by developing novel sequences of unitary operations that engineer desired effective Hamiltonians in the time-domain. The result is a hybrid programmable analog simulator permitting a broad class of interacting spin-lattice models to be generated starting only with an arbitrary long-range native inter-particle interaction and single-qubit addressing. Specifically, our approach permits the generation of all symmetrically coupled translation-invariant two-body Hamiltonians with homogeneous on-site terms, a class which includes all spin-1/2 XYZ chains, but generalized to include long-range couplings. Building on previous work proving that universal simulation is possible using both entangling gates and single-qubit unitaries, we show that determining the "program" of unitary pulses to implement an arbitrary spin Hamiltonian can be formulated as a linear program that runs in polynomial time and scales efficiently in hardware resources. Our analysis extends from circuit model quantum information to adiabatic quantum evolutions, where our approach allows for the creation of non-native ground state solutions to a computation.
Modeling and simulation of consumer response to dynamic pricing.
Valenzuela, J.; Thimmapuram, P.; Kim, J (Decision and Information Sciences); (Auburn Univ.)
2012-08-01T23:59:59.000Z
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.
Generating generalized distributions from dynamical simulation
Barth, Eric J.; Laird, Brian Bostian; Leimkuhler, Benedict J.
2003-03-18T23:59:59.000Z
virtual momentum related to the actual momentum of the system by p˜5sp.3 The equations of motion generated by the Nose´ Hamiltonian @Eq. ~1!# are dq dt 5M 21p˜/s2, ~2! dp˜ dt 52„V~q!, ~3! ds dt 5 p Q , ~4! dp dt 5 p˜TM21p˜ s3 2gkBT/s . ~5! The Nose´ method... regulates the temperature of the sys- tem through a dynamical time transformation given by dt/dt5s , where t is the Nose´ ~virtual! time and t is real time. The remarkable property of Nose´ dynamics is that mi- crocanonical sampling of the extended phase...
Dynamic simulation of high speed rotating machinery
Morgan, Eddie Lee
1977-01-01T23:59:59.000Z
with emphasis on rotor-bearing system stability are presented in this text. Theoretical discussions are presented to describe several of the forcing mechanisms which initiate instabilities 1n high speed rotating equipment. Also included are observations... of instabilities from in- dustrial experience which are not well understood. The design and construction of a dynamic model of the rotor- bearing system of a centrifugal compressor are reviewed. In addition, the results of stability tests performed on two d1...
Lessons Learned From Dynamic Simulations of Advanced Fuel Cycles
Steven J. Piet; Brent W. Dixon; Jacob J. Jacobson; Gretchen E. Matthern; David E. Shropshire
2009-04-01T23:59:59.000Z
Years of performing dynamic simulations of advanced nuclear fuel cycle options provide insights into how they could work and how one might transition from the current once-through fuel cycle. This paper summarizes those insights from the context of the 2005 objectives and goals of the Advanced Fuel Cycle Initiative (AFCI). Our intent is not to compare options, assess options versus those objectives and goals, nor recommend changes to those objectives and goals. Rather, we organize what we have learned from dynamic simulations in the context of the AFCI objectives for waste management, proliferation resistance, uranium utilization, and economics. Thus, we do not merely describe “lessons learned” from dynamic simulations but attempt to answer the “so what” question by using this context. The analyses have been performed using the Verifiable Fuel Cycle Simulation of Nuclear Fuel Cycle Dynamics (VISION). We observe that the 2005 objectives and goals do not address many of the inherently dynamic discriminators among advanced fuel cycle options and transitions thereof.
Mesoscale simulations of polymer dynamics in microchannel flows
L. Cannavacciuolo; R. G. Winkler; G. Gompper
2007-09-24T23:59:59.000Z
The non-equilibrium structural and dynamical properties of flexible polymers confined in a square microchannel and exposed to a Poiseuille flow are investigated by mesoscale simulations. The chain length and the flow strength are systematically varied. Two transport regimes are identified, corresponding to weak and strong confinement. For strong confinement, the transport properties are independent of polymer length. The analysis of the long-time tumbling dynamics of short polymers yields non-periodic motion with a sublinear dependence on the flow strength. We find distinct differences for conformational as well as dynamical properties from results obtained for simple shear flow.
Analytical Rescaling of Polymer Dynamics from Mesoscale Simulations
I. Y. Lyubimov; J. McCarty; A. Clark; M. G. Guenza
2011-03-10T23:59:59.000Z
We present a theoretical approach to scale the artificially fast dynamics of simulated coarse-grained polymer liquids down to its realistic value. As coarse-graining affects entropy and dissipation, two factors enter the rescaling: inclusion of intramolecular vibrational degrees of freedom, and rescaling of the friction coefficient. Because our approach is analytical, it is general and transferable. Translational and rotational diffusion of unentangled and entangled polyethylene melts, predicted from mesoscale simulations of coarse-grained polymer melts using our rescaling procedure, are in quantitative agreement with united atom simulations and with experiments.
Lisal, Martin
diffusion) as well as reaction equilibria for chemically reacting mixtures. DOI: 10.1103/PhysRevE.70.) on chemical reaction equilibria is critical in many fields of science including mixture separationReaction ensemble molecular dynamics: Direct simulation of the dynamic equilibrium properties
Fayer, Michael D.
dynamics MD simulations and quantum mechanical electronic structure calculations are used to investigate agreement. The electronic structure calculations show that the complex is T shaped. The classical potential of the electronic structure calculations. A variety of other features is extracted from the simulations including
High speed simulation of microprocessor systems using LTU dynamic binary translation
Jones, Daniel
2010-01-01T23:59:59.000Z
This thesis presents new simulation techniques designed to speed up the simulation of microprocessor systems. The advanced simulation techniques may be applied to the simulator class which employs dynamic binary translation ...
Recycling Krylov subspaces for CFD applications
Amritkar, Amit; ?wirydowicz, Katarzyna; Tafti, Danesh; Ahuja, Kapil
2015-01-01T23:59:59.000Z
The most popular iterative linear solvers in Computational Fluid Dynamics (CFD) calculations are restarted GMRES and BiCGStab. At the beginning of most incompressible flow calculations, the computation time and the number of iterations to converge for the pressure Poisson equation are quite high. In this case, the BiCGStab algorithm, with relatively cheap but non-optimal iterations, may fail to converge for stiff problems. Thus, a more robust algorithm like GMRES, which guarantees monotonic convergence, is preferred. To reduce the large storage requirements of GMRES, a restarted version - GMRES(m) or its variants - is used in CFD applications. However, GMRES(m) can suffer from stagnation or very slow convergence. For this reason, we use the rGCROT method. rGCROT is an algorithm that improves restarted GMRES by recycling a selected subspace of the search space from one restart of GMRES(m) to the next as well as building and recycling this outer vector space from one problem to the next (subsequent time steps i...
Ab initio molecular dynamics simulations of ion–solid interactio...
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
of ion–solid interactions in Gd2Zr2O7 and Gd2Ti2O7. Ab initio molecular dynamics simulations of ion–solid interactions in Gd2Zr2O7 and Gd2Ti2O7. Abstract: The...
DYNAMIC IMAGE SIMULATIONS FOR ADAPTIVE SENSOR PERFORMANCE PREDICTIONS
Kerekes, John
devices such as MEMS-based micromirrors can be modeled, but the desired overall sensor application oftenDYNAMIC IMAGE SIMULATIONS FOR ADAPTIVE SENSOR PERFORMANCE PREDICTIONS Michael D. Presnara,b , John is necessary for predicting real-life performance of adaptive sensor models. Physics-based modeling
SIMULATING MARKET TRANSFORMATION DYNAMICS USING A HYBRID ENERGY ECONOMY MODEL
ii SIMULATING MARKET TRANSFORMATION DYNAMICS USING A HYBRID ENERGY ECONOMY MODEL: A LOOK to society in the long run. My goal was to use a "hybrid" energy economy model (CIMS), which combines.............................................. 1 1.2 The Challenge of Energy-Economy Modelling
Thermodiffusion in model nanofluids by molecular dynamics simulations
Paris-Sud XI, Université de
1 Thermodiffusion in model nanofluids by molecular dynamics simulations G. Galliero1,2,* , S. Volz3-Jones fluids and for model nanofluids (spherical non-metallic nanoparticles + Lennard-Jones fluid) where concentration. Then, in nanofluids in the liquid state, by changing the nature of the nanoparticle (size, mass
Simulational nanoengineering: Molecular dynamics implementation of an atomistic Stirling engine
Rapaport, Dennis C.
Simulational nanoengineering: Molecular dynamics implementation of an atomistic Stirling engine D 2009; published 30 April 2009 A nanoscale-sized Stirling engine with an atomistic working fluid has s : 02.70.Ns, 05.70.Ln, 47.61. k The Stirling engine, an external combustion engine in- vented almost two
The stressstrain behavior of polymernanotube composites from molecular dynamics simulation
Brenner, Donald W.
-3538(03)00059-9 Composites Science and Technology 63 (2003) 16551661 www.elsevier.com/locate/compscitech * CorrespondingThe stressstrain behavior of polymernanotube composites from molecular dynamics simulation S, Hampton, VA 23681, USA c Department of Materials Science and Engineering, North Carolina State University
Hydrogen Raman shifts in carbon nanotubes from molecular dynamics simulation
Brenner, Donald W.
Hydrogen Raman shifts in carbon nanotubes from molecular dynamics simulation S.J.V. Frankland *, D hydrogen in individual single-shell carbon nanotubes and nanotube ropes using a semiclassical model. The calculations predict that isolated hydrogen molecules inside of nanotubes have a Raman frequency that increases
Simulation of electron cooling dynamic ( December 16, 2003)
approach in BetaCool code also leads to fast cooling of beam core Â benchmarking in progress different and momentum are being benchmarked cooling #12;Progress Â· We have better understanding of friction forceSimulation of electron cooling dynamic ( December 16, 2003) A. Fedotov, I. Ben-zvi, Yu. Eidelman, V
Dynamic Simulation of DFIG Wind Turbines on FPGA Boards
Zambreno, Joseph A.
Dynamic Simulation of DFIG Wind Turbines on FPGA Boards Hao Chen, Student Member, IEEE, Song Sun is a friction coefficient. The wind turbine model is based on the relation between the upstream wind speed V w and the mechanical power Pm extracted from the wind [10]. The pertinent equations are Pm == ~P1fR~Cp(A,(3)V~ (7) Cp
Simulation of the Dynamic Inefficiency of the CMS Pixel Detector
Márton Bartók
2015-01-22T23:59:59.000Z
The Pixel Detector is the innermost part of the CMS Tracker. It therefore has to prevail in the harshest environment in terms of particle fluence and radiation. There are several mechanisms that may decrease the efficiency of the detector. These are mainly caused by data acquisition (DAQ) problems and/or Single Event Upsets (SEU). Any remaining efficiency loss is referred to as the dynamic inefficiency. It is caused by various mechanisms inside the Readout Chip (ROC) and depends strongly on the data occupancy. In the 2012 data, at high values of instantaneous luminosity the inefficiency reached 2\\% (in the region closest to the interaction point) which is not negligible. In the 2015 run higher instantaneous luminosity is expected, which will result in lower efficiencies; therefore this effect needs to be understood and simulated. A data-driven method has been developed to simulate dynamic inefficiency, which has been shown to successfully simulate the effects.
Lisal, Martin
Mesoscale simulation of polymer reaction equilibrium: Combining dissipative particle dynamics. R. Smith, J. Chem. Phys. 125, 16490 2006 , a mesoscale simulation technique for studying polymer
Coupling all-atom molecular dynamics simulations of ions in water with Brownian dynamics
Radek Erban
2015-08-12T23:59:59.000Z
Molecular dynamics (MD) simulations of ions (K$^+$, Na$^+$, Ca$^{2+}$ and Cl$^-$) in aqueous solutions are investigated. Water is described using the SPC/E model. A stochastic coarse-grained description for ion behaviour is presented and parameterized using MD simulations. It is given as a system of coupled stochastic and ordinary differential equations, describing the ion position, velocity and acceleration. The stochastic coarse-grained model provides an intermediate description between all-atom MD simulations and Brownian dynamics (BD) models. It is used to develop a multiscale method which uses all-atom MD simulations in parts of the computational domain and (less detailed) BD simulations in the remainder of the domain.
Generic solar photovoltaic system dynamic simulation model specification.
Ellis, Abraham; Behnke, Michael Robert; Elliott, Ryan Thomas
2013-10-01T23:59:59.000Z
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.
Lisal, Martin
Mesoscale simulation of polymer reaction equilibrium: Combining dissipative particle dynamics a mesoscale simulation technique, called the reaction ensemble dissipative particle dynamics RxDPD method. Coarse-grained, particle- based mesoscale models that retain only the most essential features
CFD analyses of natural circulation in the air-cooled reactor cavity cooling system
Hu, R. [Nuclear Engineering Division, Argonne National Laboratory, Argonne IL (United States); Pointer, W. D. [Reactor and Nuclear Systems Division, Oak Ridge National Laboratory, Oak Ridge TN (United States)
2013-07-01T23:59:59.000Z
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)
Dislocation dynamics simulations of plasticity at small scales
Zhou, Caizhi
2010-12-15T23:59:59.000Z
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.
Creech, Angus; Maguire, A Eoghan
2014-01-01T23:59:59.000Z
We present here a computational fluid dynamics (CFD) simulation of Lillgrund offshore wind farm, which is located in the {\\O}resund Strait between Sweden and Denmark. The simulation combines a dynamic representation of wind turbines embedded within a Large-Eddy Simulation CFD solver, and uses hr-adaptive meshing to increase or decrease mesh resolution where required. This allows the resolution of both large scale flow structures around the wind farm, and local flow conditions at individual turbines; consequently, the response of each turbine to local conditions can be modelled, as well as the resulting evolution of the turbine wakes. This paper provides a detailed description of the turbine model which simulates interactions between the wind, turbine rotors, and turbine generators by calculating the forces on the rotor, the body forces on the air, and instantaneous power output. This model was used to investigate a selection of key wind speeds and directions, investigating cases where a row of turbines would ...
Abgrall, RÃ©mi
uncertainties exist in the models and/or the data. We only consider non intrusive methods so that existing CFD. To this aim, we pursue the study of a non intrusive, accurate method, which is also non sensitive for very non linear systems of PDEs, where the solutions are often discontinuous and/or chaotic
Long-term system dynamics simulation methods. Final report
Manke, J.W.; Pauly, W.R.; Hemmaplardh, K.
1985-02-01T23:59:59.000Z
The focus of long-term dynamic simulations is to analyze the effects of wide excursions of voltage, frequency and power flows for extended periods of time on the bulk power system. The emphasis on modeling the sequence of system events over an extended period of time that follows a major disturbance distinguishes long-term dynamics from transient and midterm stability analysis where the effects of inter-machine oscillations on synchronous machines is the primary focus. The assumption of a uniform system frequency during quiscent system conditions makes it possible to use a numerical stepsize of one or more seconds for long-term studies, as opposed to a fraction of a cycle for transient/midterm stability, and to simulate the voltage and frequency effects of such system events as automatic load shedding and unit tripping for long periods of time. Both the time frame and the type of system events of interest in long-term dynamic studies establish the modeling and simulation requirements for a long-term program and the need for system data to validate the models and program. The sequence of system events that occur during the long-term time frame may introduce step changes in the system, i.e., load shedding, which cause transients that must be modeled on the transient stability time scale. This is the basis for the requirements that a long-term program have an adequate interface with a transient stability program.
Reweighted ensemble dynamics simulations: theory, improvement, and application
Linchen Gong; Xin Zhou; Zhong-Can Ou-Yang
2015-02-22T23:59:59.000Z
Based on multiple parallel short molecular dynamics simulation trajectories, we designed the reweighted ensemble dynamics (RED) method to more efficiently sample complex (biopolymer) systems, and to explore their hierarchical metastable states. Here we further present an improvement to depress statistical errors of the RED and we discuss a few keys in practical application of the RED, provides schemes on selection of basis functions, determination of free parameter in the RED. We illustrate the application of the improvements in two toy models and in the solvated alanine dipeptide. The results show the RED enable to capture the topology of multiple-state transition networks, to detect the diffusion-like dynamical behavior in entropy-dominated system, and to identify solvent effects in the solvated peptides. The illustrations serve as general applications of the RED in more complex biopolymer systems.
Large-Scale Molecular Dynamics Simulations for Highly Parallel Infrastructures
Pazúriková, Jana
2014-01-01T23:59:59.000Z
Computational chemistry allows researchers to experiment in sillico: by running a computer simulations of a biological or chemical processes of interest. Molecular dynamics with molecular mechanics model of interactions simulates N-body problem of atoms$-$it computes movements of atoms according to Newtonian physics and empirical descriptions of atomic electrostatic interactions. These simulations require high performance computing resources, as evaluations within each step are computationally demanding and billions of steps are needed to reach interesting timescales. Current methods decompose the spatial domain of the problem and calculate on parallel/distributed infrastructures. Even the methods with the highest strong scaling hit the limit at half a million cores: they are not able to cut the time to result if provided with more processors. At the dawn of exascale computing with massively parallel computational resources, we want to increase the level of parallelism by incorporating parallel-in-time comput...
Molecular Dynamics Simulations of Temperature Equilibration in Dense Hydrogen
Glosli, J; Graziani, F; More, R; Murillo, M; Streitz, F; Surh, M; Benedict, L; Hau-Riege, S; Langdon, A; London, R
2008-02-14T23:59:59.000Z
The temperature equilibration rate in dense hydrogen (for both T{sub i} > T{sub e} and T{sub i} < T{sub e}) has been calculated with large-scale molecular dynamics simulations for temperatures between 10 and 300 eV and densities between 10{sup 20}/cc to 10{sup 24}/cc. Careful attention has been devoted to convergence of the simulations, including the role of semiclassical potentials. We find that for Coulomb logarithms L {approx}> 1, Brown-Preston-Singleton [Brown et al., Phys. Rep. 410, 237 (2005)] with the sub-leading corrections and the fit of Gericke-Murillo-Schlanges [Gericke et al., PRE 65, 036418 (2003)] to the T-matrix evaluation of the collision operator, agrees with the MD data to within the error bars of the simulation. For more strongly-coupled plasmas where L {approx}< 1, our numerical results are consistent with the fit of Gericke-Murillo-Schlanges.
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.
Recovering position-dependent diffusion from biased molecular dynamics simulations
Ljubeti?, Ajasja; Urban?i?, Iztok; Štrancar, Janez, E-mail: janez.strancar@ijs.si [Laboratory of Biophysics, Condensed Matter Physics Department, “Jožef Stefan” Institute, 1000 Ljubljana (Slovenia)] [Laboratory of Biophysics, Condensed Matter Physics Department, “Jožef Stefan” Institute, 1000 Ljubljana (Slovenia)
2014-02-28T23:59:59.000Z
All atom molecular dynamics (MD) models provide valuable insight into the dynamics of biophysical systems, but are limited in size or length by the high computational demands. The latter can be reduced by simulating long term diffusive dynamics (also known as Langevin dynamics or Brownian motion) of the most interesting and important user-defined parts of the studied system, termed collective variables (colvars). A few hundred nanosecond-long biased MD trajectory can therefore be extended to millisecond lengths in the colvars subspace at a very small additional computational cost. In this work, we develop a method for determining multidimensional anisotropic position- and timescale-dependent diffusion coefficients (D) by analysing the changes of colvars in an existing MD trajectory. As a test case, we obtained D for dihedral angles of the alanine dipeptide. An open source Mathematica{sup ®} package, capable of determining and visualizing D in one or two dimensions, is available at https://github.com/lbf-ijs/DiffusiveDynamics . Given known free energy and D, the package can also generate diffusive trajectories.
Bjørnstad, Ottar Nordal
Role of dynamics in tuning fidelity of RNA-dependent RNA polymerase elucidated by molecular dynamics simulation Ibrahim M. Moustafa Department of Biochemistry and Molecular Biology Eberly College fidelity is not clear but suggested to be linked to dynamics of the enzyme [1]. By using molecular dynamics
Gerhard Strydom; Su-Jong Yoon
2014-04-01T23:59:59.000Z
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 Simulation of Infiltration Heat Recovery
Buchanan, C.R.
2011-01-01T23:59:59.000Z
due to infiltration. Previous studies have measured lumpwas due to infiltration. In another study of residentialdue to infiltration. The results of a recent study (12) of
CFD Simulation of Infiltration Heat Recovery
Buchanan, C.R.
2011-01-01T23:59:59.000Z
Energy Efficiency and Renewable Energy, Office of BuildingEnergy Efficiency and Renewable Energy, Office of Building
Thermostat for non-equilibrium multiparticle collision dynamics simulations
Chien-Cheng Huang; Anoop Varghese; Gerhard Gompper; Roland G. Winkler
2015-01-23T23:59:59.000Z
Multiparticle collision dynamics (MPC), a particle-based mesoscale simulation technique for com- plex fluid, is widely employed in non-equilibrium simulations of soft matter systems. To maintain a defined thermodynamic state, thermalization of the fluid is often required for certain MPC variants. We investigate the influence of three thermostats on the non-equilibrium properties of a MPC fluid under shear or in Poiseuille flow. In all cases, the local velocities are scaled by a factor, which is either determined via a local simple scaling approach (LSS), a Monte Carlo-like procedure (MCS), or by the Maxwell-Boltzmann distribution of kinetic energy (MBS). We find that the various scal- ing schemes leave the flow profile unchanged and maintain the local temperature well. The fluid viscosities extracted from the various simulations are in close agreement. Moreover, the numerically determined viscosities are in remarkably good agreement with the respective theoretically predicted values. At equilibrium, the calculation of the dynamic structure factor reveals that the MBS method closely resembles an isothermal ensemble, whereas the MCS procedure exhibits signatures of an adi- abatic system at larger collision-time steps. Since the velocity distribution of the LSS approach is non-Gaussian, we recommend to apply the MBS thermostat, which has been shown to produce the correct velocity distribution even under non-equilibrium conditions.
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)
2011-12-12T23:59:59.000Z
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.
Simulation studies on the standing and traveling wave thermoacoustic prime movers
Skaria, Mathew; Rasheed, K. K. Abdul; Shafi, K. A. [Department of Mechanical Engineering, TKM College of Engineering, Kollam, Kerala (India); Kasthurirengan, S.; Behera, Upendra [Center for Cryogenic Technology, Indian Institute of Science, Bangalore, Karnataka (India)
2014-01-29T23:59:59.000Z
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.
Kinetic distance and kinetic maps from molecular dynamics simulation
Noe, Frank
2015-01-01T23:59:59.000Z
Characterizing macromolecular kinetics from molecular dynamics (MD) simulations requires a distance metric that can distinguish slowly-interconverting states. Here we build upon diffusion map theory and define a kinetic distance for irreducible Markov processes that quantifies how slowly molecular conformations interconvert. The kinetic distance can be computed given a model that approximates the eigenvalues and eigenvectors (reaction coordinates) of the MD Markov operator. Here we employ the time-lagged independent component analysis (TICA). The TICA components can be scaled to provide a kinetic map in which the Euclidean distance corresponds to the kinetic distance. As a result, the question of how many TICA dimensions should be kept in a dimensionality reduction approach becomes obsolete, and one parameter less needs to be specified in the kinetic model construction. We demonstrate the approach using TICA and Markov state model (MSM) analyses for illustrative models, protein conformation dynamics in bovine...
Molecular Dynamics Simulations of Solutions at Constant Chemical Potential
Perego, Claudio; Parrinello, Michele
2015-01-01T23:59:59.000Z
Molecular Dynamics studies of chemical processes in solution are of great value in a wide spectrum of applications, that range from nano-technology to pharmaceutical chemistry. However, these calculations are affected by severe finite-size effects, such as the solution being depleted as the chemical process proceeds, that influence the outcome of the simulations. To overcome these limitations, one must allow the system to exchange molecules with a macroscopic reservoir, thus sampling a Grand-Canonical ensemble. Despite the fact that different remedies have been proposed, this still represents a key challenge in molecular simulations. In the present work we propose the C$\\mu$MD method, which introduces an external force that controls the environment of the chemical process of interest. This external force, drawing molecules from a finite reservoir, maintains the chemical potential constant in the region where the process takes place. We have applied the C$\\mu$MD method to the paradigmatic case of urea crystall...
Dynamic Simulations of Elastic Rods for Medical Applications
Nuti, Sravani
2014-12-05T23:59:59.000Z
stream_source_info NUTI-THESIS-2014.pdf.txt stream_content_type text/plain stream_size 49220 Content-Encoding UTF-8 stream_name NUTI-THESIS-2014.pdf.txt Content-Type text/plain; charset=UTF-8 DYNAMIC SIMULATIONS... of Committee, J. N. Reddy Co-Chair of Committee, Annie Ruimi Committee Member, Arun Srinivasa Head of Department, A. A. Polycarpou December 2014 Major Subject: Mechanical Engineering Copyright 2014 Sravani Nuti ii ABSTRACT This study...
Investigations of Solar Prominence Dynamics Using Laboratory Simulations
Paul M Bellan
2008-05-28T23:59:59.000Z
Laboratory experiments simulating many of the dynamical features of solar coronal loops have been carried out. These experiments manifest collimation, kinking, jet flows, and S-shapes. Diagnostics include high-speed photography and x-ray detectors. Two loops having opposite or the same magnetic helicity polarities have been merged and it is found that counter-helicity merging provides much greater x-ray emission. A non-MHD particle orbit instability has been discovered whereby ions going in the opposite direction of the current flow direction can be ejected from a magnetic flux tube.
Description of waste pretreatment and interfacing systems dynamic simulation model
Garbrick, D.J.; Zimmerman, B.D.
1995-05-01T23:59:59.000Z
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.
