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Note: This page contains sample records for the topic "dynamics cfd simulations" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


1

Computational fluid dynamics (CFD) simulations of aerosol in a u-shaped steam generator tube  

E-Print Network [OSTI]

as the physical model replicated for numerical simulation. Realizable k-? and standard k-? turbulence models were selected from the computational fluid dynamics (CFD) code, FLUENT, to provide the Eulerian description of the gaseous phase. Flow field simulation...

Longmire, Pamela

2009-05-15T23:59:59.000Z

2

Coupled multi-body dynamics and CFD for wind turbine simulation including explicit wind turbulence  

Science Journals Connector (OSTI)

Abstract A high fidelity approach for wind turbine aero-elastic simulations including explicit representation of the atmospheric wind turbulence is presented. The approach uses a dynamic overset computational fluid dynamics (CFD) code for the aerodynamics coupled with a multi-body dynamics (MBD) code for the motion responses to the aerodynamic loads. Mann's wind turbulence model was implemented into the CFD code as boundary and initial conditions. The wind turbulence model was validated by comparing the theoretical one-point spectrum for the three components of the velocity fluctuations, and by comparing the expected statistics from the CFD simulated wind turbulent field with the explicit wind turbulence inlet boundary from Mann model. Extensive simulations based on the proposed coupled approach were conducted with the conceptual NREL 5-MW offshore wind turbine in an increasing level of complexity, analyzing the turbine behavior as elasticity, wind shear and atmospheric wind turbulence are added to the simulations. Results are compared with the publicly available simulations results from OC3 participants, showing good agreement for the aerodynamic loads and blade tip deflections in time and frequency domains. Wind turbulence/turbine interaction was examined for the wake flow. It was found that explicit turbulence addition results in considerably increased wake diffusion. The coupled CFD/MBD approach can be extended to include multibody models of the shaft, bearings, gearbox and generator, resulting in a promising tool for wind turbine design under complex operational environments.

Y. Li; A.M. Castro; T. Sinokrot; W. Prescott; P.M. Carrica

2015-01-01T23:59:59.000Z

3

On spurious behavior of CFD simulations  

SciTech Connect (OSTI)

Spurious behavior in underresolved grids and/or semi-implicit temporal discretizations for four computational fluid dynamics (CFD) simulations are studied. The numerical simulations consist of (a) a 1-D chemically relaxed nonequilibrium model, (b) the direct numerical simulation (DNS) of 2-D incompressible flow over a backward facing step, (c) a loosely-coupled approach for a 2-D fluid-structure interaction, and (d) a 3-D compressible unsteady flow simulation of vortex breakdown in delta wings. Using knowledge from dynamical systems theory, various types of spurious behaviors that are numerical artifacts were systematically identified. These studies revealed the various possible dangers of misinterpreting numerical simulation of realistic complex flows that are constrained by the available computing power. In large scale computations underresolved grids, semi-implicit procedures, loosely-coupled implicit procedures, and insufficiently long time integration in DNS are most often unavoidable. Consequently, care must be taken in both computation and in interpretation of the numerical data. The results presented confirm the important role that dynamical systems theory can play in the understanding of the nonlinear behavior of numerical algorithms and in aiding the identification of the sources of numerical uncertainties in CFD.

Yee, H.C. [National Aeronautics and Space Administration, Moffett Field, CA (United States). Ames Research Center; Torczynski, J.R. [Sandia National Labs., Albuquerque, NM (United States); Morton, S.A.; Visbal, M.R. [Wright Lab., Wright-Patterson AFB, OH (United States); Sweby, P.K. [Univ. of Reading (United Kingdom)

1997-05-01T23:59:59.000Z

4

Computational Fluid Dynamics (CFD) simulations of dilute fluid-particle flows in aerosol concentrators  

E-Print Network [OSTI]

's turbulent dispersion model. A detailed literature survey revealed the inherent technical deficiencies in the model, even for particle dispersion. Based on the results of this study, it was determined that while the code can be used for simulating aerosol...

Hari, Sridhar

2005-02-17T23:59:59.000Z

5

Semester project Lattice Boltzmann simulations of fluid flow: An unconventional approach to CFD  

E-Print Network [OSTI]

Semester project Lattice Boltzmann simulations of fluid flow: An unconventional approach to CFD Background: The lattice Boltzmann method is a new numerical method of computational fluid dynamics (CFD). Con on a continuous picture of matter. The lattice Boltzmann method instead relies on discrete particles having

Müller,Bernhard

6

Gasification CFD Modeling for Advanced Power Plant Simulations  

SciTech Connect (OSTI)

In this paper we have described recent progress on developing CFD models for two commercial-scale gasifiers, including a two-stage, coal slurry-fed, oxygen-blown, pressurized, entrained-flow gasifier and a scaled-up design of the PSDF transport gasifier. Also highlighted was NETL’s Advanced Process Engineering Co-Simulator for coupling high-fidelity equipment models with process simulation for the design, analysis, and optimization of advanced power plants. Using APECS, we have coupled the entrained-flow gasifier CFD model into a coal-fired, gasification-based FutureGen power and hydrogen production plant. The results for the FutureGen co-simulation illustrate how the APECS technology can help engineers better understand and optimize gasifier fluid dynamics and related phenomena that impact overall power plant performance.

Zitney, S.E.; Guenther, C.P.

2005-09-01T23:59:59.000Z

7

CFD simulation of neutral ABL flows Xiaodong Zhang  

E-Print Network [OSTI]

Title: CFD simulation of neutral ABL flows Division: Aero-elastic Design ­ Wind Energy Division Risø flow field over different terrains employing Fluent 6.3 software. How accurate the simulation could.5 Comparison and conclusion 22 3.6 Closure 24 4 CFD Simulation of the Askervein Hill 24 4.1 Simulation

8

CFD Simulation of Riser VIV  

E-Print Network [OSTI]

jsjj , ?? ??? ? +?= m DB s?2 , 1=C , Eq. (13) is simplified as 0** 2 =++ CGBGA , and the amplification factor G is given by: A ACBBG 2 42 2,1 ???= . 17 For the special case of 0=sD and 0=w (i.e., Tj = const), the present... OF TABLES .................................................................................................... xx CHAPTER I INTRODUCTION AND LITERATURE REVIEW............................ 1 II VIV SIMULATION TECHNIQUES...

Huang, Zhiming

2012-07-16T23:59:59.000Z

9

CFD simulation of leak in residential HVAC ducts  

Science Journals Connector (OSTI)

A three-dimensional computational fluid dynamics model was used to simulate fluid flow in a duct and its simulated leaks with six different air leak geometries placed respectively on its periphery. The k–? turbulence model for high Reynolds numbers flows was used for that purpose and the Reynolds numbers were varied to simulate a variety of flow conditions between 27,000 and 82,000. The computer code was used to produce pressure drop data and leak flow rates across the holes necessary to compute the pressure loss coefficients, as well as to produce flow field and static pressure plots that offer insight into the physics of the flow field. The flow coefficient and pressure exponent (C and n) were found for different leak geometries by curve fitting the pressure and leak flow data derived from CFD simulations and were compared to available data in the literature.

Samir Moujaes; Radhika Gundavelli

2012-01-01T23:59:59.000Z

10

CFD Simulation of the NREL Phase VI Rotor  

E-Print Network [OSTI]

The simulation of the turbulent and potentially separating flow around a rotating, twisted, and tapered airfoil is a challenging task for CFD simulations. This paper describes CFD simulations of the NREL Phase VI turbine that was experimentally characterized in the 24.4m x 36.6m NREL/NASA Ames wind tunnel (Hand et al., 2001). All computations in this article are performed on the experimental base configuration of 0o yaw angle, 3o tip pitch angle, and a rotation rate of 72 rpm. The significance of specific mesh resolution regions to the accuracy of the CFD prediction is discussed. The ability of CFD to capture bulk quantities, such as the shaft torque, and the detailed flow characteristics, such as the surface pressure distributions, are explored for different inlet wind speeds. Finally, the significant three-dimensionality of the boundary layer flow is demonstrated.

Song, Yang

2014-01-01T23:59:59.000Z

11

Multiscale CFD simulations of entrained flow gasification  

E-Print Network [OSTI]

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, ...

Kumar, Mayank, Ph. D. Massachusetts Institute of Technology

2011-01-01T23:59:59.000Z

12

SciTech Connect: Development of CFD-Based Simulation Tools for...  

Office of Scientific and Technical Information (OSTI)

Development of CFD-Based Simulation Tools for In-Situ Thermal Processing of Oil ShaleSands Citation Details In-Document Search Title: Development of CFD-Based Simulation Tools for...

13

Computational Fluid Dynamics (CFD) Modeling for High Rate Pulverized Coal Injection (PCI) into the Blast Furnace  

SciTech Connect (OSTI)

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.

Dr. Chenn Zhou

2008-10-15T23:59:59.000Z

14

Modeling and CFD Simulation of Water Desalination Using Nanoporous Membrane Contactors  

Science Journals Connector (OSTI)

Modeling and CFD Simulation of Water Desalination Using Nanoporous Membrane Contactors ... It also avoids common problems encountered in conventional contactors such as flooding, foaming, and entraining. ... A series of CFD simulations have been carried out for single-fiber modules using simplified 2D heat-transfer models. ...

Mehdi Ghadiri; Safoora Fakhri; Saeed Shirazian

2013-02-07T23:59:59.000Z

15

CFD Simulation of Brine-Seawater Mixing in a Rotary Energy Recovery Device  

Science Journals Connector (OSTI)

CFD Simulation of Brine-Seawater Mixing in a Rotary Energy Recovery Device ... The effects of operational conditions on the mixing behavior of rotary energy recovery device have been systematically investigated through the combined methods of computational fluid dynamics and validating experiments in this paper. ... The obtained formulas between mixing and dimensionless flow length provide a simple way to calculate and predict the mixing of device, which will be beneficial to design and operate the rotary energy recovery device in a lower mixing level. ...

Enle Xu; Yue Wang; Liming Wu; Shichang Xu; Yuxin Wang; Shichang Wang

2014-11-05T23:59:59.000Z

16

A CFD simulation on how the different sizes of silica gel will affect the adsorption performance of silica gel  

Science Journals Connector (OSTI)

The application of computational fluid dynamics (CFD) in the area of porous media and adsorption cooling system is becoming more practical due to the significant improvement in computer power. The results from previous studies have shown that CFD can ...

John White

2012-01-01T23:59:59.000Z

17

CFD Numerical Simulation of Vortex-Induced Vibration of a Stay Cable under a Wind Profile  

Science Journals Connector (OSTI)

VIV (Vortex-induced vibration) of a stay cable subjected to a wind profile is numerically simulated through combining CFD ... numerical model. Under a profile of mean wind speed, unsteady aerodynamic lift coeffic...

Wenli Chen; Hui Li

2009-01-01T23:59:59.000Z

18

CFD Simulation and Measurement Validation of Air Distribution at the Hunan International Exhibition Center  

E-Print Network [OSTI]

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

19

Numerical simulation of the air flow field in a laboratory fume hood using the CFD-ACE(TM) computational fluid dynamics code  

E-Print Network [OSTI]

turbulence models. These models expressed in differential and or algebraic form with the Navier-Stokes and continuity equations make a closed set. The turbulence models simulate the averaged character of the real turbulence. In 1877, Boussinesq proposed... (15) The Reynolds stress tensor based on the Boussinesq assumption is then given by (pp SUJET 2 c~x zsxi (16) where Ps is the Kronecker delta and rc is the kinetic energy of turbulence. In equation 16, o?. . = 1 for i = j and o, = 0 for i w j...

D'Sousa, Cedric Benedict

2012-06-07T23:59:59.000Z

20

Performance of Coupled Building Energy and CFD Simulations Zhiqiang (John) Zhai  

E-Print Network [OSTI]

and CFD. This investigation implemented these concepts and developed an integrated building design tool, E, West Lafayette, IN 47907-2088, USA Abstract The integration of building energy simulation (ES of the integrated building simulation over the separated energy simulation and computational

Chen, Qingyan "Yan"

Note: This page contains sample records for the topic "dynamics cfd simulations" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


21

CFD Simulation of Open Channel Flooding Flows and Scouring Around Bridge Structures  

E-Print Network [OSTI]

CFD Simulation of Open Channel Flooding Flows and Scouring Around Bridge Structures B. D. ADHIKARYKalb, IL 60115 U.S.A. Email: kostic@niu.edu; Web: http://www.kostic.niu.edu Abstract: - Simulation of scour caused by flooding and pressure flow conditions, is of significant interest nowadays to computational

Kostic, Milivoje M.

22

Development of CFD Simulation for 3-D Flooding Flow and Scouring Around a Bridge Structure  

E-Print Network [OSTI]

Development of CFD Simulation for 3-D Flooding Flow and Scouring Around a Bridge Structure B of bridge failure during storms and floods. Simulation of scour-hole formation under the bridge deck and around the bridge piers, due to sediment entrainment and transport caused by flooding flow conditions

Kostic, Milivoje M.

23

European Conference on Computational Fluid Dynamics ECCOMAS CFD 2006  

E-Print Network [OSTI]

aluminum tubes due to the passage of ethylene-oxygen detonation waves is presented. 1 INTRODUCTION The Center for Simulation of Dynamic Response of Materials at the California In- stitute of Technology has reliably with such a "weakly coupled" method, when the evolving interface geometry and velocities

Barr, Al

24

Dynamic Positioning Simulator Dynamic Positioning Simulator  

E-Print Network [OSTI]

Simulator 5 / 24 #12;Dynamic Positioning Simulator Dynamic Positioning Why Dynamic Positioning? Advantages Dynamic Positioning: No tugboats needed; Offshore set-up is quick; Power saving; Precision situations more on Ship: Wind Force Fw = 1 2 air V 2 rw CXw (rw )AT 1 2 air V 2 rw CYw (rw )AL Mw = 1 2 air V 2 rw CMw (rw

Vuik, Kees

25

Accurate Predictions of Fuel Effects on Combustion and Emissions in Engines Using CFD Simulations With Detailed Fuel Chemistry  

Broader source: Energy.gov [DOE]

Accurate fuel models with hundreds of species in advanced CFD with reasonable simulation times. Reaction workbench used for surrogate blend formulation and model reduction. FORTE CFD used for HCCI and LTC diesel engine and validated for PRF-ethanol and diesel

26

CFD simulations of enhanced condensational growth (ECG) applied to respiratory drug delivery with comparisons to in vitro data  

E-Print Network [OSTI]

CFD simulations of enhanced condensational growth (ECG) applied to respiratory drug delivery t Enhanced condensational growth (ECG) is a newly proposed concept for respiratory drug delivery in which and evaluate a CFD model of ECG in a simple tubular geometry with direct comparisons to in vitro results

Frey, Pascal

27

Designing high power targets with computational fluid dynamics (CFD)  

SciTech Connect (OSTI)

High power liquid hydrogen (LH2) targets, up to 850 W, have been widely used at Jefferson Lab for the 6 GeV physics program. The typical luminosity loss of a 20 cm long LH2 target was 20% for a beam current of 100 ?A rastered on a square of side 2 mm on the target. The 35 cm long, 2500 W LH2 target for the Qweak experiment had a luminosity loss of 0.8% at 180 ?A beam rastered on a square of side 4 mm at the target. The Qweak target was the highest power liquid hydrogen target in the world and with the lowest noise figure. The Qweak target was the first one designed with CFD at Jefferson Lab. A CFD facility is being established at Jefferson Lab to design, build and test a new generation of low noise high power targets.

Covrig, S. D. [Thomas Jefferson National Laboratory, Newport News, VA 23606 (United States)

2013-11-07T23:59:59.000Z

28

Developing an integrated building design tool by coupling building energy simulation and computational fluid dynamics programs  

E-Print Network [OSTI]

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 ...

Zhai, Zhiqiang, 1971-

2003-01-01T23:59:59.000Z

29

CFD SIMULATION OF PROPOSED VALIDATION DATA FOR A FLOW PROBLEM RECONFIGURED TO ELIMINATE AN UNDESIRABLE FLOW INSTABILITY  

SciTech Connect (OSTI)

The U. S. Department of Energy (DOE) is supporting the development of a next generation nuclear plant (NGNP), which will be based on a very high temperature reactor (VHTR) design. The VHTR is a single-phase helium-cooled reactor wherein the helium will be heated initially to 750 °C and later to temperatures approaching 1000 °C. The high temperatures are desired to increase reactor efficiency and to provide a heat source for the manufacture of hydrogen and other applications. While computational fluid dynamics (CFD) has not been used in the past to design or license nuclear reactors in the U. S., it is expected that CFD will be used in the design and safety analysis of forthcoming designs. This is partly because of the maturity of CFD and partly because detailed information is desired of the flow and heat transfer inside the reactor to avoid hot spots and other conditions that might compromise reactor safety. Numerical computations of turbulent flow should be validated against experimental data for flow conditions that contain some or all of the physics expected in the thermal fluid machinery of interest. To this end, a scaled model of a narrow slice of the lower plenum of the prismatic VHTR was constructed and installed in the Idaho National Laboratory’s (INL) matched index of refraction (MIR) test facility and data were taken. The data were then studied and compared to CFD calculations to help determine their suitability for validation data. One of the main findings was that the inlet data, which were measured and controlled by calibrated mass flow rotameters and were also measured using detailed stereo particle image velocimetry (PIV) showed considerable discrepancies in mass flow rate between the two methods. The other finding was that a randomly unstable recirculation zone occurs in the flow. This instability has a very significant effect on the flow field in the vicinity of the inlet jets. Because its time scale is long and because it is apparently a random instability, it was deemed undesirable for a validation data set. It was predicted using CFD that by eliminating the first of the four jets, the recirculation zone could be stabilized. The present paper reports detailed results for the three-jet case with comparisons to the four-jet data inasmuch as three-jet data are still unavailable. Hence, the present simulations are true or blind predictions.

Richard W. Johnson; Hugh M. McIlroy

2010-08-01T23:59:59.000Z

30

CFD Simulation of Combustion in a 150 MWe CFB Boiler  

Science Journals Connector (OSTI)

Eulerian granular multiphase model with meso-scale modeling of drag coefficient and mass transfer coefficient, based on the energy minimization multi-scale (EMMS) model, was presented to simulate a 150 MWe CFB bo...

Nan Zhang; Wei Wang; Jinghai Li

2013-01-01T23:59:59.000Z

31

With faster processors and better numerical techniques, computational fluid dynamics (CFD) tools have revolutionized engineering design and optimization--  

E-Print Network [OSTI]

With faster processors and better numerical techniques, computational fluid dynamics (CFD) tools have revolutionized engineering design and optimization-- limiting expensive experimentation and Engineering Division (GED) at Southwest Research Institute® (SwRI®) has extensive experience and capabilities

Chapman, Clark R.

32

Three-dimensional Computational Fluid Dynamics (CFD) modeling of dry spent nuclear fuel storage canisters  

SciTech Connect (OSTI)

One of the interim storage configurations being considered for aluminum-clad foreign research reactor fuel, such as the Material and Testing Reactor (MTR) design, is in a dry storage facility. To support design studies of storage options, a computational and experimental program was conducted at the Savannah River Site (SRS). The objective was to develop computational fluid dynamics (CFD) models which would be benchmarked using data obtained from a full scale heat transfer experiment conducted in the SRS Experimental Thermal Fluids Laboratory. The current work documents the CFD approach and presents comparison of results with experimental data. CFDS-FLOW3D (version 3.3) CFD code has been used to model the 3-dimensional convective velocity and temperature distributions within a single dry storage canister of MTR fuel elements. For the present analysis, the Boussinesq approximation was used for the consideration of buoyancy-driven natural convection. Comparison of the CFD code can be used to predict reasonably accurate flow and thermal behavior of a typical foreign research reactor fuel stored in a dry storage facility.

Lee, S.Y.

1997-06-01T23:59:59.000Z

33

Demonstration of a Computational Fluid Dynamics (CFD) Tool Used for Data  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Demonstration of a Computational Fluid Dynamics (CFD) Tool Used for Data Demonstration of a Computational Fluid Dynamics (CFD) Tool Used for Data Center Modeling, Thermal Analysis and Operational Management Speaker(s): Saket Karajgikar Date: November 11, 2010 - 12:00pm Location: 90-3122 Seminar Host/Point of Contact: Henry Coles Every Data Center built today is designed with a total capacity in mind, as well as a plan to grow into this final-day load. On a daily basis, Data Center Operations/Management professionals work toward keeping their Data Center as close to this plan as possible by concurrently managing the available power, space, cooling and airflow resources. Unfortunately, lack of communication and information, the pace of change and difficulty in coping with the ever growing power densities of IT equipment can prevent a

34

Application of computational fluid dynamics (CFD) to nuclear applications.  

SciTech Connect (OSTI)

Detailed analysis of a quarter channel was performed using VIPRE and CFX. Results show that VIPRE and CFX agree closely in both cross-sectionally averaged axial temperature and cross-sectionally averaged axial velocity profiles. Detailed temperature distributions in the radial direction over 1mm from the clad surface towards the center of the channel were calculated using CFX, showing significant local variation. This information can be used for example, to determine if this temperature will lead to bubble nucleation. Quarter subassembly calculations were made with both VIPRE and STAR-CD. Comparison between the solutions show that the two codes yield very similar solutions under comparable conditions. However, the STAR-CD CFD calculation provides the analyst with much more detailed flow and temperature distributions than can be predicted by a one-dimensional code such as VIPRE. In addition, a 60 million cell one-eighth reactor core calculation was made using STAR-CD. This analysis showed the importance of accurately predicting the flow and temperature fields in all assemblies simultaneously with modern parallel processing technology, practical turnaround for these types of calculation can be obtained.

Brewster, R. A.; Jonnavithula, S.; Rizwan-Uddin; Rock, D. T.; Weber, D. P.; Wei, T. Y. C.

1999-02-08T23:59:59.000Z

35

Vehicle Technologies Office Merit Review 2014: CFD Simulations and Experiments to Determine the Feasibility of Various Alternate Fuels for Compression Ignition Engine Applications  

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...

36

CFD model for the simulation of chemical looping combustion  

Science Journals Connector (OSTI)

Abstract A chemical looping combustion (CLC) system uses a metal oxide solid carrier to combust a source of fuel in isolation from the source of oxygen which produces an exhaust gas of primarily carbon dioxide and water. In this work, a full three-dimensional model of a chemical looping combustion system was developed to simulate the particle–fluid hydrodynamics, thermal characteristics, and reaction efficiency of the CLC system using coal particles as a fuel source. Multiple heterogeneous and homogenous reactions are considered in the CLC model including the oxidation and reduction reactions of the metal oxide carrier and gasification reactions. Within each coal particle, the temperature-dependent devolatilization, moisture release, and particle swelling effects are included. Modeling results showing fluidization regimes, circulation rate, reactor efficiencies, and temperature profiles are presented to demonstrate the utility of the model.

James M. Parker

2014-01-01T23:59:59.000Z

37

Development of CFD-Based Simulation Tools for In-Situ Thermal Processing of Oil Shale/Sands  

SciTech Connect (OSTI)

In our research, we are taking the novel approach of developing and applying high performance computing, computational fluid dynamics (CFD)-based simulation tools to a modified in-situ process for production of oil from oil shale. The simulation tools being developed capture the relevant physical processes and data from a large-scale system. The modified in-situ application is a pilot-scale heat transfer process inside Red Leaf Resourcesâ?? EcoShale capsule. We demonstrate the need to understand fluid flow behavior in the convective channels of the rubblized shale bed as convective heating greatly decreases the time required to heat the oil shale to the production temperature when compared with conductive heating alone. We have developed and implemented a geometry creation strategy for a representative section of the EcoShale capsule, developed a meshing approach to deal with the complicated geometry and produce a well-behaved mesh, analyzed the effects of boundary conditions on the simulation results, and devised a new operator splitting solution algorithm that reduces computational costs by taking advantage of the differing convective and conductive time scales occurring in the simulation. These simulation tools can be applied to a wide range of processes involving convective fluid flow heating in rubblized beds.

None

2012-04-30T23:59:59.000Z

38

Uncovering MIT wind myths through micro-climatological CFD analysis  

E-Print Network [OSTI]

Popular campus myths of unusually strong pedestrian level winds are investigated with a Computational Fluid Dynamics (CFD) approach. The numerical simulations confirm the existence of the reported phenomena and provide a qualitative explanation of their physical mechanisms.

Kalmikov, Alexander

2013-01-01T23:59:59.000Z

39

COMPUTATIONAL FLUID DYNAMICS MODELING OF SCALED HANFORD DOUBLE SHELL TANK MIXING - CFD MODELING SENSITIVITY STUDY RESULTS  

SciTech Connect (OSTI)

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.

JACKSON VL

2011-08-31T23:59:59.000Z

40

CFD [computational fluid dynamics] And Safety Factors. Computer modeling of complex processes needs old-fashioned experiments to stay in touch with reality.  

SciTech Connect (OSTI)

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.

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

Note: This page contains sample records for the topic "dynamics cfd simulations" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


41

Improving the representation of thermal boundary conditions of livestock during CFD modelling of the indoor environment  

Science Journals Connector (OSTI)

The use of computational fluid dynamics (CFD) to evaluate the climate distribution in agricultural buildings has grown in importance in recent years. Convection and radiation are the dominant forms of heat transfer from an animal's body, and accurately ... Keywords: Airflow, Animal house, CFD, Computational fluid dynamics, Livestock building, Optimisation, Simulation, Temperature, Ventilation

Tomás Norton; Jim Grant; Richard Fallon; Da-Wen Sun

2010-07-01T23:59:59.000Z

42

Multidimensional CFD simulation of syngas combustion in a micro-pilot-ignited dual-fuel engine using a constructed chemical kinetics mechanism  

Science Journals Connector (OSTI)

A multidimensional computational fluid dynamics (CFD) simulation of a constructed syngas chemical kinetic mechanism was performed to evaluate the combustion of syngas in a supercharged dual-fuel engine for various syngas initial compositions under lean conditions. The modelled results were validated by comparing predictions against corresponding experimental data for a supercharged dual-fuel engine. The predicted and measured in-cylinder pressure, temperature, and rate of heat release (ROHR) data were in good agreement. The effect of the hydrogen peroxide chain-propagation reaction on the progress of combustion under supercharged conditions was examined for different types of syngas using various initial H2 concentrations. The effect of the main syngas kinetic mechanism reactions on the combustion progress was analysed in terms of their contribution to the total heat of the reaction. The best results compared with experimental data were obtained in the range of equivalence ratios below about 0.8 for all types of syngas considered in this paper. As the equivalence ratio increased above 0.8, the results deviated from the experiment data. The spatial distribution of the in-cylinder temperature and OH? within this equivalence-ratio range showed the completeness of the combustion. The present CFD model captured the overall combustion process well and could be further developed into a useful tool for syngas-engine combustion simulations.

Ulugbek Azimov; Masahiro Okuno; Kazuya Tsuboi; Nobuyuki Kawahara; Eiji Tomita

2011-01-01T23:59:59.000Z

43

A Simple Interface to Computational Fluid Dynamics Programs for Building Environment Simulations  

E-Print Network [OSTI]

. SCI can be easily integrated into new CFD programs. Introduction Advanced building design requests and pressure distributions that are crucial for thermal comfort and building structure designs. TraditionallyA Simple Interface to Computational Fluid Dynamics Programs for Building Environment Simulations

Chen, Qingyan "Yan"

44

CFD Simulation of the CANDU-6 Moderator Circulation Under Normal Operating Conditions  

SciTech Connect (OSTI)

A steady-state 3D simulation for predicting the local subcooling of the moderator in the vicinity of the calandria tubes in a CANDU-6 reactor is performed. For the current simulation, a set of grid structures with the same geometry as the CANDU-6 moderator tank, called 'calandria vessel', is generated and the momentum, heat and continuity equations are solved by CFX-4.3, a CFD code developed by AEA technology. The standard k-{epsilon} turbulence model associated with logarithmic wall treatment is used to model turbulence generation and dissipation within the vessel. The moderator fluid is heavy water. Buoyancy forces are modeled using the Boussinesq approximation in which density is assumed to be a linear function of temperature. The matrix of the calandria tubes in the center region of the calandria vessel is simplified by the porous media approach. The anisotropic hydraulic impedance of the calandria tubes is modeled using the frictional pressure drop correlations suggested by Idelchik and Szymanski. The heat load in this steady-state simulation is conservatively set as 103 MW of 103% full power, consisting of 96.7 MW to the core region and 6.3 MW to the reflector region. The total volumetric flow rate through eight inlet nozzles is 940 L/s and the outlet temperature is constantly 71.0 deg. C. The thermal boundary condition of the circumferential vessel wall is assumed a little heat flux out. As a result, the velocity field and temperature distribution of a CANDU-6 moderator in the operating condition are presented. The flow pattern identified in this simulation is the weak jet momentum-dominated flow, which is generated by the interaction between the buoyancy force by heating and the dominant momentum forces by inlet jets. The calculated maximum temperature of the moderator is 83.0 deg. C at the lower center region of the core, which corresponds to the minimum subcooling of 33.0 deg. C considering the boiling point increase due to the hydrostatic pressure change. (authors)

Bo Wook Rhee; Churl Yoon; Byung-Joo Min [Korea Atomic Energy Research Institute, 150, Dukjin-Dong, Yusong-Gu, Taejon 305-353 (Korea, Republic of)

2002-07-01T23:59:59.000Z

45

Dynamic simulation of Odoo  

Science Journals Connector (OSTI)

Abstract The thermal habits of Odoo were examined and energy consumption data were also predicted. Special tests were performed for the time of the competition, and whole year was also analysed. The climatic data were of Madrid as the competition took place there. The modelling environment was MATLAB's Simulink with a built-in module of Simscape. It is for especially examining thermal behaviours. MATLAB itself is capable of solving differential equations by time, for this reason dynamic simulations can be performed. First the building structure was created, and then the heatflows affecting the internal temperature were added. In this paper detailed process of creating the model is presented, and some results are discussed, including some possibilities of further improvements.

Gábor Haas-Schnabel; Csaba Szikra

2014-01-01T23:59:59.000Z

46

CFD simulating the transient thermal–hydraulic characteristics in a 17 × 17 bundle for a spent fuel pool under the loss of external cooling system accident  

Science Journals Connector (OSTI)

Abstract This paper develops a three-dimensional (3-D) transient computational fluid dynamics (CFD) model to simulate the thermal–hydraulic characteristics in a fuel bundle located in a spent fuel pool (SFP) under the loss of external cooling system accident. The SFP located in the Maanshan nuclear power plant (NPP) is selected herein. Without adopting the porous media approach usually used in the previous CFD works, this model uses a real-geometry simulation of a 17 × 17 fuel bundle, which can obtain the localized distributions of the flow and heat transfer during the accident. These distribution characteristics include several peaks in the axial distributions of flow, pressure, temperature, and Nusselt number (Nu) near the support grids, the non-uniform distribution of secondary flow, and the non-uniform temperature distribution due to flow mixing between rods, etc. According to the conditions adopted in the Procedure 597.1 (MNPP Plant Procedure 597.1, 2010) for the management of the loss-of-cooling event of the spent fuel pool in the Maanshan NPP, the temperature rising rate predicted by the present model can be equivalent to 1.26 K/h, which is the same order as that of 3.5 K/h in the this procedure. This result also confirms that the temperature rising rate used in the Procedure 597.1 for the Maanshan NPP is conservative. In addition, after the loss of external cooling system, there are about 44 h for the operator to repair the malfunctioning system or provide the alternative water source for the pool inventory to avoid the occurrence of the local boiling in the SFP based on the present predicted temperature rising rate.

S.R. Chen; W.C. Lin; Y.M. Ferng; C.C. Chieng; B.S. Pei

2014-01-01T23:59:59.000Z

47

Evaluation of a CFD-model for simulation of simplified flow conditioners  

SciTech Connect (OSTI)

Perforated plate flow conditioners are used to generate a fully developed turbulent flow profile upstream of an orifice meter. It is very time-consuming to measure the effect of a flow conditioner for different upstream flow profiles. Therefore a project is initiated to evaluate the performance of a computational fluid computer code for this purpose. If the code correctly predicts the flow characteristics downstream of more complex flow conditioners. In this study a k-{var_epsilon} CFD-model was used to predict the flow downstream of obstruction plates having one large or nine small holes. Both mean velocity, turbulent kinetic energy, k, and the dissipation rate of turbulent kinetic energy, {var_epsilon}, were calculated and compared against measured data. The results indicate that it is possible to predict the mean velocity well and that the accuracy of the predicted k and {var_epsilon} depends on the complexity of the flow.

Erdal, A. [Statoil/K-LAB, Haugesund (Norway); Torbergsen, L.E.; Rimestad, S.; Krogstad, P.A. [Norwegian Inst. of Technology, Trondheim (Norway)

1995-12-31T23:59:59.000Z

48

The MAX facility for CFD code validation  

SciTech Connect (OSTI)

ANL has recently completed construction of a fluid dynamics test facility devised to provide validation data for CFD simulation tools used to evaluate various aspects of nuclear power plant design and safety. Experiments with the facility involve mixing air jets within a 1x1x1.7m long glass tank at atmospheric pressure. A particle image velocimetry system measures flow velocity and turbulence quantities within the tank while a high-speed infrared camera records temperatures across the tank lid. The tandem of high fidelity thermal and turbulence data is particularly useful for benchmarking transient heat transfer phenomena such as thermal striping. This paper describes the MAX facility, preliminary data obtained during shakedown tests, and the results of companion CFD calculations employing RANS-based Star-CCM+ and large eddy simulations with Nek 5000. (authors)

Lomperski, S.; Merzari, E.; Obabko, A.; Pointer, W. D.; Fischer, P. [Argonne National Laboratory, Bldg. 206, 9700 S. Cass Ave, Argonne, IL 60439 (United States)

2012-07-01T23:59:59.000Z

49

CFD simulation of heat transfer enhancement of Al2O3/water and Al2O3/ethylene glycol nanofluids in a car radiator  

Science Journals Connector (OSTI)

Abstract The present numerical study simulated turbulent and laminar flow heat transfer in nanofluids (Al2O3 particles in water and ethylene glycol-based fluid) passing through a flat tube in 3D using computational fluid dynamics (CFD) for single and two-phase approaches. The advantages over pure base fluids were evaluated. Empirical correlations were used to calculate nanofluid viscosity and thermal conductivity as a function of the volumetric concentration of the nanoparticles. First, the Nusselt numbers of the pure water and pure ethylene glycol in flat tubes were compared with the experimental data. Next, the Nusselt numbers for both approaches were compared with those for experimental data at the same Reynolds number for different concentrations of nanoparticles. A small difference in the friction factors of the tube was observed between the two approaches and the Nusselt number for the two-phase model was markedly different from that for the single-phase model; however, the volumetric flow for the same heat transfer rate decreased and less pumping power was required for the nanofluids.

Vahid Delavari; Seyed Hassan Hashemabadi

2014-01-01T23:59:59.000Z

50

Modeling Molecular Dynamics from Simulations  

SciTech Connect (OSTI)

Many important processes in biology occur at the molecular scale. A detailed understanding of these processes can lead to significant advances in the medical and life sciences. For example, many diseases are caused by protein aggregation or misfolding. One approach to studying these systems is to use physically-based computational simulations to model the interactions and movement of the molecules. While molecular simulations are computationally expensive, it is now possible to simulate many independent molecular dynamics trajectories in a parallel fashion by using super- or distributed- computing methods such as Folding@Home or Blue Gene. The analysis of these large, high-dimensional data sets presents new computational challenges. In this seminar, I will discuss a novel approach to analyzing large ensembles of molecular dynamics trajectories to generate a compact model of the dynamics. This model groups conformations into discrete states and describes the dynamics as Markovian, or history-independent, transitions between the states. I will discuss why the Markovian state model (MSM) is suitable for macromolecular dynamics, and how it can be used to answer many interesting and relevant questions about the molecular system. I will also discuss many of the computational and statistical challenges in building such a model, such as how to appropriately cluster conformations, determine the statistical reliability, and efficiently design new simulations.

Hinrichs, Nina Singhal (University of Chicago) [University of Chicago

2009-01-28T23:59:59.000Z

51

NUMERICAL DETERMINATION AND TREATMENT OF CONVECTIVE HEAT TRANSFER COEFFICIENT IN THE COUPLED BUILDING ENERGY AND CFD SIMULATION  

E-Print Network [OSTI]

for the correct prediction of the convective heat. A finer grid resolution in CFD does not always lead to a more conservation equations of flow on these grid cells. As shown in Figure 1(a), CFD calculates convective heat1 NUMERICAL DETERMINATION AND TREATMENT OF CONVECTIVE HEAT TRANSFER COEFFICIENT IN THE COUPLED

Chen, Qingyan "Yan"

52

Accelerated Molecular Dynamics Simulation of Thermal Desorption.  

E-Print Network [OSTI]

??Desorption is a process ubiquitous in phenomena involving surfaces. However, it has rarely been simulated on the molecular level. Molecular dynamics simulation can provide the… (more)

Becker, Kelly

2008-01-01T23:59:59.000Z

53

Performance of a municipal solid waste (MSW) incinerator predicted with a computational fluid dynamics (CFD) code  

SciTech Connect (OSTI)

The purpose of this paper is to investigate by the means of numerical simulation the performance of the MSW incinerator with of Vercelli (Italy). FLUENT, a finite-volumes commercial code for Fluid Dynamics has been used to predict the 3-D reacting flows (gaseous phase) within the incinerator geometry, in order to estimate if the three conditions settled by the Italian law (P.D. 915 / 82) are respected: (a) Flue gas temperature at the input of the secondary combustion chamber must exceed 950 C. (b) Oxygen concentration in the same section must exceed 6 %. (c) Residence time for the flue gas in the secondary combustion chamber must exceed 2 seconds. The model of the incinerator has been created using the software pre-processing facilities (wall, input, outlet and live cells), together with the set-up of boundary conditions. There are also imposed the combustion constants (stoichiometry, heat of combustion, air excess). The solving procedure transforms at the level of each live cell the partial derivative equations in algebraic equations, computing the velocities field, the temperatures, gases concentration, etc. These predicted values were compared with the design properties, and the conclusion was that the conditions (a), (b), (c), are respected in normal operation. The powerful graphic interface helps the user to visualize the magnitude of the computed parameters. These results may be successfully used for the design and operation improvements for MSW incinerators. This fact will substantially increase the efficiency, reduce pollutant emissions and optimize the plant overall performance.

Anglesio, P.; Negreanu, G.P.

1998-07-01T23:59:59.000Z

54

Radiation in molecular dynamic simulations  

SciTech Connect (OSTI)

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.

Glosli, J; Graziani, F; More, R; Murillo, M; Streitz, F; Surh, M

2008-10-13T23:59:59.000Z

55

Two-Dimensional Computational Fluid Dynamics and Conduction Simulations of Heat Transfer in Horizontal Window Frames with Internal Cavities  

SciTech Connect (OSTI)

This paper assesses the accuracy of the simplified frame cavity conduction/convection and radiation models presented in ISO 15099 and used in software for rating and labeling window products. Temperatures and U-factors for typical horizontal window frames with internal cavities are compared; results from Computational Fluid Dynamics (CFD) simulations with detailed radiation modeling are used as a reference. Four different frames were studied. Two were made of polyvinyl chloride (PVC) and two of aluminum. For each frame, six different simulations were performed, two with a CFD code and four with a building-component thermal-simulation tool using the Finite Element Method (FEM). This FEM tool addresses convection using correlations from ISO 15099; it addressed radiation with either correlations from ISO 15099 or with a detailed, view-factor-based radiation model. Calculations were performed using the CFD code with and without fluid flow in the window frame cavities; the calculations without fluid flow were performed to verify that the CFD code and the building-component thermal-simulation tool produced consistent results. With the FEM-code, the practice of subdividing small frame cavities was examined, in some cases not subdividing, in some cases subdividing cavities with interconnections smaller than five millimeters (mm) (ISO 15099) and in some cases subdividing cavities with interconnections smaller than seven mm (a breakpoint that has been suggested in other studies). For the various frames, the calculated U-factors were found to be quite comparable (the maximum difference between the reference CFD simulation and the other simulations was found to be 13.2 percent). A maximum difference of 8.5 percent was found between the CFD simulation and the FEM simulation using ISO 15099 procedures. The ISO 15099 correlation works best for frames with high U-factors. For more efficient frames, the relative differences among various simulations are larger. Temperature was also compared, at selected locations on the frames. Small differences was found in the results from model to model. Finally, the effectiveness of the ISO cavity radiation algorithms was examined by comparing results from these algorithms to detailed radiation calculations (from both programs). Our results suggest that improvements in cavity heat transfer calculations can be obtained by using detailed radiation modeling (i.e. view-factor or ray-tracing models), and that incorporation of these strategies may be more important for improving the accuracy of results than the use of CFD modeling for horizontal cavities.

