A STUDY OF MULTIPLE GRID PROBLEMS ON CONCURRENT PROCESSING COMPUTERS (NUMERICAL ANALYSIS)

Three computer codes have been studied which make use of concurrent processing computer architectures in computational fluid dynamics (CFD). The purpose of the study is to gain experience using a multiple-instruction/multiple-data (MIMD) computer for CFD applications.;The first code studied is a well-known program which makes use of the Beam and Warming, implicit, approximate factored algorithm. This study demonstrates the parallelism found in a well-known scheme and it achieved speedups exceeding 1.9 on the two processor MIMD test facility.;The second code studied made use of an embedded grid scheme which is used to solve problems having complex geometries. The particular application for this study considered an airfoil/flap geometry in an incompressible flow. The scheme eliminates some of the inherent difficulties found in adapting approximate factorization techniques onto MIMD machines and allows the use of chaotic relaxation and asynchronous iteration techniques.;The third code studied is an application of overset grids to a supersonic blunt body problem. The code addresses the difficulties encountered when using embedded grids on a compressible, and therefore nonlinear, problem. The complex numerical boundary system associated with overset grids is discussed and several boundary schemes are suggested. A boundary scheme based on the method of characteristics achieved the best results.;MIMD architectures are being suggested as the most likely candidate for the next generation of super computers. In order to make efficient use of the multiple processor architectures, the user will have to learn the skills of parallel programming. The three parallel codes written for this study, and tested on a two processor MIMD facility at NASA-Ames Research Center, are suggested for efficient parallel computations.;A brief review of computer architectures is also presented and the particular machine used in this study is described.