Molecular Dynamics Simulations of Shock-Induced Thermite Reaction Vikas Tomar1,a
Tomar, Vikas
Molecular Dynamics Simulations of Shock-Induced Thermite Reaction Vikas Tomar1,a and Min Zhou1,b 1 Dynamics, Thermite Mixture Abstract. A computational framework for molecular dynamics (MD) simulations of shock-induced reactions in thermite mixtures is developed. The system under study is an Fe2O3+Al
Choi, Min-Hyung
Simulation Systems Hongjun Jeon1 Min-Hyung Choi2 Min Hong3 1 Dept. of Electrical and Computer Engineering and trajectories of dynamically simulated entities. Therefore, effective and efficient enforcement and proper describes the formulation and integration of geometric constraints in a dynamic simulation and provides
Vijaykumar, Anand
2011-02-22T23:59:59.000Z
The flow field in an annular seal is simulated for synchronous circular whirl orbits with 60Hz whirl frequency and a clearance/radius ratio of 0.0154 using the Fluent Computational Fluid Dynamics (CFD) code. Fluent's Moving Reference Frame model...
MOLECULAR DYNAMICS SIMULATIONS OF DISPLACEMENT CASCADES IN MOLYBDENUM
Smith, Richard Whiting
2003-09-08T23:59:59.000Z
Molecular dynamics calculations have been employed to simulate displacement cascades in neutron irradiated Mo. A total of 90 simulations were conducted for PKA energies between 1 and 40 keV and temperatures from 298 to 923K. The results suggest very little effect of temperature on final defect count and configuration, but do display a temperature effect on peak defect generation prior to cascade collapse. Cascade efficiency, relative to the NRT model, is computed to lie between 1/4 and 1/3 in agreement with simulations performed on previous systems. There is a tendency for both interstitials and vacancies to cluster together following cascade collapse producing vacancy rich regions surrounded by interstitials. Although coming to rest in close proximity, the point defects comprising the clusters generally do not lie within the nearest neighbor positions of one another, except for the formation of dumbbell di-interstitials. Cascades produced at higher PKA energies (20 or 40 keV) exhibit the formation of subcascades.
Pasta Nucleosynthesis: Molecular dynamics simulations of nuclear statistical equilibrium
M. E. Caplan; A. S. Schneider; C. J. Horowitz; D. K. Berry
2014-12-29T23:59:59.000Z
Background: Exotic non-spherical nuclear pasta shapes are expected in nuclear matter at just below saturation density because of competition between short range nuclear attraction and long range Coulomb repulsion. Purpose: We explore the impact of nuclear pasta on nucleosynthesis, during neutron star mergers, as cold dense nuclear matter is ejected and decompressed. Methods: We perform classical molecular dynamics simulations with 51200 and 409600 nucleons, that are run on GPUs. We expand our simulation region to decompress systems from an initial density of 0.080 fm^{-3} down to 0.00125 fm^{-3}. We study proton fractions of Y_P=0.05, 0.10, 0.20, 0.30, and 0.40 at T =0.5, 0.75, and 1.0 MeV. We calculate the composition of the resulting systems using a cluster algorithm. Results: We find final compositions that are in good agreement with nuclear statistical equilibrium models for temperatures of 0.75 and 1 MeV. However, for proton fractions greater than Y_P=0.2 at a temperature of T = 0.5 MeV, the MD simulations produce non-equilibrium results with large rod-like nuclei. Conclusions: Our MD model is valid at higher densities than simple nuclear statistical equilibrium models and may help determine the initial temperatures and proton fractions of matter ejected in mergers.
Towards Microsecond Biological Molecular Dynamics Simulations on Hybrid Processors
Hampton, Scott S [ORNL; Agarwal, Pratul K [ORNL
2010-01-01T23:59:59.000Z
Biomolecular simulations continue to become an increasingly important component of molecular biochemistry and biophysics investigations. Performance improvements in the simulations based on molecular dynamics (MD) codes are widely desired. This is particularly driven by the rapid growth of biological data due to improvements in experimental techniques. Unfortunately, the factors, which allowed past performance improvements of MD simulations, particularly the increase in microprocessor clock frequencies, are no longer improving. Hence, novel software and hardware solutions are being explored for accelerating the performance of popular MD codes. In this paper, we describe our efforts to port and optimize LAMMPS, a popular MD framework, on hybrid processors: graphical processing units (GPUs) accelerated multi-core processors. Our implementation is based on porting the computationally expensive, non-bonded interaction terms on the GPUs, and overlapping the computation on the CPU and GPUs. This functionality is built on top of message passing interface (MPI) that allows multi-level parallelism to be extracted even at the workstation level with the multi-core CPUs as well as extend the implementation on GPU clusters. The results from a number of typically sized biomolecular systems are provided and analysis is performed on 3 generations of GPUs from NVIDIA. Our implementation allows up to 30-40 ns/day throughput on a single workstation as well as significant speedup over Cray XT5, a high-end supercomputing platform. Moreover, detailed analysis of the implementation indicates that further code optimization and improvements in GPUs will allow {approx}100 ns/day throughput on workstations and inexpensive GPU clusters, putting the widely-desired microsecond simulation time-scale within reach to a large user community.
Hirunsit, Pussana
2009-05-15T23:59:59.000Z
Classical molecular dynamics (MD) simulations are performed to study structural and dynamic properties of water confined within graphite surfaces. The surfaces are separated at distances varying between 7 and 14.5 Å and the water density is held...
The Momentum Cloud Method for Dynamic Simulation of Rigid Body Systems
Sweetman, Bert
The Momentum Cloud Method for Dynamic Simulation of Rigid Body Systems Bert Sweetman1 , Lei Wang2 Abstract A new formulation of multibody dynamics, the momentum cloud method (MCM), is presented. The method
How trehalose protects DNA in the dry state: a molecular dynamics simulation
Fu, Xuebing
2008-10-10T23:59:59.000Z
Molecular dynamics simulations were conducted on a system consisting of a decamer DNA solvated by trehalose and water (molecular ratio= 1:2), to mimic a relatively dry state for the DNA molecule. Simulations were performed ...
Strategies for coupling energy simulation and computational fluid dynamics programs
Zhai, Zhiqiang; Chen, Qingyan; Klems, Joseph H.; Haves, Philip
2001-01-01T23:59:59.000Z
2000. “EnergyPlus: Energy Simulation Program” . ASHRAEA Coupled Airflow-and-Energy Simulation Program for IndoorSTRATEGIES FOR COUPLING ENERGY SIMULATION AND COMPUTATIONAL
Fatkullin, Ibrahim
Sediment Dynamics Simulation via Cellular Automata Artificial Intelligence - SYNOPSIS 1.0 Dr. Juan guidance. Scope of Project This project is compromised of study into two primary interests: sediment dynamics and artificial intelligence. Sediment Dynamics Sediment dynamics is the physics of sedimentary
Sader, Charles Avery
2015-01-01T23:59:59.000Z
Electronic Structure Theory Calculations and Molecular DynamicsElectronic Structure Theory Calculations and Molecular Dynamicsdynamics simulation requires identification of an electronic structure calculation
Como, Giacomo
Automating efficiency-targeted approximations in modelling and simulation tools: dynamic decoupling (classical) efficiency-targeted approximation tech- niques, within a unified framework. Some application
Beam dynamics simulations of the NML photoinjector at Fermilab
Piot, P.; /Fermilab /Northern Illinois U.; Sun, Y.-E.; Church, M.; /Fermilab
2010-08-01T23:59:59.000Z
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.
Molecular dynamics simulations of methane hydrate using polarizable force fields
Jiang, H.N.; Jordan, K.D.; Taylor, C.E.
2007-03-01T23:59:59.000Z
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.
CFD Modeling for Mercury Control Technology
Madsen, J.I.
2006-12-01T23:59:59.000Z
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 could limit the overall capture of mercury. For example, capture may be severely limited in situations where the dispersion of sorbent is poor, or where adsorption rates are low because of relatively high temperatures. Application examples taken from the DOE/NETL field test program were considered. The sites considered include Brayton Point, Meramec, Monroe, and Yates. Some general lessons learned concerning the impact of turbulence and flow stratification on dispersion and capture will be presented.
Use of a fictitious Marangoni number for natural convection simulation
Arias, Francisco J.; Parks, Geoffrey T.
2015-05-14T23:59:59.000Z
, boilers, nuclear reactor systems, energy storage devices, etc. In the design of such systems numerical simulation using computational fluid dynamics (CFD) and experimental testing of prototypes are exten- sively used. However, these methods are not well... theory and to recent research outputs [5–14] and the book by Lappa [15] to obtain an overview of thermal convec- tion and the state of the art. II. THEORETICAL BACKGROUND A. The fictitious Marangoni approach (FMA) Let us start by considering the Navier...
RECENT PROGRESS IN DYNAMIC PROCESS SIMULATION OF CRYOGENIC REFRIGERATORS
Kuendig, A. [Linde Kryotechnik AG, Dattlikonerstrasse 5, CH-8422 Pfungen (Switzerland)
2008-03-16T23:59:59.000Z
At the CEC 2005 a paper with the title 'Helium refrigerator design for pulsed heat load in Tokamaks' was presented. That paper highlighted the control requirements for cryogenic refrigerators to cope with the expected load variations of future nuclear fusion reactors. First dynamic computer simulations have been presented.In the mean time, the computer program is enhanced and a new series of process simulations are available. The new program considers not only the heat flows and the temperature variations within the heat exchangers, but also the variation of mass flows and pressure drops. The heat transfer numbers now are calculated in dependence of the flow speed and the gas properties. PI-controllers calculate the necessary position of specific valves for maintaining pressures, temperatures and the rotation speed of turbines.Still unsatisfactory is the fact, that changes in the process arrangement usually are attended by adjustments in the program code. It is the main objective of the next step of development a more flexible code which enables that any user defined process arrangements can be assembled by input data.
Photoionization analysis of chemo-dynamical dwarf galaxies simulations
Melekh, B; Hensler, G; Buhajenko, O
2015-01-01T23:59:59.000Z
Photoionization modelling allows to follow the transport, the emergence, and the absorption of photons taking into account all important processes in nebular plasmas. Such modelling needs the spatial distribution of density, chemical abundances and temperature, that can be provided by chemo-dynamical simulations (ChDS) of dwarf galaxies. We perform multicomponent photoionization modelling (MPhM) of the ionized gas using 2-D ChDSs of dwarf galaxies. We calculate emissivity maps for important nebular emission lines. Their intensities are used to derive the chemical abundance of oxygen by the so-called Te- and R23-methods. Some disagreements are found between oxygen abundances calculated with these methods and the ones coming from the ChDSs. We investigate the fraction of ionizing radiation emitted in the star-forming region which is able to leak out the galaxy. The time- and direction-averaged escape fraction in our simulation is 0.35-0.4. Finally, we have calculated the total Halpha lumi- nosity of our model g...
Enhanced molecular dynamics for simulating porous interphase layers in batteries.
Zimmerman, Jonathan A.; Wong, Bryan Matthew; Jones, Reese E.; Templeton, Jeremy Alan; Lee, Jonathan (Rice University, Houston, TX)
2009-10-01T23:59:59.000Z
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.
Skogestad, Sigurd
be carried out. The type and complexity of the model of each heat exchanger significantly affect the efforts required for HEN simulation, and focus is on the development of a general heat exchanger model countercurrent heat exchangers are briefly described, and the chapter closes by explaining how dynamic simulation
http://rcc.its.psu.edu/hpc Advanced CFD Models for Next-Generation Combustion Systems
Bjørnstad, Ottar Nordal
http://rcc.its.psu.edu/hpc Advanced CFD Models for Next-Generation Combustion Systems S: Requirements for next-generation combustion systems include: Increased performance, Reduced fuel consumption, and for direct-injection diesel engines Models carried intact from simulations of laboratory flames give good
Southern California, University of
films that form on aluminum and aluminum alloys in air protect the surface against further oxidationMolecular dynamics simulations of the nano-scale room-temperature oxidation of aluminum single Abstract The oxidation of aluminum single crystals is studied using molecular dynamics (MD) simulations
Molecular Dynamics Simulation of Nafion Oligomer Solvation in Equimolar Methanol-Water Mixture
Muzzio, Fernando J.
synthesis of chlorine and alkali,9 and particularly, in polymer electrolyte fuel cells, which are seenMolecular Dynamics Simulation of Nafion Oligomer Solvation in Equimolar Methanol-Water Mixture in equimolar water-methanol solution was studied by means of molecular dynamics simulations. The skeleton
EFFICIENT PARTICLE-PAIR FILTERING FOR ACCELERATION OF MOLECULAR DYNAMICS SIMULATION
Herbordt, Martin
EFFICIENT PARTICLE-PAIR FILTERING FOR ACCELERATION OF MOLECULAR DYNAMICS SIMULATION Matt Chiu ABSTRACT The acceleration of molecular dynamics (MD) simulations using high performance reconfigurable: determining the short-range force between particle pairs. In particular, we present the first FPGA study
Kjelstrup, Signe
Molecular dynamics simulations of a chemical reaction; conditions for local equilibrium have examined a simple chemical reaction in a temperature gradient; 2F $ F2. A mechanical model molecular dynamics simulations showed that the chemical reaction is in local thermodynamic as well
A Simple Interface to Computational Fluid Dynamics Programs for Building Environment Simulations
Chen, Qingyan "Yan"
A Simple Interface to Computational Fluid Dynamics Programs for Building Environment Simulations for architects and HVAC engineers to simulate airflows in and around buildings by Computational Fluid Dynamics Charles R. Broderick III Qingyan Chen Building Technology Program Massachusetts Institute of Technology
Fleming, Andrew J.
and imperfections during the manufactur- ing process of the tube on the dynamics-coupling-caused errors in openSimulation of dynamics-coupling in piezoelectric tube scanners by reduced order finite element as the compensation of dynamics-coupling effects. The present article gives a detailed description of the fully
Simulating Buoyancy-Driven Airflow in Buildings by1 Coarse-Grid Fast Fluid Dynamics2
Chen, Qingyan "Yan"
1 Simulating Buoyancy-Driven Airflow in Buildings by1 Coarse-Grid Fast Fluid Dynamics2 Mingang Jin1. Introduction33 Whole-building airflow simulations are required in applications such as natural ventilation34 design, coupled building airflow and energy simulation, smoke control, and air quality diagnosis35
Instabilities in Molecular Dynamics Integrators used in Hybrid Monte Carlo Simulations
B. Joo; UKQCD Collaboration
2001-10-11T23:59:59.000Z
We discuss an instability in the leapfrog integration algorithm, widely used in current Hybrid Monte Carlo (HMC) simulations of lattice QCD. We demonstrate the instability in the simple harmonic oscillator (SHO) system where it is manifest. We demonstrate the instability in HMC simulations of lattic QCD with dynamical Wilson-Clover fermions and discuss implications for future simulations of lattice QCD.
Novel morphologies for laterally decorated metaparticles: Molecular dynamics simulation
A. Y. Slyusarchuk; J. M. Ilnytskyi
2015-01-12T23:59:59.000Z
We consider a mesoscale model for nano-sized metaparticles (MPs) composed of a central sphere decorated by polymer chains with laterally attached spherocylinder. The latter mimics the mesogenic (e.g., cyanobiphenyl) group. Molecular dynamics simulations of $100$ MPs reveal the existence of two novel morphologies: $\\textrm{uCol}_\\mathrm{h}$ (hexagonal columnar arrangement of MPs with strong uniaxial order of mesogens collinear to the columns axis) and $\\mathrm{wCol}_\\mathrm{h}$ [the same arrangement of MPs but with weak or no liquid crystalline (LC) order]. Collinearity of the LC director and the columnar axis in $\\textrm{uCol}_\\mathrm{h}$ morphology indicates its potentially different opto-mechanical response to an external perturbation as compared to the columnar phase for the terminally attached mesogens. Preliminary analysis of the structures of both phases is performed by studying the order parameters and by visualisation of the MPs arrangements. Different mechanisms for the mesogens reorientation are pointed out for the cases of their terminal and lateral attachment.
Development of CFD models to support LEU Conversion of ORNL s High Flux Isotope Reactor
Khane, Vaibhav B [ORNL] [ORNL; Jain, Prashant K [ORNL] [ORNL; Freels, James D [ORNL] [ORNL
2012-01-01T23:59:59.000Z
The US Department of Energy s National Nuclear Security Administration (NNSA) is participating in the Global Threat Reduction Initiative to reduce and protect vulnerable nuclear and radiological materials located at civilian sites worldwide. As an integral part of one of NNSA s subprograms, Reduced Enrichment for Research and Test Reactors, HFIR is being converted from the present HEU core to a low enriched uranium (LEU) core with less than 20% of U-235 by weight. Because of HFIR s importance for condensed matter research in the United States, its conversion to a high-density, U-Mo-based, LEU fuel should not significantly impact its existing performance. Furthermore, cost and availability considerations suggest making only minimal changes to the overall HFIR facility. Therefore, the goal of this conversion program is only to substitute LEU for the fuel type in the existing fuel plate design, retaining the same number of fuel plates, with the same physical dimensions, as in the current HFIR HEU core. Because LEU-specific testing and experiments will be limited, COMSOL Multiphysics was chosen to provide the needed simulation capability to validate against the HEU design data and previous calculations, and predict the performance of the proposed LEU fuel for design and safety analyses. To achieve it, advanced COMSOL-based multiphysics simulations, including computational fluid dynamics (CFD), are being developed to capture the turbulent flows and associated heat transfer in fine detail and to improve predictive accuracy [2].
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 [Southeast University, Nanjing (China). Key Laboratory of Clean Coal Power Generation and Combustion Technology of Ministry of Education
2008-05-15T23:59:59.000Z
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.
S. O. Diallo; L. Vlcek; E. Mamontov; J. K. Keum; Jihua Chen; J. S. Hayes Jr.; A. A. Chialvo
2014-12-15T23:59:59.000Z
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 ($\\sim$ 150 K), leading to a metastable liquid state with remarkable physical properties. We have investigated the ambient pressure diffusive dynamics of water in microporous Kynol\\texttrademark ACF-10 (average pore size $\\sim$11.6 {\\AA}, 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 $$ when compared to previous findings indicate that it is the size of the confining pores - not their shape - that primarily affects the dynamics of water for pore sizes larger than 10 {\\AA}. 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 {\\AA} 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\\le 0.9$ \\AA${^{-1}}$). At high $Q$ however, where localized dynamics becomes relevant, this ideal system does not satisfactorily reproduce the measurements. 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 bi-modal exponential model, is used to parameterize the self-correlation function $I(Q,t)$.
Strategic Plan for Nuclear Energy -- Knowledge Base for Advanced Modeling and Simulation (NE-KAMS)
Kimberlyn C. Mousseau
2011-10-01T23:59:59.000Z
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-defined, well-characterized data. Element 3. Standards will be established for the design and operation of experiments for the generation of new validation data sets that are to be submitted to NE-CAMS that addresses the completeness and characterization of the dataset. Element 4. Standards will be developed for performing verification and validation (V&V) to establish confidence levels in CFD analyses of nuclear reactor processes; such processes will be acceptable and recognized by both CFD experts and the NRC.
Standing crop dynamics under simulated short-duration grazing at four stocking rates
Casco, Jose Francisco
1984-01-01T23:59:59.000Z
) David D. Briske (Member) Ethan C. olt (Member) Joseph L. Sch er (Head of Department) August 1984 111 ABSTRACT Standing Crop Dynamics under Simulated Short-Duration Graxing at Pour Stocking Rates. (August 1984) Jose Prancisco Casco, Ingeniero...
Kim, Jun Mo
Plastic deformation of the stack of alternating crystal and amorphous layers typical of semicrystalline polyethylene is studied by molecular dynamics simulation. A previous investigation of the semicrystalline layered stack ...
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
2011-09-01T23:59:59.000Z
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 experiments. The development of the Multiphase Shock Tube and associated diagnostic capabilities offers experimental capability to a previously inaccessible regime, which can provide unprecedented data concerning particle dynamics of dense gas-solid flows.
Dynamical Simulation of Fluidized Beds --- Hydrodynamically Interacting Granular Particles
Kengo Ichiki; Hisao Hayakawa
1995-03-01T23:59:59.000Z
A numerical simulation of a gas-fluidized bed is performed without introduction of any empirical parameters. Realistic bubbles and slugs are observed in our simulation. It is found that the convective motion of particles is important for the bubbling phase and there is no convection in the slugging phase. From the simulation results, non-Gaussian distributions are found in the particle velocities and the relation between the deviation from Gaussian and the local density of particles is suggested. It is also shown that the power spectra of particle velocities obey power laws. A brief explanation on the relationship between the simulation results and the Kolmogorov scaling argument is discussed.
CFD-based Optimization for Automotive Aerodynamics
Dumas, Laurent
Chapter 1 CFD-based Optimization for Automotive Aerodynamics Laurent Dumas Abstract The car drag- ments. An overview of the main characteristics of automotive aerodynamics and a detailed presentation.dumas@upmc.fr) 1 #12;2 Laurent Dumas 1.1 Introducing Automotive Aerodynamics 1.1.1 A Major Concern for Car
Simulation of particle agglomeration using dissipative particle dynamics
Mokkapati, Srinivas Praveen
2009-05-15T23:59:59.000Z
. . . . . . . . . . . . . . . . . . . . . 10 1. Molecular Dynamics . . . . . . . . . . . . . . . . . . . 11 2. Discrete Element Method . . . . . . . . . . . . . . . . 12 3. Dissipative Particle Dynamics . . . . . . . . . . . . . . 12 4. Lattice Boltzmann Method.... Stochastic approaches are based on the probability distribution function of the particles positions and velocities. They include, but not limited to, Lattice Boltzmann method, Monte Carlo methods and Lattice Gas Automata . 4. Lattice Boltzmann Method We also...
To appear in Journal of Computational Physics Parallel Discrete Molecular Dynamics Simulation
Herbordt, Martin
To appear in Journal of Computational Physics Parallel Discrete Molecular Dynamics Simulation and Automated Design Laboratory Department of Electrical and Computer Engineering Boston University; Boston, MA 02215 www.bu.edu/caadlab; email: azkhan@bu.edu, herbordt@bu.edu Abstract: Discrete molecular dynamics
Brenner, Donald W.
binding electronic structure calculations, pertur- bation models, and quantum-classical Hamiltonians [6 depends on the degree of approximation used in solving the electronic structure problem, which can add-scale molecular dynamics (MD) simulation is not to model electron dynamics, but rather to numerically solve
Molecular Dynamics Simulation of Damage Cascade Formation in Ion Bombarded Solids
Chen, Di
2012-10-19T23:59:59.000Z
………………….….…………………..…….……..…….…………xi CHAPTER I INTRODUCTION………………………………….………………….…...1 CHAPTER II MOLECULAR DYNAMICS…………………….……………………….6 2.1 Molecular Dynamics Background…….…...…………….......…………………....6 2.2 The Simulation Proceeds... important to develop understanding the precursor formation in defect clustering in such a case. v DEDICATION To my family vi ACKNOWLEDGEMENTS I would like to thank Dr. Lin Shao without whom this thesis would not have been finished. His...
Molecular dynamics simulations of atomic-level brittle fracture mechanisms in amorphous silica
Deymier, Pierre
Molecular dynamics simulations of atomic-level brittle fracture mechanisms in amorphous silica Abstract We have examined the atomic dynamics of the brittle fracture process in amorphous silica using the change in local coordina- tion of atoms. Introduction The brittle fracture process has been a subject
Coarse-grained Molecular Dynamics Simulation Approach for Polymer Nano-Composites Rubber
Katsumoto, Shingo
-composite materials are widely used in our daily life. Improvements by nano science and technology are required in orCoarse-grained Molecular Dynamics Simulation Approach for Polymer Nano-Composites Rubber Katsumi dynamics of entangled long- polymer melts and filled polymer rubber by us- ing coarse-grained model. We
Simulation of an atomistic dynamic field theory for monatomic liquids: Freezing and glass formation
Grant, Martin
Simulation of an atomistic dynamic field theory for monatomic liquids: Freezing and glass formation regime. The thermodynamics and dynamics of freezing and glass formation in this model system are studied.70.P , 64.70.D , 61.43. j, 81.05.Kf When a simple liquid is supercooled below its freezing temperature
Local and chain dynamics in miscible polymer blends: A Monte Carlo simulation study
Luettmer-Strathmann, Jutta
. In general, the friction coefficients that describe the segmental dynamics of the two components in a blend in the interaction energies between nonbonded nearest neighbors distinguish the two components of a blend19 and simulation works1925 it is found that the local dynamics of the two blend components differ from each other
Simulating Perforation of Thin Plates Using Molecular Dynamics Approach Anton M. Krivtsov
Krivtsov, Anton M.
1 Simulating Perforation of Thin Plates Using Molecular Dynamics Approach Anton M. Krivtsov or molecules, but as elements of the mesoscale level, such as material grains [4,5]. Fig.1: Oblique perforation of plate by ogive-nose projectile. This approach is used in the current work to simulate perforation
Large-Scale First-Principles Molecular Dynamics simulations on the BlueGene/L Platform
Franchetti, Franz
. Keywords Electronic structure. Molecular Dynamics. Ab initio simulations. First-principles simulations of the electronic properties of the system. The electronic structure calculation is the most time-consuming part the past three decades to the development of efficient implementations of the electronic structure
Climate Dynamics Diagnosis of the Marine Low Cloud Simulation in the NCAR Community Earth System
Bretherton, Chris
-of-the-art coupled atmosphere-ocean models: the NCAR Community Earth System Model (CESM) and the NCEP Global of the Marine Low Cloud Simulation in the NCAR1 Community Earth System Model (CESM) and the NCEP Global2Climate Dynamics Diagnosis of the Marine Low Cloud Simulation in the NCAR Community Earth System
Simons, Jack
Understanding graphene production by ionic surfactant exfoliation: A molecular dynamics simulation simulated sodium dodecyl sulfate (SDS) surfactant/water þ bilayer graphene mixture system to investigate two mechanisms of graphene exfoliation: changing the interlayer distance and sliding away the relative distance
Nonadiabatic molecular dynamics simulation: An approach based on quantum measurement picture
Feng, Wei; Xu, Luting [Department of Physics, Beijing Normal University, Beijing 100875 (China); Li, Xin-Qi, E-mail: lixinqi@bnu.edu.cn [Department of Physics, Beijing Normal University, Beijing 100875 (China); Key Laboratory of Theoretical and Computational Photochemistry of Ministry of Education, Beijing Normal University, Beijing 100875 (China); Fang, Weihai [Key Laboratory of Theoretical and Computational Photochemistry of Ministry of Education, Beijing Normal University, Beijing 100875 (China); Department of Chemistry, Beijing Normal University, Beijing 100875 (China); Yan, YiJing [Department of Chemistry, Hong Kong University of Science and Technology, Kowloon (Hong Kong)
2014-07-15T23:59:59.000Z
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.
