Accession Number : ADA298918

Title :   Some Developments of the Equilibrium Particle Simulation Method for the Direct Simulation of Compressible Flows.

Descriptive Note : Contract rept.,

Corporate Author : INSTITUTE FOR COMPUTER APPLICATIONS IN SCIENCE AND ENGINEERING HAMPTON VA

Personal Author(s) : Macrossan, M. N.

PDF Url : ADA298918

Report Date : JUN 1995

Pagination or Media Count : 35

Abstract : The direct simulation Monte Carlo (DSMC) method is the established technique for the simulation of rarefied gas flows. In some flows of engineering interest, such as occur for aerobraking spacecraft in the upper atmosphere, DSMC can become prohibitively expensive in CPU time because some regions of the flow, particularly on the windward side of blunt bodies, become collision dominated. As an alternative to using a hybrid DSMC and continuum gas solver (Euler or Navier Stokes solver) this work is aimed at making the particle simulation method efficient in the high density regions of the flow. A high density, infinite collision rate limit of DSMC, the Equilibrium Particle Simulation method (EPSM) was proposed some 15 years ago. EPSM is developed here for the flow of a gas consisting of many different species of molecules and is shown to be computationally efficient (compared to DSMC) for high collision rate flows. It thus offers great potential as part of a hybrid DSMC/EPSM code which could handle flows in the transition regime between rarefied gas flows and fully continuum flows. As a first step towards this goal a pure EPSM code is described. The next step of combining DSMC and EPSM is not attempted here but should be straightforward. EPSM and DSMC are applied to Taylor En = 0.02 and 0.0133 and Sw = 3). Toroidal vortices develop for both methods but some differences are found, as might be expected for the given flow conditions. EPSM appears to be less sensitive to the sequence of random numbers used in the simulation than is DSMC and may also be more dissipative. The question of the origin and the magnitude of the dissipation in EPSM is addressed.

Descriptors :   *COMPRESSIBLE FLOW, SIMULATION, SPACECRAFT, COMPUTATIONS, RANDOM VARIABLES, EFFICIENCY, EQUILIBRIUM(GENERAL), VORTICES, MONTE CARLO METHOD, LIMITATIONS, HIGH DENSITY, WIND DIRECTION, DECOUPLING, TOROIDS, AUSTRALIA, BLUNT BODIES, UPPER ATMOSPHERE, GAS FLOW, RAREFIED GASES.

Subject Categories : Fluid Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE