Engineering and Scientific Software Inc.

Rio Rancho, NM, United States

Engineering and Scientific Software Inc.

Rio Rancho, NM, United States

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Xiao J.,Karlsruhe Institute of Technology | Travis J.R.,Engineering and Scientific Software Inc. | Royl P.,Karlsruhe Institute of Technology | Necker G.,Karlsruhe Institute of Technology | And 2 more authors.
Nuclear Engineering and Design | Year: 2016

GASFLOW is a three dimensional semi-implicit all-speed CFD code which can be used to predict fluid dynamics, chemical kinetics, heat and mass transfer, aerosol transportation and other related phenomena involved in postulated accidents in nuclear reactor containments. The main purpose of the paper is to give a brief review on recent GASFLOW code development, validations and applications in the field of nuclear safety. GASFLOW code has been well validated by international experimental benchmarks, and has been widely applied to hydrogen safety analysis in various types of nuclear power plants in European and Asian countries, which have been summarized in this paper. Furthermore, four benchmark tests of a lid-driven cavity flow, low Mach number jet flow, 1-D shock tube and supersonic flow over a forward-facing step are presented in order to demonstrate the accuracy and wide-ranging capability of ICE'd ALE solution algorithm for all-speed flows. GASFLOW has been successfully parallelized using the paradigms of Message Passing Interface (MPI) and domain decomposition. The parallel version, GASFLOW-MPI, adds great value to large scale containment simulations by enabling high-fidelity models, including more geometric details and more complex physics. It will be helpful for the nuclear safety engineers to better understand the hydrogen safety related physical phenomena during the severe accident, to optimize the design of the hydrogen risk mitigation systems and to fulfill the licensing requirements by the nuclear regulatory authorities. GASFLOW-MPI is targeting a high performance, efficient, robust, well verified and validated all-speed CFD code for safety analysis of nuclear reactor containments and other large scale conventional industrial applications. © 2016 Elsevier B.V. All rights reserved.


Travis J.R.,Engineering and Scientific Software Inc. | Piccioni Koch D.,Karlsruhe Institute of Technology
International Journal of Hydrogen Energy | Year: 2014

The Computational Fluid Dynamic (CFD) code GASFLOW was used to simulate a Bonfire test for studying the safety performance of high-pressure hydrogen vessels for vehicular storage applications. A thermal loading model representing the azimuthal temperature dependency of the internal gas was implemented in the simulation code GASFLOW and is described in details in this paper. The GASFLOW simulations show good agreement with previous simulation results and with data. © 2014 Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.


Xiao J.,Karlsruhe Institute of Technology | Travis J.R.,Engineering and Scientific Software Inc. | Kuznetsov M.,Karlsruhe Institute of Technology
International Journal of Hydrogen Energy | Year: 2015

In hydrogen safety analysis, structure response due to the pressure and thermal loads from the combustion is of great concern. It is of high significance to understand not only the combustion process itself, but also the heat losses from the combustion products to the solid structures which may have strong impacts on the pressure and temperature decays. In many previous numerical simulations, heat losses from turbulent hydrogen flames to the confinement structures were usually considered to be negligible or less important. However, it has been revealed by many experimental studies that modeling of heat losses from the combustion products is important for accurate predictions. Our objectives are to study the importance of various heat transfer mechanisms and their relative contributions to the total energy losses. Numerical investigations on the mechanisms of heat losses caused by propagating turbulent flames were performed using a semi-implicit pressure-based all-speed CFD code GASFLOW-MPI. Heat losses from turbulent sonic flames to the structures of the ENACCEF facility at IRSN were studied. It appears that the effect of heat losses on the flame propagation properties is not significant. However, the impacts of heat losses on the pressure peak and pressure decay after hydrogen combustions should not be neglected. It indicates from our simulation results that the convective heat transfer and thermal radiative heat transfer are the main contributors of the total energy losses to the structures of ENACCEF. In our cases, the effect of steam condensation heat transfer is relatively small but not negligible. The relative contributions of various heat transfer mechanisms could be different in other experimental facilities with various geometrical configurations, various internal structures, and various optical and thermal characteristics of the burnable gas mixtures. In general, it is suggested to include the heat transfer mechanisms in order to improve the reliability and accuracy of numerical analyses of hydrogen safety issues. © 2015 Hydrogen Energy Publications, LLC.


