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A multithreaded parallel upwind sweep algorithm for the S_(N) transport equations discretized with discontinuous finite elements

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Nuclear Science and Techniques 2023年第12期34卷 229-241页

作者： Zhi‑Wei Zong Mao‑Song Cheng Ying‑Chi Yu Zhi‑Min Dai Shanghai Institute of Applied Physics Chinese Academy of SciencesShanghai 201800China University of Chinese Academy of Sciences Beijing 100049China

The complex structure and strong heterogeneity of advanced nuclear reactor systems pose challenges for high-fidelity neutron-shielding calculations. Unstructured meshes exhibit strong geometric adaptability and can overcome the deficiencies of conventionally structured meshes in complex geometry modeling. A multithreaded parallel upwind sweep algorithm for S_(N) transport was proposed to achieve a more accurate geometric description and improve the computational efficiency. The spatial variables were discretized using the standard discontinuous Galerkin finite-element method. The angular flux transmission between neighboring meshes was handled using an upwind scheme. In addition, a combination of a mesh transport sweep and angular iterations was realized using a multithreaded parallel technique. The algorithm was implemented in the 2D/3D S_(N) transport code ThorSNIPE, and numerical evaluations were conducted using three typical benchmark problems:IAEA, Kobayashi-3i, and VENUS-3. These numerical results indicate that the multithreaded parallel upwind sweep algorithm can achieve high computational efficiency. ThorSNIPE, with a multithreaded parallel upwind sweep algorithm, has good reliability, stability, and high efficiency, making it suitable for complex shielding calculations.

关键词： Shielding calculation discrete ordinates method Discontinuous Galerkin finite element method Unstructured meshes

Effects of Flame Temperature and Absorption Coefficient on Premixed Flame Interactions with Radiation

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Journal of Thermal Science 2021年第3期30卷 1046-1056页

作者： KANG Sang Hun Department of Aerospace System Engineering Sejong UniversitySeoul 05006Republic of Korea

The effects of the flame temperature and the absorption coefficient on interactions between radiative heat transfer and the flame behavior were numerically investigated using high-fidelity numerical code with the discrete ordinates *** study the effects of the flame temperature and the absorption coefficient,three different flame temperatures and four different absorption coefficient conditions were selected,so twelve test cases were studied in *** the numerical test results,radiation effects resulted in preheating of the reactant gases and heat loss from the product gases.A higher flame temperature resulted in stronger preheating effects in reactants near the *** to the preheating effects,with the appropriate absorption coefficient,the peak temperature appeared at the flame *** flame temperatures resulted in larger reabsorption effects in the product *** peak temperature at the flame front and the flame speed were influenced by the combined effects of preheating and radiative heat loss at the flame *** on the conditions,due to those effects,the peak temperature and the flame speed could increase or *** the absorption coefficient was sufficiently large,the temperature decrease was reduced in the product zone.

关键词： radiation high-fidelity numerical simulation discrete ordinates method premixed flame

Neutronic calculations of the China dual-functional lithium–lead test blanket module with the parallel discrete ordinates code Hydra

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Nuclear Science and Techniques 2020年第8期31卷 1-12页

作者： Guang-Chun Zhang Jie Liu Liang-Zhi Cao Hong-Chun Wu Xian-Bao Yuan Science and Technology on Parallel and Distributed Processing Laboratory National University of Defense TechnologyChangsha 410073China Laboratory of Software Engineering for Complex Systems National University of Defense TechnologyChangsha 410073China School of Nuclear Science and Technology Xi’an Jiaotong UniversityXi’an 710049China College of Mechanical and Power Engineering China Three Gorges UniversityYichang 443002China

The China dual-functional lithium–lead test blanket module(DFLL-TBM) is a liquid Li Pb blanket concept developed by the Institute of Nuclear Energy Safety Technology of the Chinese Academy of Sciences for testing in ITER to validate relevant tritium breeding and shielding technologies. In this study, neutronic calculations of DFLL-TBM were carried out using a massively parallel three-dimensional transport code, Hydra, with the Fusion Evaluated Nuclear Data Library/MG. Hydra was developed by the Nuclear Engineering Computational Physics Lab based on the discrete ordinates method and has been devoted to neutronic analysis and shielding evaluation for nuclear facilities. An in-house Monte Carlo code(MCX) was employed to verify the discretized calculation model used by Hydra for the DFLL-TBM calculations. The results showed two key aspects:(1) In most material zones,Hydra solutions are in good agreement with the reference MCX results within 1%, and the maximal relative difference of the neutron flux is merely 3%, demonstrating the correctness of the calculation model;(2) while the current DFLL-TBM design meets the operation shielding requirement of ITER for 4 years, it does not satisfy the tritium self-sufficiency requirement. Compared to the two-step approach, Hydra produces higher accuracies as it does not rely on the homogenization technique during the calculation process. The parallel efficiency tests of Hydra using the DFLL-TBM model also showed that this code maintains a high parallel efficiency on O(100) processors and, as a result, is able to significantly improve computing performance through parallelization. Parameter studies have been carried out by varying the thickness of the beryllium armor layer and the tritium breeding zone to understand the influence of the beryllium layer and breeding zone thickness on tritium breeding performance. This establishes a foundation for further improvement in the tritium production performance of DFLL-TBM.