Gustavsen, Arlid; Kohler, Christian; Dalehaug, Arvid; Arasteh, Dariush

2008-12-01T23:59:59.000Z

56

Numerical modelling of solid fuel combustion processes using advanced CFD-based simulation tools  

Science Journals Connector (OSTI)

Computational modelling of combustion processes has been the subject of coninuous research at the Institute of Process Engineering and Power Plant Technology (IVD) over the last two decades. To this end, finite-volume-based computer codes have been developed. In the present paper, some fundamental ideas and approaches of the applied mathematical models and the numerical methods are described, followed by some examples of typical applications of the procedures with special emphasis on the validation of simulation results. These examples show that the application of combustion simulation codes has been extended to comprise a wide range of several different areas ranging from huge bituminous coal-fired utility boilers for electricity production to decentralised small-scale furnaces and tile stove heating inserts for domestic heating.

Uwe Schnell

2001-01-01T23:59:59.000Z

57

3D Computational Fluid Dynamics Simulation of Natural Coke Steam Gasification in General and Improved Fluidized Beds  

Science Journals Connector (OSTI)

The thermal characteristics of natural coke steam gasification in a fluidized bed were three-dimensionally (3D) simulated based on the computational fluid dynamics (CFD) method using Fluent code. ... However, this technology seems difficult to carry out due to its abradability, hard ignition, hot burst, and so on. ... In short, all the results in this work have a significance to provide the theoretical basis for the design, operational optimization, and scale-up of the natural coke steam gasification process. ...

Ya-li Tang; Dai-jun Liu; Yu-hong Liu; Qian Luo

2010-09-30T23:59:59.000Z

58

Efficient simulation of press hardening process through integrated structural and CFD analyses  

SciTech Connect (OSTI)

Press hardened steel parts are being increasingly used in automotive structures for their higher strength to meet safety standards while reducing vehicle weight to improve fuel consumption. However, manufacturing of sheet metal parts by press hardening process to achieve desired properties is extremely challenging as it involves complex interaction of plastic deformation, metallurgical change, thermal distribution, and fluid flow. Numerical simulation is critical for successful design of the process and to understand the interaction among the numerous process parameters to control the press hardening process in order to consistently achieve desired part properties. Until now there has been no integrated commercial software solution that can efficiently model the complete process from forming of the blank, heat transfer between the blank and tool, microstructure evolution in the blank, heat loss from tool to the fluid that flows through water channels in the tools. In this study, a numerical solution based on Altair HyperWorks® product suite involving RADIOSS®, a non-linear finite element based structural analysis solver and AcuSolve®, an incompressible fluid flow solver based on Galerkin Least Square Finite Element Method have been utilized to develop an efficient solution for complete press hardening process design and analysis. RADIOSS is used to handle the plastic deformation, heat transfer between the blank and tool, and microstructure evolution in the blank during cooling. While AcuSolve is used to efficiently model heat loss from tool to the fluid that flows through water channels in the tools. The approach is demonstrated through some case studies.

Palaniswamy, Hariharasudhan [Altair, 1820 East Big Beaver Road, Troy, MI 48083 (United States); Mondalek, Pamela; Wronski, Maciek [Altair Development France, Sophia Antipolis Cedex 06903 (France); Roy, Subir [Altair, 1820 East Big Beaver Road, Troy, MI 48083 (France)

2013-12-16T23:59:59.000Z

59

CFD analysis of laminar oscillating flows  

SciTech Connect (OSTI)

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.

Booten, C. W. Charles W.); Konecni, S. (Snezana); Smith, B. L. (Barton L.); Martin, R. A. (Richard A.)

2001-01-01T23:59:59.000Z

60

American Institute of Aeronautics and Astronautics Coupled Flight Dynamics and CFD Analysis of Pilot  

E-Print Network [OSTI]

of the ship airwake on the rotorcraft as well as the effect of the rotorcraft on the ship airwake can of Pilot Workload in Ship Airwakes Derek O. Bridges,1 Joseph F. Horn,2 Emre Alpman,3 and Lyle N. Long4 of the helicopter/ship dynamic interface, in which pilot workload is examined using a novel coupling of flight

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61

Sandia National Laboratories: Computational Fluid Dynamics Simulations...  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Canal, Yakima Washington Sandia Publishes Five Reports on the Environmental Effects of Wave-Energy Converters Computational Fluid Dynamics Simulations Provide Insight for Rotor...

62

MOLECULAR DYNAMICS SIMULATIONS OF NANOPARTICLE INTERACTIONS.  

E-Print Network [OSTI]

??Molecular dynamics simulations using the Embedded Atom Method were performed to describe the interparticle behavior of two single crystal spherical nickel nanoparticles during compaction based… (more)

Stone, Tonya Williams

2006-01-01T23:59:59.000Z

63

Dynamic Simulators | netl.doe.gov  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

to Develop Dynamic Simulators for Supercritical Pulverized Coal and Natural Gas Combined Cycle Power Plants A screen shot of the new generic supercritical once-through...

64

Molecular dynamics simulation studies of electrolytes andelectrolyte...  

Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

Merit Review and Peer Evaluation Meeting, May 18-22, 2009 -- Washington D.C. es40smith.pdf More Documents & Publications Molecular Dynamics Simulation Studies of...

65

Design strategy for a Chemical Looping Combustion system using process simulation and Computational Fluid Dynamics  

Science Journals Connector (OSTI)

A strategy for design and optimisation of chemical processes involving multiple fluidised bed reactors is presented through a combination of standard design calculations, process simulation and Computational Fluid Dynamics (CFD). The strategy is demonstrated in designing a Chemical Looping Combustion (CLC) process that generates 12.5 kW of heat in the air reactor. The resulting design strategy will allow for very economical investigations into various design and optimisation considerations. It also offers a platform from which to conduct virtual prototyping investigations for new process concepts, which will lead to significant economic benefits when compared with a traditional experimental process development strategy.

Schalk Cloete; Shahriar Amini

2012-01-01T23:59:59.000Z

66

DEMAND SIMULATION FOR DYNAMIC TRAFFIC ASSIGNMENT  

E-Print Network [OSTI]

of the response of travelers to real-time pre- trip information. The demand simulator is an extension of dynamicDEMAND SIMULATION FOR DYNAMIC TRAFFIC ASSIGNMENT Constantinos Antoniou, Moshe Ben-Akiva, Michel Bierlaire, and Rabi Mishalani Massachusetts Institute of Technology, Cambridge, MA 02139 Abstract

Bierlaire, Michel

67

Predicting aerodynamic characteristic of typical wind turbine airfoils using CFD  

SciTech Connect (OSTI)

An investigation was conducted into the capabilities and accuracy of a representative computational fluid dynamics code to predict the flow field and aerodynamic characteristics of typical wind-turbine airfoils. Comparisons of the computed pressure and aerodynamic coefficients were made with wind tunnel data. This work highlights two areas in CFD that require further investigation and development in order to enable accurate numerical simulations of flow about current generation wind-turbine airfoils: transition prediction and turbulence modeling. The results show that the laminar-to turbulent transition point must be modeled correctly to get accurate simulations for attached flow. Calculations also show that the standard turbulence model used in most commercial CFD codes, the k-e model, is not appropriate at angles of attack with flow separation. 14 refs., 28 figs., 4 tabs.

Wolfe, W.P. [Sandia National Labs., Albuquerque, NM (United States); Ochs, S.S. [Iowa State Univ., Ames, IA (United States). Aerospace Engineering Dept.

1997-09-01T23:59:59.000Z

68

Ship hull resistance calculations using CFD methods  

E-Print Network [OSTI]

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 ...

Voxakis, Petros

2012-01-01T23:59:59.000Z

69

Nuclear Energy CFD Application Management System  

SciTech Connect (OSTI)

In modeling and simulation (M&S), it is virtually impossible to separately evaluate the effectiveness of the model from the data used because the results produced rely heavily on the interaction between the two. Both the data and the simulation are responsible for achieving the ultimate goal of providing defensible research and development (R&D) products and decisions. It is therefore vital that data verification and validation (V&V) activities, along with stringent configuration management, be considered part of the overall M&S accreditation process. In support of these goals is the Nuclear Energy CFD Application Management System (NE-CAMS) for nuclear system design and safety analysis. Working with Bettis Laboratory and Utah State University, a plan of action is being developed by the Idaho National Laboratory (INL) that will address the highest and most immediate needs to track and manage computational fluid dynamics (CFD) models and experimental data in an electronic database. The database will intrinsically incorporate the Nuclear Regulatory Commission (NRC) approved policies and procedures for quality. The quality requirements will be such that the model and data must conform to the quality specifications outlined by the NRC before they can be entered into the database. The primary focus of this database is CFD V&V for nuclear industry needs and will, in practice, serve as the best practice guideline that will accommodate NRC regulations. Such a database, along with a prescriptive methodology for how to utilize it, will provide the NRC with accepted CFD results that could potentially be used for licensing. NE-CAMS will incorporate data V&V as key precursors to the distribution of nuclear systems design and safety data, ensuring that these data are appropriate for use in a particular M&S application. Verification will be conducted to provide a level of confidence that the data selected are the most appropriate for the simulation and are properly prepared, i.e., they are complete, correct and conform to predefined procedures and requirements. Validation will ensure that the data accurately represent the real world activity that is being simulated, ensuring the analytical quality of the data. The level of detail and stringency applied against the data V&V activities will be based on a graded approach principle; the higher the risk, the more rigorous the V&V activities. For the V&V activities to be complete, it will be necessary to scrutinize the physical and statistical properties of the extracted data during the overall process. Regardless of the specific technique or methodology, data V&V will be an important component of NE-CAMS.

Hyung Lee; Kimberlyn C. Mousseau

2001-09-01T23:59:59.000Z

70

Two-Dimensional Computational Fluid Dynamics and Conduction Simulations of Heat Transfer in Horizontal Window Frames with Internal Cavities  

E-Print Network [OSTI]

the two-dimensional heat transfer through building products.Gustavsen, A. 2001. Heat transfer in window frames withand CFD Simulations of Heat Transfer in Horizontal Window

Gustavsen, Arlid

2008-01-01T23:59:59.000Z

71

VALIDATION OF MASSIVELY PARALLEL SIMULATIONS OF DYNAMIC FRACTURE AND  

E-Print Network [OSTI]

VALIDATION OF MASSIVELY PARALLEL SIMULATIONS OF DYNAMIC FRACTURE AND FRAGMENTATION OF BRITTLE element simulations of dynamic fracture and fragmentation of brittle solids are presented. Fracture the results of massively parallel numerical simulations of dynamic fracture and fragmentation in brittle

Barr, Al

72

Model Validation with Hybrid Dynamic Simulation  

SciTech Connect (OSTI)

Abstract—Model validation has been one of the central topics in power engineering studies for years. As model validation aims at obtaining reasonable models to represent actual behavior of power system components, it has been essential to validate models against actual measurements or known benchmark behavior. System-wide model simulation results can be compared with actual recordings. However, it is difficult to construct a simulation case for a large power system such as the WECC system and to narrow down to problematic models in a large system. Hybrid dynamic simulation with its capability of injecting external signals into dynamic simulation enables rigorous comparison of measurements and simulation in a small subsystem of interest. This paper presents such a model validation methodology with hybrid dynamic simulation. Two application examples on generator and load model validation are presented to show the validity of this model validation methodology. This methodology is further extended for automatic model validation and dichotomous subsystem model validation.

Huang, Zhenyu; Kosterev, Dmitry; Guttromson, Ross T.; Nguyen, Tony B.

2006-06-18T23:59:59.000Z

73

CFD analysis for solar chimney power plants  

Science Journals Connector (OSTI)

Abstract Solar chimney power plants are investigated numerically using ANSYS Fluent and an in-house developed Computational Fluid Dynamics (CFD) code. Analytical scaling laws are verified by considering a large range of scales with tower heights between 1 m (sub-scale laboratory model) and 1000 m (largest envisioned plant). A model with approximately 6 m tower height is currently under construction at the University of Arizona. Detailed time-dependent high-resolution simulations of the flow in the collector and chimney of the model provide detailed insight into the fluid dynamics and heat transfer mechanisms. Both transversal and longitudinal convection rolls are identified in the collector, indicating the presence of a Rayleigh–Bénard–Poiseuille instability. Local separation is observed near the chimney inflow. The flow inside the chimney is fully turbulent.

Hermann F. Fasel; Fanlong Meng; Ehsan Shams; Andreas Gross

2013-01-01T23:59:59.000Z

74

Mixed Mode Simulation Tools  

E-Print Network [OSTI]

ANSYS CFX, ANSYS Fluent, Autodesk Simulation CFD (formerly CFDesign), Autodesk Vasari, FloVENT, Flowdesigner,

Gandhi, Priya; Brager, Gail; Dutton, Spencer

2014-01-01T23:59:59.000Z

75

CFD simulation of hydrodynamics on the dense zone on a 65 t/h oil shale-fired high–low bed CFB boiler  

Science Journals Connector (OSTI)

Abstract Gas–solid flow behavior in a 65 t/h oil shale-fired high–low bed CFB boiler obtained by the revamping of a 75 t/h pulverized coal-fired boiler has been simulated using a Eulerian–Eulerian model (EEM) with kinetic theory of granular flow by the commercial CFD software package, Fluent. Two-dimensional (2D) transient and three-dimensional (3D) steady flows were simulated for the gas and the solid phase, respectively. The comparative study with regard to turbulence and drag model was performed by 2D simulation. The simulated results agreed reasonably with the experimental data and showed that Swirl-modified RNG k-?-Per phase model and Gidaspow drag model could predict preferably the internal circulation process. Gas–solid flow profiles were obtained by 3D steady simulation for solid velocity, pressure, solid volume fraction, and granular temperature and the internal circulation characteristics of the boiler were further understood in detail. The results showed that the pressure difference between the main and side bed and the distributions of solid velocity and volume fraction illustrated the mechanism of internal circulation process. The fluidized velocity in the side beds is lower and wear of immersed tubes is also lower. The granular temperature is higher near the immersed tube bundle. This research established the foundation for the design and large-scale of high–low bed CFB.

Qing Wang; Jianbo Xiao; Hongpeng Liu

2013-01-01T23:59:59.000Z

76

Numerical Simulation of Flow Field Inside a Squeeze Film Damper and the Study of the Effect of Cavitation on the Pressure Distribution  

E-Print Network [OSTI]

of SFDs can be expensive and time consuming. The current work simulates the flow field inside the dynamically deforming annular gap of a SFD using the commercial computational fluid dynamics (CFD) code Fluent and compares the results to the experimental...

Khandare, Milind Nandkumar

2012-02-14T23:59:59.000Z

77

A computational fluid dynamics model for wind simulation: model implementation and experimental validation  

Science Journals Connector (OSTI)

To provide physically based wind modelling for wind erosion research at regional scale, a 3D computational fluid dynamics (CFD) wind model was developed. The model was programmed ... analysis and modelling tool (...

Zhuo-dong Zhang; Ralf Wieland; Matthias Reiche…

2012-04-01T23:59:59.000Z

78

Molecular Dynamics Simulations of Supported Pt Nanoclusters  

E-Print Network [OSTI]

¤Introduction and Background ¤Constructing a Physical Model ¤Details of the Simulation ¤Results and Conclusions · Petroleum reformation · Gasification of biomass for biofuels #12;Previous Investigation of NanoclustersMolecular Dynamics Simulations of Supported Pt Nanoclusters Jeffrey Moore #12;A Brief Outline

Washington at Seattle, University of - Department of Physics, Electroweak Interaction Research Group

79

Multi-phase CFD modeling of solid sorbent carbon capture system  

SciTech Connect (OSTI)

Computational fluid dynamics (CFD) simulations are used to investigate a low temperature post-combustion carbon capture reactor. The CFD models are based on a small scale solid sorbent carbon capture reactor design from ADA-ES and Southern Company. The reactor is a fluidized bed design based on a silica-supported amine sorbent. CFD models using both Eulerian–Eulerian and Eulerian–Lagrangian multi-phase modeling methods are developed to investigate the hydrodynamics and adsorption of carbon dioxide in the reactor. Models developed in both FLUENT® and BARRACUDA are presented to explore the strengths and weaknesses of state of the art CFD codes for modeling multi-phase carbon capture reactors. The results of the simulations show that the FLUENT® Eulerian–Lagrangian simulations (DDPM) are unstable for the given reactor design; while the BARRACUDA Eulerian–Lagrangian model is able to simulate the system given appropriate simplifying assumptions. FLUENT® Eulerian–Eulerian simulations also provide a stable solution for the carbon capture reactor given the appropriate simplifying assumptions.

Ryan, E. M.; DeCroix, D.; Breault, Ronald W. [U.S. DOE; Xu, W.; Huckaby, E. David [U.S. DOE

2013-01-01T23:59:59.000Z

80

Multi-Phase CFD Modeling of Solid Sorbent Carbon Capture System  

SciTech Connect (OSTI)

Computational fluid dynamics (CFD) simulations are used to investigate a low temperature post-combustion carbon capture reactor. The CFD models are based on a small scale solid sorbent carbon capture reactor design from ADA-ES and Southern Company. The reactor is a fluidized bed design based on a silica-supported amine sorbent. CFD models using both Eulerian-Eulerian and Eulerian-Lagrangian multi-phase modeling methods are developed to investigate the hydrodynamics and adsorption of carbon dioxide in the reactor. Models developed in both FLUENT® and BARRACUDA are presented to explore the strengths and weaknesses of state of the art CFD codes for modeling multi-phase carbon capture reactors. The results of the simulations show that the FLUENT® Eulerian-Lagrangian simulations (DDPM) are unstable for the given reactor design; while the BARRACUDA Eulerian-Lagrangian model is able to simulate the system given appropriate simplifying assumptions. FLUENT® Eulerian-Eulerian simulations also provide a stable solution for the carbon capture reactor given the appropriate simplifying assumptions.

Ryan, Emily M.; DeCroix, David; Breault, Ronald W.; Xu, Wei; Huckaby, E. D.; Saha, Kringan; Darteville, Sebastien; Sun, Xin

2013-07-30T23:59:59.000Z

Note: This page contains sample records for the topic "dynamics cfd simulations" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


81

Dynamics Simulation in a Wave Environment  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Coupled Dynamic Simulation in a Wave Coupled Dynamic Simulation in a Wave Environment (Navatek, AEGIR, and WECs) Marine and Hydrokinetics Instrumentation Workshop 9 July 2012 David Kring, Navatek Ltd. Presentation Overview * Introduction to Navatek * AEGIR brief: resistance, seakeeping, global and local loads a 3D, NURBS-based, high-order, Rankine boundary element method ... from same lab as at MIT as WAMIT and SWAN, with pFFT acceleration coupling with controls, structures, aerodynamics, power take-offs * Some WEC applications at Navatek 2 Honolulu, Hawaii, USA Company Background A "Research Shipyard" based in Honolulu, HI Combining simulation-based design with prototype construction

82

Physical simulation study of dynamic voltage instability  

SciTech Connect (OSTI)

This paper presents a physical simulation of the dynamic behavior of voltage instability in an interconnected multimachine environment. The dynamic evolving process leading to eventual voltage collapse, the scenario of the progressive reactive support reduction resulting from the MXL protection relays, the OLTC operation, and the effect of switched-in capacitor banks are examined using physical facilities in the laboratory. The physical simulation results are also compared with digital simulation results. This physical investigation provides a reliable foundation for the effective development of assessment approaches and countermeasures.

Tso, S.K.; Zhu, T.X. [Univ. of Hong Kong (Hong Kong); Zeng, Q.Y. [Electric Power Research Inst., Beijing (China); Lo, K.L. [Univ. of Strathclyde, Glasgow (United Kingdom). Dept. of Electrical and Electrical Engineering

1995-12-31T23:59:59.000Z

83

CFD calculations of S809 aerodynamic characteristics  

SciTech Connect (OSTI)

Steady-state, two-dimensional CFD calculations were made for the S809 laminar-flow, wind-turbine airfoil using the commercial code CFD-ACE. Comparisons of the computed pressure and aerodynamic coefficients were made with wind tunnel data from the Delft University 1.8 m x 1.25 m low-turbulence wind tunnel. This work highlights two areas in CFD that require further investigation and development in order to enable accurate numerical simulations of flow about current generation wind-turbine airfoils: transition prediction and turbulence modeling. The results show that the laminar-to-turbulent transition point must be modeled correctly to get accurate simulations for attached flow. Calculations also show that the standard turbulence model used in most commercial CFD codes, the k-{epsilon} model, is not appropriate at angles of attack with flow separation.

Wolfe, W.P. [Sandia National Labs., Albuquerque, NM (United States); Ochs, S.S. [Iowa State Univ., Ames, IA (United States)

1997-01-01T23:59:59.000Z

84

Experimental and CFD Analysis of Advanced Convective Cooling Systems  

SciTech Connect (OSTI)

The objective of this project is to study the fundamental physical phenomena in the reactor cavity cooling system (RCCS) of very high-temperature reactors (VHTRs). One of the primary design objectives is to assure that RCCS acts as an ultimate heat sink capable of maintaining thermal integrity of the fuel, vessel, and equipment within the reactor cavity for the entire spectrum of postulated accident scenarios. Since construction of full-scale experimental test facilities to study these phenomena is impractical, it is logical to expect that computational fluid dynamics (CFD) simulations will play a key role in the RCCS design process. An important question then arises: To what extent are conventional CFD codes able to accurately capture the most important flow phenomena, and how can they be modified to improve their quantitative predictions? Researchers are working to tackle this problem in two ways. First, in the experimental phase, the research team plans to design and construct an innovative platform that will provide a standard test setting for validating CFD codes proposed for the RCCS design. This capability will significantly advance the state of knowledge in both liquid-cooled and gas-cooled (e.g., sodium fast reactor) reactor technology. This work will also extend flow measurements to micro-scale levels not obtainable in large-scale test facilities, thereby revealing previously undetectable phenomena that will complement the existing infrastructure. Second, in the computational phase of this work, numerical simulation of the flow and temperature profiles will be performed using advanced turbulence models to simulate the complex conditions of flows in critical zones of the cavity. These models will be validated and verified so that they can be implemented into commercially available CFD codes. Ultimately, the results of these validation studies can then be used to enable a more accurate design and safety evaluation of systems in actual nuclear power applications (both during normal operation and accident scenarios).

Yassin A. Hassan; Victor M. Ugaz

2012-06-27T23:59:59.000Z

85

Dynamic procedure for filtered gyrokinetic simulations  

SciTech Connect (OSTI)

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.

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

86

A visual simulation playground for engineering dynamics  

E-Print Network [OSTI]

A VISUAL SIMULATION PLAYGROUND FOR ENGINEERING DYNAMICS A Thesis by DONALD BRIAN FONG Submitted to the O ce of Graduate Studies of Texas A&M University in partial ful llment of the requirements for the degree of MASTER OF SCIENCE August 2008 Major... Subject: Visualization Sciences A VISUAL SIMULATION PLAYGROUND FOR ENGINEERING DYNAMICS A Thesis by DONALD BRIAN FONG Submitted to the O ce of Graduate Studies of Texas A&M University in partial ful llment of the requirements for the degree of MASTER...

Fong, Donald Brian

2008-10-10T23:59:59.000Z

87

Model Validation with Hybrid Dynamic Simulation  

SciTech Connect (OSTI)

Abstract—Model validation has been one of the central topics in power engineering studies for years. As model validation aims at obtaining reasonable models to represent actual behavior of power system components, it has been essential to validate models against actual measurements or known benchmark behavior. System-wide model simulation results can be compared with actual recordings. However, it is difficult to construct a simulation case for a large power system such as the WECC system and to narrow down to problematic models in a large system. Hybrid dynamic simulation with its capability of injecting external signals into dynamic simulation enables rigorous comparison of measurements and simulation in a small subsystem of interest. This paper presents such a model validation methodology with hybrid dynamic simulation. Two application examples on generator and load model validation are presented to show the validity of this model validation methodology. This methodology is further extended for automatic model validation and dichotomous subsystem model validation. A few methods to define model quality indices have been proposed to quantify model error for model validation criteria development.

Huang, Zhenyu; Kosterev, Dmitry; Guttromson, Ross T.; Nguyen, Tony B.

2006-06-22T23:59:59.000Z

88

Dynamic simulation of a reverse Brayton refrigerator  

SciTech Connect (OSTI)

A test refrigerator based on the modified Reverse Brayton cycle has been developed in the Chinese Academy of Sciences recently. To study the behaviors of this test refrigerator, a dynamic simulation has been carried out. The numerical model comprises the typical components of the test refrigerator: compressor, valves, heat exchangers, expander and heater. This simulator is based on the oriented-object approach and each component is represented by a set of differential and algebraic equations. The control system of the test refrigerator is also simulated, which can be used to optimize the control strategies. This paper describes all the models and shows the simulation results. Comparisons between simulation results and experimental data are also presented. Experimental validation on the test refrigerator gives satisfactory results.

Peng, N.; Xiong, L. Y.; Dong, B.; Liu, L. Q. [State Key Laboratory of Technologies in Space Cryogenic Propellants, Technical Institute of Physics and Chemistry, CAS, Beijing, 100190 (China); Lei, L. L.; Tang, J. C. [State Key Laboratory of Technologies in Space Cryogenic Propellants, Technical Institute of Physics and Chemistry, CAS, Beijing, 100190 China and Graduate University of Chinese Academy of Sciences, Beijing, 100190 (China)

2014-01-29T23:59:59.000Z

89

Dynamic simulation of polyester mooring lines  

E-Print Network [OSTI]

A numerical scheme, known as CABLE3D, originally developed for the simulation of dynamics of steel chain-wire mooring lines is extended to allow for the large elongation in a mooring line, the dependence of the modulus on tension, and energy...

Kim, Min Suk

2004-09-30T23:59:59.000Z

90

Dynamic simulation , 1.1 INTRODUCTION  

E-Print Network [OSTI]

storage tank to prevent flashing in the line. 1.2.2 Propane Storage System Product propane from either receipt as well as product loading. Each of the storage tanks is equipped with one circulation pump Compressor Control system . Dynamic simulation , , , . STEADY STATE

Hong, Deog Ki

91

CFD modeling of entrained-flow coal gasifiers with improved physical and chemical sub-models  

SciTech Connect (OSTI)

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.

Ma, J.; Zitney, S.

2012-01-01T23:59:59.000Z

92

Molecular dynamics simulation of hydration in myoglobin  

SciTech Connect (OSTI)

This study was carried out to evaluate the stability of the 89 bound water molecules that were observed in the neutron diffraction study of CO myoglobin. The myoglobin structure derived from the neutron analysis was used as the starting point in the molecular dynamics simulation using the software package CHARMM. After salvation of the protein, energy minimization and equilibration of the system, 50 pico seconds of Newtonian dynamics was performed. This data showed that only 4 water molecules are continously bound during the length of this simulation while the other solvent molecules exhibit considerable mobility and are breaking and reforming hydrogen bonds with the protein. At any instant during the simulation, 73 of the hydration sites observed in the neutron structure are occupied by water.

Gu, Wei [New Mexico Univ., Albuquerque, NM (United States). Dept. of Biochemistry; Schoenborn, B.P. [Los Alamos National Lab., NM (United States)

1995-09-01T23:59:59.000Z

93

Using CFD Capabilities of CONTAM 3.0 for Simulating Airflow and Contaminant Transport In and Around Buildings  

E-Print Network [OSTI]

of Standards and Technology 2 School of Mechanical Engineering, Purdue University Abstract CONTAM.0 for simulating airflow and contaminant transport in and around buildings," Accepted by HVAC&R Research. #12

Chen, Qingyan "Yan"

94

Physics results from dynamical overlap fermion simulations  

E-Print Network [OSTI]

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.

Shoji Hashimoto

2008-11-08T23:59:59.000Z

95

Molecular dynamics simulation and ab intio studies of electrolytes...  

Broader source: Energy.gov (indexed) [DOE]

Molecular dynamics simulations: Properties of bulk electrolytes (structure, thermodynamics, transport), interfacial properties of electrolyte at electroactive interfaces,...

96

IGCC Dynamic Simulator and Training Center  

SciTech Connect (OSTI)

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.

Zitney, S.E.; Erbes, M.R. (Enginomix, LLC)

2006-10-01T23:59:59.000Z

97

Software Framework for Advanced Power Plant Simulations  

SciTech Connect (OSTI)

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.

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

98

Simulation results of an inductively-coupled rf plasma torch in two and three dimensions for producing a metal matrix composite for nuclear fuel cladding  

E-Print Network [OSTI]

. In this work, a magnetohydrodynamic (MHD) model is used along with a computational fluid dynamic (CFD) software package called FLUENT© to simulate an ICPT. To solve the electromagnetic equations and incorporate forces and resistive heating, several userdefined...

Holik III, Eddie Frank (Trey)

2009-05-15T23:59:59.000Z

99

Computational fluid dynamics simulation of the air/suppressant flow in an uncluttered F18 engine nacelle  

SciTech Connect (OSTI)

For the purposes of designing improved Halon-alternative fire suppression strategies for aircraft applications, Computational Fluid Dynamics (CFD) simulations of the air flow, suppressant transport, and air-suppressant mixing within an uncluttered F18 engine nacelle were performed. The release of inert gases from a Solid Propellant Gas Generator (SPGG) was analyzed at two different injection locations in order to understand the effect of injection position on the flow patterns and the mixing of air and suppression agent. An uncluttered engine nacelle was simulated to provide insight into the global flow features as well as to promote comparisons with previous nacelle fire tests and recent water tunnel tests which included little or no clutter. Oxygen concentration levels, fuel/air residence times that would exist if a small fuel leak were present, velocity contours, and streamline patterns are presented inside the engine nacelle. The numerical results show the influence of the gent release location on regions of potential flame extinction due to oxygen inerting and high flame strain. The occurrence of inflow through the exhaust ducts on the aft end of the nacelle is also predicted. As expected, the predicted oxygen concentration levels were consistently higher than the measured levels since a fire was not modeled in this analysis. Despite differences in the conditions of these simulations and the experiments, good agreement was obtained between the CFD predictions and the experimental measurements.

Lopez, A.R.; Gritzo, L.A.; Hassan, B.

1997-06-01T23:59:59.000Z

100

CFD Modeling of a CFB Riser Using Improved Inlet Boundary Conditions  

Science Journals Connector (OSTI)

A computational fluid dynamics (CFD) model based on Eulerian?Eulerian approach coupled with granular kinetics theory was adopted to investigate the hydrodynamics and flow structures in a circulating fluidized bed (CFB) riser column. A new approach to specify the inlet boundary conditions was proposed in this study to simulate gas?solids flow in CFB risers more accurately. Simulation results were compared with the experimental data and good agreement between the numerical results and experimental data was observed under different operating conditions which indicates the effectiveness and accuracy of the CFD model with the proposed inlet boundary conditions. The results also illustrate a clear core annulus structure in the CFB riser under all operating conditions both experimentally and numerically.

B. T. Peng; C. Zhang; J. X. Zhu; X. B. Qi

2010-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "dynamics cfd simulations" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


101

CFD Analysis of Core Bypass Phenomena  

SciTech Connect (OSTI)

The U.S. Department of Energy is exploring the potential for the VHTR which will be either of a prismatic or a pebble-bed type. One important design consideration for the reactor core of a prismatic VHTR is coolant bypass flow which occurs in the interstitial regions between fuel blocks. Such gaps are an inherent presence in the reactor core because of tolerances in manufacturing the blocks and the inexact nature of their installation. Furthermore, the geometry of the graphite blocks changes over the lifetime of the reactor because of thermal expansion and irradiation damage. The existence of the gaps induces a flow bias in the fuel blocks and results in unexpected increase of maximum fuel temperature. Traditionally, simplified methods such as flow network calculations employing experimental correlations are used to estimate flow and temperature distributions in the core design. However, the distribution of temperature in the fuel pins and graphite blocks as well as coolant outlet temperatures are strongly coupled with the local heat generation rate within fuel blocks which is not uniformly distributed in the core. Hence, it is crucial to establish mechanistic based methods which can be applied to the reactor core thermal hydraulic design and safety analysis. Computational Fluid Dynamics (CFD) codes, which have a capability of local physics based simulation, are widely used in various industrial fields. This study investigates core bypass flow phenomena with the assistance of commercial CFD codes and establishes a baseline for evaluation methods. A one-twelfth sector of the hexagonal block surface is modeled and extruded down to whole core length of 10.704m. The computational domain is divided vertically with an upper reflector, a fuel section and a lower reflector. Each side of the sector grid can be set as a symmetry boundary

Richard W. Johnson; Hiroyuki Sato; Richard R. Schultz

2010-03-01T23:59:59.000Z

102

CFD Analysis of Core Bypass Phenomena  

SciTech Connect (OSTI)

The U.S. Department of Energy is exploring the potential for the VHTR which will be either of a prismatic or a pebble-bed type. One important design consideration for the reactor core of a prismatic VHTR is coolant bypass flow which occurs in the interstitial regions between fuel blocks. Such gaps are an inherent presence in the reactor core because of tolerances in manufacturing the blocks and the inexact nature of their installation. Furthermore, the geometry of the graphite blocks changes over the lifetime of the reactor because of thermal expansion and irradiation damage. The existence of the gaps induces a flow bias in the fuel blocks and results in unexpected increase of maximum fuel temperature. Traditionally, simplified methods such as flow network calculations employing experimental correlations are used to estimate flow and temperature distributions in the core design. However, the distribution of temperature in the fuel pins and graphite blocks as well as coolant outlet temperatures are strongly coupled with the local heat generation rate within fuel blocks which is not uniformly distributed in the core. Hence, it is crucial to establish mechanistic based methods which can be applied to the reactor core thermal hydraulic design and safety analysis. Computational Fluid Dynamics (CFD) codes, which have a capability of local physics based simulation, are widely used in various industrial fields. This study investigates core bypass flow phenomena with the assistance of commercial CFD codes and establishes a baseline for evaluation methods. A one-twelfth sector of the hexagonal block surface is modeled and extruded down to whole core length of 10.704m. The computational domain is divided vertically with an upper reflector, a fuel section and a lower reflector. Each side of the one-twelfth grid can be set as a symmetry boundary

Richard W. Johnson; Hiroyuki Sato; Richard R. Schultz

2009-11-01T23:59:59.000Z

103

Bonneville Project: CFD of the Spillway Tailrace  

SciTech Connect (OSTI)

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.

Rakowski, Cynthia L.; Serkowski, John A.; Richmond, Marshall C.; Romero Gomez, Pedro DJ

2012-11-19T23:59:59.000Z

104

Numerical simulations of particle growth in a silicon-CVD fluidized bed reactor via a CFD–PBM coupled model  

Science Journals Connector (OSTI)

Abstract A Eulerian–Eulerian two-fluid model coupled with population balance equations was applied to simulate the evolution of silicon particle growth by chemical vapor deposition of silane pyrolysis in a three-dimensional slugging fluidized bed reactor using FLUENT. The simulation of the particle growth considering surface deposition, cluster scavenging, aggregation and wall deposition was carried out after the verification of flow and heat transfer characteristics based on the well-accepted correlations. The results showed that the scavenging effect was responsible for the particle growth, and the growth rate agreed well with the experimental data by Tejero-Ezpeleta et al. (2004) when the scavenging factor was set to 0.1 under the condition of 923 K and atmospheric pressure. Moreover, the formation of light silicon hydrides by silane homogeneous pyrolysis in the dilute phase was also investigated in the form of CHMEKIN mechanism, which showed that disilane turned to be the main silicon hydride and the silane conversion was underestimated by 12.5%. Finally, the effects of operating conditions on the growth rate were studied in detail with the observation of defluidization phenomenon during the evolution of particle growth.

Si-Si Liu; Wen-De Xiao

2014-01-01T23:59:59.000Z

105

CFD simulation of airflow over a regular array of cubes. Part I: Three-dimensional simulation of the flow and validation with wind-tunnel measurements  

Science Journals Connector (OSTI)

Air flow inside an array of cubes is simulated. Cubes (edge length 0.15 m) are arranged in a regular array, separated by 0.15 m in the streamwise and spanwise directions. Numerical simulations are performed based...

Jose Luis Santiago; Alberto Martilli; Fernando Martín

2007-03-01T23:59:59.000Z

106

Computational fluid dynamics simulation of hydrodynamics and chemical reaction in a CFB downer  

Science Journals Connector (OSTI)

Abstract A computational fluid dynamics (CFD) model for simulating the chemical reaction process in a gas–particle circulating fluidized bed (CFB) downer is introduced by combining the two-fluid model (TFM) for the gas–particle turbulent flows and the c 2 ¯ ? ? c model for the turbulent mass transfer. With the proposed model, the species concentration and solid volume fraction as well as the velocity distributions along the CFB downer are able to be predicted. In mathematical expression of the proposed model, the recently developed formulations of c 2 ¯ ? ? c is adopted to close the turbulent mass transfer equations so that the turbulent mass diffusivity can be determined without relying on empirical methods. As for the gas–solid two phase turbulent momentum transfer equations, the methodology of kg ? ?g ? kp ? ?p ? ? is used for their closures. To validate the proposed model, simulation is carried out for the catalytic ozone decomposition in a gas–solid CFB downer. The simulation results are compared with the experimental data and satisfactory agreement is found between them in both axial/radial distributions of concentration and solid volume fraction. Furthermore, the simulations reveal that the turbulent mass diffusivity varies along axial and radial directions, and the turbulent Schmidt number is not a constant throughout the CFB downer.

Wenbin Li; Kuotsung Yu; Botan Liu; Xigang Yuan

2015-01-01T23:59:59.000Z

107

Brownian Dynamics Simulation of Protein Solutions: Structural and Dynamical Properties  

SciTech Connect (OSTI)

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.

Mereghetti, Paolo; Gabdoulline, Razif; Wade, Rebecca C.

2010-12-01T23:59:59.000Z

108

Nanoparticle coalescence and sintering: molecular dynamics simulation  

Science Journals Connector (OSTI)

Molecular Dynamics (MD) simulations are employed to better understand coalescence and sintering processes of gold nanoparticles. During coalescence in the liquid phase, the initial neck growth can be well described by the viscous flow model. With initial temperature right below the single particle melting temperature, the initial neck growth is controlled by viscous flow at first and then, by grain boundary diffusion. At initial temperatures well below melting, the sintering process occurs very rapidly, which may be attributed to a formation of liquid-like neck regions. The sintering of two free Au nanoparticles irradiated by a femtosecond laser pulse is also simulated by combining the two-temperature and MD models. It is shown that by increasing laser input energy, nanoparticles can be melted forming a single larger nanoparticle. The effects of multinanoparticle melting, solidification and sintering are also investigated.

N. Wang; S.I. Rokhlin; D.F. Farson

2007-01-01T23:59:59.000Z

109

Petascale, Adaptive CFD | Argonne Leadership Computing Facility  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Petascale, Adaptive CFD Petascale, Adaptive CFD Petascale, Adaptive CFD PI Name: Kenneth Jansen PI Email: jansenke@colorado.edu Institution: U. Colorado-Boulder Allocation Program: ESP Allocation Hours at ALCF: 150 Million Year: 2010 to 2013 Research Domain: Engineering The aerodynamic simulations proposed will involve modeling of active flow control based on synthetic jet actuation that has been shown experimentally to produce large-scale flow changes (e.g., re-attachment of separated flow or virtual aerodynamic shaping of lifting surfaces) from micro-scale input (e.g., a 0.1 W piezoelectric disk resonating in a cavity alternately pushes/pulls out/in the fluid through a small slit to create small-scale vortical structures that interact with, and thereby dramatically alter, the cross flow). This is a process that has yet to be understood fundamentally.

110

E-Print Network 3.0 - advanced cfd codes Sample Search Results  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Laboratory Collection: Engineering 13 Solution characters of iterative coupling between energy simulation and CFD programs Summary: 1 Solution characters of iterative coupling...

111

TANK48 CFD MODELING ANALYSIS  

SciTech Connect (OSTI)

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.

Lee, S.

2011-05-17T23:59:59.000Z

112

Simulation of systems with dynamically varying model structure  

Science Journals Connector (OSTI)

Hybrid systems are dynamical systems composed of components with discrete and continuous behavior. Some systems change their structure during simulation, or their components behavior is essentially changing. This ''structural dynamics'' can be described ... Keywords: Discrete-continuous simulation, Hybrid systems, Modelica, Structural dynamics, VHDL-AMS

Peter Schwarz

2008-12-01T23:59:59.000Z

113

A New Motorcycle Simulator Platform: Mechatronics Design, Dynamics Modeling  

E-Print Network [OSTI]

A New Motorcycle Simulator Platform: Mechatronics Design, Dynamics Modeling and Control L. Nehaoua of these techniques to other simulators (cars and motorcycles) is possible but not direct. Indeed, the dynamics motorcycle driving simulators were build. The first prototype was developed by Honda in 1988

Paris-Sud XI, Université de

114

2005-3-21 1 Dynamic Equipment and Process Simulation  

E-Print Network [OSTI]

, reduced order) Simulation-based technology, manufacturing and ESH Metrics Current physical and chemical understanding Simulation ToolDynamic behavior through process cycle Verification Guidelines for equipment) · Gas phase transport · Reactant adsorption and byproduct desorption · Surface

Rubloff, Gary W.