Travis J.R.,Engineering and Scientific Software Inc. | Piccioni Koch D.,Karlsruhe Institute of Technology | Breitung W.,Simaps GmbH
International Journal of Hydrogen Energy | Year: 2012

A non-equilibrium two-phase single-component critical (choked) flow model for cryogenic fluids is developed from first principle thermodynamics. Modern equations-of-state (EOS) based upon the Helmholtz free energy concepts are incorporated into the methodology. Extensive validation of the model is provided with the NASA cryogenic data tabulated for hydrogen, methane, nitrogen, and oxygen critical flow experiments performed with four different nozzles. The model is used to develop a hydrogen critical flow map for stagnation states in the liquid and supercritical regions. Copyright © 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights.


Travis J.R.,Engineering and Scientific Software Inc. | Piccioni Koch D.,Karlsruhe Institute of Technology | Xiao J.,Karlsruhe Institute of Technology | Xu Z.,Karlsruhe Institute of Technology
International Journal of Hydrogen Energy | Year: 2013

GASFLOW is a finite-volume computer code that solves the time-dependent, two-phase homogeneous equilibrium model, compressible Navier-Stokes equations for multiple gas species with turbulence. The fluid-dynamics algorithm is coupled with conjugate heat and mass transfer models to represent walls, floors, ceilings, and other internal structures to describe complex geometries, such as those found in nuclear containments and facilities. Recent applications involve simulations of cryogenic hydrogen tanks at elevated pressures. These applications, which often have thermodynamic conditions near the critical point, require more accurate real-gas Equations-of-State (EoS) and transport properties than the standard ideal gas EoS and classical kinetic-theory transport properties. This paper describes the rigorous implementation of the generalized real-gas EoS into the GASFLOW CFD code, as well as the specific implementation of respective real-gas models (Leachman's NIST hydrogen EoS, a modified van der Waals EoS and a modified Nobel-Abel EoS); it also includes a logical testing procedure based upon a numerically exact benchmark problem. An example of GASFLOW simulations is presented for an ideal cryo-compressed hydrogen tank of the type utilized in fuel cell vehicles. © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights.


Xiao J.,Karlsruhe Institute of Technology | Travis J.R.,Engineering and Scientific Software Inc. | Redlinger R.,Karlsruhe Institute of Technology | Kuznetsov M.,Karlsruhe Institute of Technology | And 3 more authors.
International Topical Meeting on Nuclear Reactor Thermal Hydraulics 2015, NURETH 2015 | Year: 2015

It is well known that the risk of hydrogen combustion has become one of the key safety issues for the further evolution of nuclear power plants (NPP) especially after energetic hydrogen explosions occurred at units No. 1, No. 3 and No. 4 in the Fukushima Daiichi nuclear disaster in 2011. Complex physics phenomena are involved in NPP containments during a postulated severe accident. such as steam condensation and evaporation, heat conduction in solid structures, convective heat transfer, radiation heat transfer, turbulent flow, flashing of water, behavior of spray droplets, draining water film, hydrogen deflagration and detonation, hydrogen mitigation measures, aerosol and fission product behavior and so on. A high performance fully validated best-estimate tool is highly desired to accurately predict these phenomena in complex accident sequences GASFLOW-MPI solves 3-D transient, two-phase, compressible Navier-Stokes equations for multi-species using a proven algorithm of Implicit Continuous Eulerian-Arbitrary Lagrangian-Eulerian (ICE'd-ALE) methodology for all-speed flows. The objective is to achieve seamless comprehensive simulations of major physics phenomena in the containment using the high-performance, scalable CFD code GASFLOW-MPI. The code has heen applied to SARNET 2 hydrogen fast deflagration experimental data from the ENACCEF facility. The effects of blockage ratio, diluents, steam condensation, convective and radiation heat transfer were studied. It indicates that flame propagation of the deflagration, pressure increase rates and peak pressures in the obstructed tube can be well predicted by GASFLOW-MPI. Further validation work will be performed for the recently extended combustion models and conjugate heat transfer models in the GASFLOW-MPI code in the future.