Fluidic Catalytic Cracking Power Recovery Dynamic Computer Simulation
Samurin, N. A.
1980-01-01T23:59:59.000Z
operation of the primary mechanical components, specifically the axial compressor and hot gas expander. The present work expands upon the steady state model to add the dynamic characteristics of these elements as well as the effects of the controlling...
Fluidic Catalytic Cracking Power Recovery Dynamic Computer Simulation
Samurin, N. A.
1980-01-01T23:59:59.000Z
operation of the primary mechanical components, specifically the axial compressor and hot gas expander. The present work expands upon the steady state model to add the dynamic characteristics of these elements as well as the effects of the controlling...
An Analysis Tool for Flight Dynamics Monte Carlo Simulations
Restrepo, Carolina 1982-
2011-05-20T23:59:59.000Z
and analysis work to understand vehicle operating limits and identify circumstances that lead to mission failure. A Monte Carlo simulation approach that varies a wide range of physical parameters is typically used to generate thousands of test cases...
Office Of Nuclear Energy Annual Review Meeting Dynamic Simulation...
Office of Environmental Management (EM)
Simulations of SMRs 2 FY14 molten salt cooled model deliverable due. n FY15 web application deliverable due. n FY15 model repository establishment due. n FY15...
Liese, Eric [U.S. DOE; Zitney, Stephen E. [U.S. DOE
2013-01-01T23:59:59.000Z
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.
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
2014-12-31T23:59:59.000Z
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 decades ago, when High Performance Computing (HPC) resources were not commonly available.
Darlington tritium removal facility and station upgrading plant dynamic process simulation
Busigin, A. [NITEK USA, Inc., 6405 NW 77 PL, Parkland, FL 33067 (United States); Williams, G. I. D.; Wong, T. C. W.; Kulczynski, D.; Reid, A. [Ontario Power Generation Nuclear, Box 4000, Bowmanville, ON L1C 3Z8 (Canada)
2008-07-15T23:59:59.000Z
Ontario Power Generation Nuclear (OPGN) has a 4 x 880 MWe CANDU nuclear station at its Darlington Nuclear Div. located in Bowmanville. The station has been operating a Tritium Removal Facility (TRF) and a D{sub 2}O station Upgrading Plant (SUP) since 1989. Both facilities were designed with a Distributed Control System (DCS) and programmable logic controllers (PLC) for process control. This control system was replaced with a DCS only, in 1998. A dynamic plant simulator was developed for the Darlington TRF (DTRF) and the SUP, as part of the computer control system replacement. The simulator was used to test the new software, required to eliminate the PLCs. The simulator is now used for operator training and testing of process control software changes prior to field installation. Dynamic simulation will be essential for the ITER isotope separation system, where the process is more dynamic than the relatively steady-state DTRF process. This paper describes the development and application of the DTRF and SUP dynamic simulator, its benefits, architecture, and the operational experience with the simulator. (authors)
Huang, Samuel H.
. Huang, J. Shi Intelligent CAM Systems Laboratory Department of Mechanical, Industrial and Nuclear and Erlandur Steinthorsson Gas Turbine Fuel Systems Division Parker Hannifin Corporation 9200 Tyler Boulevard Finite Element Analysis (FEA) and Computational Fluid Dynamics (CFD) are used extensively in almost every
Automatic Generation of Quadrilateral Multi-Block Topology for FEA/CFD Applications Samuel H. Huang1
Huang, Samuel H.
Department of Mechanical, Industrial and Nuclear Engineering, University of Cincinnati, Cincinnati, OH 45221 2 Hauenstein & Burmeister, Inc., 2629 30th Avenue South, Minneapolis, MN 55406 3 Gas Turbine Fuel) and Computational Fluid Dynamics (CFD) are used extensively in almost every industry imaginable, including aerospace
Dynamic Particle Coupling for GPU-based Fluid Simulation
Blanz, Volker
-vi ¯j 2 W( Pi -Pj ,h). Here pj = k( ¯j - 0) is the pressure with gas constant k and rest density 0 for modeling dynamic particle coupling solely based on individual particle contributions. This technique does and µ is the fluid viscosity constant. To model the surface tension, M¨uller et.al. [MCG03] use the so
Dynamic Simulation of Performance Development: Prediction and Optimal Scheduling
Perl, JÃ¼rgen
of Performance Analysis of Sport-e, Volume 4, Number 2. (a) offline analysis (b) online prediction load profile analysis (b) online prediction load profile original performance profile simulated performance profile output depends on load input in different and specific ways. On the one hand, the kinds of load
Molecular Dynamics Simulations to Study Protein Folding and Unfolding
Caflisch, Amedeo
and results are essential in validating the force fields (V7 10/11 13:29) VCH/G J-1079 Buchner I PMU: WSL data is conditio sine qua non to validate the simulation results and very helpful for improv- ing force
Real-time dynamic simulator for the Topaz II reactor power system
Kwok, K.S.
1994-10-01T23:59:59.000Z
A dynamic simulator of the TOPAZ II reactor system has been developed for the Nuclear Electric Propulsion Space Test Program. The simulator is a self-contained IBM-PC compatible based system that executes at a speed faster than real-time. The simulator combines first-principle modeling and empirical correlations in its algorithm to attain the modeling accuracy and computational through-put that are required for real-time execution. The overall execution time of the simulator for each time step is 15 ms when no data is written to the disk, and 18 ms when nine double precision data points are written to the disk once in every time step. The simulation program has been tested and it is able to handle a step decrease of $8 worth of reactivity. It also provides simulation of fuel, emitter, collector, stainless steel, and ZrH moderator failures. Presented in this paper are the models used in the calculations, a sample simulation session, and a discussion of the performance and limitations of the simulator. The simulator has been found to provide realistic real-time dynamic response of the TOPAZ II reactor system under both normal and causality conditions.
Recent CFD-Related Activities at the High
Tennessee, University of
The Goal #12;Freels ,CFD Colloquium at UTK,in honor of A, J. Baker, 05/18/2010 · spent fuel re: Convert to LEU Fuel #12;Freels ,CFD Colloquium at UTK,in honor of A, J. Baker, 05/18/2010 COMSOL Models;Freels ,CFD Colloquium at UTK,in honor of A, J. Baker, 05/18/2010 COMSOL 2D Development of Fluid
Adding quantum effects to the semi-classical molecular dynamics simulations
Yang, Siyang
2011-01-01T23:59:59.000Z
Simulating the molecular dynamics (MD) using classical or semi-classical trajectories provides important details for the understanding of many chemical reactions, protein folding, drug design, and solvation effects. MD simulations using trajectories have achieved great successes in the computer simulations of various systems, but it is difficult to incorporate quantum effects in a robust way. Therefore, improving quantum wavepacket dynamics and incorporating nonadiabatic transitions and quantum effects into classical and semi-classical molecular dynamics is critical as well as challenging. In this paper, we present a MD scheme in which a new set of equations of motion (EOM) are proposed to effectively propagate nuclear trajectories while conserving quantum mechanical energy which is critical for describing quantum effects like tunneling. The new quantum EOM is tested on a one-state one-dimensional and a two-state two-dimensional model nonadiabatic systems. The global quantum force experienced by each trajecto...
Lühmann, Dirk-Sören; Sengstock, Klaus
2015-01-01T23:59:59.000Z
In the recent years, ultracold atoms in optical lattices have proven their great value as quantum simulators for studying strongly-correlated phases and complex phenomena in solid-state systems. Here we reveal their potential as quantum simulators for molecular physics and propose a technique to image the three-dimensional molecular orbitals with high resolution. The outstanding tunability of ultracold atoms in terms of potential and interaction offer fully-adjustable model systems for gaining deep insight into the electronic structure of molecules. We study the orbitals of an artificial benzene molecule and discuss the effect of tunable interactions in its conjugated pi electron system with special regard to localization and spin order. The dynamical timescale of ultracold atom simulators are on the order milliseconds which allow for the time-resolved monitoring of a broad range of dynamical processes. As an example, we compute the hole dynamics in the conjugated pi system of the artificial benzene molecule.
Molecular dynamics simulation of chains mobility in polyethylene crystal
V. I. Sultanov; V. V. Atrazhev; D. V. Dmitriev; S. F. Burlatsky
2014-01-17T23:59:59.000Z
The mobility of polymer chains in perfect polyethylene (PE) crystal was calculated as a function of temperature and chain length through Molecular dynamics (MD) in united atom approximation. The results demonstrate that the chain mobility drastically increases in the vicinity of the phase transition from the orthorhombic to quasi-hexagonal phase. In the quasi-hexagonal phase, the chain mobility is almost independent on temperature and inversely proportional to the chain length.
Helmet Streamers with Triple Structures: Simulations of resistive dynamics
T. Wiegelmann; K. Schindler; T. Neukirch
2008-01-21T23:59:59.000Z
Recent observations of the solar corona with the LASCO coronagraph on board of the SOHO spacecraft have revealed the occurrence of triple helmet streamers even during solar minimum, which occasionally go unstable and give rise to large coronal mass ejections. There are also indications that the slow solar wind is either a combination of a quasi-stationary flow and a highly fluctuating component or may even be caused completely by many small eruptions or instabilities. As a first step we recently presented an analytical method to calculate simple two-dimensional stationary models of triple helmet streamer configurations. In the present contribution we use the equations of time- dependent resistive magnetohydrodynamics to investigate the stability and the dynamical behaviour of these configurations. We particularly focus on the possible differences between the dynamics of single isolated streamers and triple streamers and on the way in which magnetic reconnection initiates both small scale and large scale dynamical behaviour of the streamers. Our results indicate that small eruptions at the helmet streamer cusp may incessantly accelerate small amounts of plasma without significant changes of the equilibrium configuration and might thus contribute to the non-stationary slow solar wind. On larger time and length scales, large coronal eruptions can occur as a consequence of large scale magnetic reconnection events inside the streamer configuration. Our results also show that triple streamers are usually more stable than a single streamer.
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...
Levitt, Michael
Calibration and Testing of a Water Model for Simulation of the Molecular Dynamics of Proteins important in biological macromolecules, where fewer experimental results are available for calibration. Our
Michael Vogel
2009-02-20T23:59:59.000Z
Molecular dynamics simulations are performed to study the temperature-dependent dynamics and structures of the hydration shells of elastin-like and collagen-like peptides. For both model peptides, it is consistently observed that, upon cooling, the mechanisms for water dynamics continuously change from small-step diffusive motion to large-step jump motion, the temperature dependence of water dynamics shows a weak crossover from fragile behavior to strong behavior, and the order of the hydrogen-bond network increases. The temperature of the weak crossover from fragile to strong behavior is found to coincide with the temperature at which maximum possible order of the hydrogen-bond network is reached so that the structure becomes temperature independent. In the strong regime, the temperature dependence of water translation and rotational dynamics is characterized by an activation energy of ca. E_a=0.43 eV, consistent with results from previous dielectric spectroscopy and nuclear magnetic resonance studies on protein hydration waters. At these temperatures, a distorted pi-flip motion about the twofold molecular symmetry axes, i.e., a water-specific beta process is an important aspect of water dynamics, at least at the water-peptide interfaces. In addition, it is shown that the hydration waters exhibit pronounced dynamical heterogeneities, which can be traced back to a strong slowdown of water motion in the immediate vicinity of peptide molecules due to formation of water-peptide hydrogen bonds.
Chang, Hung-Tzu; Cheng, Yuan-Chung [Department of Chemistry and Center for Quantum Science and Engineering, National Taiwan University, Taipei City 106, Taiwan (China)] [Department of Chemistry and Center for Quantum Science and Engineering, National Taiwan University, Taipei City 106, Taiwan (China); Zhang, Pan-Pan [Department of Physics and Institute of Modern Physics, Ningbo University, Ningbo 315211 (China)] [Department of Physics and Institute of Modern Physics, Ningbo University, Ningbo 315211 (China)
2013-12-14T23:59:59.000Z
The small polaron quantum master equation (SPQME) proposed by Jang et al. [J. Chem. Phys. 129, 101104 (2008)] is a promising approach to describe coherent excitation energy transfer dynamics in complex molecular systems. To determine the applicable regime of the SPQME approach, we perform a comprehensive investigation of its accuracy by comparing its simulated population dynamics with numerically exact quasi-adiabatic path integral calculations. We demonstrate that the SPQME method yields accurate dynamics in a wide parameter range. Furthermore, our results show that the accuracy of polaron theory depends strongly upon the degree of exciton delocalization and timescale of polaron formation. Finally, we propose a simple criterion to assess the applicability of the SPQME theory that ensures the reliability of practical simulations of energy transfer dynamics with SPQME in light-harvesting systems.
Conjugate gradient methods for power system dynamic simulation on parallel computers
Decker, I.C.; Falcao, D.M.; Kaszkurewicz, E. [COPPE/Federal Univ. of Rio de Janeiro (Brazil)] [COPPE/Federal Univ. of Rio de Janeiro (Brazil)
1996-08-01T23:59:59.000Z
Parallel processing is a promising technology for the speedup of the dynamic simulations required in transient stability analysis. In this paper, three methods for dynamic simulation on parallel computers are described and compared. The methods are based on the concepts of spatial and/or time parallelization. In all of them, sets of linear algebraic equations are solved using different versions of Conjugate Gradient methods which have been successfully applied in other scientific and engineering applications. The algorithms presented in the paper were tested in a commercially available parallel computer using an actual large power system model. The results obtained in the tests showed a considerable reduction in computation time.
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. (University of California, San Diego); Winey, J. Michael (Washington State University); Gupta, Yogendra Mohan (Washington State University); Lane, J. Matthew D.; Ditmire, Todd (University of Texas at Austin); Quevedo, Hernan J. (University of Texas at Austin)
2011-10-01T23:59:59.000Z
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.
Characteristics and control response of the TOPAZ II Reactor System Real-time Dynamic Simulator
Kwok, K.S.
1993-11-12T23:59:59.000Z
A dynamic simulator of the TOPAZ II reactor system has been developed for the Nuclear Electric Propulsion Space Test Program. The simulator combines first-principle modeling and empirical correlations in its algorithm to attain the modeling accuracy and computational through-put that are required for real-time execution. The overall execution time of the simulator for each time step is 15 ms when no data is written to the disk, and 18 ms when nine double precision data points are written to the disk once in every time step. The simulation program has been tested and it is able to handle a step decrease of $8 worth of reactivity. It also provides simulations of fuel, emitter, collector, stainless steel, and ZrH moderator failures. Presented in this paper are the models used in the calculations, a sample simulation session, and a discussion of the performance and limitations of the simulator. The simulator has been found to provide realistic real-time dynamic response of the TOPAZ II reactor system under both normal and casualty conditions.
Donna Post Guillen; Daniel S. Wendt; Steven P. Antal; Michael Z. Podowski
2007-11-01T23:59:59.000Z
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
2007-11-01T23:59:59.000Z
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.
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.
2012-08-01T23:59:59.000Z
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.
Martini, Matus; Gustafson, William I.; Yang, Qing; Xiao, Heng
2014-11-27T23:59:59.000Z
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.
Practical issues on CFD use and some industry aspects on research with CFD
Zevenhoven, Ron
of non-catalytic NOx reduction in FBC freeboard CFD project planning Fast pyrolysis model, 18.6.2010 2-catalytic NOx reduction in FBC freeboard target: Finding optimal locations for urea injection Injections temperature for NOx reduction is between blue and red areas. Courtesy Metso Power Oy #12;Geometry Fast
Simulations of beam envelope dynamics in circular accelerators
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Chao, Hung-Chun; Lee, S.?Y.
2015-02-01T23:59:59.000Z
The envelope instability of high intensity beams in circular accelerators is studied via multiparticle simulations. The space charge kicks are derived from a Gaussian potential model for an efficient tracking. The evolution of the envelope phase space coordinates are derived from the bunch distribution. We found that the envelope stop band played an important role in emittance growth. Correction schemes of the envelope stop bands are studied. Because the space charge force pushes the envelope tunes downward, harmonics less than twice the betatron tunes are also important on emittance growth. Our code is efficient and fast, it can be usedmore »to study the effect of space charge force on high power accelerators.« less
CFD evaluation of pipeline gas stratification at low fluid flow due to temperature effects
Brar, Pardeep Singh
2005-02-17T23:59:59.000Z
*A*?T On simplifying the above equation, applying forward difference and integrating both sides from west (W) to east (E), we get the following form of equation: ()() 2*( )* WW P WEE E P P EW kA T TkA T T rh T T x xx ? ?? ? ?? ? =?? 18 This is the general equation... and how much it differs from the CFD Analysis results. 41 0 2040608010 Z/D -1 0 1 2 P e rcen t D i fferen c e Single Elbow Upstream Simulated USM Compared To CFD Results, ?T Constant 5.5 o K (10 o F), 0.15 m/s (0.5 ft/s) 13.8 o K (25 o F), 0.15 m/s (0...
Southern California, University of
Molecular Surgery with Pulsed Electric Fields: Molecular Dynamics Simulations of Nanopore Formation Family Department of Chemical Engineering and Materials Science, §Department of Electrical Engineering of water molecules spanning the membrane, decay within a few nanoseconds when the electric field is removed
Maruyama, Shigeo
Non-Fourier heat conduction in a single-walled carbon nanotube: Classical molecular dynamics of the simulations exhibit non-Fourier heat conduction where the distinct amount of heat is transported in a wavelike called non-Fourier heat conduction equations in order to investigate the applicability
Exploring the Dynamic Costs of Process-aware Information Systems through Simulation
Ulm, UniversitÃ¤t
Exploring the Dynamic Costs of Process-aware Information Systems through Simulation Bela Mutschler systems, case handling systems) is associated with high costs. Though cost evaluation has received utilizes si- mulation models for investigating costs related to PAIS engineering projects. We motivate
Molecular dynamics simulations of gold-catalyzed growth of silicon bulk crystals and nanowires
Cai, Wei
ARTICLES Molecular dynamics simulations of gold-catalyzed growth of silicon bulk crystals of the orientation, yield, and quality of the NWs. Much of the studies on the VLS growth mechanism have been focused. In this article, we present the first set of MD simu- lations of NW growth using this AuSi potential model
Observations, Simulations, and Dynamics of Jet Stream Variability and Annular Modes JOSEPH KIDSTON
Kidston, Joseph
Observations, Simulations, and Dynamics of Jet Stream Variability and Annular Modes JOSEPH KIDSTON jet stream. It is shown that the strength of the thermally indirect circulation that gives rise- lation of the equivalent barotropic eddy-driven jet streams and embedded storm tracks (Kidson 1988; Mo
DYNAMIC SIMULATION OF MONO-TUBE CAVITY RECEIVERS FOR DIRECT STEAM GENERATION
transports superheated steam via rotary joints to the ground and then to a 4 cylinder steam engine and therefore a vent valve has been installed at the receiver outlet to vent a portion of the superheated steamDYNAMIC SIMULATION OF MONO-TUBE CAVITY RECEIVERS FOR DIRECT STEAM GENERATION José Zapata 1 , John
Adaptive Accelerated ReaxFF Reactive Dynamics with Validation from Simulating Hydrogen Combustion
Goddard III, William A.
Adaptive Accelerated ReaxFF Reactive Dynamics with Validation from Simulating Hydrogen Combustion concept (BB), which we validate here for describing hydrogen combustion. The bond order, undercoordination determined the detailed sequence of reactions for hydrogen combustion with and without the BB. We validate
Molecular Dynamics Simulation of Damage Cascade Formation in Ion Bombarded Solids
Chen, Di
2012-10-19T23:59:59.000Z
.......................................................................................................... 10 CHAPTER III MOLECULAR DYNAMICS SIMULATION OF DEFECT……………... CREATION DUE TO INTERACTIONS OF DAMAGE CASCADE IN SELF ION…… IRRADIATED SI………….…….………........................................................................12 3... ....................................................................................... 14 CHAPTER IV USING CLUSTER ION BOMBARDMENT TO DETERMINE………… AMORPHIZATION MODE..…………………………………………...........................26 4.1 Introduction of Irradiated Amorphization ........................................................... 26 4...
Molecular Dynamics Simulation of Thin Films with Rough and Asymmetric Interfaces
Walker, D. Greg
Molecular Dynamics Simulation of Thin Films with Rough and Asymmetric Interfaces N.A. Roberts with the use of interfaces and shows that pristine, imperfect and asymmetric interfaces in thin films can interface whose features are of the order of the phonon wavelength. At a constant temperature difference
Large-scale molecular dynamics simulation of magnetic properties of amorphous iron under pressure
) Enhanced refrigerant capacity and magnetic entropy flattening using a two-amorphous FeZrB(Cu) compositeLarge-scale molecular dynamics simulation of magnetic properties of amorphous iron under pressure Appl. Phys. Lett. 99, 232501 (2011) Nonlinear motion of magnetic vortex under alternating
Simulation of exhaust gas pollution within an eventdriven multimodal dynamic traffic model
Toint, Philippe
pollution caused by urban vehicles (cars and busses), a major source of urban environment deterioration1 Simulation of exhaust gas pollution within an eventdriven multimodal dynamic traffic model E concerns. Among the drawbacks of urban life, one often mentions the level of pollution, mostly resulting
A next-generation modeling capability assesses wind turbine array fluid dynamics and aeroelastic simulations Characterizing and optimizing overall performance of wind plants composed of large numbers at the National Renewable Energy Laboratory (NREL) are coupling physical models of the atmosphere and wind
DYNAMIC SIMULATION OF MONO-TUBE CAVITY RECEIVERS FOR DIRECT STEAM GENERATION
for intended deployment in large arrays of dishes, with steam directed to a central large steam turbine powerDYNAMIC SIMULATION OF MONO-TUBE CAVITY RECEIVERS FOR DIRECT STEAM GENERATION José Zapata 1 , John dish has been in operation since 2010 with a mono-tube steam cavity receiver, the SG4 system
Molecular dynamics simulation of the plastic to triclinic phase transition in clusters of SF6
Paris-Sud XI, Université de
41 Molecular dynamics simulation of the plastic to triclinic phase transition in clusters of SF6 A agrégats n'a pas été entreprise. Abstract. 2014 Clusters of 512 SF6 molecules in their condensed phases of finite systems such as clusters [2]. Liquid sulphur hexafluoride, SF6, forms on cooling what is known
Molecular Dynamics Simulations of Folding and Insertion of the Ebola Virus Fusion Peptide into a
Molecular Dynamics Simulations of Folding and Insertion of the Ebola Virus Fusion Peptide- residue Ebola virus fusion peptide into a membrane bilayer. We applied a multi-resolution computational viruses, the filoviruses contain a highly compact genome, consisting of only seven encoded proteins
Non-linear and Non-planar Free Thermal Vibration of SWNT in Molecular Dynamic Simulation
Maruyama, Shigeo
Non-linear and Non-planar Free Thermal Vibration of SWNT in Molecular Dynamic Simulation Heeyuen Koh, James Cannon, Shohei Chiashi, Junichiro Shiomi and Shigeo Maruyama Department of Mechanical-mail: maruyama@photon.t.u-tokyo.ac.jp 1. Introduction Vibration of suspended and cantilevered nanotubes
Southern California, University of
: A parallel molecular dynamics simulation Satyavani Vemparala, Rajiv K. Kalia, Aiichiro Nakano, and Priya on the atomistic structure of PEG terminated SAMs using molecular dynamics simulations on parallel computersElectric field induced switching of poly,,ethylene glycol... terminated self-assembled monolayers
Faeder, Jim
Hamiltonian model of electronic structure with nonadiabatic molecular dynamics simulations, we calculate of the electronic structure of a manifold of states strongly coupled to the many solvent degrees of freedomUltrafast reaction dynamics in cluster ions: Simulation of the transient photoelectron spectrum
Glinsky, M.E.; Amendt, P.A.; Bailey, D.S.; London, R.A.; Rubenchik, A.M. [Lawrence Livermore National Lab., CA (United States); Strauss, M. [Israel Atomic Energy Commission, Beersheba (Israel). Nuclear Research Center-Negev
1997-03-04T23:59:59.000Z
The validity of an extended Rayleigh model for laser generated bubbles in soft tissue is examined. This model includes surface tension, viscosity, a realistic water equation of state, material strength and failure, stress wave emission, and linear growth of interface instabilities. It is compared to dynamic simulations using LATIS, which include stress wave propagation, water equation of state, material strength and failure, and viscosity. The model and the simulations are compared using 1-D spherical geometry with bubble in center and a 2-D cylindrical geometry of a laser fiber in water with a bubble formed at the end of the fiber. The model executes over 300x faster on computer than the dynamic simulations.
Open systems dynamics: Simulating master equations in the computer
Carlos Navarrete-Benlloch
2015-04-22T23:59:59.000Z
Master equations are probably the most fundamental equations for anyone working in quantum optics in the presence of dissipation. In this context it is then incredibly useful to have efficient ways of coding and simulating such equations in the computer, and in this notes I try to introduce in a comprehensive way how do I do so, focusing on Matlab, but making it general enough so that it can be directly translated to any other language or software of choice. I inherited most of my methods from Juan Jos\\'e Garc\\'ia-Ripoll (whose numerical abilities I cannot praise enough), changing them here and there to accommodate them to the way my (fairly limited) numerical brain works, and to connect them as much as possible to how I understand the theory behind them. At present, the notes focus on how to code master equations and find their steady state, but I hope soon I will be able to update them with time evolution methods, including how to deal with time-dependent master equations. During the last 4 years I've tested these methods in various different contexts, including circuit quantum electrodynamics, the laser problem, optical parametric oscillators, and optomechanical systems. Comments and (constructive) criticism are greatly welcome, and will be properly credited and acknowledged.