115

A Quasi-Dynamic HVAC and Building Simulation Methodology  

E-Print Network [OSTI]

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...

Davis, Clinton Paul

2012-07-16T23:59:59.000Z

116

Avestar® - Integrated Gasification Combined Cycle (IGCC) Dynamic Simulator  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Integrated Gasification Combined Cycle (IGCC) Dynamic Simulator Integrated Gasification Combined Cycle (IGCC) Dynamic Simulator The AVESTAR® center offers courses using the Integrated Gasification Combined Cycle (IGCC) Dynamic Simulator. The IGCC simulator builds on and reaches beyond existing combined-cycle and conventional-coal power plant simulators to combine--for the first time--a Gasification with CO2 Capture process simulator with a Combined-Cycle power simulator together in a single dynamic simulation framework. The AVESTAR® center IGCC courses provide unique, comprehensive training on all aspects of an IGCC plant, illustrating the high-efficiency aspects of the gasifier, gas turbine, and steam turbine integration. IGCC Operator training station HMI display for overview of IGCC Plant - Train A Reference:

117

Molecular dynamics simulations of osmosis and reverse osmosis in solutions  

Science Journals Connector (OSTI)

Computer simulation studies using the method of molecular dynamics have been carried out to investigate osmosis and reverse osmosis in solutions separated by semi-permeable membranes....

S. Murad

1996-01-01T23:59:59.000Z

118

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...

119

Computational fluid dynamic simulations of chemical looping fuel reactors utilizing gaseous fuels  

SciTech Connect (OSTI)

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.

Mahalatkar, K.; Kuhlman, J.; Huckaby, E.D.; O'Brien, T.

2011-01-01T23:59:59.000Z

120

A two-component heavy fuel oil evaporation model for CFD studies in marine Diesel engines  

Science Journals Connector (OSTI)

Abstract The paper presents an evaporation model for Heavy Fuel Oil (HFO) combustion studies. In the present work, HFO is considered as a mixture of a heavy and a light fuel component, with the thermophysical properties of the heavy component calculated from the recently introduced model of Kyriakides et al. (2009) [1]. The model proposes a proper treatment of convective heat transfer to the evaporating fuel droplets. Computational Fluid Dynamics (CFD) simulations of HFO spray combustion in constant volume chambers are performed, utilizing a modified characteristic time combustion model. The results are in good agreement with literature experimental data. Computational results for a two-stroke marine Diesel engine also compare favorably against experiments. The present development yields a basis for detailed CFD studies of HFO combustion in large marine Diesel engines.

Nikolaos Stamoudis; Christos Chryssakis; Lambros Kaiktsis

2014-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "dynamics cfd simulations" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


121

AVESTAR® - Natural Gas Combined Cycle (NGCC) Dynamic Simulator  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Natural Gas Combined Cycle (NGCC) Dynamic Simulator Natural Gas Combined Cycle (NGCC) Dynamic Simulator A simulator that can provide future engineers with realistic, hands-on experience for operating advanced natural gas combined cycle (NGCC) power plants will soon be available at an innovative U.S. Department of Energy training center. Under a new cooperative research and development agreement signed by the Office of Fossil Energy's National Energy Technology Laboratory (NETL) and Invensys Operations Management, the partners will develop, test, and deploy a dynamic simulator and operator training system (OTS) for a generic NGCC power plant equipped for use with post-combustion carbon capture. NETL will operate the new dynamic simulator/OTS at the AVESTAR (Advanced Virtual Energy Simulation Training and Research) Center in Morgantown, W.Va.

122

Annual Report 1999 Environmental Dynamics and Simulation  

SciTech Connect (OSTI)

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.

NS Foster-Mills

2000-06-28T23:59:59.000Z

123

Three-dimensional CFD analysis for simulating the greenhouse effect in solar chimney power plants using a two-band radiation model  

Science Journals Connector (OSTI)

Abstract The greenhouse effect in the solar collector has a fundamental role to produce the upward buoyancy force in solar chimney power plant systems. This study underlines the importance of the greenhouse effect on the buoyancy-driven flow and heat transfer characteristics through the system. For this purpose, a three-dimensional unsteady model with the RNG k–? turbulence closure was developed, using computational fluid dynamics techniques. In this model, to solve the radiative transfer equation the discrete ordinates (DO) radiation model was implemented, using a two-band radiation model. To simulate radiation effects from the sun's rays, the solar ray tracing algorithm was coupled to the calculation via a source term in the energy equation. Simulations were carried out for a system with the geometry parameters of the Manzanares power plant. The effects of the solar insolation and pressure drop across the turbine on the flow and heat transfer of the system were considered. Based on the numerical results, temperature profile of the ground surface, thermal collector efficiency and power output were calculated and the results were validated by comparing with experimental data of this prototype power plant. Furthermore, enthalpy rise through the collector and energy loss from the chimney outlet between 1-band and two-band radiation model were compared. The analysis showed that simulating the greenhouse effect has an important role to accurately predict the characteristics of the flow and heat transfer in solar chimney power plant systems.

Ehsan Gholamalizadeh; Man-Hoe Kim

2014-01-01T23:59:59.000Z

124

CFD modeling of commercial-scale entrained-flow coal gasifiers  

SciTech Connect (OSTI)

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.

Ma, J.; Zitney, S.

2012-01-01T23:59:59.000Z

125

Fan-shape optimisation using CFD and genetic algorithms for increasing the efficiency of electric motors  

Science Journals Connector (OSTI)

The electric motor efficiency represents the effectiveness with which the motor converts electrical energy into mechanical energy. As the energy losses are converted into heat, which is dissipated by the motor frame aided by internal and external fans, a better cooling system adds up to better efficiency. In recent years, improvements in motor efficiency have been achieved but at higher costs. By using Genetic Algorithms (GAs), changes are introduced to the fan shape looking for a better aerodynamic performance. The evaluation of the achieved fan efficiency with the modified shapes is performed with Computational Fluid Dynamics (CFD) simulation software.

Noel Leon-Rovira; Eduardo Uresti; Waldo Arcos

2007-01-01T23:59:59.000Z

126

Avestar® - Syngas-Fired Combined Cycle Dynamic Simulator  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Syngas-Fired Combined Cycle Dynamic Simulator Syngas-Fired Combined Cycle Dynamic Simulator The AVESTAR® center offers courses using the Combined Cycle Simulator, focusing on the power generation process after gasification. This simulator is well-suited for concentrated training on operation and control of the gas and steam turbines; condensate, feed water, and circulating water systems; heat recovery steam generator; and selective catalytic reduction (SCR) unit. Combined cycle simulator startup operations include bringing up the gas turbine to rated speed on natural gas and then switching over to the firing of synthesis gas. Key capabilities of the Combined Cycle Simulator include: Combined Cycle Simulator Operator training station HMI display for overview of Gas Turbine - Train A Normal base load operation

127

Ad hoc continuum-atomistic thermostat for modeling heat flow in molecular dynamics simulations  

E-Print Network [OSTI]

Ad hoc continuum-atomistic thermostat for modeling heat flow in molecular dynamics simulations J 2004) An ad hoc thermostating procedure that couples a molecular dynamics (MD) simulation

Brenner, Donald W.

128

Use of High Dynamic Range Images for Improved Medical Simulations  

Science Journals Connector (OSTI)

Here we describe the use of high-dynamic range lighting techniques to improve the rendering quality of real-time medical simulation systems. Specifically we show our method of extracting the lighting information ...

Meagan Leflar; Omar Hesham; Chris Joslin

2009-01-01T23:59:59.000Z

129

Modelica® Library for Dynamic Simulation of Thermoelectric Generators  

Science Journals Connector (OSTI)

The contribution presents a new modeling library for the dynamic simulation of thermoelectric generators (TEG) in 1D spatial resolution. The core of the library is a model of the thermoelectric legs (TEL), which ...

M. Nesarajah; L. Exel; G. Frey

2014-01-01T23:59:59.000Z

130

Molecular Dynamics Simulation of Homogeneous Crystal Nucleation in Polyethylene  

E-Print Network [OSTI]

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 ...

Yi, Peng

131

Molecular Dynamics Simulation Studies of Electrolytes andElectrolyte...  

Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

Merit Review and Peer Evaluation Meeting, June 7-11, 2010 -- Washington D.C. es058smith2010p.pdf More Documents & Publications Molecular dynamics simulation and ab intio...

132

Visualization of the recovery-bioler flow fields predicted by computational fluid dynamics  

SciTech Connect (OSTI)

Flow patterns in the kraft recovery furnace can be simulated using models based on computational fluid dynamics (CFD). The use of CFD is becoming increasingly common as computer workstations become more powerful and CFD software is improved. In this article, the authors present simulated results for flow fields in the lower furnace. Because the flows in the lower furnace are dominated by the air system, the authors chose to simulate flow fields under isothermal conditions. The predicted flow fields were used to supplement results obtained from physical modeling. When a physical model is used for testing, each air-system configuration is typically evaluated based on air and gas velocities and the mixing distribution as measured at a limited number of test planes. Such measurements are commonly used to quantitatively assess air-system configurations for modeling studies or to validate CFD models.

Chapman, P.J.; Janik, S.G. (Kreisinger Development Lab. ABB Combustion Engineering Systems, Windsor, CT (United States)); Jones, A.K. (ABB Canada, Ottawa, ON (Canada))

1992-03-01T23:59:59.000Z

133

Dynameomics Database of Molecular Dynamics Simulations Project...  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

in determining protein behavior and function. Accomplishments: Over 11,000 protein folding simulations are now available in the world's largest public database of protein...

134

Detonation shock dynamics and comparisons with direct numerical simulation  

E-Print Network [OSTI]

Detonation shock dynamics and comparisons with direct numerical simulation Tariq D. Aslam # , and D­ nation and detonation shock dynamics (DSD) is made. The theory of DSD defines the motion of the detonation shock in terms of intrinsic geometry of the shock surface, in particular for condensed phase ex

Aslam, Tariq

135

Detonation shock dynamics and comparisons with direct numerical simulation  

E-Print Network [OSTI]

Detonation shock dynamics and comparisons with direct numerical simulation Tariq D. Aslam , and D- nation and detonation shock dynamics (DSD) is made. The theory of DSD defines the motion of the detonation shock in terms of intrinsic geometry of the shock surface, in particular for condensed phase ex

Aslam, Tariq

136

Patch dynamics: macroscopic simulation of multiscale systems , Y. Kevrekidis2  

E-Print Network [OSTI]

Patch dynamics: macroscopic simulation of multiscale systems G. Samaey1 , Y. Kevrekidis2 , D. Rose1-called "equation-free" framework, based on the idea of a so-called coarse-grained time-stepper. The patch dynamics microscopic model in small portions of the space-time domain (the patches). We present some theoretical

Gorban, Alexander N.

137

Parallel Transient Dynamics Simulations: Algorithms for Contact Detection  

E-Print Network [OSTI]

February 5, 1998 Abstract Transient dynamics simulations are commonly used to model phenomena such as car and deform with the objects as they undergo stress. Fluids (gasoline, water) or fluid­ like materials (soil is a natural candidate for the power of parallel computers. Unfortunately, these kinds of simulations have

Plimpton, Steve

138

Lattice Boltzmann versus Molecular Dynamics Simulation of Nanoscale Hydrodynamic Flows  

SciTech Connect (OSTI)

A fluid flow in a simple dense liquid, passing an obstacle in a two-dimensional thin film geometry, is simulated by molecular dynamics (MD) computer simulation and compared to results of lattice Boltzmann (LB) simulations. By the appropriate mapping of length and time units from LB to MD, the velocity field as obtained from MD is quantitatively reproduced by LB. The implications of this finding for prospective LB-MD multiscale applications are discussed.

Horbach, Juergen [Institut fuer Physik, Johannes-Gutenberg-Universitaet Mainz, Staudinger Weg 7, D-55099 Mainz (Germany); Succi, Sauro [Istituto Applicazioni Calcolo, CNR, Via le del Policlinico 137, 00161, Rome (Italy)

2006-06-09T23:59:59.000Z

139

Molecular Dynamics Simulations of Protein Folding  

Science Journals Connector (OSTI)

I illustrate the use of the replica exchange molecular dynamics (REMD) algorithm to study the folding of a small (57 amino acids) protein that folds into a three-helix bundle, protein A. The REMD is a triviall...

Angel E. Garcia

2008-01-01T23:59:59.000Z

140

Conformational statistics of poly(dimethylsiloxane). 1. Probability distribution of rotational isomers from molecular dynamics simulations  

Science Journals Connector (OSTI)

Conformational statistics of poly(dimethylsiloxane). 1. Probability distribution of rotational isomers from molecular dynamics simulations ...

Ivet Bahar; Ignacio Zuniga; Robert Dodge; Wayne L. Mattice

1991-05-01T23:59:59.000Z

Note: This page contains sample records for the topic "dynamics cfd simulations" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


141

Development and Verification of a Computational Fluid Dynamics Model of a Horizontal-Axis Tidal Current Turbine  

SciTech Connect (OSTI)

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.

Lawson, M. J.; Li, Y.; Sale, D. C.

2011-10-01T23:59:59.000Z

142

Computational fluid dynamic applications  

SciTech Connect (OSTI)

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.

Chang, S.-L.; Lottes, S. A.; Zhou, C. Q.

2000-04-03T23:59:59.000Z

143

Dynamic Ball & Socket Joint Force Simulator  

E-Print Network [OSTI]

................................................. 137 Appendix F Results ............................................................................................... 144 vi LIST OF FIGURES Figure 1. Autodesk rendering of the DBSJFS mounted inside the 858 Mini Bionix Machine... the perpendicular axes. Additionally, Figure 1 on the following page is an Autodesk rending of the DBSJFS that shows the orientation of the X’, Y’, and Z axes on the simulator. 15 Figure 1. Autodesk rendering of the DBSJFS mounted inside the 858 Mini Bionix...

Farmer, Ryan Neal

2011-07-26T23:59:59.000Z

144

The numerical simulation of liquid sloshing on board spacecraft  

Science Journals Connector (OSTI)

The subject of study is the influence of sloshing liquid on the dynamics of spacecraft. A combined theoretical and experimental approach has been followed. On the one hand, CFD simulations have been carried out to predict the combined liquid/solid body ... Keywords: 45.20.D-, 47.11.-j, 47.55.N-, Computational fluid dynamics, Free-surface flow, Microgravity, Sloshing, Sloshsat FLEVO, Solid-liquid interaction, Spacecraft dynamics

A. E. P. Veldman; J. Gerrits; R. Luppes; J. A. Helder; J. P. B. Vreeburg

2007-05-01T23:59:59.000Z

145

Design of Cleanroom Airflows for Particle Control Using CFD Analysis: Case Studies  

Science Journals Connector (OSTI)

This paper describes two case studies involving the use of Computational Fluid Dynamics (CFD) analysis for evaluating the designs of significantly different types (and cleanliness classes) of cleanrooms: a cla...

Ken Goldstein; John Divelbiss

1993-01-01T23:59:59.000Z

146

CFD validation in OECD/NEA t-junction benchmark.  

SciTech Connect (OSTI)

When streams of rapidly moving flow merge in a T-junction, the potential arises for large oscillations at the scale of the diameter, D, with a period scaling as O(D/U), where U is the characteristic flow velocity. If the streams are of different temperatures, the oscillations result in experimental fluctuations (thermal striping) at the pipe wall in the outlet branch that can accelerate thermal-mechanical fatigue and ultimately cause pipe failure. The importance of this phenomenon has prompted the nuclear energy modeling and simulation community to establish a benchmark to test the ability of computational fluid dynamics (CFD) codes to predict thermal striping. The benchmark is based on thermal and velocity data measured in an experiment designed specifically for this purpose. Thermal striping is intrinsically unsteady and hence not accessible to steady state simulation approaches such as steady state Reynolds-averaged Navier-Stokes (RANS) models.1 Consequently, one must consider either unsteady RANS or large eddy simulation (LES). This report compares the results for three LES codes: Nek5000, developed at Argonne National Laboratory (USA), and Cabaret and Conv3D, developed at the Moscow Institute of Nuclear Energy Safety at (IBRAE) in Russia. Nek5000 is based on the spectral element method (SEM), which is a high-order weighted residual technique that combines the geometric flexibility of the finite element method (FEM) with the tensor-product efficiencies of spectral methods. Cabaret is a 'compact accurately boundary-adjusting high-resolution technique' for fluid dynamics simulation. The method is second-order accurate on nonuniform grids in space and time, and has a small dispersion error and computational stencil defined within one space-time cell. The scheme is equipped with a conservative nonlinear correction procedure based on the maximum principle. CONV3D is based on the immersed boundary method and is validated on a wide set of the experimental and benchmark data. The numerical scheme has a very small scheme diffusion and is the second and the first order accurate in space and time, correspondingly. We compare and contrast simulation results for three computational fluid dynamics codes CABARET, Conv3D, and Nek5000 for the T-junction thermal striping problem that was the focus of a recent OECD/NEA blind benchmark. The corresponding codes utilize finite-difference implicit large eddy simulation (ILES), finite-volume LES on fully staggered grids, and an LES spectral element method (SEM), respectively. The simulations results are in a good agreement with experimenatl data. We present results from a study of sensitivity to computational mesh and time integration interval, and discuss the next steps in the simulation of this problem.

Obabko, A. V.; Fischer, P. F.; Tautges, T. J.; Karabasov, S.; Goloviznin, V. M.; Zaytsev, M. A.; Chudanov, V. V.; Pervichko, V. A.; Aksenova, A. E. (Mathematics and Computer Science); (Cambridge Univ.); (Moscow Institute of Nuclar Energy Safety)

2011-08-23T23:59:59.000Z

147

Comparative Study: CFD ?P Versus Measured ?P for 30% Flexible Ducts  

E-Print Network [OSTI]

foot-long circular ducts placed 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...) computer model. Fluent 6.2.16 CFD software package was used to simulate the static pressure drop inside the flexible duct. 3-D computer model of 6” diameter flexible duct was generated for 30% compression in 5 ft. long. The laboratory data...

Ugursal, A.; Culp, C.

2006-01-01T23:59:59.000Z

148

Metascalable quantum molecular dynamics simulations of hydrogen-on-demand  

Science Journals Connector (OSTI)

We enabled an unprecedented scale of quantum molecular dynamics simulations through algorithmic innovations. A new lean divide-and-conquer density functional theory algorithm significantly reduces the prefactor of the O(N) computational ... Keywords: density functional theory, divide-and-conquer, on-demand hydrogen production

Ken-ichi Nomura, Rajiv K. Kalia, Aiichiro Nakano, Priya Vashishta, Kohei Shimamura, Fuyuki Shimojo, Manaschai Kunaseth, Paul C. Messina, Nichols A. Romero

2014-11-01T23:59:59.000Z

149

Dynamic Simulation of DFIG Wind Turbines on FPGA Boards  

E-Print Network [OSTI]

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 + 1 where p is the air density; Rw is the wind turbine radius; cp (A, (3) is the performance

Zambreno, Joseph A.

150

Molecular dynamics simulations of boronnitride nanotubes embedded in  

E-Print Network [OSTI]

, theoretical studies suggest that BN nanotubes exhibit an energy gap of about 4--5 eV independent of chiralityMolecular dynamics simulations of boron­nitride nanotubes embedded in amorphous Si­B­N Michael In this article, we examine the elastic properties of boron­nitride nanotubes, which are embedded in amorphous

Ferrari, Patrik L.

151

Simulational nanoengineering: Molecular dynamics implementation of an atomistic Stirling engine  

E-Print Network [OSTI]

centuries ago and an early competitor of the steam engine, continues to attract interest owing to itsSimulational 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

Rapaport, Dennis C.

152

Interactive visual simulation of dynamic ink diffusion effects  

Science Journals Connector (OSTI)

This paper presents an effective method that simulates the ink diffusion process with visual plausible effects and real-time performance. Our algorithm updates the dynamic ink volume with a hybrid grid-particle representation: the fluid velocity field ... Keywords: industrial animation, ink diffusion, interaction, motion blur

Shibiao Xu; Xing Mei; Weiming Dong; Zhiyi Zhang; Xiaopeng Zhang

2011-12-01T23:59:59.000Z

153

A Molecular Dynamics Simulation of Hydrogen Storage with SWNTs  

E-Print Network [OSTI]

A Molecular Dynamics Simulation of Hydrogen Storage with SWNTs S. Maruyama and T. Kimura, Bunkyo-ku, Tokyo 113-8656, Japan The mechanism of efficient hydrogen storage (1) with SWNTs (2, and the storage amount became about 5 wt % regardless of the tube radius. The number of absorbed hydrogen

Maruyama, Shigeo

154

Hydrogen Raman shifts in carbon nanotubes from molecular dynamics simulation  

E-Print Network [OSTI]

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

Brenner, Donald W.

155

Standard Problems for CFD Validation for NGNP - Status Report  

SciTech Connect (OSTI)

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.

Richard W. Johnson; Richard R. Schultz

2010-08-01T23:59:59.000Z

156

Development of a CFD Analysis Plan for the first VHTR Standard Problem  

SciTech Connect (OSTI)

Data from a scaled model of a portion of the lower plenum of the helium-cooled very high temperature reactor (VHTR) are under consideration for acceptance as a computational fluid dynamics (CFD) validation data set or standard problem. A CFD analysis will help determine if the scaled model is a suitable geometry for validation data. The present article describes the development of an analysis plan for the CFD model. The plan examines the boundary conditions that should be used, the extent of the computational domain that should be included and which turbulence models need not be examined against the data. Calculations are made for a closely related 2D geometry to address these issues. It was found that a CFD model that includes only the inside of the scaled model in its computational domain is adequate for CFD calculations. The realizable k~e model was found not to be suitable for this problem because it did not predict vortex-shedding.

Richard W. Johnson

2008-09-01T23:59:59.000Z

157

DOE/NETL IGCC Dynamic Simulator Research and Training Center  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

NETL IGCC Dynamic Simulator NETL IGCC Dynamic Simulator Research and Training Center 01 Aug 2008 Volume 2: IGCC Process Descriptions DOE/NETL-2008/1324 NETL Collaboratory for Process & Dynamic Systems Research Disclaimer This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference therein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement,

158

Simulating Field-Scale Soil Organic Carbon Dynamics Using EPIC  

SciTech Connect (OSTI)

Simulation models integrate our knowledge of soil organic C (SOC) dynamics and are useful tools for evaluating impacts of crop management on soil C sequestration; yet, they require local calibration. Our objectives were to calibrate the Environmental Policy Integrated Climate (EPIC) model, and evaluate its performance for simulating SOC fractions as affected by soil landscape and management. An automated parameter optimization procedure was used to calibrate the model for a site-specific experiment in the Coastal Plain of central Alabama. The ability of EPIC to predict corn (Zea mays L.) and cotton (Gossypium hirsutum L.) yields and SOC dynamics on different soil landscape positions (summit, sideslope and drainageway) during the initial period of conservation tillage adoption (5 years) was evaluated using regression and mean squared deviations. Simulated yield explained 88% of measured yield variation, with greatest disagreement on the sideslope position and highest agreement in the drainageway. Simulations explained approximately 1, 34 and 40% of the total variation in microbial biomass C (MBC), particulate organic C (POC) and total organic C (TOC), respectively. Lowest errors on TOC simulations (0-20 cm) were found on the sideslope and summit. We conclude that the automated parameterization was generally successful, although further work is needed to refine the MBC and POC fractions, and to improve EPIC predictions of SOC dynamics with depth. Overall, EPIC was sensitive to spatial differences in C fractions that resulted from differing soil landscape positions. The model needs additional refinement for accurate simulations of field-scale SOC dynamics affected by short-term management decisions.

Causarano, Hector J.; Shaw, Joey N.; Franzluebbers, A. J.; reeves, D. W.; Raper, Randy L.; Balkcom, Kipling S.; Norfleet, M. L.; Izaurralde, R Cesar

2007-07-01T23:59:59.000Z

159

CFD Calculation of Internal Natural Convection in the Annulus between Horizontal Concentric Cylinders  

SciTech Connect (OSTI)

The objective of this heat transfer and fluid flow study is to assess the ability of a computational fluid dynamics (CFD) code to reproduce the experimental results, numerical simulation results, and heat transfer correlation equations developed in the literature for natural convection heat transfer within the annulus of horizontal concentric cylinders. In the literature, a variety of heat transfer expressions have been developed to compute average equivalent thermal conductivities. However, the expressions have been primarily developed for very small inner and outer cylinder radii and gap-widths. In this comparative study, interest is primarily focused on large gap widths (on the order of half meter or greater) and large radius ratios. From the steady-state CFD analysis it is found that the concentric cylinder models for the larger geometries compare favorably to the results of the Kuehn and Goldstein correlations in the Rayleigh number range of about 10{sup 5} to 10{sup 8} (a range that encompasses the laminar to turbulent transition). For Rayleigh numbers greater than 10{sup 8}, both numerical simulations and experimental data (from the literature) are consistent and result in slightly lower equivalent thermal conductivities than those obtained from the Kuehn and Goldstein correlations.

N.D. Francis, Jr; M.T. Itamura; S.W. Webb; D.L. James

2002-10-01T23:59:59.000Z

160

Visualizations and Simulations from the Center for Simulation of Dynamic Response of Materials (ASC/ASAP)  

DOE Data Explorer [Office of Scientific and Technical Information (OSTI)]

In Phase 1 of the ASC/ASAP program, The Caltech Center for Simulation of Dynamic Response of Materials developed a proof of concept for a Virtual shock physics Test Facility (VTF) in which the full three-dimensional response of a variety of target materials can be simulated for a wide range of compressive, tensional, and shear loadings, including those produced by detonation of energetic materials. The VTF is being applied to a series of integrated multiphysics simulations each with direct relevance to fundamental scientific issues in the dynamic response of materials that in turn are directly connected to proposed and existing experiments. New generations of multiscale models and terascale simulations are being created. The ASC/ASAP Gallery provides access to visualizations in the areas of materials, fluids, solids, and those related to the VTF. A section of tools and resources is available, as well as the full text of a long list of graphics-rich publications.

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161

Survey of Dynamic Simulation Programs for Nuclear Fuel Reprocessing  

SciTech Connect (OSTI)

The absence of any industrial scale nuclear fuel reprocessing in the U.S. has precluded the necessary driver for developing the advanced simulation capability now prevalent in so many other industries. Modeling programs to simulate the dynamic behavior of nuclear fuel separations and processing were originally developed to support the US government’s mission of weapons production and defense fuel recovery. Consequently there has been little effort is the US devoted towards improving this specific process simulation capability during the last two or three decades. More recent work has been focused on elucidating chemical thermodynamics and developing better models of predicting equilibrium in actinide solvent extraction systems. These equilibrium models have been used to augment flowsheet development and testing primarily at laboratory scales. The development of more robust and complete process models has not kept pace with the vast improvements in computational power and user interface and is significantly behind simulation capability in other chemical processing and separation fields.

Troy J. Tranter; Daryl R. Haefner

2008-06-01T23:59:59.000Z

162

Computer Simulation of Quantum Dynamics in a Classical Spin Environment  

E-Print Network [OSTI]

In this paper a formalism for studying the dynamics of quantum systems coupled to classical spin environments is reviewed. The theory is based on generalized antisymmetric brackets and naturally predicts open-path off-diagonal geometric phases in the evolution of the density matrix. It is shown that such geometric phases must also be considered in the quantum-classical Liouville equation for a classical bath with canonical phase space coordinates; this occurs whenever the adiabatics basis is complex (as in the case of a magnetic field coupled to the quantum subsystem). When the quantum subsystem is weakly coupled to the spin environment, non-adiabatic transitions can be neglected and one can construct an effective non-Markovian computer simulation scheme for open quantum system dynamics in classical spin environments. In order to tackle this case, integration algorithms based on the symmetric Trotter factorization of the classical-like spin propagator are derived. Such algorithms are applied to a model comprising a quantum two-level system coupled to a single classical spin in an external magnetic field. Starting from an excited state, the population difference and the coherences of this two-state model are simulated in time while the dynamics of the classical spin is monitored in detail. It is the author's opinion that the numerical evidence provided in this paper is a first step toward developing the simulation of quantum dynamics in classical spin environments into an effective tool. In turn, the ability to simulate such a dynamics can have a positive impact on various fields, among which, for example, nano-science.

Alessandro Sergi

2014-04-24T23:59:59.000Z

163

Library for modeling and simulating the thermal dynamics of buildings  

Science Journals Connector (OSTI)

Today's buildings consume more energy than any other sector of the U.S. economy, including transportation and industry; a similar importance can be expected in most European countries. Due to the increased interest in saving energy in buildings, new dynamic thermal models that describe transient response in more flexible modeling languages become necessary. Traditional building simulation software (e.g. TRNSYS or Energy Plus) are based on almost intractable simulation codes, difficult to maintain and modify, that predict system quantities at fixed time intervals. More clear code, properly separated from the simulation environment, with variable time step solvers would be necessary for the assessment of HVAC system performance with quicker dynamics. Following some ideas from a previous building thermal behavior library, a new enhanced Modelica library for modeling buildings is presented. The library basically consists of a combination of lumped parameter models and one-dimensional distributed parameter models that interconnects with each other through a set of common interfaces. Object-oriented features like class parameters and multiple-inheritance are used to improve the library structure making it easy to read and use. Complex building topologies can be built-up from component blocks that result in physically correct compound models that can be efficiently simulated and studied in any Modelica simulation environment.

Juan I. Videla; Bernt Lie

2006-01-01T23:59:59.000Z

164

A Groundwater Dynamic Simulation Model: Application to the Upper San Pedro Basin  

E-Print Network [OSTI]

A Groundwater Dynamic Simulation Model: Application to the Upper San Pedro Basin Report Prepared by using tools such as tracers to determine groundwater travel times and this dynamic simulation modeling

Fay, Noah

165

Technical Review of the CENWP Computational Fluid Dynamics Model of the John Day Dam Forebay  

SciTech Connect (OSTI)

The US Army Corps of Engineers Portland District (CENWP) has developed a computational fluid dynamics (CFD) model of the John Day forebay on the Columbia River to aid in the development and design of alternatives to improve juvenile salmon passage at the John Day Project. At the request of CENWP, Pacific Northwest National Laboratory (PNNL) Hydrology Group has conducted a technical review of CENWP's CFD model run in CFD solver software, STAR-CD. PNNL has extensive experience developing and applying 3D CFD models run in STAR-CD for Columbia River hydroelectric projects. The John Day forebay model developed by CENWP is adequately configured and validated. The model is ready for use simulating forebay hydraulics for structural and operational alternatives. The approach and method are sound, however CENWP has identified some improvements that need to be made for future models and for modifications to this existing model.

Rakowski, Cynthia L.; Serkowski, John A.; Richmond, Marshall C.

2010-12-01T23:59:59.000Z

166

Simulating Soil Carbon Dynamics, Erosion and Tillage with EPIC  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Simulating Soil Carbon Dynamics, Erosion Simulating Soil Carbon Dynamics, Erosion and Tillage with EPIC 1 R. C. Izaurralde (cesar.izaurralde@pnl.gov; 202-646-5227) Joint Global Change Research Institute (JGCRI) Pacific Northwest Nat'l Lab. - Univ. of Maryland 901 D St. S.W., Suite 900 Washington, DC 20024-2115 J. R. Williams (williams@brc.tamus.edu; 254-774-6124) Texas A&M University Blackland Research Center 808 East Blackland Road Temple, TX 76502 W. B. McGill (mcgill@unbc.ca) Faculty of Science and Management University of Northern British Columbia 3333 University Way, Prince George, BC V2N 4Z9 N. J. Rosenberg (nj.rosenberg@pnl.gov; 202-646-5029) Joint Global Change Research Institute (JGCRI) Pacific Northwest Nat'l Lab. - Univ. of Maryland 901 D St. S.W., Suite 900 Washington, DC 20024-2115

167

AVESTAR® - Oxy-Coal Carbon Capture (OCCC) Dynamic Simulator  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Oxy-Coal Carbon Capture (OCCC) Dynamic Simulator Oxy-Coal Carbon Capture (OCCC) Dynamic Simulator FutureGen 2.0 is a first-of-its-kind, near-zero emissions coal-fueled power plant using oxy-combustion technology to capture the plant's carbon emissions. To help meet the Nation's ever growing demand for clean energy, the FutureGen Industrial Alliance (Alliance) was formed to test and commercialize advanced coal-based systems fully integrated with carbon capture and geologic storage technologies. In cooperation with the U.S. Department of Energy (DOE), the Alliance and its project partners AirLiquide and Babcock & Wilcox, will upgrade an existing power plant in Meredosia, Illinois with oxy-coal carbon capture (OCCC) technology to capture and permanantly store approximately 1.0 million tonnes of CO2 each year.

168

Cellular-automaton-based simulation of 2D polymer dynamics  

Science Journals Connector (OSTI)

A cellular-automaton-based model that simulates flexible polymers in good solvents is constructed. Excluded-volume effects as well as hydrodynamic interactions are incorporated in this model in a very natural way. The center-of-mass velocity autocorrelation function of a single polymer chain in a 2D solution is found to obey a dynamic scaling relation which violates the nondraining concept.

J. M. Vianney A. Koelman

1990-04-16T23:59:59.000Z

169

Simulational nanoengineering: Molecular dynamics implementation of an atomistic Stirling engine  

Science Journals Connector (OSTI)

A nanoscale-sized Stirling engine with an atomistic working fluid has been modeled using molecular dynamics simulation. The design includes heat exchangers based on thermostats, pistons attached to a flywheel under load, and a regenerator. Key aspects of the behavior, including the time-dependent flows, are described. The model is shown to be capable of stable operation while producing net work at a moderate level of efficiency.

D. C. Rapaport

2009-04-30T23:59:59.000Z

170

Short-Range Order and Collective Dynamics of DMPC Bilayers: A Comparison between Molecular Dynamics Simulations, X-Ray,  

E-Print Network [OSTI]

Simulations, X-Ray, and Neutron Scattering Experiments Jochen S. Hub,* Tim Salditt,y Maikel C. Rheinsta derived by molecular dynamics simulations, elastic x-ray, and inelastic neutron scattering experiments dynamics obtained from the simulations and from inelastic neutron scattering are analyzed and compared

de Groot, Bert

171

Molecular dynamics simulations of the nano-scale room-temperature oxidation of aluminum single crystals  

E-Print Network [OSTI]

Molecular 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 with dynamic charge transfer between atoms. The simulations are performed on three aluminum low-index surfaces

Southern California, University of

172

MODELING PLANT COMPETITION WITH THE GAPS OBJECT-ORIENTED DYNAMIC SIMULATION MODEL  

E-Print Network [OSTI]

MODELING PLANT COMPETITION WITH THE GAPS OBJECT-ORIENTED DYNAMIC SIMULATION MODEL David G. Rossiter of Agronomy, Inc. #12;MODELING PLANT COMPETITION WITH THE GAPS OBJECT-ORIENTED DYNAMIC SIMULATION MODEL Abstract Modeling inter-species competition is a natural application for dynamic simulation models

Rossiter, D G "David"

173

Simulations of an offshore wind farm using large eddy simulation and a torque-controlled actuator disc model  

E-Print Network [OSTI]

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 ...

Creech, Angus; Maguire, A Eoghan

2014-01-01T23:59:59.000Z

174

A Multi-Model Approach for Uncertainty Propagation and Model Calibration in CFD Applications  

E-Print Network [OSTI]

Proper quantification and propagation of uncertainties in computational simulations are of critical importance. This issue is especially challenging for CFD applications. A particular obstacle for uncertainty quantifications in CFD problems is the large model discrepancies associated with the CFD models used for uncertainty propagation. Neglecting or improperly representing the model discrepancies leads to inaccurate and distorted uncertainty distribution for the Quantities of Interest. High-fidelity models, being accurate yet expensive, can accommodate only a small ensemble of simulations and thus lead to large interpolation errors and/or sampling errors; low-fidelity models can propagate a large ensemble, but can introduce large modeling errors. In this work, we propose a multi-model strategy to account for the influences of model discrepancies in uncertainty propagation and to reduce their impact on the predictions. Specifically, we take advantage of CFD models of multiple fidelities to estimate the model ...

Wang, Jian-xun; Xiao, Heng

2015-01-01T23:59:59.000Z

175

Molecular Dynamics Simulations from SNL's Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS)  

DOE Data Explorer [Office of Scientific and Technical Information (OSTI)]

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.

Plimpton, Steve; Thompson, Aidan; Crozier, Paul

176

CFD analyses of natural circulation in the air-cooled reactor cavity cooling system  

SciTech Connect (OSTI)

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)

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

177

Low Energy Buildings: CFD Techniques for Natural Ventilation and Thermal  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Low Energy Buildings: CFD Techniques for Natural Ventilation and Thermal Low Energy Buildings: CFD Techniques for Natural Ventilation and Thermal Comfort Prediction Speaker(s): Malcolm Cook Date: February 14, 2013 - 12:00pm Location: 90-3122 Seminar Host/Point of Contact: Michael Wetter Malcolm's presentation will cover both his research and consultancy activities. This will cover the work he has undertaken during his time spent working with architects on low energy building design, with a particular focus on natural ventilation and passive cooling strategies, and the role computer simulation can play in this design process. Malcolm will talk about the simulation techniques employed, as well as the innovative passive design principles that have led to some of the UK's most energy efficient buildings. In addition to UK building projects, the talk will

178

Molecular dynamics simulation of hydrogen diffusion in titanium  

National Nuclear Security Administration (NNSA)

9: Computation Physics 9: Computation Physics Atomistic Simulation of Hydrogen Diffusion in Titanium. Alexandr S. Rokhmanenkov, Alexey Yu. Kuksin, and Vladimir V. Stegailov All-Russia Research Institute of Automatics, Moscow 125412, Russia rohmanenkov@gmail.com Summary Study of the behavior of hydrogen in metals and alloys. The study is based on classical molecular dynamics (MD) and density functional theory (DFT) calculations. Study of the behavior of hydrogen in metals and alloys is of great importance due to the practical uses of hydrogen-metal systems for absorption of nuclear radiation, in neutron sources, for storage of hydrogen, or as catalyzers. This work is devoted to atomistic simulation of hydrogen diffusion in titanium hydrides and the effect of stresses and lattice defects on diffusivity.

179

Molecular Dynamics Simulations of Solutions at Constant Chemical Potential  

E-Print Network [OSTI]

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...

Perego, Claudio; Parrinello, Michele

2015-01-01T23:59:59.000Z

180

Molecular dynamics simulations of optical conductivity of dense plasmas  

Science Journals Connector (OSTI)

The optical conductivity ?(?) for dense Coulomb systems is investigated using molecular dynamics simulations on the basis of pseudopotentials to mimic quantum effects. Starting from linear response theory, the response in the long-wavelength limit k=0 can be expressed by different types of autocorrelation functions (ACF’s) such as the current ACF, the force ACF, or the charge density ACF. Consistent simulation data for transverse as well as longitudinal ACF’s are shown which are based on calculations with high numerical accuracy. Results are compared with perturbation expansions which are restricted to small values of the plasma parameter. The relevance with respect to a quantum Coulomb plasma is discussed. Finally, results are presented showing a consistent description of these model plasmas in comparison to quantum statistical approaches and to experimental data.

I. Morozov, H. Reinholz, G. Röpke, A. Wierling, and G. Zwicknagel

2005-06-22T23:59:59.000Z

Note: This page contains sample records for the topic "dynamics cfd simulations" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


181

CFD?Phenomenological Diesel Spray Analysis under Evaporative Conditions  

Science Journals Connector (OSTI)

CFD?Phenomenological Diesel Spray Analysis under Evaporative Conditions ... Despite their great uncertainties compared to the experimental studies, numerical simulations permit carrying out extensive parametric studies, isolating every single variable involved in the general process at any point in time and at any position in physical space. ... The thermodynamic codes assume that the cylinder charge is uniform in both composition and temperature, at all times during the cycle. ...

J. M. Desantes; X. Margot; J. M. Pastor; M. Chavez; A. Pinzello

2009-07-13T23:59:59.000Z

182

Molecular Dynamics Simulation of Hydrogen Storage with Single Walled Carbon Nanotubes Shigeo MARUYAMA1,2  

E-Print Network [OSTI]

Molecular Dynamics Simulation of Hydrogen Storage with Single Walled Carbon Nanotubes * Shigeo-8656 The hydrogen storage mechanism of SWNTs was studied through molecular dynamics simulations. Assuming the simple : Molecular Dynamics Method, Hydrogen Storage, Single Walled Carbon Nanotubes, Lennard-Jones, Adsorption

Maruyama, Shigeo

183

Modeling dilute sediment suspension using large-eddy simulation with a dynamic mixed model  

E-Print Network [OSTI]

Modeling dilute sediment suspension using large-eddy simulation with a dynamic mixed model Yi Transport of suspended sediment in high Reynolds number channel flows Re=O 600 000 is simulated using large-eddy simulation along with a dynamic-mixed model DMM . Because the modeled sediment concentration is low

Fringer, Oliver B.

