Application of adaptively refined unstructured grids in DSMC to shock wave simulations

Saurabh S. Sawant, Ozgur Tumuklu, Revathi Jambunathan, Deborah A. Levin

Research output: Contribution to journalArticle

Abstract

An efficient, new DSMC framework based on AMR/octree unstructured grids is demonstrated for the modeling of near-continuum, strong shocks in hypersonic flows. The code is able to capture the different length scales in such flows through the use of a linearized representation of the unstructured grid using Morton-Z space filling curve for efficient access of collision cells. Strategies were developed to achieve a strong scaling of nearly ideal speed up to 4096 processors and 87% efficiency (weak scaling) for 8192 processors for a strong shock created by flow over a hemisphere. To achieve these very good scalings, algorithms were developed to weight the computational work of a processor by the use of profiled run time data, create maps to optimize processor point-to-point communications, and efficiently generate new DSMC particles every time step. Rigorous thermal non-equilibrium required for modeling high Mach number shocks was achieved through the accurate modeling of collision temperatures on a sampling grid designed to be compatible with the above approaches. The simulation of a nitrogen flow over a double wedge configuration for near-continuum conditions revealed complex hypersonic SWBLIs as well as three-dimensional gas-surface kinetic effects such as velocity and temperature slip. The simulations showed that three-dimensional effects are important in predicting the size of the separation bubble, which in turn, influences gas-surface measurements such as pressure and heat flux.

Original languageEnglish (US)
Pages (from-to)197-212
Number of pages16
JournalComputers and Fluids
Volume170
DOIs
StatePublished - Jul 15 2018

Keywords

  • AMR
  • DSMC
  • Double wedge
  • Gas-surface interactions
  • Hypersonics
  • MPI
  • Morton-Z space filling curve
  • Non-equilibrium
  • Performance optimization
  • Relaxation
  • Shock wave boundary layer interactions
  • Slip
  • Strong scaling
  • Weak scaling

ASJC Scopus subject areas

  • Computer Science(all)
  • Engineering(all)

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