Long-time protein folding dynamics from short-time molecular dynamics simulations
Chodera, J D; Swope, W C; Pitera, J W; Dill, Ken A
2006-01-01T23:59:59.000Z
On the simulation of protein folding by short time scaleand W. A. Eaton, The protein folding “speed limit,” Curr.and T. Head-Gordon, Protein folding by distributed computing
Liese, E.; Zitney, S.
2012-01-01T23:59:59.000Z
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.
Particle dynamics in two-dimensional random energy landscapes - experiments and simulations
Florian Evers; Christoph Zunke; Richard D. L. Hanes; Joerg Bewerunge; Imad Ladadwa; Andreas Heuer; Stefan U. Egelhaaf
2013-06-13T23:59:59.000Z
The dynamics of individual colloidal particles in random potential energy landscapes were investigated experimentally and by Monte Carlo simulations. The value of the potential at each point in the two-dimensional energy landscape follows a Gaussian distribution. The width of the distribution, and hence the degree of roughness of the energy landscape, was varied and its effect on the particle dynamics studied. This situation represents an example of Brownian dynamics in the presence of disorder. In the experiments, the energy landscapes were generated optically using a holographic set-up with a spatial light modulator, and the particle trajectories were followed by video microscopy. The dynamics are characterized using, e.g., the time-dependent diffusion coefficient, the mean squared displacement, the van Hove function and the non-Gaussian parameter. In both, experiments and simulations, the dynamics are initially diffusive, show an extended sub-diffusive regime at intermediate times before diffusive motion is recovered at very long times. The dependence of the long-time diffusion coefficient on the width of the Gaussian distribution agrees with theoretical predictions. Compared to the dynamics in a one-dimensional potential energy landscape, the localization at intermediate times is weaker and the diffusive regime at long times reached earlier, which is due to the possibility to avoid local maxima in two-dimensional energy landscapes.
Computational Particle Dynamic Simulations on Multicore Processors (CPDMu) Final Report â?? Phase I
Mark S. Schmalz
2011-07-24T23:59:59.000Z
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 parallel computation of particle and fluid dynamics simulations. These problems occur throughout DOE, military and commercial sectors: the potential payoff is high. We plan to license or sell the solution to contractors for military and domestic applications such as disaster simulation (aerodynamic and hydrodynamic), Government agencies (hydrological and environmental simulations), and medical applications (e.g., in tomographic image reconstruction). Keywords - High-performance Computing, Graphic Processing Unit, Fluid/Particle Simulation. Summary for Members of Congress - Department of Energy has many simulation codes that must compute faster, to be effective. The Phase I research parallelized particle/fluid simulations for rocket combustion, for high-performance computing systems.
Atomistic Simulation of Nafion Membrane: 2. Dynamics of Water Molecules and Hydronium Ions
Devanathan, Ram; Venkatnathan, Arun; Dupuis, Michel
2007-10-20T23:59:59.000Z
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.
Ab-initio molecular dynamics simulation of liquid water by Quantum Monte Carlo
Andrea Zen; Ye Luo; Guglielmo Mazzola; Leonardo Guidoni; Sandro Sorella
2015-04-21T23:59:59.000Z
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.
Quantum simulations of dissipative dynamics: time-dependence instead of size
Benjamin Dive; Florian Mintert; Daniel Burgarth
2015-05-08T23:59:59.000Z
The simulation of quantum systems has been a key aim of quantum technologies for decades, and the generalisation to open systems is necessary to include physically realistic systems. We introduce an approach for quantum simulations of open system dynamics in terms of an environment of minimal size and a time-dependent Hamiltonian. This enables the implementation of a continuous-time simulation with a finite environment, whereas state of the art methods require an infinite environment or only match the simulation at discrete times. We find necessary and sufficient conditions for this Hamiltonian to be well behaved and, when these are not met, we show that there exists an approximate Hamiltonian that is, and look into its applications.
Chen, Qingyan "Yan"
Fast and Informative Flow Simulations in a Building by Using Fast Fluid Dynamics Model on Graphics simulations are necessary for building emergency management, preliminary design of sustainable buildings for a whole building. This paper reports our efforts on further accelerating FFD simulation by running
Development of a Prototype Lattice Boltzmann Code for CFD of Fusion Systems.
Pattison, Martin J; Premnath, Kannan N; Banerjee, Sanjoy; Dwivedi, Vinay
2007-02-26T23:59:59.000Z
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 ability of the LBM to scale almost linearly. The equation for magnetic induction was also solved using a lattice Boltzmann method. This approach has the advantage that it fits in well to the framework used for the hydrodynamic equations, but more importantly that it preserves the ability of the code to run efficiently on parallel architectures. Since the LBM is a relatively recent model, a number of new developments were needed to solve the magnetic induction equation for practical problems. Existing methods were only suitable for cases where the fluid viscosity and the magnetic resistivity are of the same order, and a preconditioning method was used to allow the simulation of liquid metals, where these properties differ by several orders of magnitude. An extension of this method to the hydrodynamic equations allowed faster convergence to steady state. A new method of imposing boundary conditions using an extrapolation technique was derived, enabling the magnetic field at a boundary to be specified. Also, a technique by which the grid can be stretched was formulated to resolve thin layers at high imposed magnetic fields, allowing flows with Hartmann numbers of several thousand to be quickly and efficiently simulated. In addition, a module has been developed to calculate the temperature field and heat transfer. This uses a total variation diminishing scheme to solve the equations and is again very amenable to parallelisation. Although, the module was developed with thermal modelling in mind, it can also be applied to passive scalar transport. The code is fully three dimensional and has been applied to a wide variety of cases, including both laminar and turbulent flows. Validations against a series of canonical problems involving both MHD effects and turbulence have clearly demonstrated the ability of the LBM to properly model these types of flow. As well as applications to fusion engineering, the resulting code is flexible enough to be applied to a wide range of other flows, in particular those requiring parallel computations with many processors. For example, at
Pan, Jianjun [ORNL; Cheng, Xiaolin [ORNL; Heberle, Frederick A [ORNL; Mostofian, Barmak [ORNL; Kucerka, Norbert [Canadian Neutron Beam Centre and Comelius University (Slovakia); Drazba, Paul [ORNL; Katsaras, John [ORNL
2012-01-01T23:59:59.000Z
Cholesterol and ether lipids are ubiquitous in mammalian cell membranes, and their interactions are crucial in ether lipid mediated cholesterol trafficking. We report on cholesterol s molecular interactions with ether lipids as determined using a combination of small-angle neutron and Xray scattering, and all-atom molecular dynamics (MD) simulations. A scattering density profile model for an ether lipid bilayer was developed using MD simulations, which was then used to simultaneously fit the different experimental scattering data. From analysis of the data the various bilayer structural parameters were obtained. Surface area constrained MD simulations were also performed to reproduce the experimental data. This iterative analysis approach resulted in good agreement between the experimental and simulated form factors. The molecular interactions taking place between cholesterol and ether lipids were then determined from the validated MD simulations. We found that in ether membranes cholesterol primarily hydrogen bonds with the lipid headgroup phosphate oxygen, while in their ester membrane counterparts cholesterol hydrogen bonds with the backbone ester carbonyls. This different mode of interaction between ether lipids and cholesterol induces cholesterol to reside closer to the bilayer surface, dehydrating the headgroup s phosphate moiety. Moreover, the three-dimensional lipid chain spatial density distribution around cholesterol indicates anisotropic chain packing, causing cholesterol to tilt. These insights lend a better understanding of ether lipid-mediated cholesterol trafficking and the roles that the different lipid species have in determining the structural and dynamical properties of membrane associated biomolecules.
Wall, Michael E. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Van Benschoten, Andrew H. [Univ. of California, San Francisco, CA (United States); Sauter, Nicholas K. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Adams, Paul D. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States); Fraser, James S. [Univ. of California, San Francisco, CA (United States); Terwilliger, Thomas C. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2014-12-01T23:59:59.000Z
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 protein–solvent interactions contribute substantially to the overall diffuse intensity. We conclude that diffuse scattering can be used to validate predictions from MD simulations and can provide information to improve MD models of protein motions.
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Wall, Michael E.; Van Benschoten, Andrew H.; Sauter, Nicholas K.; Adams, Paul D.; Fraser, James S.; Terwilliger, Thomas C.
2014-12-01T23:59:59.000Z
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 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. We conclude that diffuse scattering can be used to validate predictions from MD simulations and can provide information to improve MD models of protein motions.« less
The computer BESK and an early attempt to simulate galactic dynamics
Lindblad, Per Olof
2015-01-01T23:59:59.000Z
The first N-body simulation of interacting galaxies, even producing spiral arms, was performed by Erik Holmberg in Lund (1941), not with a numerical computer, but by his arrangement of movable light-bulbs and photocells to measure the luminosity at each bulb and thereby estimate the gravitational force. A decade later, and with the arrival of the first programable computers, computations of galactic dynamics were performed, which were later transferred into a N-body simulation movie. I present here the background details for this work with a description of the important elements to note in the movie which may be retrieved at http://ttt.astro.su.se/~po .
van de Meent, Jan-Willem; Somfai, Ellak; Sultan, Eric; van Saarloos, Wim
2008-01-01T23:59:59.000Z
We present simulations of coherent structures in compressible flows near the transition to turbulence using the Dissipative Particle Dynamics (DPD) method. The structures we find are remarkably consistent with experimental observations and DNS simulations of incompressible flows, despite a difference in Mach number of several orders of magnitude. The bifurcation from the laminar flow is bistable and shifts to higher Reynolds numbers when the fluid becomes more compressible. This work underlines the robustness of coherent structures in the transition to turbulence and illustrates the ability of particle-based methods to reproduce complex non-linear instabilities.
Water harvesting using a conducting polymer: A study by molecular dynamics simulation
Ostwal, Mayur M.; Sahimi, Muhammad; Tsotsis, Theodore T. [Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, California 90089-1211 (United States)
2009-06-15T23:59:59.000Z
The results of extensive molecular simulations of adsorption and diffusion of water vapor in polyaniline, made conducting by doping it with HCl or HBr over a broad range of temperatures, are reported. The atomistic model of the polymers was generated using energy minimization, equilibrium molecular dynamics simulations, and two different force fields. The computed sorption isotherms are in excellent agreement with the experimental data. The computed activation energies for the diffusion of water molecules in the polymers also compare well with what has been reported in the literature. The results demonstrate the potential of conducting polyaniline for water harvesting from air.
Towards the Integration of APECS and VE-Suite for Virtual Power Plant Co-Simulation
Zitney, S.E.; McCorkle, D. (Iowa State University, Ames, IA); Yang, C. (Reaction Engineering International, Salt Lake City, UT); Jordan, T.; Swensen, D. (Reaction Engineering International, Salt Lake City, UT); Bryden, M. (Iowa State University, Ames, IA)
2007-05-01T23:59:59.000Z
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.
Batista, V.S.; Miller, W.H. [Department of Chemistry, University of California, and Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)] [Department of Chemistry, University of California, and Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)
1998-01-01T23:59:59.000Z
In this paper we investigate the nonadiabatic ultrafast dynamics of interconversion between the two lower lying excited states of {sup 1}A{sup {double_prime}} symmetry (1 {sup 1}A{sup {double_prime}} and 2 {sup 1}A{sup {double_prime}}) of ozone following photoexcitation of the molecule in the gas phase with visible light. Our algorithm involves a semiclassical initial value representation method which is able to describe electronically nonadiabatic processes within the time dependent picture through the quantization of the classical electron{endash}nuclear model Hamiltonian of Meyer and Miller [J. Chem. Phys. {bold 70}, 7 (1979)]. We explore the capabilities of these techniques as applied to studying the dynamics of a realistic reaction of photodissociation on full {ital ab initio} electronic potential energy surfaces. Our semiclassical results provide an intuitive understanding of the most fundamental dynamical features involved in the process of predissociation, such as decay and recurrence events, as well as an interpretation of experimental studies of the Chappuis band of ozone in the frequency domain. {copyright} {ital 1998 American Institute of Physics.}
Simulating Collisions for Hydrokinetic Turbines
Richmond, Marshall C.; Romero Gomez, Pedro DJ; Rakowski, Cynthia L.
2013-10-01T23:59:59.000Z
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.
Marius Buibas; Gabriel A. Silva
2010-06-22T23:59:59.000Z
We present a framework for simulating signal propagation in geometric networks (i.e. networks that can be mapped to geometric graphs in some space) and for developing algorithms that estimate (i.e. map) the state and functional topology of complex dynamic geometric net- works. Within the framework we define the key features typically present in such networks and of particular relevance to biological cellular neural networks: Dynamics, signaling, observation, and control. The framework is particularly well-suited for estimating functional connectivity in cellular neural networks from experimentally observable data, and has been implemented using graphics processing unit (GPU) high performance computing. Computationally, the framework can simulate cellular network signaling close to or faster than real time. We further propose a standard test set of networks to measure performance and compare different mapping algorithms.
Dynamical consequences of a constraint on the Langevin thermostat in molecular cluster simulation
Stinson, Jake L.; Kathmann, Shawn M.; Ford, Ian J.
2014-11-17T23:59:59.000Z
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.
Numerical simulation of high-speed penetration-perforation dynamics in layered armor shields
Ayzenberg-Stepanenko, Mark
2012-01-01T23:59:59.000Z
Penetration models and calculating algorithms are presented, describing the dynamics and fracture of composite armor shields penetrated by high-speed small arms. A shield considered consists of hard (metal or ceramic) facing and multilayered fabric backing. A simple formula is proved for the projectile residual velocity after perforation of a thin facing. A new plastic-flow jet model is proposed for calculating penetration dynamics in the case of a thick facing of ceramic or metal-ceramic FGM materials. By bringing together the developed models into a calculating algorithm, a computer tool is designed enabling simulations of penetration processes in the above-mentioned shields and analysis of optimization problems. Some results of computer simulation are presented. It is revealed in particular that strength proof of pliable backing can be better as compared with more rigid backing. Comparison of calculations and test data shows sufficient applicability of the models and the tool.
Numerical simulation of high-speed penetration-perforation dynamics in layered armor shields
Mark Ayzenberg-Stepanenko; Grigory Osharovich
2012-03-07T23:59:59.000Z
Penetration models and calculating algorithms are presented, describing the dynamics and fracture of composite armor shields penetrated by high-speed small arms. A shield considered consists of hard (metal or ceramic) facing and multilayered fabric backing. A simple formula is proved for the projectile residual velocity after perforation of a thin facing. A new plastic-flow jet model is proposed for calculating penetration dynamics in the case of a thick facing of ceramic or metal-ceramic FGM materials. By bringing together the developed models into a calculating algorithm, a computer tool is designed enabling simulations of penetration processes in the above-mentioned shields and analysis of optimization problems. Some results of computer simulation are presented. It is revealed in particular that strength proof of pliable backing can be better as compared with more rigid backing. Comparison of calculations and test data shows sufficient applicability of the models and the tool.
High Performance Molecular Dynamic Simulation on Single and Multi-GPU Systems
Villa, Oreste; Chen, Long; Krishnamoorthy, Sriram
2010-05-30T23:59:59.000Z
The programming techniques supported and employed on these GPUs and Multi-GPUs systems are not sufficient to address problems exhibiting irregular, and unbalanced workload such as Molecular Dynamic (MD) simulations of systems with non-uniform densities. In this paper, we propose a task-based dynamic load-balancing solution to employ on MD simulations for single- and multi-GPU systems. The solution allows load balancing at a finer granularity than what is supported in existing APIs such as NVIDIA’s CUDA. Experimental results with a single-GPU configuration show that our fine-grained task solution can utilize the hardware more efficiently than the CUDA scheduler. On multi-GPU systems, our solution achieves near-linear speedup, load balance, and significant performance improvement over techniques based on standard CUDA APIs.
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Yang, L.H.; Brooks III, E.D.; Belak, J.
1992-01-01T23:59:59.000Z
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.
Hard discs under steady shear: comparison of Brownian dynamics simulations and mode coupling theory
O. Henrich; F. Weysser; M. E. Cates; M. Fuchs
2010-01-19T23:59:59.000Z
Brownian dynamics simulations of bidisperse hard discs moving in two dimensions in a given steady and homogeneous shear flow are presented close to and above the glasstransition density. The stationary structure functions and stresses of shear-melted glass are compared quantitatively to parameter-free numerical calculations of monodisperse hard discs using mode coupling theory within the integration through transients framework. Theory qualitatively explains the properties of the yielding glass but quantitatively overestimatesthe shear-driven stresses and structural anisotropies.
Fast dynamics of an eel-like robot, comparisons with Navier-Stokes simulations
Boyer, Edmond
the head to the caudal 1 F. Boyer : EMN, IRCCyN, La Chantrerie 4, rue Alfred Kastler B.P. 20722 - 44307Fast dynamics of an eel-like robot, comparisons with Navier-Stokes simulations Frederic Boyer1 Nantes Cedex 3 France. Tel. : +00 33 2 51 85 83 08, Fax : +00 33 2 51 85 83 02, E-mail : frederic.boyer
Ab initio molecular dynamics simulation of proton hopping in a model polymer membrane
Devanathan, Ramaswami; Idupulapati, Nagesh B.; Baer, Marcel D.; Mundy, Christopher J.; Dupuis, Michel
2013-12-10T23:59:59.000Z
We report the results of ab initio molecular dynamics simulations of a model NafionTM polymer membrane initially equilibrated using classical molecular dynamics simulations. We studied three hydration levels (?) of 3, 9, and 15 H2O/SO3- corresponding to dry, hydrated and saturated fuel cell membrane, respectively. The barrier for proton transfer from the SO3-–H3O+ contact ion pair to a solvent-separated ion pair decreased from 2.3 kcal/mol for ? = 3 to 0.8 kcal/mol for ? = 15. The barrier for proton transfer between two water molecules was in the range from 0.7 to 0.8 kcal/mol for the ? values studied. The number of proton shuttling events between a pair of water molecules is an order of magnitude more than the number of proton hops across three distinct water molecules. The proton diffusion coefficient at ? = 15 is about 0.9x10-5 cm2/s, which is in good agreement with experiment and our previous quantum hopping molecular dynamics simulations.
Using Simulations and kinetic network models to reveal the dynamics and functions of Riboswitches
Jong-Chin Lin; Jeseong Yoon; Changbong Hyeon; D. Thirumalai
2014-10-02T23:59:59.000Z
Riboswitches, RNA elements found in the untranslated region, regulate gene expression by binding to target metaboloites with exquisite specificity. Binding of metabolites to the conserved aptamer domain allosterically alters the conformation in the downstream expression platform. The fate of gene expression is determined by the changes in the downstream RNA sequence. As the metabolite-dependent cotranscriptional folding and unfolding dynamics of riboswitches is the key determinant of gene expression, it is important to investigate both the thermodynamics and kinetics of riboswitches both in the presence and absence of metabolite. Single molecule force experiments that decipher the free energy landscape of riboswitches from their mechanical responses, theoretical and computational studies have recently shed light on the distinct mechanism of folding dynamics in different classes of riboswitches. Here we first discuss the dynamics of water around riboswitch, highlighting that water dynamics can enhance the fluctuation of nucleic acid structure. To go beyond native state fluctuations we used the Self-Organized Polymer (SOP) model to predict the dynamics of add adenine riboswitch under mechanical forces. In addition to quantitatively predicting the folding landscape of add-riboswitch our simulations also explain the difference in the dynamics between pbuE adenine- and add adenine-riboswitches. In order to probe the function {\\it in vivo} we use the folding landscape to propose a system level kinetic network model to quantitatively predict how gene expression is regulated for riboswitches that are under kinetic control.
Latecki, Longin Jan
Mapping and Immersive Building Simulation Rolf Lakaemper1 , Ali M. Malkawi2 , Ravi S. Srinivasan2. The CFD simulation module facilitates the prediction of building performance data based on the spatial], structural analysis [2], building performance [3,4], etc. CFD simulation is employed to iteratively solve
Virtual Simulation of Vision 21 Energy Plants
Syamlal, Madhava; Felix, Paul E.; Osawe, Maxwell O. (Fluent Inc.); Fiveland, Woodrow A.; Sloan, David G. (ALSTOM Power); Zitney, Stephen E. (Aspen Technology, Inc.); Joop, Frank (Intergraph Corporation); Cleetus, Joseph; Lapshin, Igor B. (Concurrent Engineering Research Center, West Virginia University)
2001-11-06T23:59:59.000Z
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 ensure that consistent and complete knowledge about the process is used for design and optimization. The technical objectives of the current project are the following: Develop a software integration tool called the V21-Controller to mediate the information exchange between FLUENT, other detailed equipment models, and Aspen Plus. Define and publish software interfaces so that software and equipment vendors may integrate their computer models into the software developed in this project. Demonstrate the application of the integrated software with two power plant simulations, one for a conventional steam plant and another for an advanced power cycle. The project was started in October 2000. Highlights of the accomplishments during the first year of the project are the following: Formed a multi-disciplinary project team consisting of chemical and mechanical engineers; computer scientists; CFD, process simulation, and plant design software developers; and power plant designers. Developed a prototype of CFD and process model integration: a stirred tank reactor model based on FLUENT was inserted into a flow sheet model based on Aspen Plus. The prototype was used to show the effect of shaft speed (a parameter in the CFD model) on the product yield and purity (results of process simulation). This demonstrated the optimization of an equipment item in the context of the entire plant rather than in isolation. Conducted a user survey and wrote the User Requirements, Software Requirements and Software Design documents for the V21-Controller. Adopted CAPE-OPEN standard interfaces for communications between equipment and process models. Developed a preliminary version of the V21-Controller based on CAPE-OPEN interfaces. Selected one unit of an existing conventional steam plant (Richmond Power & Light) as the first demonstration case and developed an Aspen Plus model of the steam-side of the unit. A model for the gas-side of the unit, based on ALSTOM's proprietary model INDVU, was integrated with the Aspen Plus model. An industrial Advisory Board was formed to guide the software deve
Computer simulation study of surface wave dynamics at the crystal--melt interface
Jorge Benet; Luis G. MacDowell; Eduardo Sanz
2014-10-01T23:59:59.000Z
We study, by means of computer simulations, the crystal-melt interface of three different systems: hard-spheres, Lennard Jones and the TIP4P/2005 water model. In particular, we focus on the dynamics of surface waves. We observe that the processes involved in the relaxation of surface waves are characterized by distinct time scales: a slow one related to the continuous recrystallization and melting, that is governed by capillary forces; and a fast one which we suggest to be due to a combination of processes that quickly cause small perturbations to the shape of the interface (like e. g. Rayleigh waves, subdiffusion, or attachment/detachment of particles to/from the crystal). The relaxation of surface waves becomes dominated by the slow process as the wavelength increases. Moreover, we see that the slow relaxation is not influenced by the details of the microscopic dynamics. In a time scale characteristic for the diffusion of the liquid phase, the relaxation dynamics of the crystal-melt interface of water is around one order of magnitude slower than that of Lennard Jones or hard spheres, which we ascribe to the presence of orientational degrees of freedom in the water molecule. Finally, we estimate the rate of crystal growth from our analysis of the capillary wave dynamics and compare it with previous simulation studies and with experiments for the case of water.
Sharadwata Pan; D. Ahirwal; Duc At Nguyen; T. Sridhar; P. Sunthar; J. Ravi Prakash
2014-10-14T23:59:59.000Z
The swelling of the viscosity radius, $\\alpha_\\eta$, and the universal viscosity ratio, $U_{\\eta R}$, have been determined experimentally for linear DNA molecules in dilute solutions with excess salt, and numerically by Brownian dynamics simulations, as a function of the solvent quality. In the latter instance, asymptotic parameter free predictions have been obtained by extrapolating simulation data for finite chains to the long chain limit. Experiments and simulations show a universal crossover for $\\alpha_\\eta$ and $U_{\\eta R}$ from $\\theta$ to good solvents in line with earlier observations on synthetic polymer-solvent systems. The significant difference between the swelling of the dynamic viscosity radius from the observed swelling of the static radius of gyration, is shown to arise from the presence of hydrodynamic interactions in the non-draining limit. Simulated values of $\\alpha_\\eta$ and $U_{\\eta R}$ are in good agreement with experimental measurements in synthetic polymer solutions reported previously, and with the measurements in linear DNA solutions reported here.
Modeling and Simulation of the Longitudinal Beam Dynamics - RF Station Interaction in the LHC Rings
Mastorides, T; Rivetta, C.; Fox, J.D.; Winkle, D.Van; /SLAC; Baudrenghien, P.; Tuckmantel, J.; /CERN
2008-07-07T23:59:59.000Z
A non-linear time-domain simulation has been developed to study the interaction between longitudinal beam dynamics and RF stations in the LHC rings. The motivation for this tool is to determine optimal LLRF configurations, to study system sensitivity on various parameters, and to define the operational and technology limits. It will be also used to study the effect of RF station noise, impedance, and perturbations on the beam life time and longitudinal emittance. It allows the study of alternative LLRF implementations and control algorithms. The insight and experience gained from our PEP-II simulation is important for this work. In this paper we discuss properties of the simulation tool that will be helpful in analyzing the LHC RF system and its initial results. Partial verification of the model with data taken during the LHC RF station commissioning is presented.
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Vencels, Juris; Delzanno, Gian Luca; Johnson, Alec; Peng, Ivy Bo; Laure, Erwin; Markidis, Stefano
2015-06-01T23:59:59.000Z
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
M. Baratlo; H. Fazli
2009-12-11T23:59:59.000Z
Planar brushes of flexible, semiflexible and rodlike diblock polyampholytes are studied using molecular dynamics simulations and scaling analysis in a wide range of the grafting density. Simulations show linear dependence of the average thickness on the grafting density for all the brushes regardless of their different equilibrium conformations and different flexibility of anchored chains. Slopes of fitted lines to the average thickness of the brushes of semiflexible and rodlike polyampholytes versus the grafting density are approximately the same and differ considerably from that of the brush of flexible chains. The average thickness of the brush of diblock polyampholytes is also obtained as a function of the grafting density using a simple scaling analysis which is in good agreement with the results of our simulations.