184

Static and Dynamic Simulation of Steam Methane Reformers  

Science Journals Connector (OSTI)

The steam-methane reaction is an essential step for many processing plants. Hydrogen, ammonia and methanol are mostly produced by means of methane steam reforming. Since hydrogen is essential for any refinery employing hydrotreating, the performance monitoring of the hydrogen plant is highly desirable. The use of models or simulation is now a standard practice in most chemical plants and refineries. However, reliable models are still lacking for speciality reactors like the methane steam reformer. This paper describes steady-state and dynamic models for the reactions involved in reforming methane and higher hydrocarbon gases. The performance of the reformer is then illustrated by sensitivity analysis to various input disturbances like inlet pressure, temperature, feed concentration and rate, fuel rate and density and steam to carbon ratio. The effect of these disturbances on exit temperature and conversion is studied and analyzed. Catalyst deactivation effects are also discussed and it is shown by sample calculations that the simulator can give insight into catalyst performance and assist in monitoring catalyst deactivation. The transient effects are also reported and dynamic elements like gains and response time are discussed. Such information should give insight into controller design and effects of various parameters.

I.M. Alatiqi; A.M. Meziou; G.A. Gasmelseed

1989-01-01T23:59:59.000Z

185

Object-oriented modelling and simulation for the ALFRED dynamics  

Science Journals Connector (OSTI)

Abstract In this paper, a control-oriented modelling and simulation tool for the study of the Advanced Lead-cooled Fast Reactor European Demonstrator (ALFRED) plant dynamics is presented. It has been developed in order to perform design-basis transient analyses aimed at providing essential feedbacks for the system design finalization. The simulator has been meant to be modular, open and efficient. In this perspective, an object-oriented modelling approach has been adopted, by employing the reliable, tested and well-documented Modelica language. Simulation of core behaviour is based on point kinetics for neutronics and one-dimensional heat transfer models for thermal-hydraulics, coherently with ALFRED specifications. An effort has been spent to model the bayonet-tube Steam Generator (SG) foreseen to be installed within the reactor vessel. The primary loop model has been built by connecting the above-mentioned components (taking into account suitable time delays) and by incorporating the cold pool, which has revealed to be fundamental for an accurate definition of the time constants characteristic of the system because of its large thermal inertia. The description of the overall plant has been finalized by connecting standard turbine, condenser and other components of the balance of plant. Afterwards, the reactor responses to three typical transient initiators have been simulated (i.e., reduction of feedwater mass flow rate, variation of the turbine admission valve coefficient and transient of overpower). Simulation outcomes confirm the strong coupling between core and SG, besides showing the characteristic time constants of the various component responses. Results of the present study constitute a starting point in the definition of plant control strategies, laying the basis for investigation and development of a model-based control-system design.

Roberto Ponciroli; Andrea Bigoni; Antonio Cammi; Stefano Lorenzi; Lelio Luzzi

2014-01-01T23:59:59.000Z

186

Simulation studies on the standing and traveling wave thermoacoustic prime movers  

SciTech Connect (OSTI)

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.

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

187

Linear interfacial polymerization: Theory and simulations with dissipative particle dynamics  

Science Journals Connector (OSTI)

Step-growth alternating interfacial polymerization between two miscible or immiscible monomer melts is investigated theoretically and by dissipative particle dynamics simulations. In both cases the kinetics for an initially bilayer system passes from the reaction to diffusion control. The polymer composed of immiscible monomers precipitates at the interface forming a film of nearly uniform density. It is demonstrated that the reaction proceeds in a narrow zone which expands much slower than the whole film so that newly formed polymer is extruded from the reaction zone. This concept of “reactive extrusion” is used to analytically predict the degree of polymerization and distribution of all components (monomers polymer and end groups) within the film in close agreement with the simulations. Increasing the comonomer incompatibility leads to thinner and more uniform films with the higher average degree of polymerization. The final product is considerably more polydisperse than expected for the homogeneous step-growth polymerization. The results extend the previous theoretical reports on interfacial polymerization and provide new insights into the internal film structure and polymer characteristics which are important for membrane preparation microencapsulation and 3D printing technologies. A systematic way of mapping the simulation data onto laboratory scales is discussed.

2014-01-01T23:59:59.000Z

188

VISION - Verifiable Fuel Cycle Simulation of Nuclear Fuel Cycle Dynamics  

SciTech Connect (OSTI)

The U.S. DOE Advanced Fuel Cycle Initiative’s (AFCI) fundamental objective is to provide technology options that - if implemented - would enable long-term growth of nuclear power while improving sustainability and energy security. The AFCI organization structure consists of four areas; Systems Analysis, Fuels, Separations and Transmutations. The Systems Analysis Working Group is tasked with bridging the program technical areas and providing the models, tools, and analyses required to assess the feasibility of design and deployment options and inform key decision makers. An integral part of the Systems Analysis tool set is the development of a system level model that can be used to examine the implications of the different mixes of reactors, implications of fuel reprocessing, impact of deployment technologies, as well as potential "exit" or "off ramp" approaches to phase out technologies, waste management issues and long-term repository needs. The Verifiable Fuel Cycle Simulation Model (VISION) is a computer-based simulation model that allows performing dynamic simulations of fuel cycles to quantify infrastructure requirements and identify key trade-offs between alternatives. It is based on the current AFCI system analysis tool "DYMOND-US" functionalities in addition to economics, isotopic decay, and other new functionalities. VISION is intended to serve as a broad systems analysis and study tool applicable to work conducted as part of the AFCI and Generation IV reactor development studies.

Steven J. Piet; A. M. Yacout; J. J. Jacobson; C. Laws; G. E. Matthern; D. E. Shropshire

2006-02-01T23:59:59.000Z

189

MOLECULAR DYNAMICS SIMULATIONS OF DISPLACEMENT CASCADES IN MOLYBDENUM  

SciTech Connect (OSTI)

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.

Smith, Richard Whiting

2003-09-08T23:59:59.000Z

190

Comparison of Homogeneous and Heterogeneous CFD Fuel Models for Phase I of the IAEA CRP on HTR Uncertainties Benchmark  

SciTech Connect (OSTI)

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.

Gerhard Strydom; Su-Jong Yoon

2014-04-01T23:59:59.000Z

191

CFD analysis of bubble hydrodynamics in a fuel reactor for a hydrogen-fueled chemical looping combustion system  

Science Journals Connector (OSTI)

Abstract This study investigates the temporal development of bubble hydrodynamics in the fuel reactor of a hydrogen-fueled chemical looping combustion (CLC) system by using a computational model. The model also investigates the molar fraction of products in gas and solid phases. The study assists in developing a better understanding of the CLC process, which has many advantages such as being a potentially promising candidate for an efficient carbon dioxide capture technology. The study employs the kinetic theory of granular flow. The reactive fluid dynamic system of the fuel reactor is customized by incorporating the kinetics of an oxygen carrier reduction into a commercial computational fluid dynamics (CFD) code. An Eulerian multiphase treatment is used to describe the continuum two-fluid model for both gas and solid phases. CaSO4 and H2 are used as an oxygen carrier and a fuel, respectively. The computational results are validated with the experimental and numerical results available in the open literature. The CFD simulations are found to capture the features of the bubble formation, rise and burst in unsteady and quasi-steady states very well. The results show a significant increase in the conversion rate with higher dense bed height, lower bed width, higher free board height and smaller oxygen carrier particles which upsurge an overall performance of the CLC plant.

Atal Bihari Harichandan; Tariq Shamim

2014-01-01T23:59:59.000Z

192

CFD Simulation of Infiltration Heat Recovery  

E-Print Network [OSTI]

Energy Efficiency and Renewable Energy, Office of BuildingEnergy Efficiency and Renewable Energy, Office of Building

Buchanan, C.R.

2011-01-01T23:59:59.000Z

193

Effects of confinement on water structure and dynamics and on proton transport: a molecular simulation study  

E-Print Network [OSTI]

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...

Hirunsit, Pussana

2009-05-15T23:59:59.000Z

194

The legacy and future of CFD at Los Alamos  

SciTech Connect (OSTI)

The early history is presented of the prolific development of CFD methods in the Fluid Dynamics Group (T-3) at Los Alamos National Laboratory in the years from 1958 to the late 1960`s. Many of the currently used numerical methods--PIC, MAC, vorticity-stream-function, ICE, ALE methods and the {kappa}-{var_epsilon} method for turbulence--originated during this time. The rest of the paper summarizes the current research in T-3 for CFD, turbulence and solids modeling. The research areas include reactive flows, multimaterial flows, multiphase flows and flows with spatial discontinuities. Also summarized are modern particle methods and techniques developed for large scale computing on massively parallel computing platforms and distributed processors.

Johnson, N.L. [Los Alamos National Lab., NM (United States). Theoretical Div.

1996-06-01T23:59:59.000Z

195

INVESTIGATION OF SYSTEM DYNAMICS APPLIED TO BUILDING SIMULATION FOR ANTI-TERRORISM RESOURCE ALLOCATION  

E-Print Network [OSTI]

INVESTIGATION OF SYSTEM DYNAMICS APPLIED TO BUILDING SIMULATION FOR ANTI-TERRORISM RESOURCE ............................................................................. 26 2.8 Terrorism-Resistant Design

Bank, Lawrence C.

196

Numerical Simulation of the Flow Field in 3D Eccentric Annular and 2D Centered Labyrinth Seals for Comparison with Experimental LDA Data  

E-Print Network [OSTI]

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...

Vijaykumar, Anand

2011-02-22T23:59:59.000Z

197

Pseudorandom number generator for massively parallel molecular-dynamics simulations  

Science Journals Connector (OSTI)

A class of uniform pseudorandom number generators is proposed for modeling and simulations on massively parallel computers. The algorithm is simple, nonrecursive, and is easily transported to serial or vector computers. We have tested the procedure for uniformity, independence, and correlations by several methods. Related, less complex sequences passed some of these tests well enough; however, inadequacies were revealed by tests for correlations and in an interesting application, namely, annealing from an initial lattice that is mechanically unstable. In the latter case, initial velocities chosen by a random number generator that is not sufficiently random lead quickly to unphysical regularity in grain structure. The new class of generators passes this dynamical diagnostic for unwanted correlations.

Brad Lee Holian; Ora E. Percus; Tony T. Warnock; Paula A. Whitlock

1994-08-01T23:59:59.000Z

198

Localized dynamic subgrid closure for simulation of magnetohydrodynamic turbulence  

SciTech Connect (OSTI)

A local dynamic kinetic energy model (LDKM) for large-eddy simulation (LES) of magnetohydrodynamic (MHD) turbulence is proposed. The proposed MHD turbulence model evaluates all model coefficients locally and dynamically without any ad hoc averaging. This model also does not assume low magnetic Reynolds numbers. The turbulent residual-helicity effect ({alpha}-effect) appearing in the magnetic induction equation is successfully modeled. For validation, high-Re decaying isotropic decay turbulence with and without a mean magnetic field are studied using LES. The effect of rotation is also studied. For the case without rotation, it is observed that the energy spectrum follows a k{sup -5/3} law. For the case with rotation, it is shown that two mechanisms, phase scrambling due to frame rotation and Joule dissipation, are competing, and two distinct regimes with respect to rotation rate are observed. There is a critical rotation rate at which the energy decays most in MHD turbulence. It is also shown that this MHD-LDKM model is applicable to wide variety of high/low magnetic Reynolds number applications.

Miki, Kenji; Menon, Suresh [Georgia Institute of Technology, School of Aerospace Engineering, Atlanta, Georgia 30332-0150 (United States)

2008-07-15T23:59:59.000Z

199

Calibrated Langevin-dynamics simulations of intrinsically disordered proteins  

Science Journals Connector (OSTI)

We perform extensive coarse-grained (CG) Langevin dynamics simulations of intrinsically disordered proteins (IDPs), which possess fluctuating conformational statistics between that for excluded volume random walks and collapsed globules. Our CG model includes repulsive steric, attractive hydrophobic, and electrostatic interactions between residues and is calibrated to a large collection of single-molecule fluorescence resonance energy transfer data on the interresidue separations for 36 pairs of residues in five IDPs: ??, ??, and ?-synuclein, the microtubule-associated protein ?, and prothymosin ?. We find that our CG model is able to recapitulate the average interresidue separations regardless of the choice of the hydrophobicity scale, which shows that our calibrated model can robustly capture the conformational dynamics of IDPs. We then employ our model to study the scaling of the radius of gyration with chemical distance in 11 known IDPs. We identify a strong correlation between the distance to the dividing line between folded proteins and IDPs in the mean charge and hydrophobicity space and the scaling exponent of the radius of gyration with chemical distance along the protein.

W. Wendell Smith; Po-Yi Ho; Corey S. O'Hern

2014-10-13T23:59:59.000Z

200

Massively Parallel Spectral Element Large Eddy Simulation of a Turbulent Channel Using Wall Models  

E-Print Network [OSTI]

the strength and ability to push forward and succeed. I owe you guys everything and nobody could ask for a better family. I love you all. iv NOMENCLATURE CFD Computational Fluid Dynamics DNS Direct Numerical Simulation RANS Reynolds Averaged Navier...-Stokes LES Large Eddy Simulation FEM Finite Element Method SEM Spectral Element Method SGS Sub-Grid Scale TLM Two Layer Method Re Reynolds Number Re Friction Reynolds Number U1 Characteristic Velocity GLL Gauss-Lobatto-Legendre Cs Smagorinski Coe...

Rabau, Joshua I

2013-05-01T23:59:59.000Z

Note: This page contains sample records for the topic "dynamics cfd simulations" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


201

L3:THM.CFD.P5.02 J.N. Shadid, T.M. Smith, R.P. Pawlowski, E....  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

2 J.N. Shadid, T.M. Smith, R.P. Pawlowski, E. C. Cyr, P.D. Weber SNL Completed: October 31, 2012 CASL-U-2012-0164-000 RANS CFD SIMULATIONS FOR CASL THM USING DREKAR::CFD J. N....

202

Fully-Coupled Simulations of the Rotorcraft / Ship Dynamic Interface Emre Alpman  

E-Print Network [OSTI]

representation of the effect of ship deck on the rotor wake (simplified ground effectFully-Coupled Simulations of the Rotorcraft / Ship Dynamic Interface Emre Alpman exa152@psu A fully- coupled simulation tool has been developed to analyze the rotorcraft/ship dynamic interface

203

A Numerical Model for the Dynamic Simulation of a Recirculation Single-Effect Absorption Chiller  

E-Print Network [OSTI]

A Numerical Model for the Dynamic Simulation of a Recirculation Single- Effect Absorption Chiller A dynamic model for the simulation of a new single-effect water/lithium bromide absorption chiller. Keywords: absorption; chiller; modelling; transient; water-lithium bromide; falling film hal-00713904

Paris-Sud XI, Université de

204

Molecular Dynamics Simulation of Hydrogen Storage with Single Walled Carbon Nanotubes  

E-Print Network [OSTI]

Molecular Dynamics Simulation of Hydrogen Storage with Single Walled Carbon Nanotubes Shigeo MARUYAMA #12;The hydrogen storage mechanism of SWNTs was studied through molecular dynamics simulations,12) Fig. 6 Hydrogen storage inside each SWNT #12;Table 1 Potential parameters between SWNTs Tube d0 [Ã?

Maruyama, Shigeo

205

A Molecular Dynamics Simulation of Hydrogen Storage by SWNTs Tatsuto Kimuraa  

E-Print Network [OSTI]

A Molecular Dynamics Simulation of Hydrogen Storage by SWNTs Tatsuto Kimuraa and Shigeo Maruyamab of efficient hydrogen storage [1] with SWNTs [2,3] was studied through classical molecular dynamics simulations adsorbed hydrogen molecules was almost proportional to the number of carbon atoms, and the storage amount

Maruyama, Shigeo

206

Molecular Dynamics Simulations of Laser Induced Incandescence Dr. Adri van Duin  

E-Print Network [OSTI]

Molecular Dynamics Simulations of Laser Induced Incandescence (LII) Dr. Adri van Duin Associate of Engineering. Laser Induced Incandescence (LII) is a popular method to estimate the properties of soot. Molecular Dynamics Simulations of Laser-Induced Incandescence of Soot Using an Extended ReaxFF Reactive

Bjørnstad, Ottar Nordal

207

Effect of Hydrodynamic Interactions on DNA Dynamics in Extensional Flow: Simulation and Single Molecule Experiment  

E-Print Network [OSTI]

a combination of single molecule experimental techniques and Brownian dynamics (BD) simulation to investigate, and chain stretch in strong flows. More recently, the advent of single molecule visualizations using. A careful coupling of single molecule visualization and Brownian dynamics simulation of polymer chains

Shaqfeh, Eric

208

Molecular Dynamics Simulation of Nucleation of SWNT from a Metal Particle on a Substrate  

E-Print Network [OSTI]

a transition metal cluster on a substrate is studied using classical molecular dynamics (MD) simulations between pure metal and metal-carbide. Graphite structure gradually precipitates from the edgeMolecular Dynamics Simulation of Nucleation of SWNT from a Metal Particle on a Substrate Yasushi

Maruyama, Shigeo

209

An Energy-Aware Simulation Model and Transaction Protocol for Dynamic Workload Distribution in Mobile Ad Hoc Networks1  

E-Print Network [OSTI]

An Energy-Aware Simulation Model and Transaction Protocol for Dynamic Workload Distribution California {tari, prong, pedram}@usc.edu Abstract This paper introduces a network simulation model

Pedram, Massoud

210

Note: Local thermal conductivities from boundary driven non-equilibrium molecular dynamics simulations  

SciTech Connect (OSTI)

We report non-equilibrium molecular dynamics simulations of heat transport in models of molecular fluids. We show that the “local” thermal conductivities obtained from non-equilibrium molecular dynamics simulations agree within numerical accuracy with equilibrium Green-Kubo computations. Our results support the local equilibrium hypothesis for transport properties. We show how to use the local dependence of the thermal gradients to quantify the thermal conductivity of molecular fluids for a wide range of thermodynamic states using a single simulation.

Bresme, F., E-mail: f.bresme@imperial.ac.uk [Department of Chemistry, Chemical Physics Section, Imperial College London, London SW7 2AZ (United Kingdom); Department of Chemistry, Norwegian University of Science and Technology, Trondheim (Norway); Armstrong, J., E-mail: j.armstrong@imperial.ac.uk [Department of Chemistry, Chemical Physics Section, Imperial College London, London SW7 2AZ (United Kingdom)

2014-01-07T23:59:59.000Z

211

Single molecule simulations in complex geometries with embedded dynamic one-dimensional structures  

E-Print Network [OSTI]

Single molecule simulations in complex geometries with embedded dynamic one-dimensional structures and shrink. In this paper we present a simulation algorithm that combines single molecule simula- tions in three-dimensional space with single molecule simulations on one-dimensional structures of arbitrary

Flener, Pierre

212

The Optimal Golf Swing An exercise in simulation of dynamic systems  

E-Print Network [OSTI]

correct handling is critical. Examples are flight-simulators and the training of operators in large power Dynamic systems have many applications, and simulators may be used for training personnel in cases where of true feeling the operators experience during the simulator training d the efficiency and accuracy

Mosegaard, Klaus

213

Diffusive Dynamics of Water inside Hydrophobic Carbon Micropores Studied by Neutron Spectroscopy and Molecular Dynamics Simulation  

E-Print Network [OSTI]

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 $I(Q,t)$.

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

214

CFD modeling of buoyancy driven cavities with internal heat source -Application to heated rooms  

E-Print Network [OSTI]

comparisons are given with regard to heat transfer to the walls as well as to heat source behavior and plume. Keywords: CFD - Computational Fluid Dynamics modeling; buoyancy driven cavity; heat source; thermal plume enclosure helps to accurately assess the heat transfer phenomena that take place across the building

215

Computational fluid dynamics modeling of coal gasification in a pressurized spout-fluid bed  

SciTech Connect (OSTI)

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.

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

216

An enhanced parallel version of kiva–3v, coupled with a 1d CFD code, and its use in general purpose engine applications  

Science Journals Connector (OSTI)

Numerical simulations of reactive flows are among the most computational demanding applications in the scientific computing world. KIVA-3V, a widely used computer program for CFD, specifically tailored to engine applications, had been deeply modified ...

Gino Bella; Fabio Bozza; Alessandro De Maio; Francesco Del Citto; Salvatore Filippone

2006-09-01T23:59:59.000Z

217

CFD-based design load analysis of 5MW offshore wind turbine  

Science Journals Connector (OSTI)

The structure and aerodynamic loads acting on NREL 5MW reference wind turbine blade are calculated and analyzed based on advanced Computational Fluid Dynamics (CFD) and unsteady Blade Element Momentum (BEM). A detailed examination of the six force components has been carried out (three force components and three moment components). Structure load (gravity and inertia load) and aerodynamic load have been obtained by additional structural calculations (CFD or BEM respectively ). In CFD method the Reynolds Average Navier-Stokes approach was applied to solve the continuity equation of mass conservation and momentum balance so that the complex flow around wind turbines was modeled. Written in C programming language a User Defined Function (UDF) code which defines transient velocity profile according to the Extreme Operating Gust condition was compiled into commercial FLUENT package. Furthermore the unsteady BEM with 3D stall model has also adopted to investigate load components on wind turbine rotor. The present study introduces a comparison between advanced CFD and unsteady BEM for determining load on wind turbine rotor. Results indicate that there are good agreements between both present methods. It is importantly shown that six load components on wind turbine rotor is significant effect under Extreme Operating Gust (EOG) condition. Using advanced CFD and additional structural calculations this study has succeeded to construct accuracy numerical methodology to estimate total load of wind turbine that compose of aerodynamic load and structure load.

T. T. Tran; G. J. Ryu; Y. H. Kim; D. H. Kim

2012-01-01T23:59:59.000Z

218

Dyna-CLUE Model Improvement Based on Exponential Smoothing Method and Land Use Dynamic Simulation  

Science Journals Connector (OSTI)

Response variables and their driving factors often vary with time in the process of land use dynamic simulation; however, there are few existing literatures mentioned it.In order to evaluate the impact of time fa...

Minghao Liu; Yaoxing Wang; Donghong Li…

2013-01-01T23:59:59.000Z

219

Lattice Boltzmann simulation to study multiple bubble dynamics Amit Gupta, Ranganathan Kumar *  

E-Print Network [OSTI]

Lattice Boltzmann simulation to study multiple bubble dynamics Amit Gupta, Ranganathan Kumar Keywords: Lattice Boltzmann Bubble Two-phase Coalescence a b s t r a c t Lattice Boltzmann method (LBM) has

Gupta, Amit

220

Finite Element Modelling and Molecular Dynamic Simulations of Carbon nanotubes/ Polymer Composites  

E-Print Network [OSTI]

Modeling of single-walled carbon nanotubes, multi-walled nanotubes and nanotube reinforced polymer composites using both the Finite Element method and the Molecular Dynamic simulation technique is presented. Nanotubes subjected to mechanical loading...

Gaddamanugu, Dhatri

2010-07-14T23:59:59.000Z

Note: This page contains sample records for the topic "dynamics cfd simulations" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


221

Research on propeller dynamic load simulation system of electric propulsion ship  

Science Journals Connector (OSTI)

A dynamic marine propeller simulation system was developed, which is ... requirement of theory research and engineering design of marine electric propulsion system. By applying an actual ship parameter...J? ? K ...

Hui Huang ? ?; Ai-di Shen ???; Jian-xin Chu ???

2013-04-01T23:59:59.000Z

222

Correlation of chemical shifts predicted by molecular dynamics simulations for partially disordered proteins  

Science Journals Connector (OSTI)

There has been a longstanding interest in being able to accurately predict NMR chemical shifts from structural data. Recent studies have focused on using molecular dynamics (MD) simulation data as input for impro...

Jerome M. Karp; Ertan Erylimaz; David Cowburn

2014-11-01T23:59:59.000Z

223

Parallel Simulation of Subsonic Fluid Dynamics on a Cluster of Workstations  

E-Print Network [OSTI]

An effective approach of simulating fluid dynamics on a cluster of non- dedicated workstations is presented. The approach uses local interaction algorithms, small communication capacity, and automatic migration of parallel ...

Skordos, Panayotis A.

1995-12-01T23:59:59.000Z

224

Nonequilibrium molecular dynamics simulations of confined fluids in contact with the bulk  

E-Print Network [OSTI]

Nonequilibrium molecular dynamics simulations of confined fluids in contact with the bulk Luzheng Zhang, Ramkumar Balasundaram,a) and Stevin H. Gehrke Department of Chemical Engineering, Kansas State University, Manhattan, Kansas 66506 Shaoyi Jiangb) Department of Chemical Engineering, University

Zhang, Luzheng

225

Three-Dimensional Computational Fluid Dynamics  

SciTech Connect (OSTI)

Computational fluid dynamics (CFD) is one discipline falling under the broad heading of computer-aided engineering (CAE). CAE, together with computer-aided design (CAD) and computer-aided manufacturing (CAM), comprise a mathematical-based approach to engineering product and process design, analysis and fabrication. In this overview of CFD for the design engineer, our purposes are three-fold: (1) to define the scope of CFD and motivate its utility for engineering, (2) to provide a basic technical foundation for CFD, and (3) to convey how CFD is incorporated into engineering product and process design.

Haworth, D.C.; O'Rourke, P.J.; Ranganathan, R.

1998-09-01T23:59:59.000Z

226

Development of CFD models to support LEU Conversion of ORNL s High Flux Isotope Reactor  

SciTech Connect (OSTI)

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].

Khane, Vaibhav B [ORNL] [ORNL; Jain, Prashant K [ORNL] [ORNL; Freels, James D [ORNL] [ORNL

2012-01-01T23:59:59.000Z

227

Ab Initio Molecular Dynamics Simulations of Low-Energy Recoil...  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

A variety of different defect configurations are created, consisting mainly of vacancies and interstitials. Charge transfer occurs during the dynamic displacement process....

228

Dynamic simulation on collision between ship and offshore wind turbine  

Science Journals Connector (OSTI)

By using ABAQUS/Explicit, the dynamic process of an offshore wind turbine(OWT) stricken by a ship of 5000DWT...

Hongyan Ding ???; Qi Zhu ? ?; Puyang Zhang ???

2014-02-01T23:59:59.000Z

229

Experimental characterization of energetic material dynamics for multiphase blast simulation.  

SciTech Connect (OSTI)

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.

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

230

Atomic detail brownian dynamics simulations of concentrated protein...  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

method. Concentrated solutions (30-40% volume fraction) of myoglobin, hemoglobin A, and sickle cell hemoglobin S were simulated, and static structure factors, oligomer formation,...

231

CFD analysis of the effects of the flow distribution and heat losses on the steam reforming of methanol in catalytic (Pd/ZnO) microreactors  

Science Journals Connector (OSTI)

Abstract A three-dimensional computational fluid dynamics (CFD) simulation study of the effects of the flow distribution and the heat losses on the performance of microchannels and microslits reactors for the steam reforming of methanol (SRM) over Pd/ZnO is presented. Several flow distributing headers covering a wide range of the flow diffuser expansion angle (?) have been considered. Large values of ? lead to flow maldistribution characterized by jet flow resulting in negative effects on the SRM conversion and hydrogen yield, especially for the microslits at high reaction temperatures and space velocities. Simulations have also evidenced that heat losses constitute a critical issue for microreactors operation, particularly at low space velocities. Heat losses may reach very high values, above 80–90% of the energy supplied to the microreactor, with the consequence that it may be necessary to provide up to 9 times the heat of the SRM reaction to achieve high methanol conversions.

I. Uriz; G. Arzamendi; P.M. Diéguez; F.J. Echave; O. Sanz; M. Montes; L.M. Gandía

2014-01-01T23:59:59.000Z

232

BEAM DYNAMICS SIMULATIONS FOR A DC GUN BASED INJECTOR F.Zhou 1,2,  

E-Print Network [OSTI]

BEAM DYNAMICS SIMULATIONS FOR A DC GUN BASED INJECTOR FOR PERL* F.Zhou 1,2, , I.Ben-Zvi2 , X for this machine are being extensively investigated at BNL. One of the possible options is photocathode DC gun. The schematic layout of a PERL DC gun based injector and its preliminary beam dynamics are presented

Brookhaven National Laboratory

233

Hybrid approach for including electronic and nuclear quantum effects in molecular dynamics simulations of hydrogen transfer  

E-Print Network [OSTI]

Hybrid approach for including electronic and nuclear quantum effects in molecular dynamics January 2001 A hybrid approach for simulating proton and hydride transfer reactions in enzymes coefficient and to investigate the real-time dynamics of reactive trajectories. This hybrid approach includes

Hammes-Schiffer, Sharon

234

Nonadiabatic Molecular Dynamics Simulations of the Energy Transfer between Building Blocks in a Phenylene Ethynylene Dendrimer  

E-Print Network [OSTI]

Nonadiabatic Molecular Dynamics Simulations of the Energy Transfer between Building Blocks E. Roitberg*, UniVersidad Nacional de Quilmes, Roque Saenz Pen~a 352, B1876BXD Bernal, Argentina, 2009 The ultrafast dynamics of electronic and vibrational energy transfer between two- and three

Tretiak, Sergei

235

Myoglobin-CO Conformational Substate Dynamics: 2D Vibrational Echoes and MD Simulations  

E-Print Network [OSTI]

Myoglobin-CO Conformational Substate Dynamics: 2D Vibrational Echoes and MD Simulations Kusai A over a range of temperatures. The A1 and A3 conformational substates of MbCO are found to have assignments for the MbCO conformational substates. INTRODUCTION Protein dynamics have been the focus of both

Fayer, Michael D.

236

Rapid hydrogen production from water using aluminum nanoclusters: A quantum molecular dynamics simulation study  

E-Print Network [OSTI]

Rapid hydrogen production from water using aluminum nanoclusters: A quantum molecular dynamics Available online 31 December 2013 Keywords: Hydrogen production Water Aluminum nanoclusters Quantum molecular dynamics simulation It is hoped that a hydrogen-on-demand generator may one day start with just

Southern California, University of

237

A Virtual Test Facility for the Simulation of Dynamic Response in Materials  

Science Journals Connector (OSTI)

The Center for Simulating Dynamic Response of Materials at the California Institute of Technology is constructing a virtual shock physics facility for studying the response of various target materials to very strong shocks. The Virtual Test Facility ... Keywords: parallel computing, shock physics simulation

Julian Cummings; Michael Aivazis; Ravi Samtaney; Raul Radovitzky; Sean Mauch; Dan Meiron

2002-08-01T23:59:59.000Z

238

Proper Orthogonal Decomposition-Based Modeling, Analysis, and Simulation of Dynamic Wind Load  

E-Print Network [OSTI]

Proper Orthogonal Decomposition-Based Modeling, Analysis, and Simulation of Dynamic Wind Load.1061/ ASCE 0733-9399 2005 131:4 325 CE Database subject headings: Simulation; Wind loads; Buildings; Random on the decomposition of the covariance and XPSD matrices is presented. A physically meaningful linkage between the wind

Chen, Xinzhong

239

On the self-similarity assumption in dynamic models for large eddy simulations  

E-Print Network [OSTI]

that the present formulation of the DP is usually incompatible with its under- lying self-similarity assumption SSAOn the self-similarity assumption in dynamic models for large eddy simulations Daniele Carati eddy simulations and their underlying self-similarity assumption is discussed. The interpretation

Van Den Eijnden, Eric

240

Building design and thermal renovation measures proposal by means of regression models issued from dynamic simulations  

E-Print Network [OSTI]

comparison between different energy reduction strategies, like improving the insulation levels or increasing the thermal inertia. An example of their use and a data comparison with a dynamic simulation is shown in last;Nowadays, the most reliable solutions to calculate the energy demand are the simulation energy tools

Boyer, Edmond

Note: This page contains sample records for the topic "dynamics cfd simulations" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


241

Understanding graphene production by ionic surfactant exfoliation: A molecular dynamics simulation study  

E-Print Network [OSTI]

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

Simons, Jack

242

Integrating Models and Simulations of Continuous Dynamics into SysML  

E-Print Network [OSTI]

and the corresponding Modelica models; and the integration of simulation experiments with other SysML constructsIntegrating Models and Simulations of Continuous Dynamics into SysML Thomas Johnson1 Christiaan J.J. Paredis1 Roger Burkhart2 1 Systems Realization Laboratory The G. W. Woodruff School of Mechanical

243

Climate Dynamics Diagnosis of the Marine Low Cloud Simulation in the NCAR Community Earth System  

E-Print Network [OSTI]

-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

Bretherton, Chris

244

Nonadiabatic molecular dynamics simulation: An approach based on quantum measurement picture  

E-Print Network [OSTI]

Mixed-quantum-classical molecular dynamics simulation implies an effective measurement on the electronic states owing to continuously tracking the atomic forces.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.

Wei Feng; Luting Xu; Xin-Qi Li; Weihai Fang; YiJing Yan

2013-12-17T23:59:59.000Z

245

Water dynamical anomalies evidenced by molecular-dynamics simulations at the solvent-protein interface  

Science Journals Connector (OSTI)

We present a computer simulation picture of the dynamical behavior, at room temperature, of water in the region close to a protein surface. We analyzed the probability distribution of water molecules diffusing near the surface, and we found that it deviates from a Gaussian, which is predicted for Brownian particles. Consistently, the mean square displacements of water oxygens show a sublinear trend with time. Moreover, the relaxation of hydration layers around the whole protein is found to follow a stretched exponential decay, typical of complex systems, which could as well be ascribed to the non-Gaussian shape of the propagator. In agreement with such findings, the analysis of water translational and reorientational diffusion showed that not only are the solvent molecule motions hindered in the region close to the protein surface, but also the very nature of the particle diffusive processes, both translational and rotational, is affected. The deviations from the bulk water properties, which put into evidence a deep influence exerted by the protein on the solvent molecule motion, are discussed in connection with the presence of spatial (protein surface roughness) and temporal (distribution of water residence times) disorder inherent in the system.

Claudia Rocchi; Anna Rita Bizzarri; Salvatore Cannistraro

1998-03-01T23:59:59.000Z

246

Structural models of bioactive glasses from molecular dynamics simulations  

Science Journals Connector (OSTI)

...to adsorb and dissociate a water molecule (Tilocca Cormack 2008...the available computational power steadily grows, it will become...surface of bioactive glasses: water adsorption and reactivity...soda-lime silicate glasses by Car-Parrinello molecular dynamics...

2009-01-01T23:59:59.000Z

247

Multiplatform Dynamic System Simulation of a DC-DC Converter.  

E-Print Network [OSTI]

??The work presented in this paper focuses on the usability testing for the Open-Modelica. The modeling and simulation of the BMR450 DC-DC converter is also… (more)

Song, Wenpeng

2012-01-01T23:59:59.000Z

248

Investigating dynamic underground coal fires by means of numerical simulation  

Science Journals Connector (OSTI)

......is the key to successful prediction of various combustion processes (Hjertager 1986). Ten years ago, limited computer...Blasi C.D. ,1993. Modeling and simulation of combustion processes of charring and non-charring solid fuels, Prog......

S. Wessling; W. Kessels; M. Schmidt; U. Krause

2008-01-01T23:59:59.000Z

249

An Analysis Tool for Flight Dynamics Monte Carlo Simulations  

E-Print Network [OSTI]

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...

Restrepo, Carolina 1982-

2011-05-20T23:59:59.000Z

250

Gasificaton Transport: A Multiphase CFD Approach & Measurements  

SciTech Connect (OSTI)

The objective of this project was to develop predictive theories for the dispersion and mass transfer coefficients and to measure them in the turbulent fluidization regime, using existing facilities. A second objective was to use our multiphase CFD tools to suggest optimized gasifier designs consistent with aims of Future Gen. We have shown that the kinetic theory based CFD codes correctly compute: (1) Dispersion coefficients; and (2) Mass transfer coefficients. Hence, the kinetic theory based CFD codes can be used for fluidized bed reactor design without any such inputs. We have also suggested a new energy efficient method of gasifying coal and producing electricity using a molten carbonate fuel cell. The principal product of this new scheme is carbon dioxide which can be converted into useful products such as marble, as is done very slowly in nature. We believe this scheme is a lot better than the canceled FutureGen, since the carbon dioxide is safely sequestered.

Dimitri Gidaspow; Veeraya Jiradilok; Mayank Kashyap; Benjapon Chalermsinsuwan

2009-02-14T23:59:59.000Z

251

Validation of a CFD Analysis Model for Predicting CANDU-6 Moderator Temperature Against SPEL Experiments  

SciTech Connect (OSTI)

A validation of a 3D CFD model for predicting local subcooling of the moderator in the vicinity of calandria tubes in a CANDU-6 reactor is performed. The small scale moderator experiments performed at Sheridan Park Experimental Laboratory (SPEL) in Ontario, Canada[1] is used for the validation. Also a comparison is made between previous CFD analyses based on 2DMOTH and PHOENICS, and the current analysis for the same SPEL experiment. For the current model, a set of grid structures for the same geometry as the experimental test section is generated and the momentum, heat and continuity equations are solved by CFX-4.3, a CFD code developed by AEA technology. The matrix of calandria tubes is simplified by the porous media approach. The standard k-{epsilon} turbulence model associated with logarithmic wall treatment and SIMPLEC algorithm on the body fitted grid are used. Buoyancy effects are accounted for by the Boussinesq approximation. For the test conditions simulated in this study, the flow pattern identified is the buoyancy-dominated flow, which is generated by the interaction between the dominant buoyancy force by heating and inertial momentum forces by the inlet jets. As a result, the current CFD moderator analysis model predicts the moderator temperature reasonably, and the maximum error against the experimental data is kept at less than 2.0 deg. C over the whole domain. The simulated velocity field matches with the visualization of SPEL experiments quite well. (authors)

Churl Yoon; Bo Wook Rhee; Byung-Joo Min [Korea Atomic Energy Research Institute, 150, Dukjin-Dong, Yusong-Gu, Taejon 305-353 (Korea, Republic of)

2002-07-01T23:59:59.000Z

252

Extended Lagrangian quantum molecular dynamics simulations of shock-induced chemistry in hydrocarbons  

SciTech Connect (OSTI)

A set of interatomic potentials for hydrocarbons that are based upon the self-consistent charge transfer tight-binding approximation to density functional theory have been developed and implemented into the quantum molecular dynamics code ''LATTE''. The interatomic potentials exhibit an outstanding level of transferability and have been applied in molecular dynamics simulations of tert-butylacetylene under thermodynamic conditions that correspond to its single-shock Hugoniot. We have achieved precise conservation of the total energy during microcanonical molecular dynamics trajectories under incomplete convergence via the extended Lagrangian Born-Oppenheimer molecular dynamics formalism. In good agreement with the results of a series of flyer-plate impact experiments, our SCC-TB molecular dynamics simulations show that tert-butylactylene molecules polymerize at shock pressures around 6.1 GPa.

Sanville, Edward J [Los Alamos National Laboratory; Bock, Nicolas [Los Alamos National Laboratory; Challacombe, William M [Los Alamos National Laboratory; Cawkwell, Marc J [Los Alamos National Laboratory; Niklasson, Anders M N [Los Alamos National Laboratory; Dattelbaum, Dana M [Los Alamos National Laboratory; Sheffield, Stephen [Los Alamos National Laboratory; Sewell, Thomas D [UNIV OF MISSOURI

2010-01-01T23:59:59.000Z

253

Dynamic Human Reliability Analysis: Benefits and Challenges of Simulating Human Performance  

SciTech Connect (OSTI)

To date, there has been considerable work on dynamic event trees and other areas related to dynamic probabilistic safety assessment (PSA). The counterpart to these efforts in human reliability analysis (HRA) has centered on the development of specific methods to account for the dynamic nature of human performance. In this paper, the author posits that the key to dynamic HRA is not in the development of specific methods but in the utilization of cognitive modeling and simulation to produce a framework of data that may be used in quantifying the likelihood of human error. This paper provides an overview of simulation approaches to HRA; reviews differences between first, second, and dynamic generation HRA; and outlines potential benefits and challenges of this approach.

R. L. Boring

2007-06-01T23:59:59.000Z

254

Computational Fluid Dynamics Simulation of Open-Channel Flows Over Bridge-Decks Under Various Flooding Conditions  

E-Print Network [OSTI]

. This study simulates limited scaled experimental data conducted elsewhere for bridge flooding in open channel simulation, Computational fluid dynamics, Flooding flows, Turbulence modeling, VOF modeling. 1. IntroductionComputational Fluid Dynamics Simulation of Open-Channel Flows Over Bridge-Decks Under Various

Kostic, Milivoje M.

