Hybrid methods in near continuum flows

Smith, Matthew Ross. (2004). Hybrid methods in near continuum flows MPhil Thesis, School of Engineering, The University of Queensland.

       
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Author Smith, Matthew Ross.
Thesis Title Hybrid methods in near continuum flows
School, Centre or Institute School of Engineering
Institution The University of Queensland
Publication date 2004
Thesis type MPhil Thesis
Supervisor Dr. Michael Macrossan
Prof Richard Morgan
Total pages 91
Collection year 2004
Language eng
Subjects 290501 Mechanical Engineering
L
Formatted abstract

Presented is a study of rarefied and near continuum gas dynamics, focusing on the simulation of these flows by hybrid techniques. The conventional numerical method for such flows is the Direct Simulation Monte Carlo (DSMC) method, which simulates gas flows by moving and colliding simulated particles. DSMC becomes prohibitively expensive as density increases, collision rates increase and the flow approaches the continuum regime. Here is presented a hybrid DSMC method which differs from standard DSMC in two ways 1) EPSM (Equilibrium Particle Simulation Method) is used in collision dominated (or near continuum) regions, and 2) EFM (Equilibrium Flux Method) is run in parallel to the direct simulation and is used to determine which regions EPSM is used in. In 2D simulations, Jacobs' MBCNS (Multi Block Compressible Navier-Stokes) was used instead of EFM. 

EFM (Equilibrium Flux Method) is a kinetic theory based flux method, which here is used to distinguish regions of the flow where DSMC and EPSM are to be used. Calculation of Birds' Breakdown Parameter throughout the flow by EFM indicates regions where the gas is expected to be in an 'equilibrium' state, thus allowing the use of EPSM instead of DSMC. 

Results are presented for various unsteady and steady flows using both unchanging and adaptive meshes, and are compared to experimental and pure DSMC simulation results. The hybrid code was found to be much faster than a purely DSMC method, up to 4 times faster, whilst obtaining results acceptably similar to those obtained by DSMC. EFM, or Equilibrium Flux Method, was only used as a guide, and does not actually form part of the simulated solution. 

Keyword Continuum mechanics

Document type: Thesis
Collection: UQ Theses (RHD) - UQ staff and students only
 
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Created: Tue, 07 Feb 2012, 09:29:24 EST by Bekti Mulatiningsih on behalf of The University of Queensland Library