DAPHNE-3D: A NEW TRANSPORT SOLVER FOR UNSTRUCTURED TETRAHEDRAL MESHES

A new Discrete Ordinates transport solver for unstructured tetrahedral meshes is presented. The solver uses the Discontinuous Galërkin Finite Element Method with linear or quadratic expansion of the flux within each cell. The solution of the one-group problem is obtained with non-preconditioned fixed-point or GMRES iterations. Precision and performances of the solver are evaluated on the 3D Radiation Transport Benchmark Problems proposed by Kobayashi, showing very good agreement with the reference and good computing times in serial execution.

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Verification for Ray Effects Elimination Module of Radiation Shielding Code ARES by Kobayashi Benchmarks

Volume 4: Radiation Protection and Nuclear Technology Applications; Fuel Cycle, Radioactive Waste Management and Decommissioning; Computational Fluid Dynamics (CFD) and Coupled Codes; Reactor Physics and Transport Theory ◽

10.1115/icone22-31196 ◽

2014 ◽

Author(s):

Mengteng Chen ◽

Bin Zhang ◽

Yixue Chen

Keyword(s):

Radiation Transport ◽

Source Region ◽

Anisotropic Scattering ◽

Relative Difference ◽

Radiation Shielding ◽

Benchmark Problems ◽

Discrete Ordinates ◽

Ray Effects ◽

Good Agreement

ARES is a multi-group of anisotropic scattering transport shielding code based on discrete ordinates method. The 3D radiation transport benchmark problems proposed by Kobayashi were calculated by ARES with sub-module ARES_RayEffect which using first collision method for ray effects mitigation. ARES_RayEffect calculates uncollided flux and first collision source moments for ARES. The uncollided flux is obtained by a ray tracing calculation between a source point and a target mesh center. In addition, ARES_RayEffect has a modifying factor function to improve the quality of uncollided flux calculation. For verification, the results of MCNP code are used as reference solution and the results of TORT with FNSUNCL3 are compared. ARES_RayEffect introduced the modifying factor to reduce the relative difference of meshes near the source region. For example, at the position (15,15,15) in Problem 1 case i, the relative difference of the result of ARES with ARES_RayEffect is −2.34%, while relative difference of the result of TORT with FNSUNCL3 is −11.92%. The calculated total neutron fluxes show good agreement with the MCNP solutions. For the pure absorber cases, the maximum differences are less than 3%. For the half scattering cases, the maximum differences are less than 11%. Numerical results demonstrate that ray effects can be effectively mitigated.

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Numerical stability analysis of lp-CMFD acceleration for the discrete ordinates neutron transport calculation discretized with discontinuous Galerkin Finite Element Method

Annals of Nuclear Energy ◽

10.1016/j.anucene.2020.108036 ◽

2021 ◽

Vol 153 ◽

pp. 108036

Author(s):

Yimeng Chan ◽

Sicong Xiao

Keyword(s):

Finite Element Method ◽

Finite Element ◽

Numerical Stability ◽

Neutron Transport ◽

Discrete Ordinates ◽

Galerkin Finite Element Method ◽

Galerkin Finite Element ◽

Discontinuous Galerkin Finite Element ◽

Numerical Stability Analysis ◽

Transport Calculation

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Performance of Adaptive Unstructured Mesh Modelling in Idealized Advection Cases over Steep Terrains

Atmosphere ◽

10.3390/atmos9110444 ◽

2018 ◽

Vol 9 (11) ◽

pp. 444 ◽

Cited By ~ 2

Author(s):

Jinxi Li ◽

Jie Zheng ◽

Jiang Zhu ◽

Fangxin Fang ◽

Christopher. Pain ◽

...

Keyword(s):

Unstructured Mesh ◽

Computational Cost ◽

Adaptive Mesh ◽

Galerkin Finite Element Method ◽

Adaptive Meshes ◽

Galerkin Finite Element ◽

Computational Costs ◽

Cut Cell ◽

Discontinuous Galerkin Finite Element ◽

Terrain Following

Advection errors are common in basic terrain-following (TF) coordinates. Numerous methods, including the hybrid TF coordinate and smoothing vertical layers, have been proposed to reduce the advection errors. Advection errors are affected by the directions of velocity fields and the complexity of the terrain. In this study, an unstructured adaptive mesh together with the discontinuous Galerkin finite element method is employed to reduce advection errors over steep terrains. To test the capability of adaptive meshes, five two-dimensional (2D) idealized tests are conducted. Then, the results of adaptive meshes are compared with those of cut-cell and TF meshes. The results show that using adaptive meshes reduces the advection errors by one to two orders of magnitude compared to the cut-cell and TF meshes regardless of variations in velocity directions or terrain complexity. Furthermore, adaptive meshes can reduce the advection errors when the tracer moves tangentially along the terrain surface and allows the terrain to be represented without incurring in severe dispersion. Finally, the computational cost is analyzed. To achieve a given tagging criterion level, the adaptive mesh requires fewer nodes, smaller minimum mesh sizes, less runtime and lower proportion between the node numbers used for resolving the tracer and each wavelength than cut-cell and TF meshes, thus reducing the computational costs.

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