255

A dynamic process model of a natural gas combined cycle -- Model development with startup and shutdown simulations  

SciTech Connect (OSTI)

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.

Liese, Eric [U.S. DOE; Zitney, Stephen E. [U.S. DOE

2013-01-01T23:59:59.000Z

256

AMIP Simulation with the CAM4 Spectral Element Dynamical Core  

SciTech Connect (OSTI)

We evaluate the climate produced by the Community Earth System Model, version 1, running with the new spectral-element atmospheric dynamical core option. The spectral-element method is congured to use a cubed-sphere grid, providing quasi-uniform resolution over the sphere, increased parallel scalability and removing the need for polar filters. It uses a fourth order accurate spatial discretization which locally conserves mass and moist total energy. Using the Atmosphere Model Intercomparison Project protocol, we compare the results from the spectral-element dy- namical core with those produced by the default nite-volume dynamical core and with observations.

Evans, Katherine J [ORNL; Lauritzen, Peter [National Center for Atmospheric Research (NCAR); Mishra, Saroj [National Center for Atmospheric Research (NCAR); Neale, Rich [National Center for Atmospheric Research (NCAR); Taylor, Mark [Sandia National Laboratories (SNL); Tribbia, Joe [National Center for Atmospheric Research (NCAR)

2013-01-01T23:59:59.000Z

257

Ion and Electron Dynamics in Nonlinear PIC Simulations  

SciTech Connect (OSTI)

ITG and ETG turbulence is investigated with the nonlinear global PIC code ORB5. The large variety of numerical schemes and simulations domains used has sometimes lead to important discrepancies in the transport predictions. In order to discuss these disagreements, emphasis must be put on ways to check the numerical accuracy, such as energy conservation and numerical noise measurement. This paper therefore presents benchmarks, new algorithms and a noise diagnostic. After having demonstrated the numerical quality of our simulations, 2 topics are visited: the unclear role of the parallel nonlinearity and the transport level in ETG turbulence, for which predictions differing by one order of magnitude had been made elsewhere.

Jolliet, S.; Angelino, P.; Tran, T. M.; McMillan, B. F.; Sauter, O.; Villard, L. [Ecole Polytechnique Federale de Lausanne, Centre de Recherches en Physique des Plasmas, Association Euratom-Confederation Suisse, CH-1015 Lausanne (Switzerland); Bottino, A.; Peeters, A. G.; Poli, E. [Max Planck Institut fuer Plasmaphysik, IPP-EURATOM Association, Garching (Germany); Hatzky, R. [Computer Center of the Max-Planck-Gesellschaft, D 85748 Garching (Germany)

2006-11-30T23:59:59.000Z

258

Integrated Dynamic Simulation for Process Optimization and Control  

E-Print Network [OSTI]

wherever possible ­ Radiative heat transfer ­ Mass balance ­ Boundary layer transport ­ Surface adsorption;Schematics of Polysilicon RT-CVD Reactor MFC gas cylinder heating lamps RTP reactor RTP pumps 1st stage 2nd-level description ­ Reduced-order models to represent high complexity (e.g., reactor fluid dynamics, heat transfer

Rubloff, Gary W.

259

Darlington tritium removal facility and station upgrading plant dynamic process simulation  

SciTech Connect (OSTI)

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)

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

260

Dynamic simulation method for transmission and distribution planning  

Science Journals Connector (OSTI)

Under the conditions of liberalised market development optimisation role is not to be decreasing but even increasing. Basic definitions and model structure of optimisation system under market conditions is discussed in a paper, as well the experience ... Keywords: development optimisation, liberalised electricity market, power generation, power system planning, power system simulation, power transmission, risk analysis, uncertainty

Z. Krishans; I. Oleinikova; A. Mutule; J. Runcs

2006-12-01T23:59:59.000Z

Note: This page contains sample records for the topic "dynamics cfd simulations" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


261

Dynamic Deployment of Executing and Simulating Software Components  

E-Print Network [OSTI]

can reduce its processor power to conserve energy when its energy supply (i.e., battery) is low in the past, simulation merely mimicked some real-world behav- ior, we argue that in the future it will become necessary to intertwine the model world with the real world. This will be essential but not limited to cases

Egyed, Alexander

262

Periodic Boundary Conditions for Dislocation Dynamics Simulations in Three Dimensions  

E-Print Network [OSTI]

, the choice of initial configurations compatible with PBC and a consistent treatment of image stress of PBC for large-scale DD simulations in 3D. INTRODUCTION Treatment of boundary conditions or external interface (surface, crack, grain or phase boundary, etc.), it is necessary to account for stress

Cai, Wei

263

NREL: Computational Science - Wind Energy Simulations  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Wind Energy Simulations Wind Energy Simulations Scientists in the Computational Science Center at the National Renewable Energy Laboratory (NREL) are performing wind-farm computational fluid dynamics (CFD) and structural dynamics simulations that will provide a better understanding of the interactions of wind turbine wakes with one another, with the surrounding winds, and with the loads they impose on turbine blades and other components. Large-scale wind power generation deployment is a realistic and largely inevitable proposition as energy security, supply uncertainties, and global climate concerns drive the U.S. to develop diverse sources of domestic, clean, and renewable energy. The U.S. is currently on a path to produce 20% of its electricity from wind energy by 2030, which is a 10-fold increase

264

Optimization of Computational Performance and Accuracy in 3?D Transient CFD Model for CFB Hydrodynamics Predictions  

Science Journals Connector (OSTI)

This work aims to present a pure 3?D CFD model accurate and efficient for the simulation of a pilot scale CFB hydrodynamics. The accuracy of the model was investigated as a function of the numerical parameters in order to derive an optimum model setup with respect to computational cost. The necessity of the in depth examination of hydrodynamics emerges by the trend to scale up CFBCs. This scale up brings forward numerous design problems and uncertainties which can be successfully elucidated by CFD techniques. Deriving guidelines for setting a computational efficient model is important as the scale of the CFBs grows fast while computational power is limited. However the optimum efficiency matter has not been investigated thoroughly in the literature as authors were more concerned for their models accuracy and validity. The objective of this work is to investigate the parameters that influence the efficiency and accuracy of CFB computational fluid dynamics models find the optimum set of these parameters and thus establish this technique as a competitive method for the simulation and design of industrial large scale beds where the computational cost is otherwise prohibitive. During the tests that were performed in this work the influence of turbulence modeling approach time and space density and discretization schemes were investigated on a 1.2 MWth CFB test rig. Using Fourier analysis dominant frequencies were extracted in order to estimate the adequate time period for the averaging of all instantaneous values. The compliance with the experimental measurements was very good. The basic differences between the predictions that arose from the various model setups were pointed out and analyzed. The results showed that a model with high order space discretization schemes when applied on a coarse grid and averaging of the instantaneous scalar values for a 20 sec period adequately described the transient hydrodynamic behaviour of a pilot CFB while the computational cost was kept low. Flow patterns inside the bed such as the core?annulus flow and the transportation of clusters were at least qualitatively captured.

I. Rampidis; A. Nikolopoulos; N. Koukouzas; P. Grammelis; E. Kakaras

2007-01-01T23:59:59.000Z

265

Slow dynamics of a protein backbone in molecular dynamics simulation revealed by time-structure based independent component analysis  

SciTech Connect (OSTI)

We recently proposed the method of time-structure based independent component analysis (tICA) to examine the slow dynamics involved in conformational fluctuations of a protein as estimated by molecular dynamics (MD) simulation [Y. Naritomi and S. Fuchigami, J. Chem. Phys. 134, 065101 (2011)]. Our previous study focused on domain motions of the protein and examined its dynamics by using rigid-body domain analysis and tICA. However, the protein changes its conformation not only through domain motions but also by various types of motions involving its backbone and side chains. Some of these motions might occur on a slow time scale: we hypothesize that if so, we could effectively detect and characterize them using tICA. In the present study, we investigated slow dynamics of the protein backbone using MD simulation and tICA. The selected target protein was lysine-, arginine-, ornithine-binding protein (LAO), which comprises two domains and undergoes large domain motions. MD simulation of LAO in explicit water was performed for 1 ?s, and the obtained trajectory of C{sub ?} atoms in the backbone was analyzed by tICA. This analysis successfully provided us with slow modes for LAO that represented either domain motions or local movements of the backbone. Further analysis elucidated the atomic details of the suggested local motions and confirmed that these motions truly occurred on the expected slow time scale.

Naritomi, Yusuke [Department of Supramolecular Biology, Graduate School of Nanobioscience, Yokohama City University, 1-7-29 Suehiro-cho, Tsurumi-ku, Yokohama 230-0045 (Japan)] [Department of Supramolecular Biology, Graduate School of Nanobioscience, Yokohama City University, 1-7-29 Suehiro-cho, Tsurumi-ku, Yokohama 230-0045 (Japan); Fuchigami, Sotaro, E-mail: sotaro@tsurumi.yokohama-cu.ac.jp [Department of Medical Life Science, Graduate School of Medical Life Science, Yokohama City University, 1-7-29 Suehiro-cho, Tsurumi-ku, Yokohama 230-0045 (Japan)] [Department of Medical Life Science, Graduate School of Medical Life Science, Yokohama City University, 1-7-29 Suehiro-cho, Tsurumi-ku, Yokohama 230-0045 (Japan)

2013-12-07T23:59:59.000Z

266

Large Eddy Simulation of wind farm aerodynamics: A review  

Science Journals Connector (OSTI)

Abstract To study wind farm aerodynamics (WFA), the Wind Power industry currently relies on simple Engineering Models (EM) that simulate wind farms using basic principles of physics and empirically established approximations. \\{EMs\\} are fast and accurate for an overview of WFA and gauging mean power production, but cannot resolve phenomena like wake meandering, effect of atmospheric stratification on wake development, a turbine?s response to partial wake interaction and yawed inflows etc., and their relation with turbine loading, which require a first principle physics-based model, namely Computational Fluid Dynamics (CFD). Although advances in computer technology have promoted the application of CFD, the study of WFA is yet unworkable with Direct Numerical Simulation, which is the most comprehensive CFD technique. Thus, as a trade-off between cost and detail, researchers must resort to Large Eddy Simulation (LES) to garner thorough knowledge of WFA, which could in succession help the industry improve engineering models. This paper summarises the contributions of various LES investigations into WFA and how they have helped broaden our understanding of the subject. Additionally, the article touches upon the optimal use of LES and of the resultant data, and also the challenges faced by LES.

D. Mehta; A.H. van Zuijlen; B. Koren; J.G. Holierhoek; H. Bijl

2014-01-01T23:59:59.000Z

267

Time-Dependent Properties of Liquid Water:? A Comparison of Car?Parrinello and Born?Oppenheimer Molecular Dynamics Simulations  

Science Journals Connector (OSTI)

Time-Dependent Properties of Liquid Water:? A Comparison of Car?Parrinello and Born?Oppenheimer Molecular Dynamics Simulations ... Dynamical information of water interacting with its local environment can be gleaned from the vibrational power spectrum. ...

I-Feng W. Kuo; Christopher J. Mundy; Matthew J. McGrath; J. Ilja Siepmann

2006-07-27T23:59:59.000Z

268

Molecular dynamics simulations of the interaction of glucose with imidazole in aqueous solution  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Molecular dynamics simulations of the interaction of glucose with imidazole in Molecular dynamics simulations of the interaction of glucose with imidazole in aqueous solution Mo Chen, Yannick J. Bomble, Michael E. Himmel, John W. Brady PII: S0008-6215(11)00592-1 DOI: 10.1016/j.carres.2011.12.008 Reference: CAR 6026 To appear in: Carbohydrate Research Received Date: 15 June 2011 Revised Date: 22 November 2011 Accepted Date: 8 December 2011 Please cite this article as: Chen, M., Bomble, Y.J., Himmel, M.E., Brady, J.W., Molecular dynamics simulations of the interaction of glucose with imidazole in aqueous solution, Carbohydrate Research (2011), doi: 10.1016/j.carres. 2011.12.008 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and

269

Molecular dynamics simulation of chains mobility in polyethylene crystal  

E-Print Network [OSTI]

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.

V. I. Sultanov; V. V. Atrazhev; D. V. Dmitriev; S. F. Burlatsky

2014-01-17T23:59:59.000Z

270

CFD-based Optimization for Automotive Aerodynamics  

E-Print Network [OSTI]

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

Dumas, Laurent

271

Helmet Streamers with Triple Structures: Simulations of resistive dynamics  

E-Print Network [OSTI]

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.

T. Wiegelmann; K. Schindler; T. Neukirch

2008-01-21T23:59:59.000Z

272

Dynamic stall analysis of horizontal-axis-wind-turbine blades using computational fluid dynamics  

Science Journals Connector (OSTI)

Dynamic stall has been widely known to significantly affect the performance of the wind turbines. In this paper aerodynamic simulation of the unsteady low-speed flow past two-dimensional wind turbine blade profiles developed by the National Renewable Energy Laboratory (NREL) will be performed. The aerodynamic simulation will be performed using Computational Fluid Dynamics (CFD). The governing equations used in the simulations are the Unsteady-Reynolds-Averaged-Navier-Stokes (URANS) equations. The unsteady separated turbulent flow around an oscillating airfoil pitching in a sinusoidal pattern in the regime of low Reynolds number is investigated numerically. The investigation employs the URANS approach with the most suitable turbulence model. The development of the light dynamic stall of the blades under consideration is studied. The S809 blade profile is simulated at different mean wind speeds. Moreover the S826 blade profile is also considered for analysis of wind turbine blade which is the most suitable blade profile for the wind conditions in Egypt over the site of Gulf of El-Zayt. In order to find the best oscillating frequency different oscillating frequencies are studied. The best frequency can then be used for the blade pitch controller. The comparisons with the experimental results showed that the used CFD code can accurately predict the blade profile unsteady aerodynamic loads.

2012-01-01T23:59:59.000Z

273

Thermophysical properties of warm dense hydrogen using quantum molecular dynamics simulations  

Science Journals Connector (OSTI)

We study the thermophysical properties of warm dense hydrogen by using quantum molecular dynamics simulations. Results are presented for the pair distribution functions, the equation of state, and the Hugoniot curve. From the dynamic conductivity, we derive the dc electrical conductivity and the reflectivity. We compare with available experimental data and predictions of the chemical picture. In particular, we discuss the nonmetal-to-metal transition, which occurs at about 40 GPa in the dense fluid.

Bastian Holst, Ronald Redmer, and Michael P. Desjarlais

2008-05-09T23:59:59.000Z

274

Development of a %22Solar Patch%22 calculator to evaluate heliostat-field irradiance as a boundary condition in CFD models.  

SciTech Connect (OSTI)

A rigorous computational fluid dynamics (CFD) approach to calculating temperature distributions, radiative and convective losses, and flow fields in a cavity receiver irradiated by a heliostat field is typically limited to the receiver domain alone for computational reasons. A CFD simulation cannot realistically yield a precise solution that includes the details within the vast domain of an entire heliostat field in addition to the detailed processes and features within a cavity receiver. Instead, the incoming field irradiance can be represented as a boundary condition on the receiver domain. This paper describes a program, the Solar Patch Calculator, written in Microsoft Excel VBA to characterize multiple beams emanating from a 'solar patch' located at the aperture of a cavity receiver, in order to represent the incoming irradiance from any field of heliostats as a boundary condition on the receiver domain. This program accounts for cosine losses; receiver location; heliostat reflectivity, areas and locations; field location; time of day and day of year. This paper also describes the implementation of the boundary conditions calculated by this program into a Discrete Ordinates radiation model using Ansys{reg_sign} FLUENT (www.fluent.com), and compares the results to experimental data and to results generated by the code DELSOL.

Khalsa, Siri Sahib S. (Sandia Staffing Alliance); Ho, Clifford Kuofei

2010-05-01T23:59:59.000Z

275

Development of a %22solar patch%22 calculator to evaluate heliostat-field irradiance as a boundary condition in CFD models.  

SciTech Connect (OSTI)

A rigorous computational fluid dynamics (CFD) approach to calculating temperature distributions, radiative and convective losses, and flow fields in a cavity receiver irradiated by a heliostat field is typically limited to the receiver domain alone for computational reasons. A CFD simulation cannot realistically yield a precise solution that includes the details within the vast domain of an entire heliostat field in addition to the detailed processes and features within a cavity receiver. Instead, the incoming field irradiance can be represented as a boundary condition on the receiver domain. This paper describes a program, the Solar Patch Calculator, written in Microsoft Excel VBA to characterize multiple beams emanating from a 'solar patch' located at the aperture of a cavity receiver, in order to represent the incoming irradiance from any field of heliostats as a boundary condition on the receiver domain. This program accounts for cosine losses; receiver location; heliostat reflectivity, areas and locations; field location; time of day and day of year. This paper also describes the implementation of the boundary conditions calculated by this program into a Discrete Ordinates radiation model using Ansys{reg_sign} FLUENT (www.fluent.com), and compares the results to experimental data and to results generated by the code DELSOL.

Khalsa, Siri Sahib; Ho, Clifford Kuofei

2010-04-01T23:59:59.000Z

276

Dynamic Simulation of Startup in Ethyl tert-Butyl Ether Reactive Distillation with Input Multiplicity  

Science Journals Connector (OSTI)

Dynamic Simulation of Startup in Ethyl tert-Butyl Ether Reactive Distillation with Input Multiplicity ... However, smaller internal rates inside the column that result from lower reboiler and condenser duty could increase the potential risk of flooding in the column and reduce the availability of reactants in the reactive section. ... Column simulations performed using both Pro/II and SpeedUp showed excellent agreement with previously published exptl. ...

Budi H. Bisowarno; Moses O. Tadé

2000-05-09T23:59:59.000Z

277

Simulation of ultrafast heating induced structural dynamics using a one-dimensional spring model  

Science Journals Connector (OSTI)

We developed a one-dimensional spring model to study the dynamics of lattice motion upon ultrafast laser heating. Using this model, we simulated atomic positions as a function of time in a free-standing thin monoatomic metal film as well as in a thin film on a substrate. In particular, we studied how the electronic thermal stress influences lattice expansion after the ultrafast laser heating. The simulation results agree very well with experimental data obtained with femtosecond electron diffraction.

Junjie Li; Rick Clinite; Xuan Wang; Jianming Cao

2009-07-22T23:59:59.000Z

278

Comparison of a semi-analytic and a CFD model uranium combustion to experimental data.  

SciTech Connect (OSTI)

Two numerical models were developed and compared for the analysis of uranium combustion and ignition in a furnace. Both a semi-analytical solution and a computational fluid dynamics (CFD) numerical solution were obtained. Prediction of uranium oxidation rates is important for fuel storage applications, fuel processing, and the development of spent fuel metal waste forms. The semi-analytical model was based on heat transfer correlations, a semi-analytical model of flow over a flat surface, and simple radiative heat transfer from the material surface. The CFD model numerically determined the flowfield over the object of interest, calculated the heat and mass transfer to the material of interest, and calculated the radiative heat exchange of the material with the furnace. The semi-analytical model is much less detailed than the CFD model, but yields reasonable results and assists in understanding the physical process. Short computation times allowed the analyst to study numerous scenarios. The CFD model had significantly longer run times, was found to have some physical limitations that were not easily modified, but was better able to yield details of the heat and mass transfer and flow field once code limitations were overcome.

Clarksean, R.

1998-04-01T23:59:59.000Z

279

CFD INVESTIGATION OF EXPERIMENTAL DATA PROPOSED TO BE A VALIDATION DATA SET  

SciTech Connect (OSTI)

The U. S. Department of Energy (DOE) is currently supporting the development of a next generation nuclear plant (NGNP). The NGNP is based on the very high temperature reactor (VHTR), which is a Gen. IV gas-cooled reactor concept that will use helium as the coolant. Computational fluid dynamics (CFD) calculations are to be employed to estimate the details of the flow and heat transfer in the lower plenum where the heated coolant empties before exiting the reactor vessel. While it is expected that CFD will be able to provide detailed information about the flow, it must be validated using experimental data. Detailed experimental data have been taken in the INL’s matched index of refraction (MIR) facility of a scaled model of a section of the prismatic VHTR lower plenum. The present article examines the data that were taken to determine the suitability of such data to be a validation data set for CFD calculations. CFD calculations were made to compare with the experimental data to explore potential issues and make recommendations regarding the MIR data.

Richard W. Johnson

2009-07-01T23:59:59.000Z

280

Simulation of transition dynamics to high confinement in fusion plasmas  

E-Print Network [OSTI]

The transition dynamics from the low (L) to the high (H) confinement mode in magnetically confined plasmas is investigated using a first-principles four-field fluid model. Numerical results are in close agreement with measurements from the Experimental Advanced Superconducting Tokamak - EAST. Particularly, the slow transition with an intermediate dithering phase is well reproduced by the numerical solutions. Additionally, the model reproduces the experimentally determined L-H transition power threshold scaling that the ion power threshold increases with increasing particle density. The results hold promise for developing predictive models of the transition, essential for understanding and optimizing future fusion power reactors.

Nielsen, A H; Madsen, J; Naulin, V; Rasmussen, J Juul; Wan, B N

2014-01-01T23:59:59.000Z

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281

Advanced Process Engineering Co-simulation  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

7 7 AdvAnced Process engineering co-simulAtion Description The National Energy Technology Laboratory (NETL) and its R&D collaboration partners are developing the Advanced Process Engineering Co-Simulator (APECS) as an innovative software tool that combines process simulation with high-fidelity equipment models based on computational fluid dynamics (CFD). Winner of a 2004 R&D 100 Award and a 2007 Federal Laboratory Consortium (FLC) Excellence in Technology Transfer Award, this powerful co-simulation technology, for the first time, provides the necessary level of detail and accuracy essential for engineers to analyze and optimize the coupled fluid flow, heat and mass transfer, and chemical reactions that drive overall plant performance. Combined with advanced visualization and high-performance computing,

282

The use of ducts to improve the control of supply air temperature rise in UFAD systems: CFD and lab study  

Science Journals Connector (OSTI)

Abstract Cool supply air flowing through the underfloor plenum is exposed to heat gain from both the concrete slab (conducted from the warm return air on the adjacent floor below the slab) and the raised floor panels (conducted from the warmer room above). The magnitude of this heat gain can be quite high, resulting in undesirable loss of control of the supply air temperature from the plenum into the occupied space. These warmer supply air temperatures can make it more difficult to maintain comfort in the occupied space (without increasing airflow rates), particularly in perimeter zones where cooling loads reach their highest levels. How to predict plenum thermal performance is one of the key design issues facing practicing engineers – evidence from completed projects indicates that excessive temperature rise in the plenum can be a problem. One of the recommended strategies for addressing temperature rise in UFAD systems is the use of ductwork (flexible or rigid) within the underfloor plenum to deliver cool air preferentially to perimeter zones or other critical areas of high cooling demand. Several experiments were carried out in a full-scale underfloor plenum test facility, in order to characterize all the phenomena that take place in an underfloor plenum equipped with a fabric or metal duct. Experimental data were collected for validation of a computational fluid dynamics (CFD) model of the plenum. This paper describes the first part of a more comprehensive work, whose aim is to use the validated CFD plenum model to conduct simulations of a broader range of plenum design and operational parameters. This work proves that using ductwork within the underfloor plenum reduce the temperature rise in the plenum.

Wilmer Pasut; Fred Bauman; Michele De Carli

2014-01-01T23:59:59.000Z

283

Hydrogen-Bonding Structure and Dynamics of Aqueous Carbonate Species from Car?Parrinello Molecular Dynamics Simulations  

Science Journals Connector (OSTI)

A comprehensive Car?Parrinello molecular dynamics (CP-MD) study of aqueous solutions of carbonic acid (H2CO3), bicarbonate (HCO3?), carbonate (CO32?), and carbon dioxide (CO2) provides new quantitative insight into the structural and dynamic aspects of the hydrogen-bonding environments for these important aqueous species and their effects on the structure, H-bonding, and dynamical behavior of the surrounding water molecules. ... The power spectra of the carbonate species were calculated as Fourier transforms of their velocity autocorrelation functions over the 14 ps production trajectories of the CP-MD simulations. ... The first solvation shell of the anion was found to contain between five and six hydrogen bonded water mols., compared to the six to seven waters found in analogous classical studies based on empirical potentials. ...

P. Padma Kumar; Andrey G. Kalinichev; R. James Kirkpatrick

2008-12-24T23:59:59.000Z

284

Beam-dynamics Simulations for Channeling Radiation Electron Source  

Science Journals Connector (OSTI)

Abstract The intensity and the brilliance of the compact X-ray sources based on channeling radiation are strongly dependant on the electron beam quality. It was recently proposed to combine a field-emission electron source with channeling radiation through a diamond crystal to produce high-spectral-brilliance X-rays. There are two experiments in preparation at Fermilab to prove this technique. The beam energy in the two cases are 5-MeV and 40-MeV respectively. The field-emitted beams have emittance in the nanometer range when the microbunch is 25 ps long and the charge is about 2.5fC. RF guns operating at 1.3 GHz can produce trains of at least 2 × 105 microbunches. In this contribution we present beam-dymamics simulations of a the field-emission and subsequent accelerator up to the channeling-radiation target.

D. Mihalcea; C.A. Brau; B.K. Choi; W. Gabella; J.D. Jarvis; J.W. Lewellen; M. Mendenhall; P. Piot

2014-01-01T23:59:59.000Z

285

Impact of Resolution on Simulation of Closed Mesoscale Cellular Convection Identified by Dynamically Guided Watershed Segmentation  

SciTech Connect (OSTI)

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.

Martini, Matus; Gustafson, William I.; Yang, Qing; Xiao, Heng

2014-11-27T23:59:59.000Z

286

High Performance Flow Simulations on Graphics Processing Units  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

High Performance Flow Simulations on Graphics Processing Units High Performance Flow Simulations on Graphics Processing Units Speaker(s): Wangda Zuo Date: June 17, 2010 - 12:00pm Location: 90-3122 Seminar Host/Point of Contact: Michael Wetter Building design and operation often requires real-time or faster-than-real-time simulations for detailed information on air distributions. However, none of the current flow simulation techniques can satisfy this requirement. To solve this problem, a Fast Fluid Dynamics (FFD) model has been developed. The FFD can solve Navier-Stokes equations at a speed of 50 times faster than Computational Fluid Dynamics (CFD). In addition, the computing speed of the FFD program has been further enhanced up to 30 times by executing in parallel on a Graphics Processing Unit (GPU) instead of a Central Processing Unit (CPU). As a whole, the FFD on a GPU

287

Two-Dimensional Computational Fluid Dynamics and Conduction Simulations of Heat Transfer in Window Frames  

E-Print Network [OSTI]

1 Two-Dimensional Computational Fluid Dynamics and Conduction Simulations of Heat Transfer Arasteh and Dragan Curcija ABSTRACT Accurately analyzing heat transfer in window frame cavities radiation heat-transfer effects.) We examine three representative complex cavity cross-section profiles

288

Effect of the sliding orientation on the tribological properties of polyethylene in molecular dynamics simulations  

E-Print Network [OSTI]

Effect of the sliding orientation on the tribological properties of polyethylene in molecular properties of polyethylene PE is investigated by using classical molecular dynamics simulations. Cross: 10.1063/1.2900884 I. INTRODUCTION Polyethylene PE is one of the most widely used poly- mers because

Sawyer, Wallace

289

Accounting for patterns of collective behavior in crowd locomotor dynamics for realistic simulations  

Science Journals Connector (OSTI)

Do people in a crowd behave like a set of isolated individuals or like a cohesive group? Studies of crowd modeling usually consider pedestrian behavior either from the point of view of an isolated individual or from that of large swarms. We introduce ... Keywords: collective behavior, crowd simulation, locomotion dynamics

Stéphane Bonneaud; Kevin Rio; Pierre Chevaillier; William H. Warren

2012-01-01T23:59:59.000Z

290

Gas Phase Reaction with FT-ICR and Molecular Dynamics Simulation of Precursor Clusters for SWNTs  

E-Print Network [OSTI]

of the random cage delayed the annealing of the cage. Number of Carbon Atoms Intensity(arbitrary) NiC38 ­ CoC38 dynamics simulations of metal-containing carbon cluster formation were performed. Metal-carbon binary clusters were generated by the laser vaporization of Ni/Co or Ni/Y loaded carbon materials used

Maruyama, Shigeo

291

Ecological Modelling 180 (2004) 135151 Simulating forest fuel and fire risk dynamics across  

E-Print Network [OSTI]

fuel module tracks fine fuel, coarse fuel and live fuel for each cell on a landscape. Fine fuel age (the oldest age cohorts) in combination with disturbance history. Live fuels, also called canopyEcological Modelling 180 (2004) 135­151 Simulating forest fuel and fire risk dynamics across

He, Hong S.

292

The robust dynamical contribution to precipitation extremes in idealized warming simulations  

E-Print Network [OSTI]

The robust dynamical contribution to precipitation extremes in idealized warming simulations across shift under climate warming on the distribution of precipitation extremes and the associated sensitivity in the frequency of the most extreme categories of the precipitation events at the poleward side of the midlatitude

Chen, Gang

293

Molecular-dynamics simulation of compressible fluid flow in two-dimensional channels  

Science Journals Connector (OSTI)

We study compressible fluid flow in narrow two-dimensional channels using a molecular-dynamics simulation method. In the simulation area, an upstream source is maintained at constant density and temperature while a downstream reservoir is kept at vacuum. The channel is sufficiently long in the direction of the flow that the finite length has little effect on the properties of the fluid in the central region. The simulated system is represented by an efficient data structure, whose internal elements are created and manipulated dynamically in a layered fashion. Consequently the computer code is highly efficient and manifests completely linear performance in simulations of large systems. We obtain the steady-state velocity, temperature, and density distributions in the system. The velocity distribution across the channel is very nearly a quadratic function of the distance from the center of the channel and reveals velocity slip at the boundaries; the temperature distribution is only approximately a quartic function of this distance from the center to the channel. The density distribution across the channel is nonuniform. We attribute this nonuniformity to the relatively high Mach number, approximately 0.5, in the fluid flow. An equation for the density distribution based on simple compressibility arguments is proposed; its predictions agree well with the simulation results. The validity of the concept of local dynamic temperature and the variation of the temperature along the channel are discussed.

M. Sun and C. Ebner

1992-10-15T23:59:59.000Z

294

CFD modelling of air-fired and oxy-fuel combustion in a large-scale furnace at Loy Yang A brown coal power station  

Science Journals Connector (OSTI)

Oxy-fuel combustion technique is a viable option to reduce several types of greenhouse gases (GHGs) emissions from the pulverized coal (PC) combustion systems. In this paper, a computational fluid dynamics (CFD) modelling study has been developed in order to investigate the Victorian brown coal combustion in a 550 MW utility boiler under the air-fired (reference case) and three oxy-fuel-fired scenarios. The reference firing case was modelled based on the operating conditions of Loy Yang A power plant located in the state of Victoria, Australia. While Chalmers’ oxy-fuel combustion approach was selected for the present oxy-fuel combustion simulations, which referred to as OF25 (25 vol.% O2), OF27 (27 vol.% O2), and OF29 (29 vol.% O2). User-defined functions (UDFs) were written and incorporated into the CFD code to calculate the following mathematical models: the PC devolatilization, char burnout, multi-step chemical reactions, mass and heat transfer, carbon in fly-ash, and \\{NOx\\} formation/destruction. A level of confidence of the CFD model was achieved validating four different parameters of the conventional combustion case, as well as the previous preliminary CFD studies that conducted on a 100 kW unit firing propane and lignite under oxy-fuel combustion environments. The numerical results of OF29 combustion condition were considerably similar to the reference firing results in terms of gas temperature levels and radiative heat transfer relative to the OF25 and OF27 combustion cases. This similarity was due to increasing the residence time of PC in the combustion zone and O2-enriched in feed oxidizer gases. A significant increase in the CO2 concentrations and a noticeable decrease in the \\{NOx\\} formation were observed under all oxy-fuel combustion scenarios. The combustion chemistry was adopted in these investigations in order to capture the effects of O2 concentrations and gas temperatures on the CO/CO2 production rate and equilibrium between H2 and H2O in the combustion zone. Also, the use of O2-enriched atmospheres during oxy-fuel-fired cases was slightly enhanced the carbon burnout rate. These predicted results were reasonably consistent with the experimental investigations and numerical modelling found in the literature. This study of Victorian brown coal oxy-fuel combustion in a large-scale tangentially-fired boiler is important prior to its implementation in real-life.

Audai Hussein Al-Abbas; Jamal Naser; David Dodds

2012-01-01T23:59:59.000Z

295

Long-time protein folding dynamics from short-time molecular dynamics simulations  

E-Print Network [OSTI]

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

Chodera, J D; Swope, W C; Pitera, J W; Dill, Ken A

2006-01-01T23:59:59.000Z

296

X-AND W-BAND EPR SPECTROSCOPY COMBINED WITH MOLECULAR DYNAMICS SIMULATIONS UNRAVEL THE STRUCTURE AND STRUCTURAL  

E-Print Network [OSTI]

X- AND W-BAND EPR SPECTROSCOPY COMBINED WITH MOLECULAR DYNAMICS SIMULATIONS UNRAVEL THE STRUCTURE (EPR) spectroscopy is combined with molecular dynamics (MD) simulations to study the structure and thus the EPR spectral line shape contain direct information about the secondary and tertiary structure

Steinhoff, Heinz-Jürgen

297

Quantum walks and quantum simulation of wavepacket dynamics with twisted photons  

E-Print Network [OSTI]

The "quantum walk" has emerged recently as a paradigmatic process for the dynamic simulation of complex quantum systems, entanglement production and quantum computation. Hitherto, photonic implementations of quantum walks have mainly been based on multi-path interferometric schemes in real space. Here, we report the experimental realization of a discrete quantum walk taking place in the orbital angular momentum space of light, both for a single photon and for two simultaneous photons. In contrast to previous implementations, the whole process develops in a single light beam, with no need of interferometers; it requires optical resources scaling linearly with the number of steps; and it allows flexible control of input and output superposition states. Exploiting the latter property, we also simulated the quantum dynamics of Gaussian wavepackets, exploring the system dispersion relation in momentum space and the associated spin-orbit topological features. Our demonstration introduces a novel versatile photonic platform for quantum simulations.

Filippo Cardano; Francesco Massa; Hammam Qassim; Ebrahim Karimi; Sergei Slussarenko; Domenico Paparo; Corrado de Lisio; Fabio Sciarrino; Enrico Santamato; Robert W. Boyd; Lorenzo Marrucci

2014-07-21T23:59:59.000Z

298

Accelerated molecular dynamics and equation-free methods for simulating diffusion in solids.  

SciTech Connect (OSTI)

Many of the most important and hardest-to-solve problems related to the synthesis, performance, and aging of materials involve diffusion through the material or along surfaces and interfaces. These diffusion processes are driven by motions at the atomic scale, but traditional atomistic simulation methods such as molecular dynamics are limited to very short timescales on the order of the atomic vibration period (less than a picosecond), while macroscale diffusion takes place over timescales many orders of magnitude larger. We have completed an LDRD project with the goal of developing and implementing new simulation tools to overcome this timescale problem. In particular, we have focused on two main classes of methods: accelerated molecular dynamics methods that seek to extend the timescale attainable in atomistic simulations, and so-called 'equation-free' methods that combine a fine scale atomistic description of a system with a slower, coarse scale description in order to project the system forward over long times.

Deng, Jie; Zimmerman, Jonathan A.; Thompson, Aidan Patrick; Brown, William Michael (Oak Ridge National Laboratories, Oak Ridge, TN); Plimpton, Steven James; Zhou, Xiao Wang; Wagner, Gregory John; Erickson, Lindsay Crowl

2011-09-01T23:59:59.000Z

299

Meridional circulation dynamics from 3D MHD global simulations of solar convection  

E-Print Network [OSTI]

The form of the solar meridional circulation is a very important ingredient for mean field flux transport dynamo models. Yet a shroud of mystery still surrounds this large-scale flow, given that its measurement using current helioseismic techniques is challenging. In this work we use results from 3D global simulations of solar convection to infer the dynamical behavior of the established meridional circulation. We make a direct comparison between the meridional circulation that arises in these simulations and the latest observations. Based on our results we argue that there should be an equatorward flow at the base of the convection zone at mid latitudes, below the current maximum depth helioseismic measures can probe (0.75 R). We also provide physical arguments to justify this behaviour. The simulations indicate that the meridional circulation undergoes substantial changes in morphology as the magnetic cycle unfolds. We close by discussing the importance of these dynamical changes for current methods of obse...

Passos, Dario; Miesch, Mark

2015-01-01T23:59:59.000Z

300

Modeling and simulation for a PEM fuel cell with catalyst layers in finite thickness.  

E-Print Network [OSTI]

??A detailed non-isothermal computational fluid dynamics (CFD) model for proton electrolyte membrane (PEM) fuel cells is developed in this thesis. This model consists of the… (more)

Yin, Jianghui (Author)

2007-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "dynamics cfd simulations" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


301

Development of a dynamic simulator for a natural gas combined cycle (NGCC) power plant with post-combustion carbon capture  

SciTech Connect (OSTI)

The AVESTAR Center located at the U.S. Department of Energy’s National Energy Technology Laboratory and West Virginia University is a world-class research and training environment dedicated to using dynamic process simulation as a tool for advancing the safe, efficient and reliable operation of clean energy plants with CO{sub 2} capture. The AVESTAR Center was launched with a high-fidelity dynamic simulator for an Integrated Gasification Combined Cycle (IGCC) power plant with pre-combustion carbon capture. The IGCC dynamic simulator offers full-scope Operator Training Simulator (OTS) Human Machine Interface (HMI) graphics for realistic, real-time control room operation and is integrated with a 3D virtual Immersive Training Simulator (ITS), thus allowing joint control room and field operator training. The IGCC OTS/ITS solution combines a “gasification with CO{sub 2} capture” process simulator with a “combined cycle” power simulator into a single high-performance dynamic simulation framework. This presentation will describe progress on the development of a natural gas combined cycle (NGCC) dynamic simulator based on the syngas-fired combined cycle portion of AVESTAR’s IGCC dynamic simulator. The 574 MW gross NGCC power plant design consisting of two advanced F-class gas turbines, two heat recovery steam generators (HRSGs), and a steam turbine in a multi-shaft 2x2x1 configuration will be reviewed. Plans for integrating a post-combustion carbon capture system will also be discussed.

Liese, E.; Zitney, S.

2012-01-01T23:59:59.000Z

302

Numerical simulation of Large Solar Hot Water system in storage tank.  

E-Print Network [OSTI]

??This research is aimed to study the storage tank design parameters effects on the efficiency of the large solar hot water system. Detailed CFD simulation… (more)

Shue, Nai-Shen

2012-01-01T23:59:59.000Z

303

A Sub-grid Model for an Array of Immersed Cylinders in Coarse-grid Multiphase Flow Simulations of a Carbon Capture Device  

SciTech Connect (OSTI)

A post-combustion carbon-capture system utilizing a bubbling fluidized bed of sorbent particles is currently being developed as a part of the Carbon Capture and Simulation Initiative (CCSI) efforts. Adsorption of carbon dioxide (CO2) by these amine based sorbent particles is exothermic and arrays of immersed cylindrical heat transfer tubes are often utilized to maintain the lower temperatures favorable for CO2 capture. In multiphase computational fluid dynamics (CFD) simulations of the full-scale devices, which can be up to 10 m in size, approximately 103 cells are required in each dimension to accurately resolve the cylindrical tubes, which are only a few centimeters in diameter. Since the tubes cannot be resolved explicitly in CFD simulations, alternate methods to account for the influence of these immersed objects need to be developed.

Sarkar, Avik; Sun, Xin; Sundaresan, Sankaran

2012-12-01T23:59:59.000Z

304

Advanced CFD Models for High Efficiency Compression Ignition Engines  

Broader source: Energy.gov [DOE]

Advanced CFD models for high efficiency compression-ignition engines can be used to show how turbulence-chemistry interactions influence autoignition and combustion.

305

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...

306

In this project, we deal with the simulation and the optimisation of flows when uncertainties exist in the models and/or the data. We only consider non intrusive methods so that existing CFD softwares  

E-Print Network [OSTI]

with the thermodynamical models for dense organic gas flows used in some energy production devices. It is knownSummary In this project, we deal with the simulation and the optimisation of flows when arising from the study of energy generators for renewable sources. The three task will be done in parallel

Abgrall, Rémi

307

Ab-initio molecular dynamics simulation of liquid water by Quantum Monte Carlo  

E-Print Network [OSTI]

Despite liquid water is ubiquitous in chemical reactions at roots of life and climate on 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 excellent 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.

Zen, Andrea; Mazzola, Guglielmo; Guidoni, Leonardo; Sorella, Sandro

2014-01-01T23:59:59.000Z

308

Ab-initio molecular dynamics simulation of liquid water by Quantum Monte Carlo  

E-Print Network [OSTI]

Despite liquid water is ubiquitous in chemical reactions at roots of life and climate on 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 excellent 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.