关键词： discrete ordinates method DFLL-TBM Neutronic analysis Tritium breeding performance

A numerical and experimental comparison of heat transfer in a quasi two-dimensional packed bed

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Particuology 2024年第1期84卷 136-144页

作者： Matthias Tyslik Mirko Ebert Martin Schiemann Siegmar Wirtz Christian Lessig Department of Energy Plant Technology Ruhr-University BochumGermany Institute for Simulation and Graphics Otto-von-Guericke-Universität MagdeburgGermany

Heat transfer plays a major role in many industrial processes taking place in packed *** accurate and reliable simulation of the heat exchange between particles is therefore crucial for a reliable operation and to optimize the processes in the *** discrete ordinates method(DOM)provides an established numerical technique to model radiative heat transfer in granular media that offers the possibility to consider the directional dependence of the radiation *** this work,DOM is compared with Monte Carlo ray tracing,which provides an alternative method for heat transfer ***-rically simple configurations are used to investigate the influence of the angular discretization on the accuracy of the results and the computation time in both *** obtained insights are then transferred to a more complex configuration of a quasi two-dimensional test rig consisting of metal rods for which also experimental results are *** results show that both DOM and Monte Carlo ray tracing allow for an accurate simulation of heat transfer in packed *** Carlo ray tracing requires thereby computation times that are surprisingly competitive(although still somewhat slower)compared to DOM and allows for an easier computation of highly accurate reference *** our preliminary comparison to the experimental test rig,Monte Carlo ray tracing also provides the advantage that it can more easily model highly specular materials such as stainless *** methods are comparable for diffuse materials such as magnesium oxide.

关键词： Heat transfer discrete ordinates method Monte Carlo ray tracing

Two Uniform Tailored Finite Point Schemes for the Two Dimensional discrete ordinates Transport Equations with Boundary and Interface Layers

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Communications in Computational Physics 2014年第3期15卷 797-826页

作者： Houde Han Min Tang Wenjun Ying Department of Mathematical Sciences Tsinghua UniversityHaidianBeijing 100084P.R.China Department of Mathematics Institute of Natural Sciences and MOE-LSCShanghai Jiao Tong UniversityMinhangShanghai 200240P.R.China

This paper presents two uniformly convergent numerical schemes for the two dimensional steady state discrete ordinates transport equation in the diffusive regime,which is valid up to the boundary and interface layers.A five-point nodecentered and a four-point cell-centered tailored finite point schemes(TFPS)are *** schemes first approximate the scattering coefficients and sources by piecewise constant functions and then use special solutions to the constant coefficient equation as local basis functions to formulate a discrete linear ***,both methods can not only capture the diffusion limit,but also exhibit uniform convergence in the diffusive regime,even with boundary *** results show that the five-point scheme has first-order accuracy and the four-point scheme has second-order accuracy,uniformly with respect to the mean free *** a relatively coarse grid can be used to capture the two dimensional boundary and interface layers.

关键词： Neutron transport equation discrete ordinates method tailored finite point method boundary layers interface layers

Inverse Radiation Problem of Boundary IncidentRadiation Heat Flux in Semitransparent Planar Slabwith Semitransparent Boundaries

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Journal of Thermal Science 1998年第2期7卷 131-138页

作者： LiunLinhua TanHeping 等 SchoolofEnergyScience＆Engineering HarbinInstituteofTechnologyHarbin150001China SchoolofEnergyScienc

An inverse method is presented for estimating the unknown boundary incident radiation heat flux onone side of one-dimensional semitransparent planar slab with semitransparent boundaries from theknowledge of the radiation intensities exiting from the other side. The inverse problem is solved usingconjugate gradient method of minimization based on discrete ordinates method (DOM) of radiativetransfer equation. The equations of sensitivity coefficients are derived and easily solved by DOM, withthe result that the complicated numerical differentiation commonly used in solving sensitivity coefficients is avoided. The effects of anisotropic scattering, absorption coefficient, scattering coefficient,boundary reflectivity, fluid temperature outside the boundaries, convection heat transfer coefficients,conduction coefficient of semitransparent media and slab thickness on the accuracy of the inverse analysis are investigated. The results show that the boundary incident radiation heat flux can be estimatedaccurately, even with noisy data.

关键词： inverse radiative problem radiation heat flux discrete ordinates method conjugate gradient method