Schmidt, W; Niemeyer, J C
2006-01-01T23:59:59.000Z
We present a one-equation subgrid scale model that evolves the turbulence energy corresponding to unresolved velocity fluctuations in large eddy simulations. The model is derived in the context of the Germano consistent decomposition of the hydrodynamical equations. The eddy-viscosity closure for the rate of energy transfer from resolved toward subgrid scales is localised by means of a dynamical procedure for the computation of the closure parameter. Therefore, the subgrid scale model applies to arbitrary flow geometry and evolution. For the treatment of microscopic viscous dissipation a semi-statistical approach is used, and the gradient-diffusion hypothesis is adopted for turbulent transport. A priori tests of the localised eddy-viscosity closure and the gradient-diffusion closure are made by analysing data from direct numerical simulations. As an a posteriori testing case, the large eddy simulation of thermonuclear combustion in forced isotropic turbulence is discussed. We intend the formulation of the sub...
Integrated two-dimensional simulations of dynamic hohlraum driven inertial fusion capsule implosions
Slutz, S. A.; Peterson, K. J.; Vesey, R. A.; Lemke, R. W.; Bailey, J. E.; Varnum, W.; Ruiz, C. L.; Cooper, G. W.; Chandler, G. A.; Rochau, G. A.; Mehlhorn, T. A. [Sandia National Laboratories, Albuquerque, New Mexico 87185-1186 (United States)
2006-10-15T23:59:59.000Z
Simulations have been useful for improving the design of dynamic hohlraums for the purpose of imploding inertial fusion capsules [S. A. Slutz, J. E. Bailey, G. A. Chandler et al., Phys. Plasmas 10, 1875 (2003)]. These design changes, which have resulted in capsule implosions with hot dense cores [J. E. Bailey, G. A. Chandler, S. A. Slutz et al., Phys. Rev. Lett. 92, 085002 (2004)] and the production of thermonuclear neutrons [C. L. Ruiz, G. Cooper, S. A. Slutz et al., Phys. Rev. Lett. 93, 015001 (2005)], were based primarily on a series of one-dimensional numerical simulations, which treated the dynamic hohlraum and the capsule implosion separately. In this paper we present simulations which are fully integrated to include the implosion of wire arrays onto foam convertors, the implosion of the capsule imbedded in the foam, and the absorption of radiation into the electrodes. These simulations yield predictions that are in remarkably good agreement with measured values considering the complexity of the problem, which spans more than 100 ns of wire implosion with the subsequent capsule implosion on a few ns timescale. For example, the predicted neutron yields are less than a factor of 2 higher than the measured values, while the predicted shock velocity is about 30% higher than the measured value. The spectroscopically inferred imploded capsule gas core temperatures are somewhat lower than predicted by the simulations, while the gas densities are about a factor of 2 higher. Simulations indicate that a more slowly rising radiation drive temperature yields higher core densities and lower temperatures and thus better agreement with experimental measurements. Possible reasons for a more slowly rising radiation drive are discussed.
Boutchko, R.
2014-01-01T23:59:59.000Z
emission tomography systems and computational fluid dynamicsa computational ?uid dynamics (CFD) model of the systemthe computational domain. A Cartesian coordinate system was
Computational Fluid Dynamic Analysis of the VHTR Lower Plenum Standard Problem
Richard W. Johnson; Richard R. Schultz
2009-07-01T23:59:59.000Z
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.
Pugliese, Andrea
The role of sex in parasite dynamics: Model simulations on transmission of Heligmosomoides Abstract We investigated possible mechanisms that could cause sex-biased parasite transmission. Two, not mutually exclusive, hypotheses were examined: that sex-bi- ased parasite transmission
Wegner, T.
We evaluate the simulation of polar stratospheric clouds (PSCs) in the Specified Dynamics version of the Whole Atmosphere Community Climate Model for the Antarctic winter 2005. In this model, PSCs are assumed to form ...
Meeks, E.; Chou, C. -P.; Garratt, T.
2013-03-31T23:59:59.000Z
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 high-fidelity kinetics simulation, while maintaining the spatial information derived from the geometrically faithful CFD model. The reduced-order models are generated in such a way that they can be easily imported into a process flowsheet simulator, using the CAPE-OPEN architecture for unit operations. The ENERGICO/CHEMKIN-PRO software produces an ERN-definition file that is read by a dynamically linked library (DLL) that can be easily linked to any CAPE-OPEN compliant software. The plug-in unitoperation module has been successfully demonstrated for complex ERNs of coal gasifiers, using both Aspen Plus and COFE process flowsheet simulators through this published CAPE-OPEN interface.
Pan, Jianjun [University of South Florida, Tampa (USF)] [University of South Florida, Tampa (USF); Cheng, Xiaolin [ORNL] [ORNL; Monticelli, Luca [Institut National de la Santé et de la Recherche Médicale (INSERM) and INTS, France] [Institut National de la Santé et de la Recherche Médicale (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
2014-01-01T23:59:59.000Z
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.
The Effects of Geometry on Flexible Duct CFD Simulations
Ugursal, A.; Culp, C.
Flexible ducts have been widely used in the building industry due to low cost and ease of installation. These ducts can be installed in a wide range of configurations, which creates a challenge for pressure loss calculations. Computational fluid...
Local and chain dynamics in miscible polymer blends: A Monte Carlo simulation study
Jutta Luettmer-Strathmann; Manjeera Mantina
2005-11-07T23:59:59.000Z
Local chain structure and local environment play an important role in the dynamics of polymer chains in miscible blends. In general, the friction coefficients that describe the segmental dynamics of the two components in a blend differ from each other and from those of the pure melts. In this work, we investigate polymer blend dynamics with Monte Carlo simulations of a generalized bond-fluctuation model, where differences in the interaction energies between non-bonded nearest neighbors distinguish the two components of a blend. Simulations employing only local moves and respecting a non-bond crossing condition were carried out for blends with a range of compositions, densities, and chain lengths. The blends investigated here have long-chain dynamics in the crossover region between Rouse and entangled behavior. In order to investigate the scaling of the self-diffusion coefficients, characteristic chain lengths $N_\\mathrm{c}$ are calculated from the packing length of the chains. These are combined with a local mobility $\\mu$ determined from the acceptance rate and the effective bond length to yield characteristic self-diffusion coefficients $D_\\mathrm{c}=\\mu/N_\\mathrm{c}$. We find that the data for both melts and blends collapse onto a common line in a graph of reduced diffusion coefficients $D/D_\\mathrm{c}$ as a function of reduced chain length $N/N_\\mathrm{c}$. The composition dependence of dynamic properties is investigated in detail for melts and blends with chains of length twenty at three different densities. For these blends, we calculate friction coefficients from the local mobilities and consider their composition and pressure dependence. The friction coefficients determined in this way show many of the characteristics observed in experiments on miscible blends.
Modeling, simulation, and testing of the mechanical dynamics of and RF MEMS switch.
Sumali, Hartono; Epp, David S.; Massad, Jordan Elias; Dyck, Christopher William; Starr, Michael James
2005-07-01T23:59:59.000Z
Mechanical dynamics can be a determining factor for the switching speed of radio-frequency microelectromechanical systems (RF MEMS) switches. This paper presents the simulation of the mechanical motion of a microswitch under actuation. The switch has a plate suspended by springs. When an electrostatic actuation is applied, the plate moves toward the substrate and closes the switch. Simulations are calculated via a high-fidelity finite element model that couples solid dynamics with electrostatic actuation. It incorporates non-linear coupled dynamics and accommodates fabrication variations. Experimental modal analysis gives results in the frequency domain that verifies the natural frequencies and mode shapes predicted by the model. An effective 1D model is created and used to calculate an actuation voltage waveform that minimizes switch velocity at closure. In the experiment, the switch is actuated with this actuation voltage, and the displacements of the switch at various points are measured using a laser Doppler velocimeter through a microscope. The experiments are repeated on several switches from different batches. The experimental results verify the model.
Interfacial water on crystalline silica: A comparative molecular dynamics simulation study
Ho, Tuan A. [University of Oklahoma, Norman; Argyris, D. [University of Oklahoma, Norman; Cole, David [Ohio State University; Striolo, Alberto [Oklahoma University
2011-01-01T23:59:59.000Z
All-atom molecular dynamics simulations were conducted to study the dynamics of aqueous electrolyte solutions confined in slit-shaped silica nanopores of various degrees of protonation. Five degrees of protonation were prepared by randomly removing surface hydrogen atoms from fully protonated crystalline silica surfaces. Aqueous electrolyte solutions containing NaCl or CsCl salt were simulated at ambient conditions. In all cases, the ionic concentration was 1 M. The results were quantified in terms of atomic density distributions within the pores, and the self-diffusion coefficient along the direction parallel to the pore surface. We found evidence for ion-specific properties that depend on ion surface, water ion, and only in some cases ion ion correlations. The degree of protonation strongly affects the structure, distribution, and the dynamic behavior of confined water and electrolytes. Cl ions adsorb on the surface at large degrees of protonation, and their behavior does not depend significantly on the cation type (either Na+ or Cs+ ions are present in the systems considered). The cations show significant ion-specific behavior. Na+ ions occupy different positions within the pore as the degree of protonation changes, while Cs+ ions mainly remain near the pore center at all conditions considered. For a given degree of protonation, the planar self-diffusion coefficient of Cs+ is always greater than that of Na+ ions. The results are useful for better understanding transport under confinement, including brine behavior in the subsurface, with important applications such as environmental remediation.
Sewell, T. D. (Thomas D.); Gan, C. K. (Chee Kwan); Jaramillo, E. (Eugenio); Strachan, A. H. (Alejandro H.)
2004-01-01T23:59:59.000Z
We are using classical molecular dynamics and condensed phase electronic-structure methods to predict some of the thermophysical and mechanical properties that are needed as input to realistic mesoscale models for plastic-bonded explosives. The main materials studied to date are HMX, PETN, Estane copolymer, and bi(2,2-dinitropropyl) formal/acetal (BDNPF/A). Emphasis is placed on non-reactive properties and thermodynamic states relevant to cookoff and shock initiation phenomena. Both crystal and liquid-state properties are of interest. Typical simulation sizes and times are {approx}10{sup 2} molecules and 2-10 ns, respectively. The overarching goal is to develop internally consistent model thermodynamic and elastic mechanical descriptions for the materials. Prioritization among the set of properties amenable to atomistic simulation is made based on ongoing interactions with mesoscale modelers at Los Alamos and elsewhere. Recent work will be summarized and our view of profitable directions for future research will be discussed, including preliminary results for large-scale molecular dynamics simulations of shock response of crystalline HMX.
Shugo Yasuda; Ryoichi Yamamoto
2014-07-16T23:59:59.000Z
The synchronized molecular dynamics simulation via macroscopic heat and momentum transfer is proposed for the non-isothermal flow behaviors of complex fluids. In this method, the molecular dynamics simulations are assigned to small fluid elements to calculate the local stresses and temperatures and are synchronized at certain time intervals to satisfy the macroscopic heat- and momentum- transport equations. This method is applied to the lubrication of a polymeric liquid composed of short chains with ten beads between parallel plates. The rheological properties and conformation of polymer chains coupled with the local viscous heating are investigated with a non-dimensional parameter, i.e., the Nahme-Griffith number, which is defined by the ratio of the viscous heating to the thermal conduction at the characteristic temperature required to sufficiently change the viscosity. The present simulation demonstrates that strong shear thinning and transitional behavior of the conformation of the polymer chains occur with a rapid temperature rise when the Nahme-Griffith number exceeds unity. The results also clarify that the reentrant transition of the linear stress-optical relation occurs for large shear stresses due to the coupling of the conformation of polymer chains and heat generation under shear flows.
Spin dynamics simulation of electron spin relaxation in Ni{sup 2+}(aq)
Rantaharju, Jyrki, E-mail: jjrantaharju@gmail.com; Mareš, Ji?í, E-mail: jiri.mares@oulu.fi; Vaara, Juha, E-mail: juha.vaara@iki.fi [NMR Research Group, Department of Physics, University of Oulu, P.O. Box 3000, Oulu, FIN-90014 (Finland)
2014-07-07T23:59:59.000Z
The ability to quantitatively predict and analyze the rate of electron spin relaxation of open-shell systems is important for electron paramagnetic resonance and paramagnetic nuclear magnetic resonance spectroscopies. We present a combined molecular dynamics (MD), quantum chemistry (QC), and spin dynamics simulation method for calculating such spin relaxation rates. The method is based on the sampling of a MD trajectory by QC calculations, to produce instantaneous parameters of the spin Hamiltonian used, in turn, to numerically solve the Liouville-von Neumann equation for the time evolution of the spin density matrix. We demonstrate the approach by simulating the relaxation of electron spin in an aqueous solution of Ni{sup 2+} ion. The spin-lattice (T{sub 1}) and spin-spin (T{sub 2}) relaxation rates are extracted directly from the simulations of the time dependence of the longitudinal and transverse magnetization, respectively. Good agreement with the available, indirectly obtained experimental data is obtained by our method.
Dynamics of the terrestrial planets from a large number of N-body simulations"! Rebecca A. Fischer1,
! 1 Dynamics of the terrestrial planets from a large number of N-body simulations"! #! Rebecca A and planetesimals was the final stage of""! terrestrial planet formation. This process is modeled using N of planetary#&! accretion as particular accretion pathways may be representative of a given dynamic#'! scenario
Diffusion of a Janus nanoparticle in an explicit solvent: A molecular dynamics simulation study
Ali Kharazmi; Nikolai V. Priezjev
2015-05-14T23:59:59.000Z
Molecular dynamics simulations are carried out to study the translational and rotational diffusion of a single Janus particle immersed in a dense Lennard-Jones fluid. We consider a spherical particle with two hemispheres of different wettability. The analysis of the particle dynamics is based on the time-dependent orientation tensor, particle displacement, as well as the translational and angular velocity autocorrelation functions. It was found that both translational and rotational diffusion coefficients increase with decreasing surface energy at the nonwetting hemisphere, provided that the wettability of the other hemisphere remains unchanged. We also observed that in contrast to homogeneous particles, the nonwetting hemisphere of the Janus particle tends to rotate in the direction of the displacement vector during the rotational relaxation time.
Spin-lattice dynamics simulation of external field effect on magnetic order of ferromagnetic iron
Chui, C. P. [Department of Electronic and Information Engineering, the Hong Kong Polytechnic University (Hong Kong)] [Department of Electronic and Information Engineering, the Hong Kong Polytechnic University (Hong Kong); Zhou, Yan, E-mail: yanzhou@hku.hk [Department of Physics, the University of Hong Kong (Hong Kong)] [Department of Physics, the University of Hong Kong (Hong Kong)
2014-03-15T23:59:59.000Z
Modeling of field-induced magnetization in ferromagnetic materials has been an active topic in the last dozen years, yet a dynamic treatment of distance-dependent exchange integral has been lacking. In view of that, we employ spin-lattice dynamics (SLD) simulations to study the external field effect on magnetic order of ferromagnetic iron. Our results show that an external field can increase the inflection point of the temperature. Also the model provides a better description of the effect of spin correlation in response to an external field than the mean-field theory. An external field has a more prominent effect on the long range magnetic order than on the short range counterpart. Furthermore, an external field allows the magnon dispersion curves and the uniform precession modes to exhibit magnetic order variation from their temperature dependence.
Calculation technique for simulation of wave and fracture dynamics in a reinforced sheet
M. Ayzenberg-Stepanenko; Z. Yanovitsky; G. Osharovich
2012-03-08T23:59:59.000Z
Mathematical models and computer algorithms are developed to calculate dynamic stress concentration and fracture wave propagation in a reinforced composite sheet. The composite consists of a regular system alternating extensible fibers and pliable adhesive layers. In computer simulations, we derive difference algorithms preventing or minimizing the parasite distortions caused by the mesh dispersion and obtain precise numerical solutions in the plane fracture problem of a pre-stretched sheet along the fibers. Interactive effects of microscale dynamic deformation and multiple damage in fibers and adhesive are studied. Two engineering models of the composite are considered: the first assumes that adhesive can be represented by inertionless bonds of constant stiffness, while in the second one an adhesive is described by inertial medium perceived shear stresses. Comparison of results allows the evaluation of facilities of models in wave and fracture patterns analysis.
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Tringe, J. W.; Ileri, N.; Levie, H. W.; Stroeve, P.; Ustach, V.; Faller, R.; Renaud, P.
2015-08-01T23:59:59.000Z
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
Entropic measure to prevent energy over-minimization in molecular dynamics simulations
Rydzewski, Jakub; Nowak, Wieslaw
2015-01-01T23:59:59.000Z
Geometry optimization via energy minimization is one of the most common steps in computer modelling of biological structures. Nowadays computer power encourage numerous researches to use conjugated gradient minimizations exceeding 1000 steps. However, our research reveals that such over-minimization may lead to thermodynamically unstable conformations. We show that these conformations are not optimum starting points for equilibrium molecular dynamics simulations. We propose a measure based on the Pareto front of total entropy for quality assessment of minimized protein which warrants a proper selection of minimization steps.
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
2007-09-01T23:59:59.000Z
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.
Cooling Energy Demand Evaluation by Meansof Regression Models Obtained From Dynamic Simulations
Catalina, T.; Virgone, J.
2011-01-01T23:59:59.000Z
was calculated to be -8.78oC (Moscow in January) and maximum of 42.9 oC (Abu-Dhabi in August). The hourly values of outdoor air temperature and solar radiation were obtained using Trnsys (Trnsys, 2006) meteonorm files. b) Glazing surface and distribution... the ,,black-box,, function, dynamic simulations were conducted using Trnsys 16 software (Trnsys, 2005). The Trnsys building model, known as, Type 56, is compliant with general requirements of European Directive on the energy performance of buildings...
Simulation of the relativistic electron dynamics and acceleration in a linearly-chirped laser pulse
Jisrawi, Najeh M; Salamin, Yousef I
2014-01-01T23:59:59.000Z
Theoretical investigations are presented, and their results are discussed, of the laser acceleration of a single electron by a chirped pulse. Fields of the pulse are modeled by simple plane-wave oscillations and a $\\cos^2$ envelope. The dynamics emerge from analytic and numerical solutions to the relativistic Lorentz-Newton equations of motion of the electron in the fields of the pulse. All simulations have been carried out by independent Mathematica and Python codes, with identical results. Configurations of acceleration from a position of rest as well as from injection, axially and sideways, at initial relativistic speeds are studied.
Mesoscale simulation of semiflexible chains. I. Endpoint distribution and chain dynamics
Robert D. Groot
2013-06-06T23:59:59.000Z
The endpoint distribution and dynamics of semiflexible fibers is studied by numerical simulation. A brief overview is given over the analytical theory of flexible and semiflexible polymers. In particular, a closed expression is given for the relaxation spectrum of wormlike chains, which determines polymer diffusion and rheology. Next a simulation model for wormlike chains with full hydrodynamic interaction is described, and relations for the bending and torsion modulus are given. Two methods are introduced to include torsion stiffness into the model. The model is validated by simulating single chains in a heat bath, and comparing the endpoint distribution of the chains with established Monte Carlo results. It is concluded that torsion stiffness leads to a slightly shorter effective persistence length for a given bending stiffness. To further validate the simulation model, polymer diffusion is studied for fixed persistence length and varying polymer length N. The diffusion constant shows crossover from Rouse to reptation behaviour. The terminal relaxation time obtained from the monomer displacement is consistent with the theory of wormlike chains. The probability for chain crossing has also been studied. This probability is so low that it does not influence the present results.
Tyler N. Shendruk; Martin Bertrand; James L. Harden; Gary W. Slater; Hendrick W. de Haan
2014-08-01T23:59:59.000Z
Given the ubiquity of depletion effects in biological and other soft matter systems, it is desirable to have coarse-grained Molecular Dynamics simulation approaches appropriate for the study of complex systems. This paper examines the use of two common truncated Lennard-Jones (WCA) potentials to describe a pair of colloidal particles in a thermal bath of depletants. The shifted-WCA model is the steeper of the two repulsive potentials considered, while the combinatorial-WCA model is the softer. It is found that the depletion-induced well depth for the combinatorial-WCA model is significantly deeper than the shifted-WCA model because the resulting overlap of the colloids yields extra accessible volume for depletants. For both shifted- and combinatorial-WCA simulations, the second virial coefficients and pair potentials between colloids are demonstrated to be well approximated by the Morphometric Thermodynamics (MT) model. This agreement suggests that the presence of depletants can be accurately modelled in MD simulations by implicitly including them through simple, analytical MT forms for depletion-induced interactions. Although both WCA potentials are found to be effective generic coarse-grained simulation approaches for studying depletion effects in complicated soft matter systems, combinatorial-WCA is the more efficient approach as depletion effects are enhanced at lower depletant densities. The findings indicate that for soft matter systems that are better modelled by potentials with some compressibility, predictions from hard-sphere systems could greatly underestimate the magnitude of depletion effects at a given depletant density.
W. Schmidt; J. C. Niemeyer; W. Hillebrandt
2006-01-23T23:59:59.000Z
We present a one-equation subgrid scale model that evolves the turbulence energy corresponding to unresolved velocity fluctuations in large eddy simulations. The model is derived in the context of the Germano consistent decomposition of the hydrodynamical equations. The eddy-viscosity closure for the rate of energy transfer from resolved toward subgrid scales is localised by means of a dynamical procedure for the computation of the closure parameter. Therefore, the subgrid scale model applies to arbitrary flow geometry and evolution. For the treatment of microscopic viscous dissipation a semi-statistical approach is used, and the gradient-diffusion hypothesis is adopted for turbulent transport. A priori tests of the localised eddy-viscosity closure and the gradient-diffusion closure are made by analysing data from direct numerical simulations. As an a posteriori testing case, the large eddy simulation of thermonuclear combustion in forced isotropic turbulence is discussed. We intend the formulation of the subgrid scale model in this paper as a basis for more advanced applications in numerical simulations of complex astrophysical phenomena involving turbulence.
Leishear, R.; Poirier, M.; Lee, S.; Fowley, M.
2012-06-26T23:59:59.000Z
This paper documents testing methods, statistical data analysis, and a comparison of experimental results to CFD models for blending of fluids, which were blended using a single pump designed with dual opposing nozzles in an eight foot diameter tank. Overall, this research presents new findings in the field of mixing research. Specifically, blending processes were clearly shown to have random, chaotic effects, where possible causal factors such as turbulence, pump fluctuations, and eddies required future evaluation. CFD models were shown to provide reasonable estimates for the average blending times, but large variations -- or scatter -- occurred for blending times during similar tests. Using this experimental blending time data, the chaotic nature of blending was demonstrated and the variability of blending times with respect to average blending times were shown to increase with system complexity. Prior to this research, the variation in blending times caused discrepancies between CFD models and experiments. This research addressed this discrepancy, and determined statistical correction factors that can be applied to CFD models, and thereby quantified techniques to permit the application of CFD models to complex systems, such as blending. These blending time correction factors for CFD models are comparable to safety factors used in structural design, and compensate variability that cannot be theoretically calculated. To determine these correction factors, research was performed to investigate blending, using a pump with dual opposing jets which re-circulate fluids in the tank to promote blending when fluids are added to the tank. 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 vertical cooling coils below the liquid surface for a full scale, liquid radioactive waste storage tank. Also, different jet 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.
Gustavsen, Arlid
2008-01-01T23:59:59.000Z
be used to calculate radiation heat transfer. The convectionat about 5×10 -10 ). Radiation heat transfer was included inof rays in the radiation heat-transfer algorithm of the CFD
Schobeiri, M.T.; Attia, M.; Lippke, C. (Texas A and M Univ., College Station, TX (United States). Dept. of Mechanical Engineering)
1994-07-01T23:59:59.000Z
The design concept, the theoretical background essential for the development of the modularly structured simulation code GETRAN, and several critical simulation cases are presented in this paper. The code being developed under contract with NASA Lewis Research Center is capable of simulating the nonlinear dynamic behavior of single- and multispool core engines, turbofan engines, and power generation gas turbine engines under adverse dynamic operating conditions. The modules implemented into GETRAN correspond to components of existing and new-generation aero- and stationary gas turbine engines with arbitrary configuration and arrangement. For precise simulation of turbine and compressor components, row-by-row diabatic and adiabatic calculation procedures are implemented that account for the specific turbine and compressor cascade, blade geometry, and characteristics. The nonlinear, dynamic behavior of the subject engine is calculated solving a number of systems of partial differential equations, which describe the unsteady behavior of each component individually. To identify each differential equation system unambiguously, special attention is paid to the addressing of each component. The code is capable of executing the simulation procedure at four levels, which increase with the degree of complexity of the system and dynamic event. As representative simulations, four different transient cases with single- and multispool thrust and power generation engines were simulated. These transient cases vary from throttling the exit nozzle area, operation with fuel schedule, rotor speed control, to rotating stall and surge.