Andrea Zen; Ye Luo; Guglielmo Mazzola; Leonardo Guidoni; Sandro Sorella

2014-12-09T23:59:59.000Z

309

CFD Domain and Turbulence Model  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Improving Durability of Turbine Components Improving Durability of Turbine Components Through Trenched Film Cooling and Contoured Endwalls Principal Investigator: Prof. David G. Bogard University of Texas at Austin Graduate research assistant: Todd Davidson Co-Principal Investigator: Prof. Karen A. Thole Pennsylvania State University Graduate research assistant: TBD Background image: [Hamed, A., Tabakoff, W., and Wenglarz, R., 2006] UTSR Peer Review Workshop October 20, 2010 2 Project Objectives a. Evaluate the degradation of performance for trench and crater film cooling configurations when subjected to active deposition of contaminants. This will be done on simulated vane and endwall models. b. Design improved trench or crater film cooling configurations that mitigate the degradation effects of deposition of contaminants.

310

Beam dynamics simulations and measurements at the Project X Test Facility  

SciTech Connect (OSTI)

Project X, under study at Fermilab, is a multitask high-power superconducting RF proton beam facility, aiming to provide high intensity protons for rare processes experiments and nuclear physics at low energy, and simultaneously for the production of neutrinos, as well as muon beams in the long term. A beam test facility - former known as High Intensity Neutrino Source (HINS) - is under commissioning for testing critical components of the project, e.g. dynamics and diagnostics at low beam energies, broadband beam chopping, RF power generation and distribution. In this paper we describe the layout of the test facility and present beam dynamics simulations and measurements.

Gianfelice-Wendt, E.; Scarpine, V.E.; Webber, R.C.; /Fermilab

2011-03-01T23:59:59.000Z

311

Molecular dynamics simulation of anhydrous lithium acetate: crystalline and molten phases  

Science Journals Connector (OSTI)

The results of molecular dynamics simulations of the crystalline and molten phase of anhydrous lithium acetate are presented. The potential parameters were obtained from empirical fitting to the crystalline phases of the material. The simulations were carried out for 216 molecules in an NPT ensemble using the DLPOLY program. A structural model is proposed for both the crystalline and molten phases of lithium acetate. Calculated values of the melting point, diffusion coefficient and structural parameters of lithium acetate are in reasonable agreement with experimental results.

L.S. Barreto; K.A. Mort; R.A. Jackson; O.L. Alves

2002-01-01T23:59:59.000Z

312

A decoupled approach for NOx–N2O 3-D CFD modeling in CFB plants  

Science Journals Connector (OSTI)

Abstract In this study, a 3D CFD model for the formation of \\{NOx\\} and N2O in a lignite fired 1.2 MWth CFB pilot plant is developed. The decoupled approach (decoupled from combustion simulation) is tested for the minimization of computational cost. As combustion simulation is prerequired, this was achieved through a simplified 3-D CFD combustion model. The developed model is then applied to the pilot-scale 1.2 MWth CFB plant and validated against experimental data. As concerns the NOx–N2O model, an extensive literature review is also carried out for the incorporation of the appropriate reactions network and respective reaction rates expressions. Results show that homogenous reactions are favoured on the lower section of the bed, due to the abundance of fuel devolatilization products. On the other hand, on the upper section, heterogeneous reactions govern nitric oxide formation/reduction. It is found that for the lignite examined in this work, HCN is released in negligible amounts during char combustion. The proposed and validated CFD model for \\{NOx\\} and N2O, is capable of examining the effect of different operational parameters and coal properties on the overall nitric oxides emissions from a CFB combustor, with low computational cost and without the additional expenses for pilot-scale experiments.

A. Nikolopoulos; I. Malgarinos; N. Nikolopoulos; P. Grammelis; S. Karrelas; E. Kakaras

2014-01-01T23:59:59.000Z

313

Dynamic transport simulation code including plasma rotation and radial electric field  

Science Journals Connector (OSTI)

A new one-dimensional transport code named TASK/TX, which is able to describe dynamic behavior of tokamak plasmas, has been developed. It solves simultaneously a set of flux-surface averaged equations composed of Maxwell's equations, continuity equations, ... Keywords: 52.25.Fi, 52.30.-q, 52.55.Fa, 52.65.-y, Finite element method, Plasma rotation, Radial electric field, SUPG, Transport simulation

M. Honda; A. Fukuyama

2008-02-01T23:59:59.000Z

314

Detonation Initiation from Spontaneous Hotspots Formed During Cook-Off Observed in Molecular Dynamics Simulations  

Science Journals Connector (OSTI)

Detonation Initiation from Spontaneous Hotspots Formed During Cook-Off Observed in Molecular Dynamics Simulations ... New equations based on Johnson?Mehl?Avrami?Kolmogorov kinetics are proposed for describing the extent of detonated material that could provide new insight into mechanisms of critical hotspot nucleation. ... Depending on the chemical and thermal properties of the energetic material as well as the size and containment of the material during cook-off, a supersonic reaction front can form; that is, the material can detonate. ...

Yanhong Hu; Donald W. Brenner; Yunfeng Shi

2011-01-06T23:59:59.000Z

315

Ultrapdeep water blowouts: COMASim dynamic kill simulator validation and best practices recommendations  

E-Print Network [OSTI]

64 3 14 30 6 8 4 3 180 Total 26.7% 35.6% 1.7% 7.8% 16.7% 3.3% 4.4% 2.2% 1.7% 100.0% * External causes are typical; storm, military activity, ship collision, fire and earthquake. Fig. 1.10 clearly shows the most blowouts occur... 1 ULTRADEEP WATER BLOWOUTS: COMASIM DYNAMIC KILL SIMULATOR VALIDATION AND BEST PRACTICES RECOMMENDATIONS A Thesis by SAMUEL F. NOYNAERT...

Noynaert, Samuel F.

2005-02-17T23:59:59.000Z

316

A Gaussian process-based approach for handling uncertainty in vehicle dynamics simulation.  

SciTech Connect (OSTI)

Advances in vehicle modeling and simulation in recent years have led to designs that are safer, easier to handle, and less sensitive to external factors. Yet, the potential of simulation is adversely impacted by its limited ability to predict vehicle dynamics in the presence of uncertainty. A commonly occurring source of uncertainty in vehicle dynamics is the road-tire friction interaction, typically represented through a spatially distributed stochastic friction coefficient. The importance of its variation becomes apparent on roads with ice patches, where if the stochastic attributes of the friction coefficient are correctly factored into real time dynamics simulation, robust control strategies could be designed to improve transportation safety. This work concentrates on correctly accounting in the nonlinear dynamics of a car model for the inherent uncertainty in friction coefficient distribution at the road/tire interface. The outcome of this effort is the ability to quantify the effect of input uncertainty on a vehicle's trajectory and the associated escalation of risk in driving. By using a space-dependent Gaussian process, the statistical representation of the friction coefficient allows for consistent space dependence of randomness. The approach proposed allows for the incorporation of noise in the observed data and a nonzero mean for inhomogeneous distribution of the friction coefficient. Based on the statistical model considered, consistent friction coefficient sample distributions are generated over large spatial domains of interest. These samples are subsequently used to compute and characterize the statistics associated with the dynamics of a nonlinear vehicle model. The information concerning the state of the road and thus the friction coefficient is assumed available (measured) at a limited number of points by some sensing device that has a relatively homogeneous noise field (satellite picture or ground sensors, for instance). The methodology proposed can be modified to incorporate information that is sensed by each individual car as it advances along its trajectory.

Schmitt, K.; Madsen, J.; Anitescu, M.; Negrut, D.; Mathematics and Computer Science; Univ. of Wisconsin at Madison

2009-01-01T23:59:59.000Z

317

Dynamic modeling of steam power cycles: Part II – Simulation of a small simple Rankine cycle system  

Science Journals Connector (OSTI)

This paper presents the second part of the work concerning the dynamic simulation of small steam cycle plants for power generation. The work is part of the preliminary study for a 600 kWe biomass fired steam power plant for which the complete open-loop, lumped parameter dynamic model of the steam cycle has been developed using the SimECS software described in Part I of this work. For these low-power plants, a dynamic simulation tool is especially useful because these systems must be designed to operate in transient mode for most of the time. The plant model presented here consists of the following components: feedwater pump, economizer, evaporator, superheater, impulse turbine, electrical generator and condenser. The primary heat source is modeled as a flue gas flow and no combustion models are incorporated yet to model the furnace. A description of the various components forming the complete steam cycle is given to illustrate the capabilities and modularity of the developed modeling technique. The model is first validated quantitatively against steady-state values obtained using a well known, reliable steady-state process modeling software. Subsequently, the dynamic validation is presented. Results can only be discussed based on the qualitative assessment of the observed trends because measurements are not available, being the plant in the preliminary design phase. The qualitative validation is based on four dynamic simulations involving three small step disturbances of different magnitude imposed on the pump rotational speed and on the flue gas mass flow and a single large ramp disturbance on the flue gas mass flow.

H. van Putten; P. Colonna

2007-01-01T23:59:59.000Z

318

An object-oriented approach to simulation of IRIS dynamic response  

Science Journals Connector (OSTI)

In this paper the development of an adequate modelling and simulation tool for Dynamics and Control tasks is presented. The key features of the developed simulator are: “Modularity” – the system model is built by connecting the models of its components, which are written independently of their boundary conditions; “Openness” – the code of each component model is clearly readable and close to the original equations and easily customised by the experienced user; “Efficiency” – the simulation code is fast; “Tool support” – the simulation tool is based on reliable, tested and well-documented software. To achieve these objectives, the Modelica language was used as a basis for the development of the simulator. The Modelica language is the result of recent advances in the field of object-oriented, multi-physics, dynamic system modelling. The language definition is open-source and it has already been successfully adopted in several industrial fields. The test bed for the application of the object-oriented approach has been the new generation, integral type, IRIS nuclear reactor. IRIS (International Reactor Innovative and Secure) is a pressurized light water cooled, small/medium power (335 MWe) reactor reactor, under development by an international consortium of nineteen organizations from ten countries. The preliminary design has been completed and the pre-application licensing process with the US-Nuclear Regulatory Commission (NRC) is underway. To provide the required capabilities for the analysis, specific models for the nuclear reactor components have been developed, to be applied for the dynamic simulation of the IRIS integral reactor, albeit keeping general validity for PWR plants. The following Modelica models have been written to satisfy the IRIS modelling requirements and are presented in this paper: point reactor kinetic, fuel heat transfer, control rods model, and a once-through type steam generator, thus obtaining a specific library of nuclear models and components. As far as other classical power generation plant components are concerned, the Thermo Power open library, developed at Politecnico di Milano as well, has been adopted and is briefly presented in the paper. Originally conceived for conventional, fossil-fired plants, the highly modular approach allowed to effectively reuse the models of the balance of plant systems, which have been connected to the models of the nuclear power generation process, to obtain a system simulator for the IRIS reactor. Finally, preliminary results of the code validation process and the reactor dynamics are presented.

Antonio Cammi; Francesco Casella; Marco E. Ricotti; Francesco Schiavo

2011-01-01T23:59:59.000Z

319

Some thoughts on exploiting CFD for turbomachinery design  

E-Print Network [OSTI]

Some thoughts on exploiting CFD for turbomachinery design M. B. Giles Oxford University Computing enormously and it is now used extensively by all turbomachinery companies in designing speci c components was presented at the IMeche Symposium on Exploiting CFD for Turbomachinery Design, on March 19th, 1998

Giles, Mike

320

3457, Page, 1 Coupled CFD/Building Envelope Model  

E-Print Network [OSTI]

Performance Buildings Conference at Purdue, 2012 (Accepted) #12;3457, Page, 2 a standard model for a single3457, Page, 1 Coupled CFD/Building Envelope Model for the Purdue Living Lab Donghun KIM (kim1077 features. In the present case we develop a procedure for coupling a building envelope model to a CFD

Gugercin, Serkan

Note: This page contains sample records for the topic "dynamics cfd simulations" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


321

Molecular Dynamic Simulation of Sodium in 7-Pin LMFBR Bundle Under Hypothetical Accident Conditions  

SciTech Connect (OSTI)

In the frame of safety analysis of liquid metal fast breeder reactors (LMFBRs) under hypothetical Unprotected Loss of Flow (ULOF) conditions two-phase flow of sodium is simulated in a 7-pin bundle, with hexagonal lattice. Molecular dynamics, with the application of the Direct Simulation Monte Carlo (DSMC) method, and a macroscopic model describing rewetting sequences due to the flow of a sodium liquid film along the pin surfaces, are applied to simulate the coolant in the bundle. The pin surfaces and the inner surface of the hexagonal canning are treated in the Monte Carlo simulation as diffusively reflecting surfaces. Collisions of sodium molecules are computed with the 'hard-sphere' model. With respect to previous work the following improvements of the computational code were made: i) The full bundle is simulated, thus allowing for asymmetries, like a skewed power distribution, to be accounted for; ii) A pin model calculates detailed temperature distributions in the pins, so that temperature boundary conditions are computed and not imposed; iii) Post processing visualisation of computed results was developed. An out of pile sodium boiling experiment run at the Nuclear Research Center of Karlsruhe, Germany, is simulated and conclusions are drawn about the applicability of the methodology in computer codes dedicated to breeder reactors safety analysis. (authors)

Bottoni, Maurizio [University of Ferrara, Physics Department, Via Paradiso 12, I-44100 Ferrara (Italy); Bottoni, Claudio; Scanu, John [University of Pisa, Lungarno Pacinotti, 43 - 56126 Pisa (Italy)

2006-07-01T23:59:59.000Z

322

Computer simulation study of surface wave dynamics at the crystal--melt interface  

E-Print Network [OSTI]

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.

Jorge Benet; Luis G. MacDowell; Eduardo Sanz

2014-10-01T23:59:59.000Z

323

The viscosity radius in dilute polymer solutions: Universal behaviour from DNA rheology and Brownian dynamics simulations  

E-Print Network [OSTI]

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.

Sharadwata Pan; D. Ahirwal; Duc At Nguyen; T. Sridhar; P. Sunthar; J. Ravi Prakash

2014-05-16T23:59:59.000Z

324

A molecular dynamics simulation of DNA damage induction by ionizing radiation  

E-Print Network [OSTI]

We present a multi-scale simulation of early stage of DNA damages by the indirect action of hydroxyl ($^\\bullet$OH) free radicals generated by electrons and protons. The computational method comprises of interfacing the Geant4-DNA Monte Carlo with the ReaxFF molecular dynamics software. A clustering method was employed to map the coordinates of $^\\bullet$OH-radicals extracted from the ionization track-structures onto nano-meter simulation voxels filled with DNA and water molecules. The molecular dynamics simulation provides the time evolution and chemical reactions in individual simulation voxels as well as the energy-landscape accounted for the DNA-$^\\bullet$OH chemical reaction that is essential for the first principle enumeration of hydrogen abstractions, chemical bond breaks, and DNA-lesions induced by collection of ions in clusters less than the critical dimension which is approximately 2-3 \\AA. We show that the formation of broken bonds leads to DNA base and backbone damages that collectively propagate ...

Abolfath, Ramin M; Chen, Zhe J; Nath, Ravinder

2013-01-01T23:59:59.000Z

325

Molecular simulations of the fluctuating conformational dynamics of intrinsically disordered proteins  

Science Journals Connector (OSTI)

Intrinsically disordered proteins (IDPs) do not possess well-defined three-dimensional structures in solution under physiological conditions. We develop all-atom, united-atom, and coarse-grained Langevin dynamics simulations for the IDP ?-synuclein that include geometric, attractive hydrophobic, and screened electrostatic interactions and are calibrated to the inter-residue separations measured in recent single-molecule fluorescence energy transfer (smFRET) experiments. We find that ?-synuclein is disordered, with conformational statistics that are intermediate between random walk and collapsed globule behavior. An advantage of calibrated molecular simulations over constraint methods is that physical forces act on all residues, not only on residue pairs that are monitored experimentally, and these simulations can be used to study oligomerization and aggregation of multiple ?-synuclein proteins that may precede amyloid formation.

W. Wendell Smith; Carl F. Schreck; Nabeem Hashem; Sherwin Soltani; Abhinav Nath; Elizabeth Rhoades; Corey S. O’Hern

2012-10-12T23:59:59.000Z

326

An adaptively refined phase-space element method for cosmological simulations and collisionless dynamics  

E-Print Network [OSTI]

Dark matter numerical simulations and the N-body method are essential for understanding how structure forms and evolves in the Universe. However, the discrete nature of N-body simulations can affect its accuracy when modelling collisionless systems. We introduce a new approach to simulate the gravitational evolution of cold collisionless fluids by solving the Vlasov-Poisson equations in terms of adaptively refineable "Lagrangian phase space elements". These geometrical elements are piecewise smooth maps between three-dimensional Lagrangian space and six-dimensional Eulerian phase space and approximate the continuum structure of the distribution function. They allow for dynamical adaptive splitting to follow the evolution even in regions of very strong mixing. We discuss various test problems which demonstrate the correctness and performance of our method. We show that it has several advantages compared to standard N-body algorithms by i) explicitly tracking the fine-grained distribution function, ii) naturall...

Hahn, Oliver

2015-01-01T23:59:59.000Z

327

Simulating Collisions for Hydrokinetic Turbines  

SciTech Connect (OSTI)

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.

Richmond, Marshall C.; Romero Gomez, Pedro DJ; Rakowski, Cynthia L.

2013-10-01T23:59:59.000Z

328

Towards the Integration of APECS and VE-Suite for Virtual Power Plant Co-Simulation  

SciTech Connect (OSTI)

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.

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

329

Multiphase flow simulations of a moving fluidized bed regenerator in a carbon capture unit  

Science Journals Connector (OSTI)

Abstract To accelerate the commercialization and deployment of carbon capture technologies, computational fluid dynamics (CFD)-based tools may be used to model and analyze the performance of carbon capture devices. This work presents multiphase CFD flow simulations for the regenerator—a device responsible for extracting CO2 from CO2-loaded particles before the sorbent is recycled. The use of solid particle sorbents in this design is a departure from previously reported systems, where aqueous sorbents are employed. Another new feature is the inclusion of a series of perforated plates along the regenerator height. The influence of these plates on sorbent distribution is examined for varying sorbent holdup, fluidizing gas velocity, and particle size. The residence time distribution of sorbents is also measured to classify the flow regime as plug flow or well-mixed flow. The purpose of this work is to better understand the sorbent flow characteristics before reaction kinetics of CO2 desorption can be implemented.

Avik Sarkar; Wenxiao Pan; DongMyung Suh; E. David Huckaby; Xin Sun

2014-01-01T23:59:59.000Z

330

Multiphase CFD-based models for chemical looping combustion process: Fuel reactor modeling  

SciTech Connect (OSTI)

Chemical looping combustion (CLC) is a flameless two-step fuel combustion that produces a pure CO2 stream, ready for compression and sequestration. The process is composed of two interconnected fluidized bed reactors. The air reactor which is a conventional circulating fluidized bed and the fuel reactor which is a bubbling fluidized bed. The basic principle is to avoid the direct contact of air and fuel during the combustion by introducing a highly-reactive metal particle, referred to as oxygen carrier, to transport oxygen from the air to the fuel. In the process, the products from combustion are kept separated from the rest of the flue gases namely nitrogen and excess oxygen. This process eliminates the energy intensive step to separate the CO2 from nitrogen-rich flue gas that reduce the thermal efficiency. Fundamental knowledge of multiphase reactive fluid dynamic behavior of the gas–solid flow is essential for the optimization and operation of a chemical looping combustor. Our recent thorough literature review shows that multiphase CFD-based models have not been adapted to chemical looping combustion processes in the open literature. In this study, we have developed the reaction kinetics model of the fuel reactor and implemented the kinetic model into a multiphase hydrodynamic model, MFIX, developed earlier at the National Energy Technology Laboratory. Simulated fuel reactor flows revealed high weight fraction of unburned methane fuel in the flue gas along with CO2 and H2O. This behavior implies high fuel loss at the exit of the reactor and indicates the necessity to increase the residence time, say by decreasing the fuel flow rate, or to recirculate the unburned methane after condensing and removing CO2.

Jung, Jonghwun (ANL); Gamwo, I.K.

2008-04-21T23:59:59.000Z

331

Molecular dynamics simulation of complex molecules at interfaces: dendritic surfactants in clay and amyloid peptides near lipid bilayers  

E-Print Network [OSTI]

We apply a molecular dynamics (MD) simulation technique to complex molecules at interfaces. Partitioning of dendritic surfactants into clay gallery and Ab protein behavior near hydrated lipids are chosen for the purpose. Using a full atomistic model...

Han, Kunwoo

2009-06-02T23:59:59.000Z

332

Simulation of polar stratospheric clouds in the specified dynamics version of the whole atmosphere community climate model  

E-Print Network [OSTI]

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 ...

Wegner, T.

333

Development of a Prototype Lattice Boltzmann Code for CFD of Fusion Systems.  

SciTech Connect (OSTI)

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

Pattison, Martin J; Premnath, Kannan N; Banerjee, Sanjoy; Dwivedi, Vinay

2007-02-26T23:59:59.000Z

334

Decision Support for Green Supply Chain Operations by Integrating Dynamic Simulation and LCA Indicators: Diaper Case Study  

Science Journals Connector (OSTI)

Decision Support for Green Supply Chain Operations by Integrating Dynamic Simulation and LCA Indicators: Diaper Case Study ... Lifecycle assessment (LCA) is widely used to measure the environmental consequences assignable to a product. ... This paper proposes a framework for green supply chain management by integrating a SC dynamic simulation and LCA indicators to evaluate both the economic and environmental impacts of various SC decisions such as inventories, distribution network configuration, and ordering policy. ...

Arief Adhitya; Iskandar Halim; Rajagopalan Srinivasan

2011-10-26T23:59:59.000Z

335

Carbon Capture Simulation Initiative: A Case Study in Multi-Scale Modeling and New Challenges  

SciTech Connect (OSTI)

Abstract: Advanced multi-scale modeling and simulation has the potential to dramatically reduce development time, resulting in considerable cost savings. The Carbon Capture Simulation Initiative is a partnership among national laboratories, industry and universities that is developing and deploying a suite of multi-scale modeling and simulation tools including basic data submodels, steady-state and dynamic process models, process optimization and uncertainty quantification tools, an advanced dynamic process control framework, high-resolution filtered computational-fluid-dynamic (CFD) submodels, validated high-fidelity device-scale CFD models with quantified uncertainty, and a risk analysis framework. These tools and models enable basic data submodels, including thermodynamics and kinetics, to be used within detailed process models to synthesize and optimize a process. The resulting process informs the development of process control systems and more detailed simulations of potential equipment to improve the design and reduce scale-up risk. Quantification and propagation of uncertainty across scales is an essential part of these tools and models.

Miller, David C [U.S. DOE; Syamlal, Madhava [U.S. DOE; Zitney, Stephen E. [U.S. DOE

2014-01-01T23:59:59.000Z

336

Ex-Core CFD Analysis Results for the Prometheus Gas Reactor  

SciTech Connect (OSTI)

This paper presents the initial nozzle-to-nozzle (N2N) reactor vessel model scoping studies using computational fluid dynamics (CFD) analysis methods. The N2N model has been solved under a variety of different boundary conditions. This paper presents some of the basic hydraulic results from the N2N CFD analysis effort. It also demonstrates how designers were going to apply the analysis results to modify a number of the design features. The initial goals for developing a preliminary CFD N2N model were to establish baseline expectations for pressure drops and flow fields around the reactor core. Analysis results indicated that the averaged reactor vessel pressure drop for all analyzed cases was 46.9 kPa ({approx}6.8 psid). In addition, mass flow distributions to the three core fuel channel regions exhibited a nearly inverted profile to those specified for the in-core thermal/hydraulic design. During subsequent design iterations, the goal would have been to modify or add design features that would have minimized reactor vessel pressure drop and improved flow distribution to the inlet of the core.

Lorentz, Donald G. [Space Engineering, Bechtel Bettis, Inc. West Mifflin, PA 15122 (United States)

2007-01-30T23:59:59.000Z

337

The Molecular Structure of a Phosphatidylserine Bilayer Determined by Scattering and Molecular Dynamics Simulations  

SciTech Connect (OSTI)

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.

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

338

Virtual Simulation of Vision 21 Energy Plants  

SciTech Connect (OSTI)

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

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

339

Computational Fluid Dynamic Analysis of the VHTR Lower Plenum Standard Problem  

SciTech Connect (OSTI)

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.

Richard W. Johnson; Richard R. Schultz

2009-07-01T23:59:59.000Z

340

Experimental study and CFD approach for scroll type expander used in low-temperature organic Rankine cycle  

Science Journals Connector (OSTI)

Abstract This study focuses on experimental test of scroll type expanders in low-temperature organic Rankine cycle (ORC) system. In this circuit, lubricant has been mixed with \\{R245fa\\} as working fluid. In this experiment, two scroll expanders with different built-in volume ratio have been experimentally tested. Main test parameters considered are the pressure difference and the rotational speed of the expanders. It is found that the expander performance could be significantly improved when bigger built-in volume ratio is used. However the internal leakage and friction loss are vital factors to influence expander performance. The maximum shaft power output by expander of 1.77 kW and deliver electricity by generator of 1.375 kW. A Computational Fluid Dynamics approach (CFD) has been employed for preliminary investigation on the thermal-hydraulic behavior of the scroll type expanders. The simulation result shows that unbalance pressure distribution were occurred in the expander by means of top scroll wrap has been modified.

Jen-Chieh Chang; Chao-Wei Chang; Tzu-Chen Hung; Jaw-Ren Lin; Kuo-Chen Huang

2014-01-01T23:59:59.000Z

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341

Dynamic modelling of MSF plants for automatic control and simulation purposes: a survey  

Science Journals Connector (OSTI)

The successful development of a control system requires an appropriate definition of the control structure (i.e., selection of output, input and disturbance variables) and an efficient dynamical model on which the design, analysis and evaluation can be carried out. Thus, the confidence in the obtained results depends on the validity of the control structure and of the model used. For multistage flash (MSF) desalination processes, several dynamical models can be found in the literature. However, most of them are not suitable for analysis and control design purposes because they bring too many variables into play. The variables, which are sharing in the control system, normally constitute a reduced subset of the total variables that can be defined in the process. Moreover, a dynamical model suitable for control is simpler than the model derived from the physics of the underlying process. Hence, the selection of variables and the model building from the point of view of control design presents a compromise between the indispensable information contained in the model and the mathematical complexity proper of the design. In this paper, different models from the literature are analysed. Their advantages and drawbacks are described taking into account simulation and automatic control purposes. Moreover, a set of wished modelling facilities from the control engineer point of view is highlighted. Finally, a block-oriented library for Matlab/Simulink is presented, so that different plant configurations can be implemented as block diagram to simulate the system and to test control algorithms.

Adrian Gambler; Essameddin Badreddin

2004-01-01T23:59:59.000Z

342

Numerical Simulation of Squeeze Film Dampers and Study of the Effect of Central Groove on the Dynamic Pressure Distribution  

E-Print Network [OSTI]

. The behavior of dynamic pressure profiles at different operating conditions, and the effect of a central groove on dynamic pressure profiles were also studied. Simulation results of a 3D case which is similar to the one experimentally studied by Delgado were...

Boppa, Praneetha

2012-10-19T23:59:59.000Z

343

Computational battery dynamics (CBD)--electrochemical/thermal coupled modeling and multi-scale modeling  

E-Print Network [OSTI]

Computational battery dynamics (CBD)--electrochemical/thermal coupled modeling and multi the development of first-principles based mathematical models for batteries developed on a framework parallel to computation fluid dynamics (CFD), herein termed computational battery dynamics (CBD). This general

344

Package Equivalent Reactor Networks as Reduced Order Models for Use with CAPE-OPEN Compliant Simulation  

SciTech Connect (OSTI)

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.

Meeks, E.; Chou, C. -P.; Garratt, T.

2013-03-31T23:59:59.000Z

345

Canonicalization and symplectic simulation of the gyrocenter dynamics in time-independent magnetic fields  

SciTech Connect (OSTI)

The gyrocenter dynamics of charged particles in time-independent magnetic fields is a non-canonical Hamiltonian system. The canonical description of the gyrocenter has both theoretical and practical importance. We provide a general procedure of the gyrocenter canonicalization, which is expressed by the series of a small variable ? depending only on the parallel velocity u and can be expressed in a recursive manner. We prove that the truncation of the series to any given order generates a set of exact canonical coordinates for a system, whose Lagrangian approximates to that of the original gyrocenter system in the same order. If flux surfaces exist for the magnetic field, the series stops simply at the second order and an exact canonical form of the gyrocenter system is obtained. With the canonicalization schemes, the canonical symplectic simulation of gyrocenter dynamics is realized for the first time. The canonical symplectic algorithm has the advantage of good conservation properties and long-term numerical accuracy, while avoiding numerical instability. It is worth mentioning that explicitly expressing the canonical Hamiltonian in new coordinates is usually difficult and impractical. We give an iteration procedure that is easy to implement in the original coordinates associated with the coordinate transformation. This is crucial for modern large-scale simulation studies in plasma physics. The dynamics of gyrocenters in the dipole magnetic field and in the toroidal geometry are simulated using the canonical symplectic algorithm by comparison with the higher-order non symplectic Runge-Kutta scheme. The overwhelming superiorities of the symplectic method for the gyrocenter system are evidently exhibited.

Zhang, Ruili; Tang, Yifa; Zhu, Beibei [LSEC, ICMSEC, Academy of Mathematics and Systems Science, Chinese Academy of Sciences, Beijing 100190 (China)] [LSEC, ICMSEC, Academy of Mathematics and Systems Science, Chinese Academy of Sciences, Beijing 100190 (China); Liu, Jian, E-mail: jliuphy@ustc.edu.cn; Xiao, Jianyuan [Department of Modern Physics and Collaborative Innovation Center for Advanced Fusion Energy and Plasma Sciences, University of Science and Technology of China, Hefei, Anhui 230026 (China)] [Department of Modern Physics and Collaborative Innovation Center for Advanced Fusion Energy and Plasma Sciences, University of Science and Technology of China, Hefei, Anhui 230026 (China); Qin, Hong [Department of Modern Physics and Collaborative Innovation Center for Advanced Fusion Energy and Plasma Sciences, University of Science and Technology of China, Hefei, Anhui 230026 (China) [Department of Modern Physics and Collaborative Innovation Center for Advanced Fusion Energy and Plasma Sciences, University of Science and Technology of China, Hefei, Anhui 230026 (China); Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543 (United States)

2014-03-15T23:59:59.000Z

346

Numerical simulation of the stochastic dynamics of inclusions in biomembranes in presence of surface tension  

E-Print Network [OSTI]

The stochastic dynamics of inclusions in a randomly fluctuating biomembrane is simulated. These inclusions can represent the embedded proteins and the external particles arriving at a cell membrane. The energetics of the biomembrane is modelled via the Canham-Helfrich Hamiltonian. The contributions of both the bending elastic-curvature energy and the surface tension of the biomembrane are taken into account. The biomembrane is treated as a two-dimensional sheet whose height variations from a reference frame is treated as a stochastic Wiener process. The lateral diffusion parameter associated with this Wiener process coupled with the longitudinal diffusion parameter obtained from the standard Einsteinian diffusion theory completely determine the stochastic motion of the inclusions. It is shown that the presence of surface tension significantly affects the overall dynamics of the inclusions, particularly the rate of capture of the external inclusions, such as drug particles, at the site of the embedded inclusions, such as the embedded proteins.

H. Rafii-Tabar; H. R. Sepangi

2005-08-30T23:59:59.000Z

347

Quantum molecular dynamics simulation of shock-wave experiments in aluminum  

SciTech Connect (OSTI)

We present quantum molecular dynamics calculations of principal, porous, and double shock Hugoniots, release isentropes, and sound velocity behind the shock front for aluminum. A comprehensive analysis of available shock-wave data is performed; the agreement and discrepancies of simulation results with measurements are discussed. Special attention is paid to the melting region of aluminum along the principal Hugoniot; the boundaries of the melting zone are estimated using the self-diffusion coefficient. Also, we make a comparison with a high-quality multiphase equation of state for aluminum. Independent semiempirical and first-principle models are very close to each other in caloric variables (pressure, density, particle velocity, etc.) but the equation of state gives higher temperature on the principal Hugoniot and release isentropes than ab initio calculations. Thus, the quantum molecular dynamics method can be used for calibration of semiempirical equations of state in case of lack of experimental data.

Minakov, D. V.; Khishchenko, K. V.; Fortov, V. E. [Joint Institute for High Temperatures RAS, Izhorskaya 13 Bldg 2, Moscow 125412 (Russian Federation); Moscow Institute of Physics and Technology, Institutskii per. 9, Dolgoprudny, Moscow Region 141700 (Russian Federation); Levashov, P. R. [Joint Institute for High Temperatures RAS, Izhorskaya 13 Bldg 2, Moscow 125412 (Russian Federation); Tomsk State University, 36 Lenin Prospekt, Tomsk 634050 (Russian Federation)

2014-06-14T23:59:59.000Z

348

Advanced computational simulation of flow phenomena associated with orifice meters  

SciTech Connect (OSTI)

This paper presents and discusses results from a series of computational fluid dynamics (CFD) simulations of fluid flow phenomena associated with orifice meters. These simulations were performed using a new, state-of-the-art CFD code developed at Southwest Research Institute. This code is based on new techniques designed to take advantage of parallel computers to increase computational performance and fidelity of simulation results. This algorithm uses a domain decomposition strategy to create grid systems for very complex geometries composed of simpler geometric subregions, allowing for the accurate representation of the fluid flow domain. The domain decomposition technique maps naturally to parallel computer architectures. Here, the concept of message-passing is used to create a parallel algorithm, using the Parallel Virtual Machine (PVM) library. This code is then used to simulate the flow through an orifice meter run consisting of an orifice with a beta ratio of 0.5 and air flowing at a Reynolds number of 91,100. The work discussed in this paper is but the first step in developing a Virtual Metering Research Facility to support research, analysis, and formulation of new standards for metering.

Freitas, C.J. [Southwest Research Inst., San Antonio, TX (United States)

1995-12-31T23:59:59.000Z

349

Induced crystallization of single-chain polyethylene on a graphite surface: Molecular dynamics simulation  

Science Journals Connector (OSTI)

Molecular dynamics (MD) simulations have been carried out on the crystallization of single-chain polyethylene (PE) which was adsorbed on a graphite (001) surface on one side and exposed to vacuum on the other at different temperatures. The MD simulation data have been analyzed to provide information about the crystallization process of polymer adsorbed on the solid substrate. The isothermal crystallization of PE proceeds in two steps: (1) adsorption and (2) orientation. The results detail the radial density distribution function, ordered parameters, local bond-orientational order parameters, and the local properties displayed in layers of the polymer parallel to the graphite and vacuum interfaces. It was also shown that the film thickness affected the critical crystallization temperature of the adsorbed polymer on the substrate surface. Furthermore, the influence of the graphite surface area on the crystallization of PE is discussed by comparing the crystallinity evolution of PE on graphite with different coverage.

Hua Yang (??); Xiao Jun Zhao (???); Miao Sun (??)

2011-07-14T23:59:59.000Z

350

Temperature-dependent mechanical properties of single-layer molybdenum disulphide: Molecular dynamics nanoindentation simulations  

SciTech Connect (OSTI)

The temperature-dependent mechanical properties of single-layer molybdenum disulphide (MoS{sub 2}) are obtained using molecular dynamics (MD) nanoindentation simulations. The Young's moduli, maximum load stress, and maximum loading strain decrease with increasing temperature from 4.2?K to 500?K. The obtained Young's moduli are in good agreement with those using our MD uniaxial tension simulations and the available experimental results. The tendency of maximum loading strain with different temperature is opposite with that of metal materials due to the short range Stillinger-Weber potentials in MoS{sub 2}. Furthermore, the indenter tip radius and fitting strain effect on the mechanical properties are also discussed.

Zhao, Junhua, E-mail: junhua.zhao@uni-weimar.de [Jiangsu Province Key Laboratory of Advanced Manufacturing Equipment and Technology of Food, Jiangnan University, 214122 Wuxi (China) [Jiangsu Province Key Laboratory of Advanced Manufacturing Equipment and Technology of Food, Jiangnan University, 214122 Wuxi (China); Institute of Structural Mechanics, Bauhaus-University Weimar, 99423 Weimar (Germany); Jiang, Jin-Wu, E-mail: jwjiang5918@hotmail.com [Institute of Structural Mechanics, Bauhaus-University Weimar, 99423 Weimar (Germany)] [Institute of Structural Mechanics, Bauhaus-University Weimar, 99423 Weimar (Germany); Rabczuk, Timon, E-mail: timon.rabczuk@uni-weimar.de [Institute of Structural Mechanics, Bauhaus-University Weimar, 99423 Weimar (Germany) [Institute of Structural Mechanics, Bauhaus-University Weimar, 99423 Weimar (Germany); School of Civil, Environmental and Architectural Engineering, Korea University, 136-701 Seoul (Korea, Republic of)

2013-12-02T23:59:59.000Z

351

Analog and digital dynamic simulations of a rigid body aircraft in straight and level flight  

E-Print Network [OSTI]

. , Texas A&M University Directed by: Dr. Balusu M. Rao A study of the dynamic response characteristics of an aircraft at low approach speeds was conducted using both a digital and an analog computer to simulate a DeHavilland "Beaver" DHC-2 in flight... to produce more sideslip and yawing motions than the rudder with analytical solutions. The problem areas of the STOL aircraft at low approach speeds as a result of a study of the DeHavilland "Beaver" were in lateral stability. The aircraft's response...

Stroman, Morris Michael

2012-06-07T23:59:59.000Z

352

Use of Aria to simulate laser weld pool dynamics for neutron generator production.  

SciTech Connect (OSTI)

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.

Noble, David R.; Notz, Patrick K.; Martinez, Mario J.; Kraynik, Andrew Michael

2007-09-01T23:59:59.000Z

353

Cooling Energy Demand Evaluation by Meansof Regression Models Obtained From Dynamic Simulations  

E-Print Network [OSTI]

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...

Catalina, T.; Virgone, J.

2011-01-01T23:59:59.000Z

354

Decision support for integrated refinery supply chains: Part 1. Dynamic simulation  

Science Journals Connector (OSTI)

Supply chain studies are increasingly given top priority in enterprise-wide management. Present-day supply chains involve numerous, heterogeneous, geographically distributed entities with varying dynamics, uncertainties, and complexity. The performance of a supply chain relies on the quality of a multitude of design and operational decisions made by the various entities. In this two-part paper, we demonstrate that a dynamic model of an integrated supply chain can serve as a valuable quantitative tool that aids in such decision-making. In this Part 1, we present a dynamic model of an integrated refinery supply chain. The model explicitly considers the various supply chain activities such as crude oil supply and transportation, along with intra-refinery supply chain activities such as procurement planning, scheduling, and operations management. Discrete supply chain activities are integrated along with continuous production through bridging procurement, production, and demand management activities. Stochastic variations in transportation, yields, prices, and operational problems are considered in the proposed model. The economics of the refinery supply chain includes consideration of different crude slates, product prices, operation costs, transportation, etc. The proposed model has been implemented as a dynamic simulator, called Integrated Refinery In-Silico (IRIS). IRIS allows the user the flexibility to modify not only parameters, but also replace different policies and decision-making algorithms in a plug-and-play manner. It thus allows the user to simulate and analyze different policies, configurations, uncertainties, etc., through an easy-to-use graphical interface. The capabilities of IRIS for strategic and tactical decision support are illustrated using several case studies.

Suresh S. Pitty; Wenkai Li; Arief Adhitya; Rajagopalan Srinivasan; I.A. Karimi

2008-01-01T23:59:59.000Z

355

Molecular dynamics simulations of damage production by thermal spikes in Ge  

SciTech Connect (OSTI)

Molecular dynamics simulation techniques are used to analyze damage production in Ge by the thermal spike process and to compare the results to those obtained for Si. As simulation results are sensitive to the choice of the inter-atomic potential, several potentials are compared in terms of material properties relevant for damage generation, and the most suitable potentials for this kind of analysis are identified. A simplified simulation scheme is used to characterize, in a controlled way, the damage generation through the local melting of regions in which energy is deposited. Our results show the outstanding role of thermal spikes in Ge, since the lower melting temperature and thermal conductivity of Ge make this process much more efficient in terms of damage generation than in Si. The study is extended to the modeling of full implant cascades, in which both collision events and thermal spikes coexist. Our simulations reveal the existence of bigger damaged or amorphous regions in Ge than in Si, which may be formed by the melting and successive quenching induced by thermal spikes. In the particular case of heavy ion implantation, defect structures in Ge are not only bigger, but they also present a larger net content in vacancies than in Si, which may act as precursors for the growth of voids and the subsequent formation of honeycomb-like structures.

