Multiblock structured algorithms in parallel CFD

Publisher Summary This chapter presents some aspects of a widely diffused solution strategy, the Multiblock Structured Algorithm (MSA) and in particular discusses its application in Parallel Computational Fluid Dynamics. From an aerodynamicist viewpoint, some of the main problems of MSA parallel implementation are underlined. It is highlighted, in particular, how aerodynamic requirements can often be in conflict with choices ruled by optimum parallel performance. The chapter provides a major distinction between domain decomposition technique (DDT) and the MSA. It defines DDT as the parallelization obtained by a simple data re-arrangement without affecting the numerical algorithm. The chapter deals with the load overhead, that is present when the computational load is not uniformly distributed among the processors, and with the communication overhead, that is caused by the physical swapping of data and information among processors and by the waiting time among the communications. The introduction of internal boundary conditions, as well as the strategies proposed to reduce the overheads, suggested to examine the consequences on the numerical stability.