Coarse-grained simulations of vortex dynamics and transition in complex high-Re flows
Grinstein, Fernando F [Los Alamos National Laboratory
2011-01-21T23:59:59.000Z
Turbulent flow complexity in applications in engineering, geophysics and astrophysics typically requires achieving accurate and dependable large scale predictions of highly nonlinear processes with under-resolved computer simulation models. Laboratory observations typically demonstrate the end outcome of complex non-linear three-dimensional physical processes with many unexplained details and mechanisms. Carefully controlled computational experiments based on the numerical solution of the conservation equations for mass, momentum, and energy, provide insights into the underlying flow dynamics. Relevant computational fluid dynamics issues to be addressed relate to the modeling of the unresolved tlow conditions at the subgrid scale (SGS) level - within a computational cell, and at the supergrid (SPG) scale - at initialization and beyond computational boundaries. SGS and SPG information must be prescribed for closure of the equations solved numerically. SGS models appear explicitly or implicitly as additional source tenns in the modified flow equations solved by the numerical solutions being calculated, while SPG models provide the necessary set of initial and boundary conditions that must be prescribed to ensure unique well-posed solutions. From this perspective, it is clear that the simulation process is inherently determined by the SGS and SPG information prescription process. On the other hand, observables in laboratory experiments are always characterized by the finite scales of the instrumental resolution of measuring/visualizing devices, and subject as well to SPG issues. It is thus important to recognize the inherently intrusive nature of observations based on numerical or laboratory experiments. Ultimately, verification and validation (V & V) frameworks and appropriate metrics for the specific problems at hand are needed to establish predictability of the simulation model. Direct numerical simulation (DNS) - resolving all relevant space/time scales, is prohibitively expensive in the foreseeable future for most practical flows of interest at moderate-to-high Reynolds number (Re). On the other end of the simulation spectrum are the Reynolds-Averaged Navier-Stokes (RANS) approaches - which model the turbulent effects. In the coarsegrained large eddy simulation (LES) strategies, the large energy containing structures are resolved, the smaller structures are filtered out, and unresolved SGS effects are modeled. By necessity - rather than choice, LES effectively becomes the intermediate approach between DNS and RANS. Extensive work has demonstrated that predictive simulations of turbulent velocity fields are possible using a particular LES denoted implicit LES (ILES), using the class of nonoscillatory finite-volume (NFV) numerical algorithms. Use of the modified equation as framework for theoretical analysis, demonstrates that leading truncation tenns associated with NFV methods provide implicit SGS models of mixed anisotropic type and regularized motion of discrete observables. Tests in fundamental applications ranging from canonical to very complex flows indicate that ILES is competitive with conventional LES in the LES realm proper - flows driven by large scale features. High-Re flows are vortex dominated and governed by short convective timescales compared to those of diffusion, and kinematically characterized at the smallest scales by slender worm vortices with insignificant internal structure. This motivates nominally inviscid ILES methods capable of capturing the high-Re dissipation dynamics and of handling vortices as shocks in shock capturing schemes. Depending on flow regimes, initial conditions, and resolution, additional modeling may be needed to emulate SGS driven physics, such as backscatter, chemical reaction, material mixing, and near-wall flow-dynamics - where typically-intertwined SGS/SPG issues need to be addressed. A major research focus is recognizing when additional explicit models and/or numerical treatments are needed and ensuring that mixed explicit and implicit SGS models can effectively act in
Herbordt, Martin
2005-01-01T23:59:59.000Z
(2005) 1 ACCELERATING MOLECULAR DYNAMICS SIMULATIONS WITH CONFIGURABLE CIRCUITS Yongfeng Gu Tom Van-space parameter for MD practitioners. 2. MOLECULAR DYNAMICS OVERVIEW Molecular Dynamics simulations generallyCourt Martin C. Herbordt Department of Electrical and Computer Engineering Boston University, Boston, MA 02215
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)
2014-09-07T23:59:59.000Z
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.
A model of lipid-free Apolipoprotein A-I revealed by iterative molecular dynamics simulation
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Zhang, Xing; Lei, Dongsheng; Zhang, Lei; Rames, Matthew; Zhang, Shengli
2015-03-20T23:59:59.000Z
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
Molecular dynamics simulation: a tool for exploration and discovery using simple models
D. C. Rapaport
2014-11-13T23:59:59.000Z
Emergent phenomena share the fascinating property of not being obvious consequences of the design of the system in which they appear. This characteristic is no less relevant when attempting to simulate such phenomena, given that the outcome is not always a foregone conclusion. The present survey focuses on several simple model systems that exhibit surprisingly rich emergent behavior, all studied by MD simulation. The examples are taken from the disparate fields of fluid dynamics, granular matter and supramolecular self-assembly. In studies of fluids modeled at the detailed microscopic level using discrete particles, the simulations demonstrate that complex hydrodynamic phenomena in rotating and convecting fluids, the Taylor-Couette and Rayleigh-B\\'enard instabilities, can not only be observed within the limited length and time scales accessible to MD, but even quantitative agreement can be achieved. Simulation of highly counterintuitive segregation phenomena in granular mixtures, again using MD methods, but now augmented by forces producing damping and friction, leads to results that resemble experimentally observed axial and radial segregation in the case of a rotating cylinder, and to a novel form of horizontal segregation in a vertically vibrated layer. Finally, when modeling self-assembly processes analogous to the formation of the polyhedral shells that package spherical viruses, simulation of suitably shaped particles reveals the ability to produce complete, error-free assembly, and leads to the important general observation that reversible growth steps contribute to the high yield. While there are limitations to the MD approach, both computational and conceptual, the results offer a tantalizing hint of the kinds of phenomena that can be explored, and what might be discovered when sufficient resources are brought to bear on a problem.
Closser, Kristina D.; Head-Gordon, Martin, E-mail: mhg@cchem.berkeley.edu [Department of Chemistry, University of California Berkeley, Berkeley, California 94720 (United States) [Department of Chemistry, University of California Berkeley, Berkeley, California 94720 (United States); Ultrafast X-Ray Science Laboratory, Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Gessner, Oliver [Ultrafast X-Ray Science Laboratory, Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)] [Ultrafast X-Ray Science Laboratory, Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)
2014-04-07T23:59:59.000Z
The dynamics resulting from electronic excitations of helium clusters were explored using ab initio molecular dynamics. The simulations were performed with configuration interaction singles and adiabatic classical dynamics coupled to a state-following algorithm. 100 different configurations of He{sub 7} were excited into the 2s and 2p manifold for a total of 2800 trajectories. While the most common outcome (90%) was complete fragmentation to 6 ground state atoms and 1 excited state atom, 3% of trajectories yielded bound, He {sub 2}{sup *}, and <0.5% yielded an excited helium trimer. The nature of the dynamics, kinetic energy release, and connections to experiments are discussed.
Hiroyuki Sato; Richard Johnson; Richard Schultz
2009-09-01T23:59:59.000Z
Three dimensional computational fluid dynamic (CFD) calculations of a typical prismatic very high temperature gas-cooled reactor (VHTR) were conducted to investigate the influence of gap geometry on flow and temperature distributions in the reactor core using commercial CFD code FLUENT. Parametric calculations changing the gap width in a whole core length model of fuel and reflector columns were performed. The simulations show the effects of core by-pass flows in the heated core region by comparing results for several gap widths including zero gap width. The calculation results underline the importance of considering inter-column gap width for the evaluation of maximum fuel temperatures and temperature gradients in fuel blocks. In addition, it is shown that temperatures of core outlet flow from gaps and channels are strongly affected by the gap width of by-pass flow in the reactor core.
Trueba, Alondra Torres [Steacie Institute for Molecular Sciences, National Research Council Canada, Ottawa, Ontario, K1A 0R6 (Canada); Eindhoven University of Technology, Department of Chemical Engineering and Chemistry, Separation Technology Group, Den Dolech 2, 5612 AZ Eindhoven (Netherlands); Kroon, Maaike C. [Eindhoven University of Technology, Department of Chemical Engineering and Chemistry, Separation Technology Group, Den Dolech 2, 5612 AZ Eindhoven (Netherlands); Peters, Cor J. [Eindhoven University of Technology, Department of Chemical Engineering and Chemistry, Separation Technology Group, Den Dolech 2, 5612 AZ Eindhoven (Netherlands); The Petroleum Institute, Chemical Engineering Department, P. O. Box 2533, Abu Dhabi (United Arab Emirates); Moudrakovski, Igor L.; Ratcliffe, Christopher I.; Ripmeester, John A., E-mail: John.Ripmeester@nrc-cnrc.gc.ca [Steacie Institute for Molecular Sciences, National Research Council Canada, Ottawa, Ontario, K1A 0R6 (Canada); Alavi, Saman [Steacie Institute for Molecular Sciences, National Research Council Canada, Ottawa, Ontario, K1A 0R6 (Canada); Department of Chemistry, University of Ottawa, Ottawa, Ontario K1N 6N5 (Canada)
2014-06-07T23:59:59.000Z
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.
PIV Uncertainty Methodologies for CFD Code Validation at the MIR Facility
Piyush Sabharwall; Richard Skifton; Carl Stoots; Eung Soo Kim; Thomas Conder
2013-12-01T23:59:59.000Z
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.
V European Conference on Computational Fluid Dynamics ECCOMAS CFD 2010
Abgrall, RÃ©mi
QUANTIFICATION OF SHOCKED FLOWS, COMPARISON WITH A NON-INTRUSIVE POLYNOMIAL CHAOS METHOD R. Abgrall , P) in the context of compressible inviscid flows. More specifically, we aim at comparing a well documented non-intrusive in some details the method recently proposed in [1]; Section 3 reviews the non-intrusive Polynomial Chaos
V European Conference on Computational Fluid Dynamics ECCOMAS CFD 2010
Paris-Sud XI, Université de
QUANTIFICATION OF SHOCKED FLOWS, COMPARISON WITH A NON-INTRUSIVE POLYNOMIAL CHAOS METHOD R. Abgrall , P) in the context of compressible inviscid flows. More specifically, we aim at comparing a well documented non-intrusive proposed in [?]; Section 3 reviews the non-intrusive Polynomial Chaos approach also employed in this study
Gnie mcanique Using the NSMB CFD solver to Compute Dynamic
Lausanne, Ecole Polytechnique Fédérale de
Sylvain Gallay Supervisors Dr. Mark Sawley Acknowledgements Dr. Mark Sawley Dr Jan B. Vos Dr. Mark Sawley
Dynamic simulations of geologic materials using combined FEM/DEM/SPH analysis
Morris, J P; Johnson, S M
2008-03-26T23:59:59.000Z
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. [Politecnico di Milano, Dept. of Energy, CeSNEF-Nuclear Engineering Div., via Ponzio 34/3, 20133 Milano (Italy)
2012-07-01T23:59:59.000Z
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)
Rich, Sarah Celeste
2008-01-01T23:59:59.000Z
Molecular dynamics simulations of the ceramic compound zirconolite (CaZrTi?O?), a potential crystalline wasteform host for plutonium, were carried out for ideal and experimental crystalline forms and a simulated molten ...
Kim, Chansoo, S.M. Massachusetts Institute of Technology
2008-01-01T23:59:59.000Z
A series of Molecular Dynamics (MD) simulations using the GROMACS® package has been performed in this thesis. It is used to mimic and simulate the hydration water in Lysozyme with three different hydration levels (h = 0.3, ...
Fenter, Paul; Kerisit, Sebastien N.; Raiteri, Paolo; Gale, Julian D.
2013-04-01T23:59:59.000Z
New insights into the structure of the calcite-water interface are obtained through direct model-independent comparison of multiple classical molecular dynamics (MD) simulations with high-resolution specular X-ray reflectivity (XR) data. This set of comparisons, with four different state-of-the-art force fields (including two non-polarizable, one polarizable, and one reactive force field), reveal new insights into the absolute accuracy of the simulated structures and the uniqueness of the XR-derived structural results. These four simulations, while qualitatively similar, have visibly distinct interfacial structure, and are distinguished through a quantitative comparison of the XR signals calculated from these simulations with experimental XR data. The results demonstrate that the simulated calcite-water interface structures, as a whole, are not consistent with the XR data (i.e., within their precision and accuracy). This disagreement is largely due to the simulation of the calcite lattice. The simulated interfacial water profiles show substantially different levels of agreement with the XR data. Of these, the rigid-ion model (RIM) simulations show the best consistency with the experimental XR data. Further model-dependent comparisons of the structural parameters that describe the interfacial structure (derived from both the MD simulations and the XR data) provide further insight into the sources of differences between these two approaches. Using the new insights from the RIM simulations, new structures of the calcite-water interface consistent with both the experimental data and the simulation are identified and compared to recent results.
National Ignition Facility computational fluid dynamics modeling and light fixture case studies
Martin, R.; Bernardin, J.; Parietti, L.; Dennison, B.
1998-02-01T23:59:59.000Z
This report serves as a guide to the use of computational fluid dynamics (CFD) as a design tool for the National Ignition Facility (NIF) program Title I and Title II design phases at Lawrence Livermore National Laboratory. In particular, this report provides general guidelines on the technical approach to performing and interpreting any and all CFD calculations. In addition, a complete CFD analysis is presented to illustrate these guidelines on a NIF-related thermal problem.
Kim, Junghan; Iype, Eldhose; Frijns, Arjan J.H.; Nedea, Silvia V.; Steenhoven, Anton A. van
2014-07-01T23:59:59.000Z
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 fluid–solid interface for a long time. In this work, the conceptual idea of Steele's potential was extended in order to simulate water–silicon and water–silica 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 silicon–water contact angle of 129°, a quartz–water contact angle of 0°, and a cristobalite–water contact angle of 40°, which are in reasonable agreement with experimental values.
Guallar, V.; Batista, V.S.; Miller, W.H. [Department of Chemistry, University of California, and Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)] [Department of Chemistry, University of California, and Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)
1999-05-01T23:59:59.000Z
An {ital ab initio} excited state potential energy surface is constructed for describing excited state double proton transfer in the tautomerization reaction of photo-excited 7-azaindole dimers, and the ultrafast dynamics is simulated using the semiclassical (SC) initial value representation (IVR). The potential energy surface, determined in a reduced dimensionality, is obtained at the CIS level of quantum chemistry, and an approximate version of the SC-IVR approach is introduced which scales {ital linearly} with the number of degrees of freedom of the molecular system. The accuracy of this approximate SC-IVR approach is verified by comparing our semiclassical results with full quantum mechanical calculations. We find that proton transfer usually occurs during the first intermonomer symmetric-stretch vibration, about 100 fs after photoexcitation of the system, and produces an initial 15 percent population decay of the reactant base-pair, which is significantly reduced by isotopic substitution. {copyright} {ital 1999 American Institute of Physics.} thinsp
Molecular dynamics simulations of grain boundary thermal resistance in UO2
Tianyi Chen; Di Chen; Bulent H. Sencer; Lin Shao
2014-09-01T23:59:59.000Z
By means of molecular dynamics (MD) simulations, we have calculated Kaptiza resistance of UO2 with or without radiation damage. For coincident site lattice boundaries of different configurations, the boundary thermal resistance of unirradiated UO2 can be well described by a parameter-reduced formula by using boundary energies as variables. We extended the study to defect-loaded UO2 by introducing damage cascades in close vicinity to the boundaries. Following cascade annealing and defect migrations towards grain boundaries, the boundary energy increases and so does Kaptiza resistance. The correlations between these two still follow the same formula extracted from the unirradiated UO2. The finding will benefit multi-scale modeling of UO2 thermal properties under extreme radiation conditions by combining effects from boundary configurations and damage levels.
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
2008-06-01T23:59:59.000Z
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
2008-08-01T23:59:59.000Z
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.
M. Baratlo; H. Fazli
2009-03-15T23:59:59.000Z
Planar brushes formed by end-grafted semiflexible polyampholyte chains, each chain containing equal number of positively and negatively charged monomers is studied using molecular dynamics simulations. Keeping the length of the chains fixed, dependence of the average brush thickness and equilibrium statistics of the brush conformations on the grafting density and the salt concentration are obtained with various sequences of charged monomers. When similarly charged monomers of the chains are arranged in longer blocks, the average brush thickness is smaller and dependence of brush properties on the grafting density and the salt concentration is stronger. With such long blocks of similarly charged monomers, the anchored chains bond to each other in the vicinity of the grafting surface at low grafting densities and buckle toward the grafting surface at high grafting densities.
Yasuda, Shugo
2015-01-01T23:59:59.000Z
The Synchronized Molecular-Dynamics simulation which was recently proposed by authors [Phys. Rev. X {\\bf 4}, 041011 (2014)] is applied to the analysis of polymer lubrication between parallel plates. The rheological properties, conformational change of polymer chains, and temperature rise due to the viscous heating are investigated with changing the values of thermal conductivity of the polymeric liquid. It is found that at a small applied shear stress on the plate, the temperature of polymeric liquid only slightly increases in inverse proportion to the thermal conductivity and the apparent viscosity of polymeric liquid is not much affected by changing the thermal conductivity. However, at a large shear stress, the transitional behaviors of the polymeric liquid occur due to the interplay of the shear deformation and viscous heating by changing the thermal conductivity. This transition is characterized by the Nahme-Griffith number $Na$ which is defined as the ratio of the viscous heating to the thermal conducti...
Tang, Yu-Hang
2013-01-01T23:59:59.000Z
We present a scalable dissipative particle dynamics simulation code, fully implemented on the Graphics Processing Units (GPUs) using a hybrid CUDA/MPI programming model, which achieves 10-30 times speedup on a single GPU over 16 CPU cores and almost linear weak scaling across a thousand nodes. A unified framework is developed within which the efficient generation of the neighbor list and maintaining particle data locality are addressed. Our algorithm generates strictly ordered neighbor lists in parallel, while the construction is deterministic and makes no use of atomic operations or sorting. Such neighbor list leads to optimal data loading efficiency when combined with a two-level particle reordering scheme. A faster in situ generation scheme for Gaussian random numbers is proposed using precomputed binary signatures. We designed custom transcendental functions that are fast and accurate for evaluating the pairwise interaction. The correctness and accuracy of the code is verified through a set of test cases ...
Molecular dynamics simulations of oscillatory Couette flows with slip boundary conditions
Priezjev, Nikolai V
2012-01-01T23:59:59.000Z
The effect of interfacial slip on steady-state and time-periodic flows of monatomic liquids is investigated using non-equilibrium molecular dynamics simulations. The fluid phase is confined between atomically smooth rigid walls, and the fluid flows are induced by moving one of the walls. In steady shear flows, the slip length increases almost linearly with shear rate. We found that the velocity profiles in oscillatory flows are well described by the Stokes flow solution with the slip length that depends on the local shear rate. Interestingly, the rate dependence of the slip length obtained in steady shear flows is recovered when the slip length in oscillatory flows is plotted as a function of the local shear rate magnitude. For both types of flows, the friction coefficient at the liquid-solid interface correlates well with the structure of the first fluid layer near the solid wall.
Molecular dynamics simulations of oscillatory Couette flows with slip boundary conditions
Nikolai V. Priezjev
2012-08-27T23:59:59.000Z
The effect of interfacial slip on steady-state and time-periodic flows of monatomic liquids is investigated using non-equilibrium molecular dynamics simulations. The fluid phase is confined between atomically smooth rigid walls, and the fluid flows are induced by moving one of the walls. In steady shear flows, the slip length increases almost linearly with shear rate. We found that the velocity profiles in oscillatory flows are well described by the Stokes flow solution with the slip length that depends on the local shear rate. Interestingly, the rate dependence of the slip length obtained in steady shear flows is recovered when the slip length in oscillatory flows is plotted as a function of the local shear rate magnitude. For both types of flows, the friction coefficient at the liquid-solid interface correlates well with the structure of the first fluid layer near the solid wall.
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Zhang, Meng; Charles, River; Tong, Huimin; Zhang, Lei; Patel, Mili; Wang, Francis; Rames, Matthew J.; Ren, Amy; Rye, Kerry-Anne; Qiu, Xiayang; et al
2015-03-04T23:59:59.000Z
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
Grant Hawkes; James O'Brien
2012-06-01T23:59:59.000Z
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
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Lee, Jeong -Hun; Yoon, Su -Jong; Cho, Hyoung -Kyu; Jae, Moosung; Park, Goon -Cherl
2015-09-01T23:59:59.000Z
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
Polymer segregation under confinement: Free energy calculations and segregation dynamics simulations
James M. Polson; Logan G. Montgomery
2014-10-09T23:59:59.000Z
Monte Carlo simulations are used to study the behavior of two polymers under confinement in a cylindrical tube. Each polymer is modeled as a chain of hard spheres. We measure the free energy of the system, F, as a function of the distance between the centers of mass of the polymers, lambda, and examine the effects on the free energy functions of varying the channel diameter D and length L, as well as the polymer length N and bending rigidity, kappa. For infinitely long cylinders, F is a maximum at lambda=0, and decreases with lambda until the polymers are no longer in contact. For flexible chains, the polymers overlap along the cylinder for low lambda, while above some critical value of lambda they are longitudinally compressed and non-overlapping while still in contact. We find that the free energy barrier height, scales as Delta F/k_BT~ND^{-1.93+/-0.01}. In addition, the overlap free energy scales as F/k_BT=Nf(lambda/N;D), where f is a function parameterized by D. For channels of finite L, the free energy barrier height increases with increasing confinement aspect ratio L/D at fixed volume fraction phi, and it decreases with increasing phi at fixed L/D. Increasing the polymer bending rigidity kappa monotonically reduces the overlap free energy. For strongly confined systems, F varies linearly with lambda with a slope that scales as F'(lambda)~-k_BT D^{-beta} P^{-alpha}, where beta approx 2 and alpha approx 0.37 for N=200 chains. These exponent values deviate slightly from those predicted using a simple model, possibly due to insufficiently satisfying the conditions defining the Odijk regime. Finally, we use Monte Carlo dynamics simulations to examine polymer segregation dynamics for fully flexible chains and observe segregation rates that decrease with decreasing entropic force magnitude. The polymers are not conformationally relaxed at later times during segregation.
Li, X.; Li, N.; Fang, F.; Zhao, D.
2006-01-01T23:59:59.000Z
computational fluid dynamics (CFD) program,and full-scale experiments were conducted to validate the calculation results in May 2005. The results show that the CFD- predicted results in the plenum were in good agreement with the measured results. Two main...
Li, X.; Li, N.; Fang, F.; Zhao, D.
2006-01-01T23:59:59.000Z
computational fluid dynamics (CFD) program,and full-scale experiments were conducted to validate the calculation results in May 2005. The results show that the CFD- predicted results in the plenum were in good agreement with the measured results. Two main...
Analysis of fluid flow and heat transfer in a rib grit roughened surface solar air heater using CFD
Karmare, S.V. [Department of Mechanical Engineering, Government College Engineering, Karad 415 124, Maharashtra (India); Shivaji University, Kolhapur, Maharashtra (India); Tikekar, A.N. [Department of Mechanical Engineering, Walchand College of Engineering, Sangli (India); Shivaji University, Kolhapur, Maharashtra (India)
2010-03-15T23:59:59.000Z
This paper presents the study of fluid flow and heat transfer in a solar air heater by using Computational Fluid Dynamics (CFD) which reduces time and cost. Lower side of collector plate is made rough with metal ribs of circular, square and triangular cross-section, having 60 inclinations to the air flow. The grit rib elements are fixed on the surface in staggered manner to form defined grid. The system and operating parameters studied are: e/D{sub h} = 0.044, p/e = 17.5 and l/s = 1.72, for the Reynolds number range 3600-17,000. To validate CFD results, experimental investigations were carried out in the laboratory. It is found that experimental and CFD analysis results give the good agreement. The optimization of rib geometry and its angle of attack is also done. The square cross-section ribs with 58 angle of attack give maximum heat transfer. The percentage enhancement in the heat transfer for square plate over smooth surface is 30%. (author)
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Chen, Sow-Hsin; Lagi, Marco; Chu, Xiang-qiang; Zhang, Yang; Kim, Chansoo; Faraone, Antonio; Fratini, Emiliano; Baglioni, Piero
2010-01-01T23:59:59.000Z
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 aroundTL= 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 form (LDL), a less fluidmore »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 temperatureTD= 220 K, for these biopolymers. In the glassy state, belowTD, 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 (?-relaxation) of protein dynamics, which is the logarithmic decay spanning 3 decades (from ps to ns). The long time?-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 substantially in a certain wave vector range when temperature crosses over theTD. Thus the increase of biological activities aboveTDhas positive correlation with activation of slower and large amplitude collective motions of a protein.« less
Quantify Water Extraction by TBP/Dodecane via Molecular Dynamics Simulations
Khomami, Bamin [Univ. of Tennessee, Knoxville, TN (United States); Cui, Shengting [Univ. of Tennessee, Knoxville, TN (United States); de Almeida, Valmor F. [Oak Ridge National Lab., Oak Ridge, TN (United States); Felker, Kevin [Oak Ridge National Lab., Oak Ridge, TN (United States)
2013-05-16T23:59:59.000Z
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/or longer chains for this particular solvent extraction application. We have proposed a simple way to circumvent the artificial crystallization of the chains at ambient temperature.
Dynamic Simulation of Shipping Package Subjected to Torque Load and Sequential Impacts
Wu, T
2006-04-17T23:59:59.000Z
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.
Xu, Yan [ORNL; Li, Fangxing [ORNL; Kueck, John D [ORNL; Rizy, D Tom [ORNL
2007-01-01T23:59:59.000Z
Distributed energy (DE) resources are power sources located near load centers and equipped with power electronics converters to interface with the grid, therefore it is feasible for DE to provide reactive power (along with active power) locally for dynamic voltage regulation. In this paper, a synchronous condenser and a microturbine with an inverter interface are implemented in parallel in a distribution system to regulate the local voltage. Developed voltage control schemes for the inverter and the synchronous condenser are presented. Experimental results show that both the inverter and the synchronous condenser can regulate the local voltage instantaneously although the dynamic response of the inverter is much faster than the synchronous condenser. In a system with multiple DEs performing local voltage regulation, the interaction between the DEs is studied. The simulation results show the relationship between the voltages in the system and the reactive power required for the voltage regulation. Also, integrated voltage regulation (multiple DEs performing voltage regulation) can increase the voltage regulation capability of DEs and reduce the capital and operating costs.
