Parallel implementation of a combustion chamber simulation with MPI-OpenMP hybrid techniques

The parallelization techniques utilized in a study of gas flow in a combustion chamber are described and discussed in this paper. Models of compressible fluid dynamics are solved with the finite volume method, and an additional algorithm, called “snapper” that handles piston and valve movement. In order to achieve an acceptable scaling on a CPU cluster with 240 cores, a two-stage parallelization with MPI in conjecture with OpenMP is implemented. For some types of physical investigations, the actual spatial region of interest is somehow changing, deforming, or moving in time in a predefined fashion. Handling gas dynamics with piston motion, even with the simplest models requires precaution. Apart from numerical and physical corrections, there are challenges, where multiple types of unstructured, and specially generated deforming grids are handled in a computer system with distributed memory. In the present work the results of the first implementations and benchmarks are presented, which prove to be well scaling for this modest-sized cluster.