Xiao J.,Karlsruhe Institute of Technology | Travis J.R.,Engineering and Scientific Software Inc.
Annals of Nuclear Energy | Year: 2013

Uncontrolled hydrogen combustion can occur in the nuclear reactor containment during a severe accident. The energetic hydrogen combustion may threaten the integrity of the containment and lead to radioactive material being released into the environment. In order to mitigate the risk of hydrogen combustion, the first step is to understand how the burnable hydrogen cloud develops in the containment. Turbulence modeling is one of the key elements in simulations of the physical phenomena that occur in containment. However, when a turbulence model is used, the computational time is increased in CFD simulations of large-scale reactor containment primarily due to the additional turbulent transport equations and the small time step controlled by the explicitly-treated turbulent diffusion in GASFLOW code. The purpose of this paper is to investigate how critical turbulence modeling is in the simulation of hydrogen/steam distribution in a large-scale, complex reactor containment. In other words, is it acceptable to neglect the turbulent viscosity in the momentum diffusion term in such a large-scale engineering simulation to save computational time? The effect of turbulence models on the gas distribution in the MISTRA 2009 campaign was investigated using the CFD code, GASFLOW. The calculation results improved locally in the region near the jet source when turbulence models were used. For most of the space in the MISTRA facility, which is located away from the source, it seems that the turbulent diffusion was over-predicted by the turbulence models, and better agreements with the experimental data were obtained by simply using molecular viscosity. These results indicate that with turbulence models, more computational time is required, and the improved calculation results are local and limited. It appears that the predictions are reasonably good when only molecular viscosity is considered in the diffusion terms. Due to the limited computational resources, we must investigate the trade-offs between computational effort and accuracy, particularly in large-scale engineering applications. © 2013 Elsevier Ltd. All rights reserved.


Travis J.R.,Engineering and Scientific Software Inc. | Piccioni Koch D.,Karlsruhe Institute of Technology
Journal of Energy Storage | Year: 2015

Cryo-compressed hydrogen vessels for automotive application were simulated by means of the GASFLOW Simulation Code by using real gas equations of state for hydrogen based on Leachman's NIST model and a modified van der Waals Model. The hydrogen tank systems here considered are those based on hydrogen storage concepts developed by the Bayerische Motoren Werke (BMW) Group and produced by the Lawrence Livermore National Laboratory (LLNL) and the Structural Composite Industries (SCI). In order to validate the GASFLOW simulations, the data and the simulation results provided in the frame of the HySIM project were used. The GASFLOW simulations show good agreement with data as well as with the HySIM simulations. The two real gas equations of state, Leachman's NIST and modified van de Waals used in this study produced nearly identical results. © 2015 Elsevier Ltd.


Xiao J.,Karlsruhe Institute of Technology | Travis J.R.,Engineering and Scientific Software Inc. | Royl P.,Karlsruhe Institute of Technology | Svishchev A.,Karlsruhe Institute of Technology | And 2 more authors.
Mathematics and Computations, Supercomputing in Nuclear Applications and Monte Carlo International Conference, M and C+SNA+MC 2015 | Year: 2015

GASFLOW is a CFD software solution used to predict fluid dynamics, heat and mass transfer, chemical kinetics, aerosol transportation and other related phenomena during a postulated severe accident in the containment of nuclear power plant (NPP). The generalized 3-D transient, two-phase, compressible Navier-Stokes equations for multi-species are solved in GASFLOW, using a proven semi-implicit pressure-based algorithm of Implicit Continuous Eulerian-Arbitrary Lagrangian-Eulerian (ICE'd-ALE) methodology which is applicable for all flow speeds. GASFLOW has been intensively validated with international experimental benchmarks, and has been widely used in the hydrogen explosion risk analysis involving NPP containments. The simulation results of the GASFLOW code have been widely accepted by the nuclear authorities in several European and Asian countries. GASFLOW was originally designed as a supercomputer serial code and could be only run on vector machines with a single processor. A project was initialized in 2013 in order to parallelize GASFLOW using the paradigms of Message Passing Interface (MPI) and domain decomposition. The data structure and parallel linear solvers in the Portable Extensible Toolkit for Scientific Computing (PETSc) were employed in the GASFLOW parallel version: GASFLOW-MPI. GASFLOW-MPI has been validated using the well accepted benchmarks by the CFD community. The computational time can be dramatically reduced depending on the size of the problem and the high-performance computing (HPC) cluster. GASFLOW parallelization adds tremendous value to large scale containment simulations by enabling high-fidelity models, including more geometric details and more complex physical phenomena that occur during a severe accident, which yield detailed and precise insights.

Loading Engineering and Scientific Software Inc. collaborators
Loading Engineering and Scientific Software Inc. collaborators