Rarefied gas flow computational with a 3D unstructured mesh on a Connection Machine (CM2)

Abstract

The implementation on a Connection Machine (CM2) of a Monte Carlo method for rarefied gas flow simulation is presented. The physical model and the algorithm are described. Because of the architecture of the CM2, the association between processors and data is very important. Two different mappings are used in order to obtain the best performance for the two different parts of the algorithm. Moreover, the displacement of a particle in a three-dimensional unstructured mesh requires a number of operations which depends on the particle and which is not a priori known. When the computation is finished for a great number of particles, it is better to work on a smaller subset in order to reduce the CPU cost even if it introduces some extra communication cost. A complex three-dimensional case is presented; the performances obtained on a 16 K configuration are comparable to those obtained on a CRAY XMP.