The Global Nuclear Futures Model: A Dynamic Simulation Tool for Energy Strategies
Bixler, N.E. [Sandia National Laboratories, Albuquerque, NM 87185-0748 (United States)
2002-07-01T23:59:59.000Z
The Global Nuclear Futures Model (GNFM) is a dynamic simulation tool that provides an integrated framework to model key aspects of nuclear energy, nuclear materials storage and disposition, global nuclear materials management, and nuclear proliferation risk. It links nuclear energy and other energy shares dynamically to greenhouse gas emissions and twelve other measures of environmental impact. It presents historical data from 1990 to 2000 and extrapolates energy demand through the year 2050. More specifically, it contains separate modules for energy, the nuclear fuel cycle front end, the nuclear fuel cycle back end, defense nuclear materials, environmental impacts, and measures of the potential for nuclear proliferation. It is globally integrated but also breaks out five regions of the world so that environmental impacts and nuclear proliferation concerns can be evaluated on a regional basis. The five regions are the United States of America (USA), The Peoples Republic of China (China), the former Soviet Union (FSU), the OECD nations excluding the USA, and the rest of the world (ROW). (author)
Many-body dissipative particle dynamics simulation of liquid/vapor and liquid/solid interactions
Arienti, Marco; Pan, Wenxiao; Li, Xiaoyi; Karniadakis, George E.
2011-05-27T23:59:59.000Z
The combination of short-range repulsive and long-range attractive forces in Many-body Dissipative Particle Dynamics (MDPD) is examined at a vapor/liquid and liquid/solid interface. Based on the radial distribution of the virial pressure in a drop at equilibrium, a systematic study is carried out to characterize the sensitivity of the surface tension coefficient with respect to the inter-particle interaction parameters. For the first time, this study highlights the approximately cubic dependence of the surface tension coefficient on the bulk density of the fluid. In capillary flow, MDPD solutions are shown to satisfy the condition on the wavelength of an axial disturbance leading to the pinch-off of a cylindrical liquid thread. Correctly, no pinch-off occurs below the cutoff wavelength. MDPD is augmented by a set of bell-shaped weight functions to model interaction with a solid wall. There, hydrophilic and hydrophobic behaviors, including the occurrence of slip in the latter, are reproduced using a modification in the weight function that avoids particle clustering. Finally, the dynamics of droplets entering an inverted Y-shaped fracture junction is correctly captured in simulations parameterized by the Bond number, proving the flexibility of MDPD in modeling interface-dominated flows.
Chang, C.; Sankaranarayanan, S; Ruzmetov, D; Engelhard, M; Kaxiras, E; Ramanathan, S
2010-01-01T23:59:59.000Z
We report on the ability to modify the structure and composition of ultrathin oxides grown on Ni and Ni-Al alloy surfaces at room temperature utilizing photon illumination. We find that the nickel-oxide formation is enhanced in the case of oxidation under photo-excitation. The enhanced oxidation kinetics of nickel in 5% Ni-Al alloy is corroborated by experimental and simulation studies of natural and photon-assisted oxide growth on pure Ni(100) surfaces. In case of pure Ni substrates, combined x-ray photoelectron spectroscopy analysis, and atomic force microscope current mapping support the deterministic role of the structure of nickel passive-oxide films on their nanoscale corrosion resistance. Atomistic simulations involving dynamic charge transfer predict that the applied electric field overcomes the activation-energy barrier for ionic migration, leading to enhanced oxygen incorporation into the oxide, enabling us to tune the mixed-oxide composition at atomic length scales. Atomic scale control of ultrathin oxide structure and morphology in the case of pure substrates as well as compositional tuning of complex oxide in the case of alloys leads to excellent passivity as verified from potentiodynamic polarization experiments.
Guido Tiana; Carlo Camilloni
2012-07-05T23:59:59.000Z
The atomistic characterization of the transition state is a fundamental step to improve the understanding of the folding mechanism and the function of proteins. From a computational point of view, the identification of the conformations that build out the transition state is particularly cumbersome, mainly because of the large computational cost of generating a statistically-sound set of folding trajectories. Here we show that a biasing algorithm, based on the physics of the ratchet-and-pawl, can be used to identify efficiently the transition state. The basic idea is that the algorithmic ratchet exerts a force on the protein when it is climbing the free-energy barrier, while it is inactive when it is descending. The transition state can be identified as the point of the trajectory where the ratchet changes regime. Besides discussing this strategy in general terms, we test it within a protein model whose transition state can be studied independently by plain molecular dynamics simulations. Finally, we show its power in explicit-solvent simulations, obtaining and characterizing a set of transition--state conformations for ACBP and CI2.
Ilpo Vattulainen; Mikko Karttunen; Gerhard Besold; J. M. Polson
2002-11-15T23:59:59.000Z
We examine the performance of various commonly used integration schemes in dissipative particle dynamics simulations. We consider this issue using three different model systems, which characterize a variety of different conditions often studied in simulations. Specifically we clarify the performance of integration schemes in hybrid models, which combine microscopic and meso-scale descriptions of different particles using both soft and hard interactions. We find that in all three model systems many commonly used integrators may give rise to surprisingly pronounced artifacts in physical observables such as the radial distribution function, the compressibility, and the tracer diffusion coefficient. The artifacts are found to be strongest in systems, where interparticle interactions are soft and predominated by random and dissipative forces, while in systems governed by conservative interactions the artifacts are weaker. Our results suggest that the quality of any integration scheme employed is crucial in all cases where the role of random and dissipative forces is important, including hybrid models where the solvent is described in terms of soft potentials.
Homogeneous SPC/E water nucleation in large molecular dynamics simulations
Angelil, R; Tanaka, K; Tanaka, H
2015-01-01T23:59:59.000Z
We perform direct large molecular dynamics simulations of homogeneous SPC/E water nucleation, using up to $\\sim 4\\cdot 10^6$ molecules. Our large system sizes allow us to measure extremely low and accurate nucleation rates, down to $\\sim 10^{19}\\,\\textrm{cm}^{-3}\\textrm{s}^{-1}$, helping close the gap between experimentally measured rates $\\sim 10^{17}\\,\\textrm{cm}^{-3}\\textrm{s}^{-1}$. We are also able to precisely measure size distributions, sticking efficiencies, cluster temperatures, and cluster internal densities. We introduce a new functional form to implement the Yasuoka-Matsumoto nucleation rate measurement technique (threshold method). Comparison to nucleation models shows that classical nucleation theory over-estimates nucleation rates by a few orders of magnitude. The semi-phenomenological nucleation model does better, under-predicting rates by at worst, a factor of 24. Unlike what has been observed in Lennard-Jones simulations, post-critical clusters have temperatures consistent with the run avera...
Yongfeng Zhang; Paul C Millett; Michael R Tonks; Xian-Ming Bai; S Bulent Biner
2014-09-01T23:59:59.000Z
The intergranular fracture behavior of UO2 was studied using molecular dynamics simulations with a bicrystal model. The anisotropic fracture behavior due to the different grain boundary characters was investigated with the View the MathML source symmetrical tilt S5 and the View the MathML source symmetrical tilt S3 ({1 1 1} twin) grain boundaries. Nine interatomic potentials, seven rigid-ion plus two core–shell ones, were utilized to elucidate possible potential dependence. Initiating from a notch, crack propagation along grain boundaries was observed for most potentials. The S3 boundary was found to be more prone to fracture than the S5 one, indicated by a lower energy release rate associated with the former. However, some potential dependence was identified on the existence of transient plastic deformation at crack tips, and the results were discussed regarding the relevant material properties including the excess energies of metastable phases and the critical energy release rate for intergranular fracture. In general, local plasticity at crack tips was observed in fracture simulations with potentials that predict low excess energies for metastable phases and high critical energy release rates for intergranular fracture.
Guseva, D. V., E-mail: d.v.guseva@tue.nl [Theory of Polymers and Soft Matter, Technische Universiteit Eindhoven, P.O. Box 513, 5600 MB, Eindhoven (Netherlands); Physics Department, Chair of Polymer and Crystal Physics, M. V. Lomonosov Moscow State University, 119991 Moscow (Russian Federation); Komarov, P. V. [Department of Theoretical Physics, Tver State University, Sadovyj per. 35, 170002 Tver, Russia and Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Vavilova st. 28, 119991 Moscow (Russian Federation)] [Department of Theoretical Physics, Tver State University, Sadovyj per. 35, 170002 Tver, Russia and Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Vavilova st. 28, 119991 Moscow (Russian Federation); Lyulin, Alexey V. [Theory of Polymers and Soft Matter, Technische Universiteit Eindhoven, P.O. Box 513, 5600 MB, Eindhoven (Netherlands)] [Theory of Polymers and Soft Matter, Technische Universiteit Eindhoven, P.O. Box 513, 5600 MB, Eindhoven (Netherlands)
2014-03-21T23:59:59.000Z
Constant temperature–constant pressure (NpT) molecular-dynamics computer simulations have been carried out for the united-atom model of a non-crosslinked (1,4) cis-polyisoprene (PI) melt confined between two amorphous, fully coordinated silica surfaces. The Lennard-Jones 12-6 potential was implemented to describe the polymer–silica interactions. The thickness H of the produced PI–silica film has been varied in a wide range, 1 < H/R{sub g} < 8, where R{sub g} is the individual PI chain radius of gyration measured under the imposed confinement. After a thorough equilibration, the PI film stratified structure and polymer segmental dynamics have been studied. The chain structure in the middle of the films resembles that in a corresponding bulk, but the polymer-density profile shows a pronounced ordering of the polymer segments in the vicinity of silica surfaces; this ordering disappears toward the film middles. Tremendous slowing down of the polymer segmental dynamics has been observed in the film surface layers, with the segmental relaxation more than 150 times slower as compared to that in a PI bulk. This effect increases with decreasing the polymer-film thickness. The segmental relaxation in the PI film middles shows additional relaxation process which is absent in a PI bulk. Even though there are fast relaxation processes in the film middle, its overall relaxation is slower as compared to that in a bulk sample. The interpretation of the results in terms of polymer glassy bridges has been discussed.
Dynamical Downscaling of GCM Simulations: Toward the Improvement of Forecast Bias over California
Chin, H S
2008-09-24T23:59:59.000Z
The effects of climate change will mostly be felt on local to regional scales. However, global climate models (GCMs) are unable to produce reliable climate information on the scale needed to assess regional climate-change impacts and variability as a result of coarse grid resolution and inadequate model physics though their capability is improving. Therefore, dynamical and statistical downscaling (SD) methods have become popular methods for filling the gap between global and local-to-regional climate applications. Recent inter-comparison studies of these downscaling techniques show that both downscaling methods have similar skill in simulating the mean and variability of present climate conditions while they show significant differences for future climate conditions (Leung et al., 2003). One difficulty with the SD method is that it relies on predictor-predict and relationships, which may not hold in future climate conditions. In addition, it is now commonly accepted that the dynamical downscaling with the regional climate model (RCM) is more skillful at the resolving orographic climate effect than the driving coarser-grid GCM simulations. To assess the possible societal impacts of climate changes, many RCMs have been developed and used to provide a better projection of future regional-scale climates for guiding policies in economy, ecosystem, water supply, agriculture, human health, and air quality (Giorgi et al., 1994; Leung and Ghan, 1999; Leung et al., 2003; Liang et al., 2004; Kim, 2004; Duffy et al., 2006). Although many regional climate features, such as seasonal mean and extreme precipitation have been successfully captured in these RCMs, obvious biases of simulated precipitation remain, particularly the winter wet bias commonly seen in mountain regions of the Western United States. The importance of regional climate research over California is not only because California has the largest population in the nation, but California has one of the most sophisticated water collection and distribution systems in the world. Therefore, adapting California's water management system to climate change presents significant challenges. Besides, the strong scale interaction between atmospheric circulation and topography in this region provides a challenging testbed for RCMs. Thus, the success of California winter precipitation forecast over mountains would greatly help develop a reliable water management system to adapt to climate change.
Zevenhoven, Ron
Introduction to Computational Fluid Dynamics 424512 E #1 - rz Introduction to Computational Fluid Dynamics (iCFD) 424512.0 E, 5 sp 1. Introduction; Fluid dynamics (lecture 1 of 4) Ron Zevenhoven Åbo to Computational Fluid Dynamics 424512 E #1 - rz maj 2015 Åbo Akademi Univ - Thermal and Flow Engineering
Lotko, William
by the soft electron precipitation to topside altitudes, where the wave-driven transverse ion heating pumps transport, wave heating, hybrid simulation Citation: Wu, X.-Y., J. L. Horwitz, and J.-N. Tu, Dynamic fluid potentials, transverse ion heating, and soft electron precipitation X.-Y. Wu, J. L. Horwitz, and J.-N. Tu
Maruyama, Shigeo
Molecular Dynamics Simulation of Heat Transfer Issues of Nanotubes. ·> Yasuhiro Igarashi, Yuki 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan Heat transfer between single-walled carbon nanotubes, which was 0.105 µm. In other words, when the length of SWNT is 0.105 µm, the radial heat transfer
Pedram, Massoud
An Energy-Aware Simulation Model and Transaction Protocol for Dynamic Workload Distribution an undesirable occurrence. Uneven distribution of energy resources and computational workloads is especially for detailed evaluation of the performance of different energy management policies in a MANET. Next it presents
Boyer, Edmond
2013-01-01T23:59:59.000Z
atmosphere of Venus (about 96.5% of CO2) where the pressure is high (up to 90 bar). Similarly, narrow involving CO2 with a few for the pure gas in the infrared at high pressure1217 and Raman Q branches.4THE JOURNAL OF CHEMICAL PHYSICS 138, 244310 (2013) Molecular dynamics simulations for CO2 spectra
de Gispert, Adrià
A molecular dynamics simulation of the melting points and glass transition temperatures of myo transition temperature are calculated for myo- and neo-inositol, using the condensed-phase optimized temperatures for myo- and neo-inositol also compare very well to the experimentally obtained data. The glass
Calculation of Protein Heat Capacity from Replica-Exchange Molecular Dynamics Simulations The heat capacity has played a major role in relating microscopic and macroscopic properties of proteins, and configurational averaging. To better understand these factors on calculating a protein heat capacity, we provide
Hypermolecular dynamics simulations of monovacancy X.M. Duan *, D.Y. Sun, X.G. Gong
Gong, Xingao
Hypermolecular dynamics simulations of monovacancy diusion X.M. Duan *, D.Y. Sun, X.G. Gong@theory.issp.ac.cn (X.M. Duan), dysun@theory.issp.ac.cn (D.Y. Sun), gong@theory.issp.ac.cn (X.G. Gong). 0927 of moving at- oms, which prohibits application to large systems. Very recently, Gong and Wilkins [17
Kessler, Jan; Spura, Thomas; Karhan, Kristof; Partovi-Azar, Pouya; Hassanali, Ali A; Kühne, Thomas D
2015-01-01T23:59:59.000Z
The structure and dynamics of the water/vapor interface is revisited by means of path-integral and second-generation Car-Parrinello ab-initio molecular dynamics simulations in conjunction with an instantaneous surface definition [A. P. Willard and D. Chandler, J. Phys. Chem. B 114, 1954 (2010)]. In agreement with previous studies, we find that one of the OH bonds of the water molecules in the topmost layer is pointing out of the water into the vapor phase, while the orientation of the underlying layer is reversed. Therebetween, an additional water layer is detected, where the molecules are aligned parallel to the instantaneous water surface.
A model simulation of white-winged dove population dynamics in the Tamaulipan Biotic Province
Martinez, Cristina Ann
2002-01-01T23:59:59.000Z
the population dynamics model. The current population dynamics model is useful in the understanding of observed patterns and processes of WWDO population dynamics. The model also serves to direct research efforts that would enhance the reliability of the model...
Computational Fluid Dynamics Study of Aerosol Transport and Deposition Mechanisms
Tang, Yingjie
2012-07-16T23:59:59.000Z
In this work, various aerosol particle transport and deposition mechanisms were studied through the computational fluid dynamics (CFD) modeling, including inertial impaction, gravitational effect, lift force, interception, and turbophoresis, within...
Guan, Fada 1982-
2012-04-27T23:59:59.000Z
Monte Carlo method has been successfully applied in simulating the particles transport problems. Most of the Monte Carlo simulation tools are static and they can only be used to perform the static simulations for the problems with fixed physics...
Simultaneous CFD evaluation of wind flow and dust emission in open storage piles
Diego, I.; Pelegry, A.; Torno, S.; Torano, J.; Menendez, M. [University of Oviedo, Asturias (Spain). School of Mines
2009-07-15T23:59:59.000Z
Dust emission from storage yards is a multivariable problem to be solved not only at any new installation in order to obtain the licenses from the involved authorities but also at existing yards to continue the operation. Engineers have a great variety of methodologies available at the market to estimate such emissions, but in general the process is divided into two independent stages: wind flow analysis and application of emission rates into such wind pattern. This paper summarizes the research developed by this group to link both steps: by using CFX version 10.0, a powerful computational fluid dynamics (CFD) software, the wind flow around the piles is predicted, or even through a complex yard, and at the same time by implementing new subroutines introduced into the standard software, the program is able to give a quantitative evaluation of the total fugitive dust.
J. E. Taylor; Arif Babul
2000-12-14T23:59:59.000Z
We have developed a simple yet surprisingly accurate analytic scheme for tracking the dynamical evolution of substructure within larger dark halos. The scheme incorporates the effects of dynamical friction, tidal mass loss and tidal heating via physically motivated approximations. Using our scheme, we can predict the orbital evolution and mass-loss history of individual subhalos in detail. We are also able to determine the impact and importance of the different physical processes on the dynamical evolution of the subhalos. To test and calibrate this model, we compare it with a set of recent high-resolution numerical simulations of mergers between galaxies and small companions. We find that we can reproduce the orbits and mass-loss rates seen in all of these simulations with considerable accuracy, using a single set of values for the three free parameters in our model. Computationally, our scheme is more than 1000 times faster than the simplest of the high-resolution numerical simulations. This means that we can carry out detailed and statistically meaningful investigations into the characteristics of the subhalo population in different cosmologies, the stripping and disruption of the subhalos, and the interactions of the subhalos with other dynamical structures such as a thin disk. This last point is of particular interest given the ubiquity of minor mergers in hierarchical models. In this regard, our method's simplicity and speed makes it particularly attractive for incorporation into semi-analytic models of galaxy formation.
Final technical report [ACCELERATED MOLECULAR DYNAMICS SIMULATIONS OF REACTIVE HYDROCARBON SYSTEMS
Stuart, Steven J.
2014-02-25T23:59:59.000Z
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.
Molecular-dynamics simulation of clustering processes in sea-ice floes
Herman, Agnieszka
2011-01-01T23:59:59.000Z
In seasonally ice-covered seas and along the margins of perennial ice pack, i.e. in regions with medium ice concentrations, the ice cover typically consists of separate floes interacting with each other by inelastic collisions. In this paper, hitherto unexplored analogies between this type of ice cover and two-dimensional granular gases are used to formulate a model of ice dynamics at the floe level. The model consists of: (i) momentum equations for floe motion between collisions, formulated in the form of a Stokes-flow problem, with floe-size dependent time constant and equilibrium velocity, and (ii) hard-disk collision model. The numerical algorithm developed is suitable for simulating particle-laden flow of $N$ disk-shaped floes with arbitrary size distribution. The model is applied to study clustering phenomena in sea ice with power-law floe-size distribution. In particular, the influence of the average ice concentration $\\bar{A}$ on the formation and characteristics of clusters is analyzed in detail. The...
Shugo Yasuda; Ryoichi Yamamoto
2015-03-25T23:59:59.000Z
The Synchronized Molecular-Dynamics simulation which was recently proposed by authors [Phys. Rev. X {\\bf 4}, 041011 (2014)] is applied to the analysis of polymer lubrication between parallel plates. The rheological properties, conformational change of polymer chains, and temperature rise due to the viscous heating are investigated with changing the values of thermal conductivity of the polymeric liquid. It is found that at a small applied shear stress on the plate, the temperature of polymeric liquid only slightly increases in inverse proportion to the thermal conductivity and the apparent viscosity of polymeric liquid is not much affected by changing the thermal conductivity. However, at a large shear stress, the transitional behaviors of the polymeric liquid occur due to the interplay of the shear deformation and viscous heating by changing the thermal conductivity. This transition is characterized by the Nahme-Griffith number $Na$ which is defined as the ratio of the viscous heating to the thermal conduction at a characteristic temperature. When the Nahme-Griffith number exceeds the unity, the temperature of polymeric liquid increases rapidly and the apparent viscosity also exponentially decreases as the thermal conductivity decreases. The conformation of polymer chains is stretched and aligned by the shear flow for $Na1$.
Thermal Degradation of Adsorbed Bottle-Brush Macromolecules: Molecular Dynamics Simulation
Andrey Milchev; Jaroslaw Paturej; Vakhtang G. Rostiashvili; Thomas A. Vilgis
2011-03-03T23:59:59.000Z
The scission kinetics of bottle-brush molecules in solution and on an adhesive substrate is modeled by means of Molecular Dynamics simulation with Langevin thermostat. Our macromolecules comprise a long flexible polymer backbone with $L$ segments, consisting of breakable bonds, along with two side chains of length $N$, tethered to each segment of the backbone. In agreement with recent experiments and theoretical predictions, we find that bond cleavage is significantly enhanced on a strongly attractive substrate even though the chemical nature of the bonds remains thereby unchanged. We find that the mean bond life time $$ decreases upon adsorption by more than an order of magnitude even for brush molecules with comparatively short side chains $N=1 \\div 4$. The distribution of scission probability along the bonds of the backbone is found to be rather sensitive regarding the interplay between length and grafting density of side chains. The life time $$ declines with growing contour length $L$ as $\\propto L^{-0.17}$, and with side chain length as $\\propto N^{-0.53}$. The probability distribution of fragment lengths at different times agrees well with experimental observations. The variation of the mean length $L(t)$ of the fragments with elapsed time confirms the notion of the thermal degradation process as a first order reaction.
Endo, Noriko S.M. Massachusetts Institute of Technology
2014-01-01T23:59:59.000Z
This thesis applies the HYDRology, Entomology and MAlaria Transmission Simulator (HYDREMATS) to the environment around a water resources reservoir in Ethiopia. HYDREMATS was modified to simulate the local hydrology and the ...
Grant L. Hawkes; James E. O'Brien; Greg Tao
2011-11-01T23:59:59.000Z
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 efficiency, cell electrical efficiency, and Gibbs free energy are discussed and reported herein.
Browning, J. R.; Jonkman, J.; Robertson, A.; Goupee, A. J.
2012-11-01T23:59:59.000Z
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.
Davis, Michael A.
2011-10-21T23:59:59.000Z
to the model that is used in EnergyPlus. 6. Demonstrate that Computational Fluid Dynamics can be used as a design tool that can be used to improve the performance of FPTU. All of the research objectives were achieved and this thesis describes the results... of the CFD model. Chapter IX summarizes the results from the project and provides conclusions from the results. 12 CHAPTER II LITERATURE REVIEW EnergyPlus is currently the standard for building energy simulations (DOE 2009) and includes a model...
Evers, Angela C.
2008-07-25T23:59:59.000Z
Frame walls enhanced with phase change materials (paraffin-based, hydrated salt-based, and eutectic) mixed in cellulose insulation were developed and tested. The frame walls were heated and allowed to cool in a dynamic wall simulator that replicated...
Mackin, Peter; Daschmans, R.; Williams, B.; Haney, B.; Hung, R.; Ellis, J.
2010-12-20T23:59:59.000Z
Utility Systems Efficiencies, Inc. was tasked by Lawrence Berkeley National Laboratory (LBNL) to conduct dynamic simulation studies of the three U.S. interconnections (Eastern, Western, and Texas). The simulations were prepared in support of LBNL's project for the Federal Energy Regulatory Commission to study frequency-response-related issues that must be addressed to operate the power system reliably with large amounts of variable renewable generation. The objective of the simulation studies of each interconnection was to assess the effects of different amounts of wind generation on frequency behavior of each interconnection following a sudden loss of generation. The scenarios created to study these effects considered an operating circumstance in which system load is at or close to its minimum. The event studied was the sudden loss of the largest amount of generation recorded within each interconnection. The simulations calculated the impact of this event on interconnection frequency for three levels of wind generation. In addition to varying the amount of wind generation, the simulations varied the amount of operating reserves between a high level representative of current operating practices and a low level representative of the minimum required by present operating rules.
User Guide for PV Dynamic Model Simulation Written on PSCAD Platform
Muljadi, E.; Singh, M.; Gevorgian, V.
2014-11-01T23:59:59.000Z
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.
D. M. McEligot; K.G. Condie; G. E. Mc Creery; H. M. Mc Ilroy
2005-09-01T23:59:59.000Z
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.
CFD Modeling for Lost Foam White Side | Department of Energy
Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site
AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home Page on Delicious RankShale_Gas.pdfService on the TargetFY12Environmentto WholeII -Langston 1TableCERC-BEEChemistry |CFD
Sandia Energy - CFD-Populated Empirical Turbine Wake Model
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE:1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level:5(Million Cubic Feet) Oregon (Including Vehicle Fuel) (Million CubicRefiners SwitchBenefitsBeam LineSandian as Permalink GalleryBob BiefeldCFD-Populated
Hajdukiewicz, M.; Keane, M.; O'Flynn, B.; O'Grady, W.
2010-01-01T23:59:59.000Z
controlled internal environments. In this research a CFD model of the internal environment of an office space will be developed. The CFD model will then be calibrated using real data taken from a well-positioned wireless sensor network and weather station...
Aalborg Universitet CFD modeling and experience of waste-to-energy plant burning waste wood
Yin, Chungen
Aalborg Universitet CFD modeling and experience of waste-to-energy plant burning waste wood Rajh, B-to- energy plant burning waste wood. In Proceedings of the 14th International Waste Management and Landfill by CISA Publisher, Italy CFD MODELING AND EXPERIENCE OF WASTE-TO-ENERGY PLANT BURNING WASTE WOOD B. RAJH
Assessment of low-order theories for analysis and design of shrouded wind turbines using CFD
Alonso, Juan J.
