Parallel Solutions of Three-Dimensional Compressible Flows

In this report, we present parallel solutions of realistic three-dimensional flows obtained on the {\tt Intel Paragon}, the {\tt Cray T3D} and the {\tt Ibm SP2} MPPs (Massively Parallel Processors). The solver under consideration is a representative subset of an existing industrial code, {\tt N3S-MUSCL} (a three-dimensional compressible Navier-Stokes solver, see Chargy\cite{Cha1}). It implements a mixed finite element/finite volume formulation on unstructured tetrahedral meshes. Defining a good strategy for the parallelisation of an unstructured mesh based solver is a challenge, particularly when one aims at reaching a high level of performance while maintaining portability of the source code between scalar, vector and parallel machines. The parallelisation strategy adopted in this study combines mesh partitioning techniques and a message-passing programming model. The mesh partitioning algorithms and the generation of the corresponding communication data-structures are gathered in a preprocessor in order to introduce a minimum change in the original serial code. The portability from one message passing parallel system to another may be enhanced with the use of a communication library such as {\tt PVM}.

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