Lopez, Pedro; Pelaz, Lourdes; Santos, Ivan; Marques, Luis A.; Aboy, Maria [Departamento de Electricidad y Electronica, Universidad de Valladolid, E.T.S.I. Telecomunicacion, Valladolid 47011 (Spain)

2012-02-01T23:59:59.000Z

356

Fully coupled time-domain simulation of dynamic positioning semi-submersible platform using dynamic surface control  

Science Journals Connector (OSTI)

A fully coupled 6-degree-of-freedom nonlinear dynamic model is presented to analyze the dynamic response of a semi-submersible platform which is equipped with the dynamic positioning...

Haizhi Liang; Luyu Li; Jinping Ou

2014-06-01T23:59:59.000Z

357

Analyzing Ventilation Effects of Different Apartment Styles by CFD  

E-Print Network [OSTI]

ICEBO2006, Shenzhen, China Renewable Renewable Energy Resources and a Greener Future Vol.VIII-3-5 Analyzing Ventilation Effects of Different Apartment Styles by CFD Xiaodong Li Lina Wang Zhixing Ye Associate Professor School...

Li, X.; Wang, L.; Ye, Z.

2006-01-01T23:59:59.000Z

358

Vacancy profile in reverse osmosis membranes studied by positron annihilation lifetime measurements and molecular dynamics simulations  

Science Journals Connector (OSTI)

The positron annihilation technique using a slow positron beam can be used for the study of the vacancy profiles in typical reverse osmosis (RO) membranes. In this study, the vacancy profile in the polyamide membrane that exhibits a high permselectivity between ions and water was studied using the positron annihilation technique and molecular dynamics simulations. Ortho-positronium (o-Ps) lifetimes in the surface region of the membranes were evaluated by using a slow positron beam. The diffusion behavior of Na+ and water in the polyamides was simulated by molecular dynamics (MD) methods using the TSUBAME2 supercomputer at the Tokyo Institute of Technology and discussed with the vacancy profile probed by the o-Ps. The results suggested that the large hydration size of Na+ compared to the vacancy size in the polyamides contributes to the increased diffusivity selectivity of water/Na+ that is related to the NaCl desalination performance of the membrane. Both the hydration size of the ions and the vacancy size appeared to be significant parameters to discuss the diffusivity selectivity of water/ions in typical polyamide membranes.

A Shimazu; H Goto; T Shintani; M Hirose; R Suzuki; Y Kobayashi

2013-01-01T23:59:59.000Z

359

Molecular dynamics simulation: a tool for exploration and discovery using simple models  

E-Print Network [OSTI]

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.

D. C. Rapaport

2014-11-13T23:59:59.000Z

360

CFD Simulations and Experiments to Determine the Feasibility...  

Broader source: Energy.gov (indexed) [DOE]

CONVERGE Dimensionality and type of grid 3D, structured with Adaptive Mesh Resolution Spatial discretization approach 2 nd order finite volume Smallest and largest...

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361

The Effects of Geometry on Flexible Duct CFD Simulations  

E-Print Network [OSTI]

shapes were compared to determine the complexity of modeling and computational requirements. The performance of each model was determined based on the agreement with the measured data. The difference of static pressure differentials between PT and HT...

Ugursal, A.; Culp, C.

362

TIME-DEPENDENT PROPERTIES OF LIQUID WATER: A COMPARISON OF CAR-PARRINELLO AND BORN-OPPENHIEMER MOLECULAR DYNAMICS SIMULATIONS  

SciTech Connect (OSTI)

A series of 30 ps first principles molecular dynamics simulations in the microcanonical ensemble were carried out to investigate transport and vibrational properties of liquid water. To allow for sufficient sampling, the thermodynamic constraints were set to an elevated temperature of around 423 K and a density of 0.71 g/cm{sup 3} corresponding to the saturated liquid density for the Becke-Lee-Yang-Parr (BLYP) representation of water. Four simulations using the Car-Parrinello molecular dynamics (CPMD) technique with varying values of the fictitious electronic mass ({mu}) and two simulations using the Born-Oppenheimer molecular dynamics (BOMD) technique are analyzed to yield structural and dynamical information. At the selected state point, the simulations are found to exhibit non-glassy dynamics and yield consistent results for the liquid structure and the self-diffusion coefficient, although the statistical uncertainties in the latter quantity are quite large. Consequently, it can be said that the CPMD and BOMD methods produce equivalent results for these properties on the time scales reported here. However, it was found that the choice of {mu} affects the frequency spectrum of the intramolecular modes, shifting them slightly to regions of lower frequency. Using a value of {mu} = 400 a.u. results in a significant drift in the electronic kinetic energy of the system over the course of 30 ps and a downward drift in the ionic temperature. Therefore, for long trajectories at elevated temperatures, lower values of this parameter are recommended for CPMD simulations of water.

Kuo, I W; Mundy, C; McGrath, M; Siepmann, J I

2005-12-29T23:59:59.000Z

363

Seventh International Conference on Computational Fluid Dynamics (ICCFD7),  

E-Print Network [OSTI]

industrial purpose CFD codes, such as TONUS [7], to investigate turbulent combustion flows. The main drawback-diffusive scheme, upwind downwind-controlled splitting 1 Introduction The use of Computational Fluids Dynamics (CFD: the reaction zone in a laminar deflagration at atmospheric condition can vary from about 1 mm to 10 mm

Boyer, Edmond

364

A CFD M&S PROCESS FOR FAST REACTOR FUEL ASSEMBLIES  

SciTech Connect (OSTI)

A CFD modeling and simulation process for large-scale problems using an arbitrary fast reactor fuel assembly design was evaluated. Three dimensional flow distributions of sodium for several fast reactor fuel assembly pin spacing configurations were simulated on high performance computers using commercial CFD software. This research focused on 19-pin fuel assembly “benchmark” geometry, similar in design to the Advanced Burner Test Reactor, where each pin is separated by helical wire-wrap spacers. Several two-equation turbulence models including the k-e and SST (Menter) k-? were evaluated. Considerable effort was taken to resolve the momentum boundary layer, so as to eliminate the need for wall functions and reduce computational uncertainty. High performance computers were required to generate the hybrid meshes needed to predict secondary flows created by the wire-wrap spacers; computational meshes ranging from 65 to 85 million elements were common. A general validation methodology was followed, including mesh refinement and comparison of numerical results with empirical correlations. Predictions for velocity, temperature, and pressure distribution are shown. The uncertainty of numerical models, importance of high fidelity experimental data, and the challenges associated with simulating and validating large production-type problems are presented.

Kurt D. Hamman; Ray A. Berry

2008-09-01T23:59:59.000Z

365

Development of an object-oriented dynamics simulator for a LFR DEMO  

SciTech Connect (OSTI)

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)

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

366

Dynamic simulations of geologic materials using combined FEM/DEM/SPH analysis  

SciTech Connect (OSTI)

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.

Morris, J P; Johnson, S M

2008-03-26T23:59:59.000Z

367

CFD study of mixing and segregation in CFB risers: Extension of EMMS drag model to binary gas–solid flow  

Science Journals Connector (OSTI)

Abstract The Energy Minimization Multi-Scale (EMMS) drag model, using Sauter mean particle diameter to represent real particle size distribution, has proven to be effective in improving the accuracy of continuum modeling of gas–solid flow. Nevertheless, mixing and segregation characteristics in circulating fluidized bed (CFB) risers are very important in many situations, which necessitates the explicit consideration of the effects of particle size distribution on the bed hydrodynamics. To this end, an attempt is made to extend the EMMS drag model to binary gas–solid system, where four input parameters that can be obtained from computational fluid dynamics (CFD) simulation, including two slip velocities between gas and each particle phase and two particle concentrations of each phase, are used to solve the proposed EMMS drag model. Heterogeneous indexes, which are used to modify the drag correlation obtained from homogeneous fluidization, are then predicted and fed into multifluid model (MFM) to predict the dynamical behavior of mixing and segregation of binary gas–solid flow in a CFB riser. The effects of different drag force models, kinetic theories and particle–particle drag force models are also systematically evaluated. It was shown that (i) MFM with the proposed EMMS drag model and the kinetic theory developed by Chao et al. (Chemical Engineering Science 2011, 66: 3605–3616) is able to correctly predict the mixing and segregation pattern in the studied riser, while MFM with homogenous drag forces and the simplified kinetic theory available in commercial software FLUENT completely fails; and (ii) with or without particle–particle drag force has a substantial influence upon the particle behavior.

Quan Zhou; Junwu Wang

2015-01-01T23:59:59.000Z

368

Two-dimensional computational fluid dynamics and conduction simulations of heat transfer in window frames with internal cavities - Part 1: Cavities only  

E-Print Network [OSTI]

1980. Numerical heat transfer and fluid flow. Washington,of heat transfer by natural convection across vertical fluidFluid Dynamics and Conduction Simulations of Heat Transfer

Gustavsen, Arild; Kohler, Christian; Arasteh, Dariush; Curcija, Dragan

2003-01-01T23:59:59.000Z

369

COMPARISON OF EXPERIMENTS TO CFD MODELS FOR MIXING USING DUAL OPPOSING JETS IN TANKS WITH AND WITHOUT INTERNAL OBSTRUCTIONS  

SciTech Connect (OSTI)

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.

Leishear, R.; Poirier, M.; Lee, S.; Fowley, M.

2012-06-26T23:59:59.000Z

370

Fast molecular-dynamics simulation for ferroelectric thin-film capacitors using a first-principles effective Hamiltonian  

Science Journals Connector (OSTI)

A newly developed fast molecular dynamics method is applied to BaTiO3 ferroelectric thin-film capacitors with short-circuited electrodes or under applied voltage. The molecular dynamics simulations based on a first-principles effective Hamiltonian clarify that dead layers (or passive layers) between ferroelectrics and electrodes markedly affect the properties of capacitors, and predict that the system is unable to hop between a uniformly polarized ferroelectric structure and a striped ferroelectric domain structure at low temperatures. Simulations of hysteresis loops of thin-film capacitors are also performed, and their dependence on film thickness, epitaxial constraints, and electrodes are discussed.

Takeshi Nishimatsu; Umesh V. Waghmare; Yoshiyuki Kawazoe; David Vanderbilt

2008-09-04T23:59:59.000Z

371

Modeling and simulation of longitudinal dynamics for Low Energy Ring–High Energy Ring at the Positron-Electron Project  

Science Journals Connector (OSTI)

A time domain dynamic modeling and simulation tool for beam-cavity interactions in the Low Energy Ring (LER) and High Energy Ring (HER) at the Positron-Electron Project (PEP-II) is presented. Dynamic simulation results for PEP-II are compared to measurements of the actual machine. The motivation for this tool is to explore the stability margins and performance limits of PEP-II radio-frequency (RF) systems at future higher currents and upgraded RF configurations. It also serves as a test bed for new control algorithms and can define the ultimate limits of the low-level RF (LLRF) architecture. The time domain program captures the dynamic behavior of the beam-cavity-LLRF interaction based on a reduced model. The ring current is represented by macrobunches. Multiple RF stations in the ring are represented via one or two macrocavities. Each macrocavity captures the overall behavior of all the 2 or 4 cavity RF stations. Station models include nonlinear elements in the klystron and signal processing. This enables modeling the principal longitudinal impedance control loops interacting via the longitudinal beam model. The dynamics of the simulation model are validated by comparing the measured growth rates for the LER with simulation results. The simulated behavior of the LER at increased operation currents is presented via low-mode instability growth rates. Different control strategies are compared and the effects of both the imperfections in the LLRF signal processing and the nonlinear drivers and klystrons are explored.

C. Rivetta; T. Mastorides; J. D. Fox; D. Teytelman; D. Van Winkle

2007-02-21T23:59:59.000Z

372

Molecular dynamics simulations of oscillatory Couette flows with slip boundary conditions  

E-Print Network [OSTI]

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.

Nikolai V. Priezjev

2012-08-27T23:59:59.000Z

373

Longitudinal beam dynamics simulation in electron rings in strong rf focusing regime  

Science Journals Connector (OSTI)

Obtaining very short bunches in an electron storage ring is one of the frontiers of the accelerator physics. The strong rf focusing (SRFF) is a way to have short bunches at a given position in the ring, thanks to the principle of the bunch length modulation. Until now, the bunch length modulation has been studied only in the limit of zero current; in this paper we present the results of a simulation code suitable to study the effects of coherent synchrotron radiation and vacuum chamber wakefields on the single bunch longitudinal dynamics in the SRFF regime . The code has been applied to three different lattices that can be realized in the Frascati e+/e- collider DA?NE for a possible experiment on bunch length modulation.

Luciano Falbo; David Alesini; Mauro Migliorati

2006-09-13T23:59:59.000Z

374

The system dynamics simulation of the expansion of the Panama Canal  

Science Journals Connector (OSTI)

The expansion of the Panama Canal could be the largest project attempted by the Republic of Panama in its 100 years of existence. The objective of this simulation study is to use the Canal Expansion Project to develop and demonstrate how more precise and applied concepts that involve complex decision-making processes can be used in a large 'system of systems'. It is an attempt to explain the decision-making processes for complex systems and develop a model that will help with the political, social and economic decision-making processes that are involved in this very large project. The challenges that are involved in this research initiative include developing the parametric expressions that explain the dynamical intricacies and validation of the expansion project.

Humberto R. Alvarez A.; Dario Solis; Arnoldo R. Cano S.; Luis Rabelo; Serge Sala-Diakanda

2009-01-01T23:59:59.000Z

375

The Melting Temperature of Bulk Silicon from ab initio Molecular Dynamics Simulations  

SciTech Connect (OSTI)

We estimated a melting temperature of Tm ~ 1540 ± 90 K at zero pressure for silicon from constant enthalpy and constant pressure (NPH) Born-Oppenheimer Molecular Dynamics (BOMD) simulations of a coexisting crystalline-liquid phase. The computed Tm is below the experimental melting point of 1685 K, but it is consistent with a previously predicted first-order liquid-liquid phase transition (LLPT) at a critical point Tc ~ 1232 K and Pc ~ - 12kB [Ganesh and Widom, Phys. Rev. Lett. 102, 075701 (2009)], which is in a highly supercooled state. This work was supported by the US Department of Energy, Office of Basic Energy Sciences, Chemical Sciences program. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

Yoo, Soohaeng; Xantheas, Sotiris S.; Zeng, Xiao Cheng

2009-10-19T23:59:59.000Z

376

Superionicity in the hydrogen storage material Li2NH: Molecular dynamics simulations  

Science Journals Connector (OSTI)

We have employed ab initio molecular dynamics simulations in an attempt to study a temperature-induced order-disorder structural phase transformation that occurs in Li2NH at about 385 K. A structural phase transition was observed by us in the temperature range 300–400 K, in good agreement with experiment. This transition is associated with a melting of the cation sublattice (Li+), giving rise to a superionic phase, which in turn is accompanied by an order-disorder transition of the N-H bond orientation. The results obtained here can contribute to a better understanding of the hydrogen storage reactions involving Li2NH and furthermore broaden its possible technological applications toward batteries and fuel cells.

C. Moysés Araújo; Andreas Blomqvist; Ralph H. Scheicher; Ping Chen; Rajeev Ahuja

2009-05-08T23:59:59.000Z

377

Solvent Electrostriction Driven Peptide Folding revealed by Quasi-Gaussian Entropy Theory and Molecular Dynamics Simulation  

SciTech Connect (OSTI)

A quantitative understanding of the complex relationship between microscopic structure and the thermodynamics driving peptide and protein folding is a major goal of biophysical chemistry. Here, we present a methodology comprising the use of an extended quasi-Gaussian entropy theory parametrized using molecular dynamics simulation that provides a complete description of the thermodynamics of peptide conformational states. The strategy is applied to analyze the conformational thermodynamics of MR121-GSGSW, a peptide well characterized in experimental studies. The results demonstrate that the extended state of the peptide possesses the lowest partial molar entropy. The origin of this entropy decrease is found to be in the increase of the density and orientational order of the hydration water molecules around the peptide, induced by the 'unfolding'. While such a reduction of the configurational entropy is usually associated with the hydrophobic effect, it is here found to be mainly due to the interaction of the solute charges with the solvent, that is, electrostriction.

Noe, F [University of Heidelberg; Daidone, Isabella [University of Heidelberg; Smith, Jeremy C [ORNL; DiNola, Alfredo [University of Rome; Amadei, Andrea [University of Rome 'Tor Vergata', Rome, Italy

2008-06-01T23:59:59.000Z

378

Solvent Electrostriction-Driven Peptide Folding Revealed by Quasi Gaussian Entropy Theory and Molecular Dynamics Simulation  

SciTech Connect (OSTI)

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

379

Polymer segregation under confinement: Free energy calculations and segregation dynamics simulations  

E-Print Network [OSTI]

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.

James M. Polson; Logan G. Montgomery

2014-08-20T23:59:59.000Z

380

National Ignition Facility computational fluid dynamics modeling and light fixture case studies  

SciTech Connect (OSTI)

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.

Martin, R.; Bernardin, J.; Parietti, L.; Dennison, B.

1998-02-01T23:59:59.000Z

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381

Air heating of passive houses in cold climates: Investigation using detailed dynamic simulations  

Science Journals Connector (OSTI)

Abstract The passive house (PH) standard was originally defined for Central Europe and has subsequently been applied to many cold climate countries. In these conditions, the relation between this standard and the air heating (AH) is not clear while both concepts are usually associated. Furthermore, the AH provides a way to simplify the space-heating distribution system. The present contribution investigates the feasibility of the AH concept in PH along with its challenges in terms of thermal dynamics: the magnitude of the AH temperature needed, the temperature difference between rooms, the impact of internal gains, the influence of thermal losses from ventilation ducts and the AH control. This is performed using detailed dynamic simulations (TRNSYS) on a typical detached house typology. Practically, four cold climate zones are considered as well as different insulation levels and construction materials. Results show limitations related to a centralized AH as well as provide guidelines for a consistent AH design in cold climates. In addition, a simple analytical method used for the design of German PH is tested and proved accurate enough to estimate the maximal AH temperature during the heating season.

Laurent Georges; Monica Berner; Hans Martin Mathisen

2014-01-01T23:59:59.000Z

382

Molecular dynamics simulation of shock induced ejection on fused silica surface  

SciTech Connect (OSTI)

Shock response and surface ejection behaviors of fused silica are studied by using non-equilibrium molecular dynamics combining with the Tersoff potential. First, bulk structure and Hugoniot curves of fused silica are calculated and compared with experimental results. Then, the dynamical process of surface ejection behavior is simulated under different loading velocities ranging from 3.5 to 5.0?km?s, corresponding to shock wave velocities from 7.1 to 8.8?km?s. The local atomistic shear strain parameter is used to describe the local plastic deformation under conditions of shock compression or releasing. Our result shows that the shear strain is localized in the bottom area of groove under the shock compression. Surface ejection is observed when the loading velocity exceeds 4.0?km?s. Meanwhile, the temperature of the micro-jet is ?5574.7?K, which is close to experiment measurement. Several kinds of structural defects including non-bridging oxygen are found in the bulk area of the sample after ejection.

Su, Rui [College of Physical Science and Technology, Sichuan University, Chengdu 610064 (China); Xiang, Meizhen; Jiang, Shengli [Institute of Applied Physics and Computational Mathematics, Beijing 100094 (China); Chen, Jun, E-mail: jun-chen@iapcm.ac.cn [Institute of Applied Physics and Computational Mathematics, Beijing 100094 (China); Center for Applied Physics and Technology, Peking University, Beijing 100087 (China); Wei, Han [Research Center of Laser Fusion, Mianyang 621900 (China)

2014-05-21T23:59:59.000Z

383

Dynamic Simulation of Shipping Package Subjected to Torque Load and Sequential Impacts  

SciTech Connect (OSTI)

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.

Wu, T

2006-04-17T23:59:59.000Z

384

Charge constrained density functional molecular dynamics for simulation of condensed phase electron transfer reactions  

SciTech Connect (OSTI)

We present a plane-wave basis set implementation of charge constrained density functional molecular dynamics (CDFT-MD) for simulation of electron transfer reactions in condensed phase systems. Following the earlier work of Wu and Van Voorhis [Phys. Rev. A 72, 024502 (2005)], the density functional is minimized under the constraint that the charge difference between donor and acceptor is equal to a given value. The classical ion dynamics is propagated on the Born-Oppenheimer surface of the charge constrained state. We investigate the dependence of the constrained energy and of the energy gap on the definition of the charge and present expressions for the constraint forces. The method is applied to the Ru{sup 2+}-Ru{sup 3+} electron self-exchange reaction in aqueous solution. Sampling the vertical energy gap along CDFT-MD trajectories and correcting for finite size effects, a reorganization free energy of 1.6 eV is obtained. This is 0.1-0.2 eV lower than a previous estimate based on a continuum model for solvation. The smaller value for the reorganization free energy can be explained by the fact that the Ru-O distances of the divalent and trivalent Ru hexahydrates are predicted to be more similar in the electron transfer complex than for the separated aqua ions.

Oberhofer, Harald; Blumberger, Jochen [Department of Chemistry, University of Cambridge, Cambridge CB2 1EW (United Kingdom)

2009-08-14T23:59:59.000Z

385

Molecular Dynamics Simulation of Cascade-Induced Ballistic Helium Resolutioning from Bubbles in Iron  

SciTech Connect (OSTI)

Molecular dynamics simulations have been used to assess the ability of atomic displacement cascades to eject helium from small bubbles in iron. This study of the ballistic resolutioning mechanism employed a recently-developed Fe-He interatomic potential in concert with an iron potential developed by Ackland and co-workers. The primary variables examined were: irradiation temperature (100 and 600K), cascade energy (5 and 20 keV), bubble radius (0.5 and 1.0 nm), and He-to-vacancy ratio in the bubble (0.25, 0.5 and 1.0). Systematic trends were observed for each of these variables. For example, ballistic resolutioning leads to a greater number of helium atoms being displaced from larger bubbles and from bubbles that have a higher He/vacancy ratio (bubble pressure). He resolutioning was reduced at 600K relative to 100K, and for 20 keV cascades relative to 5 keV cascades. Overall, the results indicate a modest level of He removal by ballistic resolutioning. The results can be used to provide guidance in selection of a resolution parameter that can be employed in cluster dynamics models to predict the bubble size distribution that evolves under irradiation.

Stoller, Roger E [ORNL] [ORNL

2013-01-01T23:59:59.000Z

386

Pattern formation and dynamics in Rayleigh-Benard convection : numerical simulations of experimentally realistic geometries.  

SciTech Connect (OSTI)

Rayleigh-Benard convection is studied and quantitative comparisons are made, where possible, between theory and experiment by performing numerical simulations of the Boussinesq equations for a variety of experimentally realistic situations. Rectangular and cylindrical geometries of varying aspect ratios for experimental boundary conditions, including fins and spatial ramps in plate separation, are examined with particular attention paid to the role of the mean flow. A small cylindrical convection layer bounded laterally either by a rigid wall, fin, or a ramp is investigated and our results suggest that the mean flow plays an important role in the observed wavenumber. Analytical results are developed quantifying the mean flow sources, generated by amplitude gradients, and its effect on the pattern wavenumber for a large-aspect-ratio cylinder with a ramped boundary. Numerical results are found to agree well with these analytical predictions. We gain further insight into the role of mean flow in pattern dynamics by employing a novel method of quenching the mean flow numerically. Simulations of a spiral defect chaos state where the mean flow is suddenly quenched is found to remove the time dependence, increase the wavenumber and make the pattern more angular in nature.

Paul, M. R.; Chiarn, K.-H.; Cross, M. C.; Fischer, P. F.; Greenside, H. S.; Mathematics and Computer Science; California Inst. of Tech.; Duke University

2003-10-01T23:59:59.000Z

387

Molecular dynamics simulation of elevated temperature interfacial behavior between silica glass and a model crystal  

SciTech Connect (OSTI)

Elevated temperature atomistic behavior was investigated using classical molecular dynamics simulations of solid state interfaces. Initially, observations on a Lennard-Jones (LJ) crystal surface interfaced with an ideal vacuum were made. Assignment of temperatures associated with specific amounts of crystal surface disorder was possible. A temperature was observed at and above which disorder propagated through all planes of mobile atoms, making it possible to establish an approximate transition temperature for surface nucleated melting of the LJ crystal. Similar high temperature simulations were then performed on silica glass/LJ crystal interfaces at two system stress levels. No significant dependence of interface behavior on the stress states which were studied was observed. The presence of the glass surface resulted in a depression of the temperature needed for the surface most planes of crystal atoms to roughen. This allowed LJ atoms to sample and occupy sites in the glass surface. Additional data presented shows this behavior was at least partly a function of the open structure inherent in glassy oxide surfaces. {copyright} {ital 1996 American Institute of Physics.}

Webb, E.B. III; Garofalini, S.H. [Department of Ceramics, Interfacial Molecular Science Laboratory, Rutgers University, Piscataway, New Jersey 08855 (United States)] [Department of Ceramics, Interfacial Molecular Science Laboratory, Rutgers University, Piscataway, New Jersey 08855 (United States)

1996-07-01T23:59:59.000Z

388

Dynamic simulation of 10 kW Brayton cryocooler for HTS cable  

SciTech Connect (OSTI)

Dynamic simulation of a Brayton cryocooler is presented as a partial effort of a Korean governmental project to develop 1?3 km HTS cable systems at transmission level in Jeju Island. Thermodynamic design of a 10 kW Brayton cryocooler was completed, and a prototype construction is underway with a basis of steady-state operation. This study is the next step to investigate the transient behavior of cryocooler for two purposes. The first is to simulate and design the cool-down process after scheduled or unscheduled stoppage. The second is to predict the transient behavior following the variation of external conditions such as cryogenic load or outdoor temperature. The detailed specifications of key components, including plate-fin heat exchangers and cryogenic turbo-expanders are incorporated into a commercial software (Aspen HYSYS) to estimate the temporal change of temperature and flow rate over the cryocooler. An initial cool-down scenario and some examples on daily variation of cryocooler are presented and discussed, aiming at stable control schemes of a long cable system.

Chang, Ho-Myung; Park, Chan Woo [Hong Ik University, Department of Mechanical Engineering, Seoul, 121-791 (Korea, Republic of); Yang, Hyung Suk; Hwang, Si Dole [KEPCO Research Institute, Daejeon, 305-760 (Korea, Republic of)

2014-01-29T23:59:59.000Z

389

Ratcheted molecular-dynamics simulations identify efficiently the transition state of protein folding  

E-Print Network [OSTI]

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.

Guido Tiana; Carlo Camilloni

2012-07-05T23:59:59.000Z

390

Dynamic simulation of 10 kW Brayton cryocooler for HTS cable  

Science Journals Connector (OSTI)

Dynamic simulation of a Brayton cryocooler is presented as a partial effort of a Korean governmental project to develop 1?3 km HTS cable systems at transmission level in Jeju Island. Thermodynamic design of a 10 kW Brayton cryocooler was completed and a prototype construction is underway with a basis of steady-state operation. This study is the next step to investigate the transient behavior of cryocooler for two purposes. The first is to simulate and design the cool-down process after scheduled or unscheduled stoppage. The second is to predict the transient behavior following the variation of external conditions such as cryogenic load or outdoor temperature. The detailed specifications of key components including plate-fin heat exchangers and cryogenic turbo-expanders are incorporated into a commercial software (Aspen HYSYS) to estimate the temporal change of temperature and flow rate over the cryocooler. An initial cool-down scenario and some examples on daily variation of cryocooler are presented and discussed aiming at stable control schemes of a long cable system.

2014-01-01T23:59:59.000Z

391

Path integral Monte Carlo and density functional molecular dynamics simulations of hot, dense helium  

Science Journals Connector (OSTI)

Two first-principles simulation techniques, path integral Monte Carlo (PIMC) and density functional molecular dynamics (DFT-MD), are applied to study hot, dense helium in the density-temperature range of 0.387–5.35?g?cm?3 and 500?K–1.28×108?K. One coherent equation of state is derived by combining DFT-MD data at lower temperatures with PIMC results at higher temperatures. Good agreement between both techniques is found in an intermediate-temperature range. For the highest temperatures, the PIMC results converge to the Debye-Hückel limiting law. In order to derive the entropy, a thermodynamically consistent free-energy fit is used that reproduces the internal energies and pressure derived from the first-principles simulations. The equation of state is presented in the form of a table as well as a fit and is compared with different free-energy models. Pair-correlation functions and the electronic density of states are discussed. Shock Hugoniot curves are compared with recent laser shock-wave experiments.

B. Militzer

2009-04-08T23:59:59.000Z

392

Molecular-dynamics simulations of thin polyisoprene films confined between amorphous silica substrates  

SciTech Connect (OSTI)

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.

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

393

A multi-scale framework for CFD modelling of multi-phase complex systems based on the EMMS approach  

Science Journals Connector (OSTI)

The averaged conservative equations in CFD modelling are inadequate to achieve a complete description of the multi-scale structures in multiphase complex systems. By considering the relationship between meso-scale structures and meso-scale energy consumption, stability conditions mathematically expressed as a mutually constrained extremum are proposed in the Energy-Minimization Multi-Scale (EMMS) approach and indispensable to reflect the compromise of different dominant mechanisms for various multiphase systems. The approach is first applied to global systems to predict and physically interpret the macro-scale structure evolution, i.e., regime transition. Then when applied to computational cells, it corrects interphase momentum transfer and greatly improves the accuracy of coarse-grid CFD simulation.

Ning Yang

2012-01-01T23:59:59.000Z

394

Non-Gaussian Fluctuation and Non-Markovian Effect in the Nuclear Fusion Process: Langevin Dynamics Emerging from Quantum Molecular Dynamics Simulations  

E-Print Network [OSTI]

Macroscopic parameters as well as precise information on the random force characterizing the Langevin type description of the nuclear fusion process are extracted from the microscopic dynamics of individual nucleons by exploiting the numerical simulation of the improved quantum molecular dynamics. It turns out that the dissipation dynamics of the relative motion between two fusing nuclei is caused by a non-Gaussian distribution of the random force. We find that the friction coefficient as well as the time correlation function of the random force takes particularly large values in a region a little bit inside of the Coulomb barrier. A clear non-Markovian effect is observed in the time correlation function of the random force. It is further shown that an emergent dynamics of the fusion process can be described by the generalized Langevin equation with memory effects by appropriately incorporating the microscopic information of individual nucleons through the random force and its time correlation function.

Wen, Kai; Li, Zhu-Xia; Wu, Xi-Zhen; Zhang, Ying-Xun; Zhou, Shan-Gui

2013-01-01T23:59:59.000Z

395

Non-Gaussian Fluctuation and Non-Markovian Effect in the Nuclear Fusion Process: Langevin Dynamics Emerging from Quantum Molecular Dynamics Simulations  

E-Print Network [OSTI]

Macroscopic parameters as well as precise information on the random force characterizing the Langevin type description of the nuclear fusion process around the Coulomb barrier are extracted from the microscopic dynamics of individual nucleons by exploiting the numerical simulation of the improved quantum molecular dynamics. It turns out that the dissipation dynamics of the relative motion between two fusing nuclei is caused by a non-Gaussian distribution of the random force. We find that the friction coefficient as well as the time correlation function of the random force takes particularly large values in a region a little bit inside of the Coulomb barrier. A clear non-Markovian effect is observed in the time correlation function of the random force. It is further shown that an emergent dynamics of the fusion process can be described by the generalized Langevin equation with memory effects by appropriately incorporating the microscopic information of individual nucleons through the random force and its time correlation function.

Kai Wen; Fumihiko Sakata; Zhu-Xia Li; Xi-Zhen Wu; Ying-Xun Zhang; Shan-Gui Zhou

2013-05-02T23:59:59.000Z

396

Dynamics  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Hydration Hydration Water on Rutile Studied by Backscattering Neutron Spectroscopy and Molecular Dynamics Simulation E. Mamontov,* ,† D. J. Wesolowski, ‡ L. Vlcek, § P. T. Cummings, §,| J. Rosenqvist, ‡ W. Wang, ⊥ and D. R. Cole ‡ Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6473, Chemical Sciences DiVision, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6110, Department of Chemical Engineering, Vanderbilt UniVersity, NashVille, Tennessee 37235-1604, Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6496, and EnVironmental Sciences DiVision, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6036 ReceiVed: December 20, 2007; ReVised Manuscript ReceiVed: June 4, 2008 The high energy resolution, coupled with the wide dynamic range, of the new backscattering

397

AVESTAR Center: Dynamic simulation-based collaboration toward achieving opertional excellence for IGCC plants with crbon capture  

SciTech Connect (OSTI)

To address challenges in attaining operational excellence for clean energy plants, the National Energy Technology Laboratory has launched a world-class facility for Advanced Virtual Energy Simulation Training And Research (AVESTAR(TM)). The AVESTAR Center brings together state-of-the-art, real-time, high-fidelity dynamic simulators with operator training systems and 3D virtual immersive training systems into an integrated energy plant and control room environment. This paper will highlight the AVESTAR Center simulators, facilities, and comprehensive training, education, and research programs focused on the operation and control of an integrated gasification combined cycle power plant (IGCC) with carbon dioxide capture.

Zitney, Strphen E. [U.S. DOE; Liese, Eric A. [U.S. DOE; Mahapatra, Priyadarshi [URS; Turton, Richard [WVU; Bhattacharyya, Debangsu [WVU; Provost, Graham [Fossil Consulting Services

2012-01-01T23:59:59.000Z

398

Test of the Gouy-Chapman Theory for a Charged Lipid Membrane against Explicit-Solvent Molecular Dynamics Simulations  

Science Journals Connector (OSTI)

A wealth of experimental data has verified the applicability of the Gouy-Chapman (GC) theory to charged lipid membranes. Surprisingly, a validation of GC by molecular dynamics (MD) simulations has been elusive. Here, we report a test of GC against extensive MD simulations of an anionic lipid bilayer solvated by water at different concentrations of NaCl or KCl. We demonstrate that the ion distributions from the simulations agree remarkably well with GC predictions when information on the adsorption of counterions to the bilayer is incorporated.

Myunggi Yi; Hugh Nymeyer; Huan-Xiang Zhou

2008-07-18T23:59:59.000Z

399

European Conference on Computational Fluid Dynamics ECCOMAS CFD 2006  

E-Print Network [OSTI]

in industrialized countries. The major CVD include coronary (or ischaemic) heart disease (heart attack), cerebrovascular disease (stroke), hypertension (high blood pressure), rheumatic heart disease and heart failure. Damage to the heart tissues from CVD or from heart surgery can disrupt the natural electrical impulses

Frangi, Alejandro

400

European Conference on Computational Fluid Dynamics ECCOMAS CFD 2006  

E-Print Network [OSTI]

21 Uppsala, Sweden e-mail: damir.valiev@fysik.uu.se 3UPPMAX, Uppsala University, Box 337, 751 05¨uller, J. Rantakokko, P. L¨otstedt and M.A. Liberman of numerous efforts, the basic mechanisms controlling challenge of the combustion theory [6, 7, 8, 9]. The classical explanation of DDT [1, 2, 3] was due to flame

Müller,Bernhard

Note: This page contains sample records for the topic "dynamics cfd simulations" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


401

Modeling an EDC Cracker using Computational Fluid Dynamics (CFD).  

E-Print Network [OSTI]

?? The process used by the Norwegian company Hydro for making Vinyl Chloride Monomer (VCM) from natural gas and sodium chloride has been studied. A… (more)

Kaggerud, Torbjørn Herder

2007-01-01T23:59:59.000Z

402

European Conference on Computational Fluid Dynamics ECCOMAS CFD 2006  

E-Print Network [OSTI]

217, 7500 AE Enschede, The Netherlands e-mail: {L.Pesch, J.J.W.vanderVegt}@math.utwente.nl web page. P´eriaux (Eds) c TU Delft, The Netherlands, 2006 A SPACE-TIME DISCONTINUOUS GALERKIN FINITE

Al Hanbali, Ahmad

403

European Conference on Computational Fluid Dynamics ECCOMAS CFD 2006  

E-Print Network [OSTI]

of Twente P.O. Box 217, Enschede, The Netherlands e-mail: o.bokhove@math.utwente.nl web page: google "Onno. P´eriaux (Eds) c TU Delft, The Netherlands, 2006 A (DIS)CONTINUOUS FINITE ELEMENT MODEL of Physics, University of Utrecht, Utrecht, The Netherlands Department of Applied Mathematics, University

Al Hanbali, Ahmad

404

Molecular Dynamics Simulation of Heat Transfer Issues of Nanotubes. > Yasuhiro Igarashi, Yuki Taniguchi, Yasushi Shibuta and Shigeo Maruyama  

E-Print Network [OSTI]

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

Maruyama, Shigeo

405

Simulation of shock-induced melting of Ni using molecular dynamics coupled to a two-temperature model  

E-Print Network [OSTI]

Department, University of Uppsala, Box 530, SE-751 21 Uppsala, Sweden 2Lawrence Livermore National Laboratory, Livermore, California 94550, USA 3National Centre for Laser Applications, Galway, Ireland 4Department at the National Ignition Facility NIF . Molecular dynamics MD simulations have been success- fully employed

Zhigilei, Leonid V.

406

Solvation of Magnesium Dication: Molecular Dynamics Simulation and Vibrational Spectroscopic Study of Magnesium Chloride in Aqueous Solutions  

E-Print Network [OSTI]

Solvation of Magnesium Dication: Molecular Dynamics Simulation and Vibrational Spectroscopic Study of Magnesium Chloride in Aqueous Solutions Karen M. Callahan, Nadia N. Casillas-Ituarte, Martina Roeselova 26, 2010 Magnesium dication plays many significant roles in biochemistry. While it is available

407

Molecular Dynamics Simulations of End-to-End Contact Formation in Hydrocarbon Chains in Water and Aqueous Urea  

E-Print Network [OSTI]

Molecular Dynamics Simulations of End-to-End Contact Formation in Hydrocarbon Chains in Water is to probe contact formation between two ends of model hydrocarbon chains in water and 6 M aqueous urea "folding" event, namely, the formation of end-to-end contact in the linear hydrocarbon chain (HC) CH3(CH2

Thirumalai, Devarajan

408

Bonneville Powerhouse 2 Fish Guidance Efficiency Studies: CFD Model of the Forebay  

SciTech Connect (OSTI)

In ongoing work, U.S. Army Corps of Engineers, Portland District (CENWP) is seeking to better understand and improve the conditions within the Bonneville Powerhouse 2 (B2) turbine intakes to improve survival of downstream migrant salmonid smolt. In this study, the existing B2 forebay computational fluid dynamics (CFD) model was modified to include a more detailed representation of all B2 turbine intakes. The modified model was validated to existing field-measured forebay ADCP velocities. The initial CFD model scenarios tested a single project operation and the impact of adding the Behavior Guidance System (BGS) or Corner Collector. These structures had impacts on forebay flows. Most notable was that the addition of the BGS and Corner Collector reduced the lateral extent of the recirculation areas on the Washington shore and Cascade Island and reduced the flow velocity parallel to the powerhouse in front of Units 11 and 12. For these same cases, at the turbine intakes across the powerhouse, there was very little difference in the flow volume into the gatewell for the clean forebay, and the forebay with the BGS in place and/or the Corner Collector operating. The largest differences were at Units 11 to 13. The CFD model cases testing the impact of the gatewell slot fillers showed no impact to the forebay flows, but large differences within the gatewells. With the slot fillers, the flow above the standard traveling screen and into the gatewell increased (about 100 cfs at each turbine intake) and the gap flow decreased across the powerhouse for all cases. The increased flow up the gatewell was further enhanced with only half the units operating. The flow into the gatewell slot was increased about 35 cfs for each bay of each intake across the powerhouse; this change was uniform across the powerhouse. The flows in the gatewell of Unit 12, the most impacted unit for the scenarios, was evaluated. In front of the vertical barrier screen, the CFD model with slot fillers showed reduced the maximum velocities (in spite of the increased the flow into the gatewell), and decreased the area of recirculation. The area near the VBS exceeding the normal velocity criteria of 1 ft/s was reduced and the flows were more balanced.

Rakowski, Cynthia L.; Serkowski, John A.; Richmond, Marshall C.

