Computation Techniques in a High Performance Parallel Simulation of Gas Dynamics in a Combustion Chamber

The article describes several techniques utilized in the author’s study of gas flow in a combustion chamber. Various models of Compressible Fluid Dynamics (CFD) are used in conjunction with the Finite Volume Method (FVM). Piston and valve movement is introduced with the grid snapping method. Several methods are investigated and implemented in order to prepare the simulation software for high performance computing environments. Some of these methods (MPI, OpenMP, and their hybrid), and their feasibility is discussed below. It proves, that when starting the proper number of MPI processes, and the adequate number of threads for each process – these are determined by the hardware environment – the MPI-OpenMP hybrid method is scalable for the underlying problem for up to 200 processor cores, with a speedup of 60. Two other delicate problems are also hand-picked, that rarely surface in static space simulations: vertex-matching in neighboring meshes, and the transformation of local physical values with interpolation during the change of space discretization, especially when swapping the mesh. Appropriate algorithms are presented for both. These need considerably smaller resources in memory and processor time, which make them applicable even runtime.