University of Illinois Urbana-Champaign

Development of an AMR Octree DSMC approach for shock dominated flows

Sawant, Saurabh S

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SAWANT-THESIS-2015.pdf

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https://hdl.handle.net/2142/89046

Description

Title
Development of an AMR Octree DSMC approach for shock dominated flows
Author(s)
Sawant, Saurabh S
Issue Date
2015-12-11
Director of Research (if dissertation) or Advisor (if thesis)
Levin, Deborah
Department of Study
Aerospace Engineering
Discipline
Aerospace Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
M.S.
Degree Level
Thesis
Date of Ingest
2016-03-02T19:34:19Z
Keyword(s)
  • Direct simulation monte carlo
  • Hypersonic
  • Octree
  • Adaptive Mesh Refinement (AMR)
  • Scalable Unstructured Gasdynamic Adaptive mesh Refinement (SUGAR)
  • Shock dominated flows
Abstract
Key strategies used in the development of a scalable, three-dimensional direct simulation Monte Carlo (DSMC) program are described. The code employs an Octree based adaptive mesh refinement (AMR) that gives flexibility in capturing multi-scale physics. It is coupled with a robust cut-cell algorithm to incorporate complex triangulated geometries. With the use of distributed memory systems and Message-Passing-Interface (MPI) for communication, the code is potentially scalable. However, to simulate continuum-like conditions involving multi-scale physics, better scalability that has yet been achieved is desirable. The thesis identifies two main performance bottlenecks in simulating at continuum-like conditions, first, improving the scalability of the code for more than 128 processors by reducing the communication and evenly balancing the computational load, and second, improve the algorithmic performance of the code by eliminating the expensive recursive tree traversal inherent in Octree based mesh structure. In order to resolve the first issue sophisticated graph-partitioners have been used, however, without success. The thesis also explains the special considerations required for embedded geometries in a parallel computational environment. An efficient algorithm is discussed that allows for the checking of particle-surface interaction only if they are close enough to the geometry. The code calculates various surface coefficients and employs the Borgnakke-Larsen continuous relaxation model to simulate inelastic collisions of diatomic molecules. Finally, these strategies and models are validated by simulating hypersonic flows of argon and nitrogen over a hemisphere and double-wedge configuration and the solutions are compared with the results obtained from an older DSMC code known as SMILE.
Graduation Semester
2015-12
Type of Resource
text
Permalink
http://hdl.handle.net/2142/89046
Copyright and License Information
Copyright 2015 Saurabh S. Sawant

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