2012-07-01T23:59:59.000Z

409

Computer Simulation of Diffusion of Pb-Bi Eutectic in Liquid Sodium by Molecular Dynamics Method  

SciTech Connect (OSTI)

Lead-bismuth eutectic is a potential candidate for coolant of secondary loops of sodium-cooled fast breeder reactors (FBR). The studies on the diffusion of liquid Pb-Bi in liquid Na are carried out corresponding to the case that liquid Pb-Bi leaks to liquid Na by accident. As the diffusion processes are the results of atomic motions, molecular dynamics method has been used to study the diffusion process. The self-diffusion coefficients of pure liquid Pb and Na, and liquid Pb-Bi are calculated and compared with ones by the empirical equations. The discrepancy between them could be eliminated by changing the densities of the liquids. The diffusion of lead-bismuth in sodium is simulated based on the changed densities under which the self-diffusion coefficients of individual liquid metals are close to those by the empirical equations. The simulation results show that the diffusion process of liquid Pb-Bi in liquid Na is a heat releasing process and the density of ternary liquid Na-Pb-Bi is higher than the average value of the densities of liquid Na and liquid Pb-Bi. It is also found that the diffusion coefficients of liquid Pb-Bi in liquid Na are much higher than their self-diffusion coefficients, indicating that liquid Pb-Bi are easy and quickly to diffuse in liquid Na. However, the diffusion coefficient of liquid Na is decreased due to the existence of liquid Pb-Bi, implying that liquid Na-Pb-Bi have a higher viscosity than that of pure liquid Na. (authors)

Yingxia Qi; Minoru Takahashi [Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550 (Japan)

2002-07-01T23:59:59.000Z

410

Dynamic modeling and simulation of hydrogen supply capacity from a metal hydride tank  

Science Journals Connector (OSTI)

Abstract The current study presents a modeling of a LaNi5 metal hydride-based hydrogen storage tank to simulate and control the dynamic processes of hydrogen discharge from a metal hydride tank in various operating conditions. The metal hydride takes a partial volume in the tank and, therefore, hydrogen discharge through the exit of the tank was driven by two factors; one factor is compressibility of pressurized gaseous hydrogen in the tank, i.e. the pressure difference between the interior and the exit of the tank makes hydrogen released. The other factor is desorption of hydrogen from the metal hydride, which is subsequently released through the tank exit. The duration of a supposed full load supply is evaluated, which depends on the initial tank pressure, the circulation water temperature, and the metal hydride volume fraction in the tank. In the high pressure regime, the duration of full load supply is increased with increasing circulation water temperature while, in the low pressure regime where the initial amount of hydrogen absorbed in the metal hydride varies sensitively with the metal hydride temperature, the duration of full load supply is increased and then decreased with increasing circulation water temperature. PID control logic was implemented in the hydrogen supply system to simulate a representative scenario of hydrogen consumption demand for a fuel cell system. The demanded hydrogen consumption rate was controlled adequately by manipulating the discharge valve of the tank at a circulation water temperature not less than a certain limit, which is increased with an increase in the tank exit pressure.

Ju-Hyeong Cho; Sang-Seok Yu; Man-Young Kim; Sang-Gyu Kang; Young-Duk Lee; Kook-Young Ahn; Hyun-Jin Ji

2013-01-01T23:59:59.000Z

411

Computational Fluid Dynamics of rising droplets  

SciTech Connect (OSTI)

The main goal of this study is to perform simulations of droplet dynamics using Truchas, a LANL-developed computational fluid dynamics (CFD) software, and compare them to a computational study of Hysing et al.[IJNMF, 2009, 60:1259]. Understanding droplet dynamics is of fundamental importance in liquid-liquid extraction, a process used in the nuclear fuel cycle to separate various components. Simulations of a single droplet rising by buoyancy are conducted in two-dimensions. Multiple parametric studies are carried out to ensure the problem set-up is optimized. An Interface Smoothing Length (ISL) study and mesh resolution study are performed to verify convergence of the calculations. ISL is a parameter for the interface curvature calculation. Further, wall effects are investigated and checked against existing correlations. The ISL study found that the optimal ISL value is 2.5{Delta}x, with {Delta}x being the mesh cell spacing. The mesh resolution study found that the optimal mesh resolution is d/h=40, for d=drop diameter and h={Delta}x. In order for wall effects on terminal velocity to be insignificant, a conservative wall width of 9d or a nonconservative wall width of 7d can be used. The percentage difference between Hysing et al.[IJNMF, 2009, 60:1259] and Truchas for the velocity profiles vary from 7.9% to 9.9%. The computed droplet velocity and interface profiles are found in agreement with the study. The CFD calculations are performed on multiple cores, using LANL's Institutional High Performance Computing.

Wagner, Matthew [Lake Superior State University; Francois, Marianne M. [Los Alamos National Laboratory

2012-09-05T23:59:59.000Z

412

Brittle dynamic fracture of crystalline cubic silicon carbide ,,3C-SiC... via molecular dynamics simulation  

E-Print Network [OSTI]

Brittle dynamic fracture of crystalline cubic silicon carbide ,,3C-SiC... via molecular dynamics for three low-index crack surfaces, i.e., 110 , 111 , and 100 , in crystalline cubic silicon carbide 3C Institute of Physics. DOI: 10.1063/1.2135896 I. INTRODUCTION Potential applications of silicon carbide Si

Southern California, University of

413

Compilation of CFD Models of Various Solid Oxide Electrolyzers Analyzed at the Idaho National Laboratory  

SciTech Connect (OSTI)

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

Grant Hawkes; James O'Brien

2012-06-01T23:59:59.000Z

414

CFD Model Of A Planar Solid Oxide Electrolysis Cell For Hydrogen Production From Nuclear Energy  

SciTech Connect (OSTI)

A three-dimensional computational fluid dynamics (CFD) model has been created to model hightemperature steam electrolysis in a planar solid oxide electrolysis cell (SOEC). The model represents a single cell as it would exist in an electrolysis stack. Details of the model geometry are specific to a stack that was fabricated by Ceramatec2, Inc. and tested at the Idaho National Laboratory. Mass, momentum, energy, and species conservation and transport are provided via the core features of the commercial CFD code FLUENT2. A solid-oxide fuel cell (SOFC) model adds the electrochemical reactions and loss mechanisms and computation of the electric field throughout the cell. The FLUENT SOFC user-defined subroutine was modified for this work to allow for operation in the SOEC mode. Model results provide detailed profiles of temperature, Nernst potential, operating potential, anode-side gas composition, cathode-side gas composition, current density and hydrogen production over a range of stack operating conditions. Mean model results are shown to compare favorably with experimental results obtained from an actual ten-cell stack tested at INL.

Grant L. Hawkes; James E. O'Brien; Carl M. Stoots; J. Stephen Herring

2005-10-01T23:59:59.000Z

415

EVALUATION OF AN EXPERIMENTAL DATA SET TO BE VALIDATION DATA FOR CFD FOR A VHTR  

SciTech Connect (OSTI)

The very high temperature reactor (VHTR) has been chosen as the concept for the next generation nuclear plant (NGNP), supported by the U. S. Department of Energy. There are two basic designs for the VHTR: a prismatic design and a pebble-bed design. In the prismatic design, the coolant (helium) exits the core into a lower plenum as jets. The helium then turns 90° and flows toward the exit duct around cylindrical support posts. Safety analysis by computational fluid dynamics (CFD) is desired to determine the level of mixing of the jets and check for hot spots. Experimental data were taken in a scaled model of a slice of the lower plenum of a prismatic VHTR. Numerical investigations have been made using CFD to determine if the data are suitable for validation. This paper provides the findings of the investigations including results for a modified version of the flow field. The investigations include a determination of the extent of the computational domain needed, the best outlet boundary condition to use, the accuracy of the inlet data, application of several turbulence models and the search for the cause of an instability that causes large random excursions of flow variables. It is found that the inlet data measured by PIV are not sufficiently accurate and that the instability is apparently caused by the presence of the first inlet jet which impinges on a recirculation zone.

Richard W. Johnson

2010-09-01T23:59:59.000Z

416

Computational Fluid Dynamics Study of Aerosol Transport and Deposition Mechanisms  

E-Print Network [OSTI]

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...

Tang, Yingjie

2012-07-16T23:59:59.000Z

417

A.G.Ramm, Dynamical systems method (DSM) for nonlinear equations in Banach spaces, Communic. in Nonlinear Sci. and Numer. Simulation, 11,  

E-Print Network [OSTI]

A.G.Ramm, Dynamical systems method (DSM) for nonlinear equations in Banach spaces, Communic. in Nonlinear Sci. and Numer. Simulation, 11, N3, (2006), 306­310. 1 #12; Dynamical systems method (DSM, KS 66506­2602, USA ramm@math.ksu.edu http://www.math.ksu.edu/#ramm Abstract The DSM (dynamical

418

A.G.Ramm, Dynamical systems method (DSM) for nonlinear equations in Banach spaces, Communic. in Nonlinear Sci. and Numer. Simulation, 11,  

E-Print Network [OSTI]

488 A.G.Ramm, Dynamical systems method (DSM) for nonlinear equations in Banach spaces, Communic. in Nonlinear Sci. and Numer. Simulation, 11, N3, (2006), 306-310. 1 #12;Dynamical systems method (DSM, KS 66506-2602, USA ramm@math.ksu.edu http://www.math.ksu.edu/ ramm Abstract The DSM (dynamical

419

Final technical report [ACCELERATED MOLECULAR DYNAMICS SIMULATIONS OF REACTIVE HYDROCARBON SYSTEMS  

SciTech Connect (OSTI)

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.

Stuart, Steven J.

2014-02-25T23:59:59.000Z

420

Investigation of Swirling Flow in Rod Bundle Subchannels Using Computational Fluid Dynamics  

SciTech Connect (OSTI)

The fluid dynamics for turbulent flow through rod bundles representative of those used in pressurized water reactors is examined using computational fluid dynamics (CFD). The rod bundles of the pressurized water reactor examined in this study consist of a square array of parallel rods that are held on a constant pitch by support grids spaced axially along the rod bundle. Split-vane pair support grids are often used to create swirling flow in the rod bundle in an effort to improve the heat transfer characteristics for the rod bundle during both normal operating conditions and in accident condition scenarios. Computational fluid dynamics simulations for a two subchannel portion of the rod bundle were used to model the flow downstream of a split-vane pair support grid. A high quality computational mesh was used to investigate the choice of turbulence model appropriate for the complex swirling flow in the rod bundle subchannels. Results document a central swirling flow structure in each of the subchannels downstream of the split-vane pairs. Strong lateral flows along the surface of the rods, as well as impingement regions of lateral flow on the rods are documented. In addition, regions of lateral flow separation and low axial velocity are documented next to the rods. Results of the CFD are compared to experimental particle image velocimetry (PIV) measurements documenting the lateral flow structures downstream of the split-vane pairs. Good agreement is found between the computational simulation and experimental measurements for locations close to the support grid. (authors)

Holloway, Mary V. [United States Naval Academy, 117 Decatur Road, Annapolis, MD 21402-5018 (United States); Beasley, Donald E. [Clemson University, Clemson, S.C. 29634 (United States); Conner, Michael E. [Westinghouse Nuclear Fuel (United States)

2006-07-01T23:59:59.000Z

Note: This page contains sample records for the topic "dynamics cfd simulations" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
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to obtain the most current and comprehensive results.


421

A CFD Model for High Pressure Liquid Poison Injection for CANDU-6 Shutdown System No. 2  

SciTech Connect (OSTI)

In CANDU reactor one of the two reactor shutdown systems is the liquid poison injection system which injects the highly pressurized liquid neutron poison into the moderator tank via small holes on the nozzle pipes. To ensure the safe shutdown of a reactor it is necessary for the poison curtains generated by jets provide quick, and enough negative reactivity to the reactor during the early stage of the accident. In order to produce the neutron cross section necessary to perform this work, the poison concentration distribution during the transient is necessary. In this study, a set of models for analyzing the transient poison concentration induced by this high pressure poison injection jet activated upon the reactor trip in a CANDU-6 reactor moderator tank has been developed and used to generate the poison concentration distribution of the poison curtains induced by the high pressure jets injected into the vacant region between the pressure tube banks. The poison injection rate through the jet holes drilled on the nozzle pipes is obtained by a 1-D transient hydrodynamic code called, ALITRIG, and this injection rate is used to provide the inlet boundary condition to a 3-D CFD model of the moderator tank based on CFX4.3, a CFD code, to simulate the formation of the poison jet curtain inside the moderator tank. For validation, an attempt was made to validate this model against a poison injection experiment performed at BARC. As conclusion this set of models is judged to be appropriate. (authors)

Bo Wook Rhee; Chang Jun Jeong [Korea Atomic Energy Research Institute, 150, Dukjin-Dong, Yusong-Gu, Taejon 305-353 (Korea, Republic of); Hye Jeong Yun; Dong Soon Jang [Choongnam National University, Daejeon 305-764 (Korea, Republic of)

2002-07-01T23:59:59.000Z

422

Molecular dynamics simulation study on surface structure and surface energy of anatase  

Science Journals Connector (OSTI)

Molecular dynamics simulations were performed to investigate the relaxed structures and surface energies of perfect and pit anatase TiO2 surfaces. It is shown that the slab containing more than two unit-cell layers away from the fixed layer expresses the surface characteristics of perfect anatase TiO2 (1?0?1) and (1?0?0) surfaces well, while the slab containing more than one unit-cell layer away from the fixed layer expresses the surface characteristics of the (0?0?1) surface well. Their surface energies follow the sequence (0?0?1) ] and [0?1?0] directions, and the changes in their surface energies are less than 0.05?J?m?2, while the surface energies increase sharply with the increase in pit depth within 1?nm. Therefore, for anatase (1?0?1) surface, in order to obtain a higher surface energy, one may increase the pit sizes, particularly along the [1?0?1] direction.

Dai-Ping Song; Ming-Jun Chen; Ying-Chun Liang; Chun-Ya Wu; Zhi-Jiang Xie; Qing-Shun Bai

2010-01-01T23:59:59.000Z

423

Molecular dynamics simulations of the melting curve of NiAl alloy under pressure  

SciTech Connect (OSTI)

The melting curve of B2-NiAl alloy under pressure has been investigated using molecular dynamics technique and the embedded atom method (EAM) potential. The melting temperatures were determined with two approaches, the one-phase and the two-phase methods. The first one simulates a homogeneous melting, while the second one involves a heterogeneous melting of materials. Both approaches reduce the superheating effectively and their results are close to each other at the applied pressures. By fitting the well-known Simon equation to our melting data, we yielded the melting curves for NiAl: 1783(1 + P/9.801){sup 0.298} (one-phase approach), 1850(1 + P/12.806){sup 0.357} (two-phase approach). The good agreement of the resulting equation of states and the zero-pressure melting point (calc., 1850 ± 25 K, exp., 1911 K) with experiment proved the correctness of these results. These melting data complemented the absence of experimental high-pressure melting of NiAl. To check the transferability of this EAM potential, we have also predicted the melting curves of pure nickel and pure aluminum. Results show the calculated melting point of Nickel agrees well with experiment at zero pressure, while the melting point of aluminum is slightly higher than experiment.

Zhang, Wenjin; Peng, Yufeng [College of Physics and electronic Engineering, Henan Normal University, Xinxiang, 453007 (China)] [College of Physics and electronic Engineering, Henan Normal University, Xinxiang, 453007 (China); Liu, Zhongli, E-mail: zhongliliu@yeah.net [College of Physics and Electric Information, Luoyang Normal University, Luoyang, 471002 (China)] [College of Physics and Electric Information, Luoyang Normal University, Luoyang, 471002 (China)

2014-05-15T23:59:59.000Z

424

A comparative study of Lotka-Volterra and system dynamics models for simulation of technology industry dynamics  

E-Print Network [OSTI]

Scholars have developed a range of qualitative and quantitative models for generalizing the dynamics of technological innovation and identifying patterns of competition between rivals. This thesis compares two predominant ...

Ünver, Hakk? Özgür

2008-01-01T23:59:59.000Z

425

Dynamical simulation of energy dissipation in asymmetric heavy-ion induced fission of Pb200, Fr213, and Es251  

Science Journals Connector (OSTI)

The dynamical model based on the asymmetric mass division has been applied to calculate pre-scission neutron multiplicity from heavy-ion induced fusion-fission reactions. Links between the pre-scission neutron multiplicity, excitation energy, and asymmetric mass distribution are clarified based on the Monte Carlo simulation and Langevin dynamics. The pre-scission neutron multiplicity is calculated and compared with the respective experimental data over a wide range of excitation energy and nonconstant viscosity. The analysis indicates a different effect for the application of asymmetric mass division in different energy regions of such processes.

S. M. Mirfathi and M. R. Pahlavani

2008-12-29T23:59:59.000Z

426

A study of local and extended migration of H and defects in a-Si by molecular dynamics simulations  

SciTech Connect (OSTI)

The author reports on extensive molecular dynamics (MD) simulations on a-Si:H for up to 5 Ps using the ab initio code of Sankey and Drabold. The supercells contain about 70 atoms and only one defect in order to minimize defect-defect interaction. Simulations on supercell samples that originally contain one bond centered (BC) H in an otherwise defect free sample exhibit BC to BC diffusion as in c-Si. However, the author also observed localized motion of defects and H atoms on a very fast time scale that probably has been observed in several experiments.

Fedders, P.A. [Washington Univ., St. Louis, MO (United States). Dept. of Physics

1996-12-31T23:59:59.000Z

427

Computational Fluid Dynamics Analysis of Very High Temperature Gas-Cooled Reactor Cavity Cooling System  

SciTech Connect (OSTI)

The design of passive heat removal systems is one of the main concerns for the modular very high temperature gas-cooled reactors (VHTR) vessel cavity. The reactor cavity cooling system (RCCS) is a key heat removal system during normal and off-normal conditions. The design and validation of the RCCS is necessary to demonstrate that VHTRs can survive to the postulated accidents. The computational fluid dynamics (CFD) STAR-CCM+/V3.06.006 code was used for three-dimensional system modeling and analysis of the RCCS. A CFD model was developed to analyze heat exchange in the RCCS. The model incorporates a 180-deg section resembling the VHTR RCCS experimentally reproduced in a laboratory-scale test facility at Texas A&M University. All the key features of the experimental facility were taken into account during the numerical simulations. The objective of the present work was to benchmark CFD tools against experimental data addressing the behavior of the RCCS following accident conditions. Two cooling fluids (i.e., water and air) were considered to test the capability of maintaining the RCCS concrete walls' temperature below design limits. Different temperature profiles at the reactor pressure vessel (RPV) wall obtained from the experimental facility were used as boundary conditions in the numerical analyses to simulate VHTR transient evolution during accident scenarios. Mesh convergence was achieved with an intensive parametric study of the two different cooling configurations and selected boundary conditions. To test the effect of turbulence modeling on the RCCS heat exchange, predictions using several different turbulence models and near-wall treatments were evaluated and compared. The comparison among the different turbulence models analyzed showed satisfactory agreement for the temperature distribution inside the RCCS cavity medium and at the standpipes walls. For such a complicated geometry and flow conditions, the tested turbulence models demonstrated that the realizable k-epsilon model with two-layer all y+ wall treatment performs better than the other k-epsilon and k-omega turbulence models when compared to the experimental results and the Reynolds stress transport turbulence model results. A scaling analysis was developed to address the distortions introduced by the CFD model in simulating the physical phenomena inside the RCCS system with respect to the full plant configuration. The scaling analysis demonstrated that both the experimental facility and the CFD model achieve a satisfactory resemblance of the main flow characteristics inside the RCCS cavity region, and convection and radiation heat exchange phenomena are properly scaled from the actual plant.

Angelo Frisani; Yassin A. Hassan; Victor M. Ugaz

2010-11-02T23:59:59.000Z

428

Utilization of computational fluid dynamics technique in low NOx burner/furnace retrofits  

SciTech Connect (OSTI)

A computational fluid dynamics (CFD) technique has been utilized to provide design guidance for retrofitting low NOx combustion systems and incorporating associated furnace modifications into existing utility boilers. The CFD program utilized is FW-FIRES (Fossil fuel, Water-walled Furnace Integrated Reaction and Emission Simulation) which simulates furnace combustion, heat transfer and pollutant formation based on fundamental principals of mass, momentum and energy conservations. The program models the gas flow field as a three-dimensional turbulent reacting continuum and the particle flow as a series of discrete particle trajectories through the gas continuum. Chemical reaction, heat transfer, and pollutant formation mechanisms are incorporated in the program. FW-FIRES furnace simulation of low NOx combustion system retrofits has been performed for various furnace configurations including front wall-fired, front and real wall-fired, and tangentially-fired furnaces, to determine the effects of burner/furnace modifications on the NOx emission, furnace exit gas temperature, furnace heat absorption, unburned carbon, and furnace wall corrosion. For front wall-fired, and front and real wall-fired furnaces, the NOx emission requirement is met by the use of Foster Wheeler lox NOx burners and overfire air (OFA) staging. Studies of burner and OFA quantify and spacing are conducted to limit NOx emission and unburned carbon to acceptable levels. A major concern in once-through supercritical units with OFA is furnace wall corrosion which is caused by high furnace wall metal temperature and corrosive hydrogen sulfide (H{sub 2}S) created in a reducing atmosphere from part of coal sulfur. The FW-FIRES code is used to minimize this corrosion potential by selecting the proper location and quantity of boundary air. A simulation of tangentially-fired unit, which has been retrofitted with low NOx burners, is used to study the effect of the burner tilt on the furnace exit gas temperature. This paper details the basis and results of several CFD analyses conducted for potential retrofit programs.

Cho, S.M.; Seltzer, A.H.; Ma, J.; Steitz, T.H.; Grusha, J.; Cole, R.W.

1999-07-01T23:59:59.000Z

429

Simulation of hydrology and population dynamics of Anopheles mosquitoes around the Koka Reservoir in Ethiopia  

E-Print Network [OSTI]

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 ...

Endo, Noriko S.M. Massachusetts Institute of Technology

2014-01-01T23:59:59.000Z

430

The Trp Cage: Folding Kinetics and Unfolded State Topology via Molecular Dynamics Simulations  

E-Print Network [OSTI]

, ) 91 ps-1). The Folding@Home distributed computing project was used to generate an aggregate simulation

Snow, Christopher

431

CFD modelling of thermal distribution in industrial server centres for configuration optimisation and energy efficiency  

Science Journals Connector (OSTI)

The use of servers for computational and communication control tasks is becoming more and more frequent in industries and institutions. Ever increasing computational power and data storage combined with reduction in chipsets size resulted in the increased heat density and need for proper configurations of the server racks to enhance cooling and energy efficiency. While different methods can be used to model and design new server centres and optimise their configuration, there is no clear guideline in the literature on the best way to design them and how to increase energy efficiency of existing server centres. This paper presents a simplified yet reliable computational fluid dynamics (CFD) model used to qualitatively evaluate different cooling solutions of a data centre and proposes guidelines to improve its energy efficiency. The influence of different parameters and configurations on the cooling load of the server room is then analysed.

Pierre-Luc Paradis; Drishtysingh Ramdenee; Adrian Ilinca; Hussein Ibrahim

2014-01-01T23:59:59.000Z

432

Process/equipment co-simulation for designe and analysis of advanced energy systems  

SciTech Connect (OSTI)

b s t r a c t The grand challenge facing the power and energy industries is the development of efficient, environmentally friendly, and affordable technologies for next-generation energy systems. To provide solutions for energy and the environment, the U.S. Department of Energy’s (DOE) National Energy Technology Laboratory (NETL) and its research partners in industry and academia are relying increasingly on the use of sophisticated computer-aided process design and optimization tools. In this paper, we describe recent progress toward developing an Advanced Process Engineering Co-Simulator (APECS) for the high-fidelity design, analysis, and optimization of energy plants. The APECS software system combines steady-state process simulation with multiphysics-based equipment simulations, such as those based on computational fluid dynamics (CFD). These co-simulation capabilities enable design engineers to optimize overall process performance with respect to complex thermal and fluid flow phenomena arising in key plant equipment items, such as combustors, gasifiers, turbines, and carbon capture devices. In this paper we review several applications of the APECS co-simulation technology to advanced energy systems, including coal-fired energy plants with carbon capture. This paper also discusses ongoing co-simulation R&D activities and challenges in areas such as CFD-based reduced-order modeling, knowledge management, advanced analysis and optimization, and virtual plant co-simulation. Continued progress in co-simulation technology – through improved integration, solution, and deployment – will have profound positive impacts on the design and optimization of high-efficiency, near-zero emission fossil energy systems.

Zitney, S.

2010-01-01T23:59:59.000Z

433

Thermal Comfort under Transient Metabolic and Dynamic Localized Airflow Conditions Combined with Neutral and Warm Ambient Temperatures  

E-Print Network [OSTI]

9.2 The mixing ventilation case of the CFD simulation (Nielsen, 2003) .................... 185 9.3 The displacement ventilation case of the CFD simulation (Nielsen, 2003) .......... 185 9.4 Computer simulated persons (CSPs) that were used...-axis ......................................................................... 189 9.9 The cross section of the displacement ventilation case and the data probes (Nielsen, 2003) ...................................................................................................... 190 9.10 Human geometry and the simulation...

Ugursal, Ahmet

2012-02-14T23:59:59.000Z

434

Case study: visual analysis of complex, time-dependent simulation results of a diesel exhaust system  

Science Journals Connector (OSTI)

In previous work we have presented visualization techniques that provide engineers with a high degree of interactivity and flexibility for analyzing large, time-dependent, and high-dimensional data sets resulting from CFD (computational fluid dynamics) ...

Helmut Doleisch; Michael Mayer; Martin Gasser; Roland Wanker; Helwig Hauser

2004-05-01T23:59:59.000Z

435

Investigation of Protein Folding by Using Combined Method of Molecular Dynamics and Monte Carlo Simulations.  

E-Print Network [OSTI]

??We used the combination of molecular dynamics and Monte Carlo method to investigate protein folding problems. The environments of proteins are very big, and often… (more)

Liao, Jun-min

2006-01-01T23:59:59.000Z

436

User Guide for PV Dynamic Model Simulation Written on PSCAD Platform  

SciTech Connect (OSTI)

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.

Muljadi, E.; Singh, M.; Gevorgian, V.

2014-11-01T23:59:59.000Z

437

Development of a ReaxFF Reactive Force Field for Ettringite and Study of its Mechanical Failure Modes from Reactive Dynamics Simulations  

Science Journals Connector (OSTI)

Development of a ReaxFF Reactive Force Field for Ettringite and Study of its Mechanical Failure Modes from Reactive Dynamics Simulations ... Ettringite is a hexacalcium aluminate trisulfate hydrate mineral that forms during Portland cement hydration. ... Here, we report on the development of this ReaxFF force field and on its validation and application using reactive molecular dynamics (RMD) simulations to characterize and understand the elastic, plastic, and failure response of ettringite at the atomic scale. ...

Lianchi Liu; Andres Jaramillo-Botero; William A. Goddard; III; Huai Sun

2012-03-13T23:59:59.000Z

438

NREL Evaluates the Thermal Performance of Uninsulated Walls to Improve the Accuracy of Building Energy Simulation Tools (Fact Sheet)  

SciTech Connect (OSTI)

This technical highlight describes NREL research to develop models of uninsulated wall assemblies that help to improve the accuracy of building energy simulation tools when modeling potential energy savings in older homes. Researchers at the National Renewable Energy Laboratory (NREL) have developed models for evaluating the thermal performance of walls in existing homes that will improve the accuracy of building energy simulation tools when predicting potential energy savings of existing homes. Uninsulated walls are typical in older homes where the wall cavities were not insulated during construction or where the insulating material has settled. Accurate calculation of heat transfer through building enclosures will help determine the benefit of energy efficiency upgrades in order to reduce energy consumption in older American homes. NREL performed detailed computational fluid dynamics (CFD) analysis to quantify the energy loss/gain through the walls and to visualize different airflow regimes within the uninsulated cavities. The effects of ambient outdoor temperature, radiative properties of building materials, and insulation level were investigated. The study showed that multi-dimensional airflows occur in walls with uninsulated cavities and that the thermal resistance is a function of the outdoor temperature - an effect not accounted for in existing building energy simulation tools. The study quantified the difference between CFD prediction and the approach currently used in building energy simulation tools over a wide range of conditions. For example, researchers found that CFD predicted lower heating loads and slightly higher cooling loads. Implementation of CFD results into building energy simulation tools such as DOE2 and EnergyPlus will likely reduce the predicted heating load of homes. Researchers also determined that a small air gap in a partially insulated cavity can lead to a significant reduction in thermal resistance. For instance, a 4-in. tall air gap (Figure 1a) led to a 15% reduction in resistance. Similarly, a 2-ft tall air gap (Figure 1c) led to 54% reduction in thermal resistance. NREL researchers plan to extend this study to include additional wall configurations, and also to evaluate the performance of attic spaces with different insulation levels. NREL's objective is to address each potential issue that leads to inaccuracies in building energy simulation tools to improve the predictions.

Not Available

2012-01-01T23:59:59.000Z

439

Parallel processing with the Wind CFD code at Boeing  

Science Journals Connector (OSTI)

Wind is a general purpose CFD code capable of either Euler or Navier–Stokes analysis (R.H. Bush, A Three Dimensional Zonal Navier–Stokes Code for Subsonic through Hypersonic Propulsion Flowfields, AIAA 88-2380, 11 July 1998; R.H. Bush, G.D. Power, The Wind Production Flow Solver For the NPARC Alliance, AIAA 98-0935, 12 January 1998). The Wind code and its predecessor NASTD have been used for CFD applications, using its parallel mode, at Boeing since 1993. The Wind code is currently developed and distributed by the NPARC alliance. For more information see the NPARC web site at http://www.lerc.nasa.gov/www/winddocs/.

M.S Fisher; M Mani; D Stookesberry

2001-01-01T23:59:59.000Z

440

Three-dimensional simulation of combustion processes in coke-battery furnace chambers  

Science Journals Connector (OSTI)

A three-dimensional model of the heating wall in a coke battery is developed by means of the Fluent CFD program. The results of simulation are in satisfactory agreement with experimental data. The mathematical...

M. V. Isaev; I. A. Sultanguzin

2010-08-01T23:59:59.000Z

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441

Molecular dynamics simulation of phosphorylation-induced conformational transitions in the mycobacterium tuberculosis response regulator PrrA  

SciTech Connect (OSTI)

Phosphorylation-activated modulation of response regulators (RR) is predominantly used by bacteria as a strategy in regulating their two-component signaling (TCS) systems, the underlying molecular mechanisms are however far from fully understood. In this work we have conducted a molecular dynamics (MD) simulation of the phosphorylation-induced conformational transitions of RRs with the Mycobacterium Tuberculosis PrrA as a particular example. Starting from the full-length inactive structure of PrrA we introduced a local disturbance by phosphorylating the conserved aspartic acid residue, Asp-58, in the regulatory domain. A Go-model-type algorithm packaged with AMBER force fields was then applied to simulate the dynamics upon phosphorylation. The MD simulation shows that the phosphorylation of Asp-58 facilitates PrrA, whose inactive state has a compact conformation with a closed interdomain interface, to open up with its interdomain separation being increased by an average of about 1.5 {angstrom} for a simulation of 20 ns. The trans-activation loop, which is completely buried within the interdomain interface in the inactive PrrA, is found to become more exposed with the phosphorylated structure as well. These results provide more structural details of how the phosphorylation of a local aspartate activates PrrA to undergo a global conformational rearrangement toward its extended active state. This work also indicates that MD simulations can serve as a fast tool to unravel the regulation mechanisms of all RRs, which is especially valuable when the structures of full-length active RRs are currently unavailable.

Chen, Guo [Los Alamos National Laboratory; Mcmahon, Benjamin H [Los Alamos National Laboratory; Tung, Chang - Shung [Los Alamos National Laboratory

2008-01-01T23:59:59.000Z

442

Combining technology roadmap and system dynamics simulation to support scenario-planning: A case of car-sharing service  

Science Journals Connector (OSTI)

Abstract Due to the volatile market environment, the use of scenario approach comes to the forefront in business strategy. As a means of scenario planning, several approaches have been proposed and conducted. However, previous research, mainly having resorted to the expert judgment for planning and evaluation, still remains conceptual and lacks a systematic link to the planning process. In response, this paper provides an integrative approach to the technology roadmap and system dynamics to support scenario planning. The proposed approach consists of three parts: scenario building, technology roadmapping, and system dynamics simulation. The first step is to construct the scenarios which are used as inputs for the scenario planning. Second, technology roadmap is developed, incorporating the scenarios built in the first step. The technology roadmap works as a strategic framework to realize the hypothetical scenarios, linking the external and hypothetical business and internal strategies. Finally, the strategic model for technology roadmap is transferred to the operational viewpoint using system dynamics. When the simulation ends, the result of each scenario is reflected to the technology roadmapping, making the multi-path technology roadmapping. As an illustrative example, three scenarios of car-sharing business are developed and analyzed.

Youngjung Geum; Sora Lee; Yongtae Park

2014-01-01T23:59:59.000Z

443

Comparison of four models simulating phosphorus dynamics in LakeVnern,Sweden Hydrology and Earth System Sciences, 8(6), 11531163 (2004) EGU  

E-Print Network [OSTI]

Comparison of four models simulating phosphorus dynamics in LakeVänern,Sweden 1153 Hydrology dynamics in Lake Vänern, Sweden Magnus Dahl1 and B. Charlotta Pers2 1 Department of Chemical Engineering, Karlstad University, SE651 88 Karlstad, Sweden 2 Swedish Meteorological and Hydrological Institute, SE601

Paris-Sud XI, Université de

444

Automating Dynamic Decoupling in Object-Oriented Modelling and Simulation Tools  

E-Print Network [OSTI]

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

Como, Giacomo

445

3D CFD Model of High Temperature H2O/CO2 Co-electrolysis  

SciTech Connect (OSTI)

3D CFD Model of High Temperature H2O/CO2 Co-Electrolysis Grant Hawkes1, James O’Brien1, Carl Stoots1, Stephen Herring1 Joe Hartvigsen2 1 Idaho National Laboratory, Idaho Falls, Idaho, grant.hawkes@inl.gov 2 Ceramatec Inc, Salt Lake City, Utah INTRODUCTION A three-dimensional computational fluid dynamics (CFD) model has been created to model high temperature co-electrolysis of steam and carbon dioxide in a planar solid oxide electrolyzer (SOE) using solid oxide fuel cell technology. A research program is under way at the Idaho National Laboratory (INL) to simultaneously address the research and scale-up issues associated with the implementation of planar solid-oxide electrolysis cell technology for syn-gas production from CO2 and steam. Various runs have been performed under different run conditions to help assess the performance of the SOE. This paper presents CFD results of this model compared with experimental results. The Idaho National Laboratory (INL), in conjunction with Ceramatec Inc. (Salt Lake City, USA) has been researching for several years the use of solid-oxide fuel cell technology to electrolyze steam for large-scale nuclear-powered hydrogen production. Now, an experimental research project is underway at the INL to produce syngas by simultaneously electrolyzing at high-temperature steam and carbon dioxide (CO2) using solid oxide fuel cell technology. A strong interest exists in the large-scale production of syn-gas from CO2 and steam to be reformed into a usable transportation fuel. If biomass is used as the carbon source, the overall process is climate neutral. Consequently, there is a high level of interest in production of syn-gas from CO2 and steam electrolysis. With the price of oil currently around $60 / barrel, synthetically-derived hydrocarbon fuels (synfuels) have become economical. Synfuels are typically produced from syngas – hydrogen (H2) and carbon monoxide (CO) -- using the Fischer-Tropsch process, discovered by Germany before World War II. High-temperature nuclear reactors have the potential for substantially increasing the efficiency of syn-gas production from CO2 and water, with no consumption of fossil fuels, and no production of greenhouse gases. Thermal CO2-splitting and water splitting for syn-gas production can be accomplished via high-temperature electrolysis, using high-temperature nuclear process heat and electricity. A high-temperature advanced nuclear reactor coupled with a high-efficiency high-temperature electrolyzer could achieve a competitive thermal-to-syn-gas conversion efficiency of 45 to 55%.

Grant Hawkes; James O'Brien; Carl Stoots; Stephen Herring; Joe Hartvigsen

2007-06-01T23:59:59.000Z

446

Early maturation processes in coal. Part 2: Reactive dynamics simulations using the ReaxFF reactive force field on Morwell Brown coal structures  

E-Print Network [OSTI]

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

Goddard III, William A.

447

WAKE-FIELDS AND BEAM DYNAMICS SIMULATIONS C.J. Glasman & R.M. Jones; Cockcroft Institute, Daresbury, WA4 4AD, UK;  

E-Print Network [OSTI]

/m and is known as the baseline configura- tion document (BCD). However, here we investigate the electromagnetic simulated in detail using paral- lel finite difference and finite element codes [7, 8] and this data has been used as input for beam dynamics simulations, using the code LIAR [9], which tracks multi

448

Anharmonic lattice dynamics of Ag2O studied by inelastic neutron scattering and first-principles molecular dynamics simulations  

SciTech Connect (OSTI)

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.

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

449

Dusts resuspension Test in the STARDUST Facility: Experimental and CFD Analysis.  

E-Print Network [OSTI]

??This thesis is related to the application of the CFD FLUENT code to the dust resuspension tests performed inside the STARDUST (Small Tank for Aerosol… (more)

FREDIANI, FRANCESCO

2009-01-01T23:59:59.000Z

450

A new shared-memory programming paradigm for molecular dynamics simulations on the Intel Paragon  

SciTech Connect (OSTI)

This report describes the use of shared memory emulation with DOLIB (Distributed Object Library) to simplify parallel programming on the Intel Paragon. A molecular dynamics application is used as an example to illustrate the use of the DOLIB shared memory library. SOTON-PAR, a parallel molecular dynamics code with explicit message-passing using a Lennard-Jones 6-12 potential, is rewritten using DOLIB primitives. The resulting code has no explicit message primitives and resembles a serial code. The new code can perform dynamic load balancing and achieves better performance than the original parallel code with explicit message-passing.

D`Azevedo, E.F.; Romine, C.H.

1994-12-01T23:59:59.000Z

451

3D CFD ELECTROCHEMICAL AND HEAT TRANSFER MODEL OF AN INTERNALLY MANIFOLDED SOLID OXIDE ELECTROLYSIS CELL  

SciTech Connect (OSTI)

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.

Grant L. Hawkes; James E. O'Brien; Greg Tao

2011-11-01T23:59:59.000Z

452

Computational Fluid Dynamics Simulations of Raw Gas Composition from a Black Liquor Gasifier—Comparison with Experiments  

Science Journals Connector (OSTI)

Computational Fluid Dynamics Simulations of Raw Gas Composition from a Black Liquor Gasifier—Comparison with Experiments ... The black liquor spray was represented by 1003 discrete particles having a fitted Rosin Rammler distribution of power 2 and a characteristic size of 200 ?m. ... Additional PFR calculations were performed using different inlet gas compositions with similar results (not presented here), i.e. the Jones and Lindstedt model showed a significantly higher reformation rate of methane than GRI-Mech at gasification conditions in the medium temperature range (1150 < T < 1500 K). ...

Per Carlsson; Kristiina Iisa; Rikard Gebart

2011-07-05T23:59:59.000Z

453

Comparison of the Properties of Xenon, Methane, and Carbon Dioxide Hydrates from Equilibrium and Nonequilibrium Molecular Dynamics Simulations  

Science Journals Connector (OSTI)

Comparison of the Properties of Xenon, Methane, and Carbon Dioxide Hydrates from Equilibrium and Nonequilibrium Molecular Dynamics Simulations† ... The VACFs of all three guests in the small cages oscillate between positive and negative values with the oscillation being damped out with increasing time. ... The oscillations are damped much more strongly for CO2 hydrate than for the Xe or methane hydrates, indicating that the coupling between the rattling motions of the encaged guest molecules and the vibrational motions of the host lattice is strongest for CO2 hydrate. ...

H. Jiang; K. D. Jordan

2009-11-11T23:59:59.000Z

454

Computational fluid dynamics modelling and experimental study on a single silica gel type B  

Science Journals Connector (OSTI)

The application of computational fluid dynamics (CFDs) in the area of porous media and adsorption cooling system is becoming more practical due to the significant improvement in computer power. The results from previous studies have shown that CFD can ...

John White

2012-01-01T23:59:59.000Z

455

Optimization of a simplified sub-model for NO emission prediction by CFD in large 4-stroke marine diesel engines  

Science Journals Connector (OSTI)

A simplified sub-model for NO emission prediction at pressurized conditions has been put forth at Åbo Akademi University [7,9] including NO formation via the thermal NO path (3 reactions) and via the nitrous oxide intermediate paths (2 + 5 reactions). CFD simulations carried out with the sub-model for marine and off-road diesel engines showed, however, that it significantly – by an order of magnitude – over-predicted NO emission as compared to measurements. The objective of this work was to find the reasons to the discrepancy and to suggest and incorporate improvements. By detailed investigations, a number of programming technical errors and chemical kinetic shortcomings were identified. The improved sub-model and its sub-parts were then tested for CFD simulation of a medium-speed, four-stroke, direct-injection marine diesel engine for different loads and fuels. The importance of NO reduction by soot and hydrocarbons was also investigated. All the sub-models correctly predicted the trend of increasing NO emission with increasing load. In absolute amounts, NO emission was over-predicted by a factor of 2 to 4, if no fitting of rate constants was allowed. Including NO reduction by soot and hydrocarbons, decreased NO emission by ca 4–25% for the cases studied.

Pia Kilpinen

2010-01-01T23:59:59.000Z