Assessment of low-order theories for analysis and design of shrouded wind turbines using CFD Aniket of a shroud around the rotor of a wind turbine has been known to augment the airflow through the rotor plane the validity of several simple theories which attempt to extend Betz theory to shrouded turbines. Two CFD
W. Schmidt; J. C. Niemeyer; W. Hillebrandt; F. K. Roepke
2006-01-23T23:59:59.000Z
The dynamics of the explosive burning process is highly sensitive to the flame speed model in numerical simulations of type Ia supernovae. Based upon the hypothesis that the effective flame speed is determined by the unresolved turbulent velocity fluctuations, we employ a new subgrid scale model which includes a localised treatment of the energy transfer through the turbulence cascade in combination with semi-statistical closures for the dissipation and non-local transport of turbulence energy. In addition, subgrid scale buoyancy effects are included. In the limit of negligible energy transfer and transport, the dynamical model reduces to the Sharp-Wheeler relation. According to our findings, the Sharp-Wheeler relation is insuffcient to account for the complicated turbulent dynamics of flames in thermonuclear supernovae. The application of a co-moving grid technique enables us to achieve very high spatial resolution in the burning region. Turbulence is produced mostly at the flame surface and in the interior ash regions. Consequently, there is a pronounced anisotropy in the vicinity of the flame fronts. The localised subgrid scale model predicts significantly enhanced energy generation and less unburnt carbon and oxygen at low velocities compared to earlier simulations.
Simulation of FCC riser flow with multiphase heat transfer and cracking reactions.
Chang, S. L.; Zhou, C. Q.; Energy Systems
2003-08-01T23:59:59.000Z
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.
Automating Dynamic Decoupling in Object-Oriented Modelling and Simulation Tools
Como, Giacomo
a Modelica transla- tor. Simulation tests demonstrate the technique, and the re- alised implementation than of simulation theory. In this work we refer as "EOO Modelling Tool" to a Modelica translator, to allow exemplifying the (more general) presented ideas. For a Modelica translator, the EOO modelling
Ren, Kui
-performance semiconductor-liquid junction solar cells. We propose in this work a macroscopic mathematical model, a sys- tem-liquid junction, solar cell simulation, naso-scale device modeling. 1 Introduction The mathematical modeling by the increasing need of simulation tools for designing efficient solar cells to harvest sunlight for clean energy
Goddard III, William A.
Early maturation processes in coal. Part 2: Reactive dynamics simulations using the ReaxFF reactive force field on Morwell Brown coal structures Elodie Salmon a , Adri C.T. van Duin b , François Lorant Brown coal using the ReaxFF reactive force field. We find that these reactive MD simulations
Using the FLUENT computational fluid dynamics code to model the NACOK corrosion test
Parks, Benjamin T
2004-01-01T23:59:59.000Z
As a part of advancing nuclear technology, computational fluid dynamics (CFD) analysis offers safer and lower-cost results relative to experimental work. Its use as a safety analysis tool is gaining much broader acceptance ...
Breault, Ronald W, [U.S. DOE; Huckaby, Ernest D. [U.S. DOE; Shadle, Lawrence J [U.S. DOE; Spenik, James L. [REM Engineering PLLC
2013-01-01T23:59:59.000Z
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.
Lan, Tian [California Institute of Technology, Pasadena] [California Institute of Technology, Pasadena; Li, Chen [ORNL] [ORNL; Niedziela, Jennifer L [ORNL] [ORNL; Smith, Hillary [California Institute of Technology, Pasadena] [California Institute of Technology, Pasadena; Abernathy, Douglas L [ORNL] [ORNL; Rossman, George [California Institute of Technology, Pasadena] [California Institute of Technology, Pasadena; Fultz, B. [California Institute of Technology, Pasadena] [California Institute of Technology, Pasadena
2014-01-01T23:59:59.000Z
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.
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
dynamics (CFD) simulations and uncertainty analyses. The project developed new mathematical uncertainty quantification techniques and applied them, in combination with...
Batista, V.S.; Zanni, M.T.; Greenblatt, B.J.; Neumark, D.M.; Miller, W.H. [Department of Chemistry, University of California, Berkeley, California 94720 (United States)] [Department of Chemistry, University of California, Berkeley, California 94720 (United States); [Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)
1999-02-01T23:59:59.000Z
In this paper we describe a new semiclassical method for simulating femtosecond pump{endash}probe photoelectron spectroscopy, and its implementation to study the excited state photodissociation dynamics of the I{sub 2}{sup {minus}} anion. Our algorithm involves a forward{endash}backward (FB) semiclassical (SC) initial value representation (IVR) method for calculating the time dependent photodetachment spectrum P({epsilon},{Delta}t) as a function of the kinetic energy {epsilon} of the photodetached electron and the delay time {Delta}t between the pump and probe pulses. We describe the radiation-chromophore interaction perturbatively to first order in both pulse fields, assuming the Condon approximation for the electronic transition dipole moments. Our computed spectra are in excellent agreement with full quantum mechanical simulations. {copyright} {ital 1999 American Institute of Physics.}
Agarwal, Animesh
2015-01-01T23:59:59.000Z
Quantum effects due to the spatial delocalization of light atoms are treated in molecular simulation via the path integral technique. Among several methods, Path Integral (PI) Molecular Dynamics (MD) is nowadays a powerful tool to investigate properties induced by spatial delocalization of atoms; however computationally this technique is very demanding. The abovementioned limitation implies the restriction of PIMD applications to relatively small systems and short time scales. One possible solution to overcome size and time limitation is to introduce PIMD algorithms into the Adaptive Resolution Simulation Scheme (AdResS). AdResS requires a relatively small region treated at path integral level and embeds it into a large molecular reservoir consisting of generic spherical coarse grained molecules. It was previously shown that the realization of the idea above, at a simple level, produced reasonable results for toy systems or simple/test systems like liquid parahydrogen. Encouraged by previous results, in this ...
Arkundato, Artoto [Physics Department, Faculty of Mathematical and Natural Sciences, Jember University, Jl. Kalimantan 37 Jember (Indonesia); Su'ud, Zaki [Physics Department, Faculty of Mathematical and Natural Sciences, Bandung Institute of Technology, Jl. Ganesha 10, Bandung (Indonesia); Sudarko [Chemistry Department, Faculty of Mathematical and Natural Sciences, Jember University, Jl. Kalimantan 37 Jember (Indonesia); Shafii, Mohammad Ali [Physics Department, Faculty of Mathematical and Natural Sciences, Andalas University, Padang (Indonesia); Celino, Massimo [ENEA, CR Casaccia, Via Anguillarese 301, Rome (Italy)
2014-09-30T23:59:59.000Z
Corrosion of structural materials in high temperature molten lead-bismuth eutectic is a major problem for design of PbBi cooled reactor. One technique to inhibit corrosion process is to inject oxygen into coolant. In this paper we study and focus on a way of inhibiting the corrosion of iron using molecular dynamics method. For the simulation results we concluded that effective corrosion inhibition of iron may be achieved by injection 0.0532 wt% to 0.1156 wt% oxygen into liquid lead-bismuth. At this oxygen concentration the structure of iron material will be maintained at about 70% in bcc crystal structure during interaction with liquid metal.
Graphite Oxidation Simulation in HTR Accident Conditions
El-Genk, Mohamed
2012-10-19T23:59:59.000Z
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.
BEAM DYNAMICS SIMULATIONS FOR A DC GUN BASED INJECTOR FOR PERL...
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
DC gun. The schematic layout of a PERL DC gun based injector and its preliminary beam dynamics are presented in this paper. The transverse and longitudinal emittance of photo-...
Ziabari, Amirkoushyar
2012-01-01T23:59:59.000Z
Power Blurring: Fast Chip-Level Static and Transient ThermalOF CALIFORNIA SANTA CRUZ FAST STATIC AND DYNAMIC GRID LEVEL3.3.3 A Static Case Study………………………………………………. 3.3.4 Transient
Stokesian dynamic simulations and analyses of interfacial and bulk colloidal fluids
Anekal, Samartha Guha
2006-10-30T23:59:59.000Z
, and hydrodynamic forces to model dynamics of colloidal dispersions. In addition, we develop theoretical expressions for quantifying self-diffusion in colloids interacting via different particle-particle and particle-wall potentials. Specifically, we have used...
Chen, Sow-Hsin
2010-01-01T23:59:59.000Z
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 ...
An innovative dynamic bus lane system and its simulation-based performance investigation
Yang, Hong
The strategy of exempting bus from other traffic through exclusive bus lanes (XBL) is prevalent. Rather than just deploying the XBL system, in this study, a new innovative dynamic bus lane (DBL) operation system which is ...
Probe, Austin Breien
2013-12-03T23:59:59.000Z
launch opportunities for verification and validation. A ground facility with the capability for six degree-of-freedom robotic spacecraft emulation that enables laboratory-based hardware-in-the-loop experiments is desired, to allow for the simulation...
Atilhan, Selma
2009-05-15T23:59:59.000Z
and molybdenum selenide, Our research focus is on polymer nanocomposites with inorganic clay particles as inclusions, in particular we used sodium montmorillonite polymer nanocomposite. In our study, modeling and simulations of sodium montmorillonite (Na...
Author's personal copy Experimental validation of large-scale simulations of dynamic fracture along
Rosakis, Ares J.
in monolithic homo- geneous brittle solids and along weak interfaces between homo- geneous solids has also been for the fitting of parameters. Then, the results of these simulations are validated against those of experiments
Experimental validation of large-scale simulations of dynamic fracture along weak planes
Huerta, Antonio
of the opening-mode crack initiation and the subsequent crack growth phenomenon both in monolithic homo- geneous are often insufficient to completely setup a simulation, which therefore leaves room for the fitting
Probe, Austin Breien
2013-12-03T23:59:59.000Z
launch opportunities for verification and validation. A ground facility with the capability for six degree-of-freedom robotic spacecraft emulation that enables laboratory-based hardware-in-the-loop experiments is desired, to allow for the simulation...
A PARTICLE SIMULATION CODE FOR LONGITUDINAL DYNAMICS OF HEAVY ION BEAMS
Sternlieb, A.
2010-01-01T23:59:59.000Z
Energy under Contract No. W-7405-ENG-48. Fiji. 1: Flow ChartEnergy under Contract W-7405-ENG-48 LBL-12205 HI-FAN-144 Aunder Contract No. W-7405-ENG-48. A Particle Simulation Code
An efficient algorithm for blade loss simulations applied to a high-order rotor dynamics problem
Parthasarathy, Nikhil Kaushik
2004-09-30T23:59:59.000Z
In this thesis, a novel approach is presented for blade loss simulation of an aircraft gas turbine rotor mounted on rolling element bearings with squeeze film dampers, seal rub and enclosed in a flexible housing. The modal truncation augmentation...
NuFact'11 Aug. 4, 2011 1 Simulation of Dynamic Interaction of
McDonald, Kirk
: Modeling of cavitation bubbles during disruption of the Hg Jet/Pool LS-Dyna simulations: #12;NuFact'11 Aug described numerically (user input into LS-DYNA) Incorporate all effects (hydrodynamic, beam, solenoid field
NuFact'11 Aug. 3, 2011 1 Simulation of Dynamic Interaction of
McDonald, Kirk
Challenge: Modeling of cavitation bubbles during disruption of the Hg Jet/Pool LS-Dyna simulations: #12;Nu described numerically (user input into LS-DYNA) Incorporate all effects (hydrodynamic, beam, solenoid field
An efficient algorithm for blade loss simulations applied to a high-order rotor dynamics problem
Parthasarathy, Nikhil Kaushik
2004-09-30T23:59:59.000Z
In this thesis, a novel approach is presented for blade loss simulation of an aircraft gas turbine rotor mounted on rolling element bearings with squeeze film dampers, seal rub and enclosed in a flexible housing. The modal truncation augmentation...
Kyohei Takae; Akira Onuki
2015-03-08T23:59:59.000Z
We study water between parallel metal walls under applied electric field accounting for the image effect at $T=298$ K. The electric field due to the surface charges serves to attract and orient nearby water molecules, while it tends to a constant determined by the mean surface charge density away from the walls. We find Stern boundary layers with thickness about $5$ $\\rm \\AA$ and a homogeneously polarized bulk region. The molecules in the layers more sensitively respond to the applied field than in the bulk. As a result, the potential drop in the layers is larger than that in the bulk unless the cell length exceeds 10 nm. We also examine the hydrogen bonds, which tend to make small angles with respect to the walls in the layers even without applied field. The average local field considerably deviates from the classical Lorentz field and the local field fluctuations are very large in the bulk. If we suppose a nanometer-size sphere around each molecule, the local field contribution from its exterior is nearly equal to that from the continuum electrostatics and that from its interior yields the deviation from the classical Lorentz field. As a nonequilibrium problem, we investigate the dynamics after a reversal of applied field, where the relaxation is mostly caused by large-angle rotational jumps after 1 ps due to the presence of the hydrogen bond network. The molecules undergoing these jumps themselves form hydrogen-bonded clusters heterogeneously distributed in space.
Yoshihito Kuno; Kenichi Kasamatsu; Yoshiro Takahashi; Ikuo Ichinose; Tetsuo Matsui
2015-06-05T23:59:59.000Z
Lattice gauge theory has provided a crucial non-perturbative method in studying canonical models in high-energy physics such as quantum chromodynamics. Among other models of lattice gauge theory, the lattice gauge-Higgs model is a quite important one because it describes wide variety of phenomena/models related to the Anderson-Higgs mechanism such as superconductivity, the standard model of particle physics, and inflation process of the early universe. In this paper, we first show that atomic description of the lattice gauge model allows us to explore real time dynamics of the gauge variables by using the Gross-Pitaevskii equations. Numerical simulations of the time development of an electric flux reveal some interesting characteristics of dynamical aspect of the model and determine its phase diagram. Next, to realize a quantum simulator of the U(1) lattice gauge-Higgs model on an optical lattice filled by cold atoms, we propose two feasible methods: (i) Wannier states in the excited bands and (ii) dipolar atoms in a multilayer optical lattice. We pay attentions to respect the constraint of Gauss's law and avoid nonlocal gauge interactions.
Ghobadi, Ahmadreza F.; Elliott, J. Richard, E-mail: elliot1@uakron.edu [Department of Chemical and Biomolecular Engineering, The University of Akron, Akron, Ohio 44325 (United States)
2013-12-21T23:59:59.000Z
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
2010-06-01T23:59:59.000Z
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.
Marzouk, Youssef M. [Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Room 3-342, Cambridge, MA 02139-4307 (United States)]. E-mail: ymarzou@sandia.gov; Ghoniem, Ahmed F. [Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Room 3-342, Cambridge, MA 02139-4307 (United States)]. E-mail: ghoniem@mit.edu
2005-08-10T23:59:59.000Z
A number of complex physical problems can be approached through N-body simulation, from fluid flow at high Reynolds number to gravitational astrophysics and molecular dynamics. In all these applications, direct summation is prohibitively expensive for large N and thus hierarchical methods are employed for fast summation. This work introduces new algorithms, based on k-means clustering, for partitioning parallel hierarchical N-body interactions. We demonstrate that the number of particle-cluster interactions and the order at which they are performed are directly affected by partition geometry. Weighted k-means partitions minimize the sum of clusters' second moments and create well-localized domains, and thus reduce the computational cost of N-body approximations by enabling the use of lower-order approximations and fewer cells. We also introduce compatible techniques for dynamic load balancing, including adaptive scaling of cluster volumes and adaptive redistribution of cluster centroids. We demonstrate the performance of these algorithms by constructing a parallel treecode for vortex particle simulations, based on the serial variable-order Cartesian code developed by Lindsay and Krasny [Journal of Computational Physics 172 (2) (2001) 879-907]. The method is applied to vortex simulations of a transverse jet. Results show outstanding parallel efficiencies even at high concurrencies, with velocity evaluation errors maintained at or below their serial values; on a realistic distribution of 1.2 million vortex particles, we observe a parallel efficiency of 98% on 1024 processors. Excellent load balance is achieved even in the face of several obstacles, such as an irregular, time-evolving particle distribution containing a range of length scales and the continual introduction of new vortex particles throughout the domain. Moreover, results suggest that k-means yields a more efficient partition of the domain than a global oct-tree.
Simulation of Thermal Stratification in BWR Suppression Pools with One Dimensional Modeling Method
Haihua Zhao; Ling Zou; Hongbin Zhang
2014-01-01T23:59:59.000Z
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 validation. Comparisons between the BMIX++, GOTHIC, and CFD calculations against the POOLEX experimental data are discussed in detail.
July 26 NuFACT Target Meeting 1 Simulation of Dynamic Interaction of the Neutrino Factory
McDonald, Kirk
pulses will be arriving, interacting with Hg jet and Hg pool (+ Jet interacting with pool How does the Hg phase diagram and introduce it to codes such as LS-DYNA Energy Deposition introduction into Hg jet/pool Dynamics and Hg Jet/Pool #12;July 26 NuFACT Target Meeting 13 Local pressure outside formed bubble can
Microscopic Mechanisms and Dynamics Simulations of S3/2) Reacting with Methane
+ under LEO conditions. Ab initio electronic structure calculations show that the interaction of O the reaction energies, the ab initio electronic structure calculations were performed by using the quantum calculation, direct dynamics, reaction mechanism, O+ + CH4 1. INTRODUCTION When space vehicles travel in low
Bell, Alexis T.
As ab initio electronic structure calculations become more accurate, inherent sources of error, facilitate reactive flux calculations. As an example we compute the dynamically corrected rate constant on which the reaction occurs. A large number of electronic structure theo- ries are available
Molecular Dynamics Simulations of Supported Pt Nanoclusters with Sutton-Chen Potentials
Washington at Seattle, University of - Department of Physics, Electroweak Interaction Research Group
-time ab-initio calculations may provide fundamental insight into the dynamical electronic and physical structure of catalytic nanoparticles, yet these calculations can prove to be extremely computationally structural disorder, negative thermal expan- sion, and thermally induced changes in electronic struc- ture.3
Smith, P. E.
2003-07-16T23:59:59.000Z
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.
Simulation of Gas Dynamic Behavior in Dry-Wall Inertial Fusion Energy Chambers
Tillack, Mark
. In this work, the code TSUNAMI [2] was used to model chamber gas dynamics for different shapes, sizes of size scaling. Previous- ly, TSUNAMI was used primarily for studying liquid protec- ted chambers which the basic response charac- teristics (with emphasis on the evolution towards a quiescent state
Particle--Mesh Ewald and rRESPA for Parallel Molecular Dynamics Simulations
Plimpton, Steve
` (` \\Gamma ` 0 ) 2 + X dihedrals K OE p [1 + d p cos(n p OE)] \\Lambda MS 1111, Sandia National Laboratories Roy Pollock y Mark Stevens z Abstract The parallel implementation of a molecular dynamics code for the system of N atoms that is typically of the form E = X bonds K b (r \\Gamma r 0 ) 2 + X angles K
Goddard III, William A.
* Materials and Process Simulation Center, Beckman Institute, 139-74, California Institute of Technology-assembly of supramolecular dendritic structures synthesized and characterized by Zimmerman and co-workers. In this method is the supramolecular structure. Through the control of environmental conditions such as pH values and ionic strength
The `neighbor effect': Simulating dynamics in consumer preferences for new vehicle technologies
under different market assumptions, using responses from two national surveys focused on hybrid gas-electric attributes beyond the purchase price in shaping consumer preferences towards clean vehicle technologies to policymakers, energy- economic simulation models must provide the most realistic projections possible, based
Dynamic Simulation and Analysis of Heating Energy Consumption in a Residential Building
Liu, J.; Yang, M.; Zhao, X.; Zhu, N.
2006-01-01T23:59:59.000Z
In winter, much of the building energy is used for heating in the north region of China. In this study, the heating energy consumption of a residential building in Tianjin during a heating period was simulated by using the EnergyPlus energy...
Sheu, Sheh-Yi
simulations of transport, a model of extreme transduction efficiency. It ex- plains the high efficiency- bution peaked at about 140 fs, in close agreement with our direct femtosecond measurements. In logic gate language this is a strongly conducting ON state resulting from small firing energies, the system otherwise
Integrating Models and Simulations of Continuous Dynamics into SysML
In this paper, we combine modeling constructs from SysML and Modelica to improve the support for Model, structures, functions, and behaviors. Complementing these SysML constructs, the Modelica language has emerged and the corresponding Modelica models; and the integration of simulation experiments with other SysML constructs
Computational Fluid Dynamics Simulation of Green Water Around a Two-dimensional Platform
Zhao, Yucheng
2010-07-14T23:59:59.000Z
An interface-preserving level set method is incorporated into the Reynolds-Averaged Navier-Stokes (RANS) numerical method to simulate the application of the green water phenomena around a platform and the breaking wave above the deck. In the present...
Dynamic Simulation and Analysis of Heating Energy Consumption in a Residential Building
Liu, J.; Yang, M.; Zhao, X.; Zhu, N.
2006-01-01T23:59:59.000Z
In winter, much of the building energy is used for heating in the north region of China. In this study, the heating energy consumption of a residential building in Tianjin during a heating period was simulated by using the EnergyPlus energy...
A Finite Element-Multibody Dynamics Co-simulation Methodology Applied to FAST
Suryakumar, Vishvas Samuel
2013-05-02T23:59:59.000Z
code developed by NREL. As with FAST, many multi-body codes which can model flexibility employ modal methods. A proposed addition for FAST to simulate flexible effects using a finite element method module offers a potential to include a variety of non...
Axisymmetric simulations of libration-driven fluid dynamics in a spherical shell geometry
. The simulations show that the zonal flow is driven by nonlinearities in the Ekman boundary layer; it is not drivenGörtler vortices form near the outer librating boundary, in agreement with the previous laboratory experiments characterize the oscillatory motion of a librating body by a single angular libration frequency, L=2 /PL, where
Bowerman, Samuel
2015-01-01T23:59:59.000Z
Eukaryotes tune the transcriptional activity of their genome by altering the nucleosome core particle through multiple chemical processes. In particular, replacement of the canonical H2A histone with the variants macroH2A and H2A.Z has been shown to affect DNA accessibility and nucleosome stability; however, the processes by which this occurs remain poorly understood. Here, we elucidate the molecular mechanisms of these variants with an extensive molecular dynamics study of the canonical nucleosome along with three variant-containing structures: H2A.Z, macroH2A, and an H2A mutant with macroH2A-like L1 loops. Simulation results show that variant L1 loops play a pivotal role in stabilizing DNA binding to the octamer through direct interactions, core structural rearrangements, and altered allosteric networks in the nucleosome. All variants influence dynamics; however, macroH2A-like systems have the largest effect on energetics. In addition, we provide a comprehensive analysis of allosteric networks in the nucleo...
Pre-test CFD Calculations for a Bypass Flow Standard Problem
Rich Johnson
2011-11-01T23:59:59.000Z
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 [Centecorp; Divo, Eduardo [Centecorp; Ceballos, Andres [Centecorp; Barriento, Carolina [Centecorp; Stephen, Barkaszi [FSEC; Hubert, Seigneur [FSEC
2014-03-21T23:59:59.000Z
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 of reducing the total installed cost of solar energy systems by 75%. The largest percentage of the total installed cost of solar energy system is associated with balance of system cost, with up to 40% going to “soft” costs; which include customer acquisition, financing, contracting, permitting, interconnection, inspection, installation, performance, operations, and maintenance. The calculator that is being developed will provide wind loads in real-time for any solar system designs and suggest the proper installation configuration and hardware; and therefore, it is anticipated to reduce system design, installation and permitting costs.
Bluff Body Flow Simulation Using a Vortex Element Method
Anthony Leonard; Phillippe Chatelain; Michael Rebel
2004-09-30T23:59:59.000Z
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.
Computer code for the atomistic simulation of lattice defects and dynamics. [COMENT code
Schiffgens, J.O.; Graves, N.J.; Oster, C.A.
1980-04-01T23:59:59.000Z
This document has been prepared to satisfy the need for a detailed, up-to-date description of a computer code that can be used to simulate phenomena on an atomistic level. COMENT was written in FORTRAN IV and COMPASS (CDC assembly language) to solve the classical equations of motion for a large number of atoms interacting according to a given force law, and to perform the desired ancillary analysis of the resulting data. COMENT is a dual-purpose intended to describe static defect configurations as well as the detailed motion of atoms in a crystal lattice. It can be used to simulate the effect of temperature, impurities, and pre-existing defects on radiation-induced defect production mechanisms, defect migration, and defect stability.
CFD based rotordynamic coefficients for labyrinth seals and impeller leakage paths
Bhattacharya, Avijit
1997-01-01T23:59:59.000Z
accurately using simple flow model like bulk flow. CFD approach is employed since it can accurately predict and capture recirculating zones using proper mesh distribution. The Impeller Leakage paths and Labyrinth Seals, typically, have a recirculation zone...
Comparative Analysis of CFD ?P vs. Measured ?P for Compressed Flexible Ducts
Ugursal, A.; Culp, C.H.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Comparative Analysis of CFD [Delta]P vs. Measured [Delta]P for Compressed Flexible Ducts Ugursal, Ahmet;Culp, Charles ASHRAE Transactions; 2007...
An Eulerian CFD Model and X-ray Radiography for Coupled Nozzle...
Broader source: All U.S. Department of Energy (DOE) Office 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...
Theoretical tools for simulations of cluster dynamics in strong laser pulses
Palade, Dragos I
2015-01-01T23:59:59.000Z
The main theoretical tools used in the physics of cluster-laser interaction are discussed starting from the basic principles of Quantum Mechanics and ending with purely classical methods. The schematic overview of the theory is complemented by direct links with various types of phenomena, regimes of interaction and quantities to be studied. Finally, the theory is reflected in a wide range of numerical simulations in order to prove their validity and the work done in the fi?eld by the author.
Computational Fluid Dynamics Simulation of Green Water Around a Two-dimensional Platform
Zhao, Yucheng
2010-07-14T23:59:59.000Z
to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Approved by: Chair of Committee, Hamn-Ching Chen Committee Members, Scott A. Socolofsky Andrew T. Duggleby Head... Chair of Advisory Committee: Dr. Hamn-Ching Chen An interface-preserving level set method is incorporated into the Reynolds- Averaged Navier-Stokes (RANS) numerical method to simulate the application of the green water phenomena around a platform...