Spectral element applications in complex nuclear reactor geometries: Tet-to-hex meshing

Haomin Yuan, Mustafa A. Yildiz, Elia Merzari, Yiqi Yu, Aleksandr Obabko, Gerrit Botha, Giacomo Busco, Yassin A. Hassan, Duy Thien Nguyen

Research output: Contribution to journalArticlepeer-review

35 Scopus citations

Abstract

The spectral element code Nek5000 is an open-source, higher-order computational fluid dynamics code developed at Argonne National Laboratory. It is designed to solve incompressible Navier-Stokes equations, but it also has a low-Mach-number approximation feature available. Large eddy simulation is approached by explicit filtering of the velocity field (and other fields) to mimic the effect of dissipation due to the unresolved scale. The computational domain is decomposed into second-order hexahedral elements that conform to the boundaries. However, generating a high-quality pure-hexahedral mesh can be challenging for some problems. For simple geometries, traditional blocking methods can be used to decompose the domain into smaller blocks to generate a so-called structural mesh. A structural mesh can maintain good orthogonality but can have a highly skewed mesh to conform to the geometry, as well as unnecessary refinement in the far field. Moreover, for geometries with relative complexity, blocking the geometry becomes impossible. To address these issues, we adopted a tet-to-hex strategy to generate a pure hexahedral mesh for Nek5000. First, we generate a pure tetrahedral mesh for the geometry; then we divide one tetrahedral element into four hexahedral elements. A pure tetrahedral mesh could be easily generated for complex geometries by using many current meshing codes. In this paper, we use the commercial codes ANSYS meshing and ANSYS ICEM to generate the pure tetrahedral mesh and then convert it to a pure hexahedral mesh. Boundary layers are extruded in ANSYSICEM to maintain near-wall resolution.

Original languageEnglish
Article number110422
JournalNuclear Engineering and Design
Volume357
DOIs
StatePublished - Feb 2020
Externally publishedYes

Funding

The submitted manuscript has been created by UChicago Argonne, LLC, Operator of Argonne National Laboratory (“Argonne”). Argonne, a U.S. Department of Energy Office of Science laboratory, is operated under Contract No. DE-AC02-06CH11357. The U.S. Government retains for itself, and others acting on its behalf, a paid-up nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan. http://energy.gov/downloads/doe-public-access-plan. This work was based upon material supported by the U.S. Department of Energy , Office of Science , under contract DE-AC02-06CH11357 . This research used resources of the Argonne Leadership Computing Facility ( ALCF ), which is a U.S. Department of Energy Office of Science User Facility supported under contract DE-AC02-06CH11357 . The authors thank the staff of ALCF of their technical supporting to this work. The authors also thank those who provided valuable suggestions to this work from both experimental side and simulation side. There is also a special thanks to Professor Paul Fischer at University of Illinois at Urbana-Champaign, who shared his expertise about Spectral Element Method and Nek5000 code. This work was based upon material supported by the U.S. Department of Energy, Office of Science, under contract DE-AC02-06CH11357. This research used resources of the Argonne Leadership Computing Facility (ALCF), which is a U.S. Department of Energy Office of Science User Facility supported under contract DE-AC02-06CH11357. The authors thank the staff of ALCF of their technical supporting to this work. The authors also thank those who provided valuable suggestions to this work from both experimental side and simulation side. There is also a special thanks to Professor Paul Fischer at University of Illinois at Urbana-Champaign, who shared his expertise about Spectral Element Method and Nek5000 code. Government License, The submitted manuscript has been created by UChicago Argonne, LLC, Operator of Argonne National Laboratory (“Argonne”). Argonne, a U.S. Department of Energy Office of Science laboratory, is operated under Contract No. DE-AC02-06CH11357. The U.S. Government retains for itself, and others acting on its behalf, a paid-up nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan. http://energy.gov/downloads/doe-public-access-plan.

Keywords

  • ANSYS ICEM
  • ANSYS meshing
  • Direct numerical simulation
  • Fuel assemblies
  • Helical coil steam generator
  • Hexahedral mesh
  • Large eddy simulation
  • Nek5000
  • Random pebble bed
  • Spacer grid
  • Spectral element code
  • Tet-to-hex conversion
  • Tetrahedral mesh

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