Computational strategies for three-dimensional flow simulations on distributed computing systems

Effective computational procedures far implementing Computational Fluid Dynamics (CFD) computer codes for simulation of three-dimensional flows are presented. The performance of two different load balancing procedures and two communications strategies for steady and unsteady flow simulations is described. An industry standard production CFD code was used as the baseline for a series of distributed flow solvers that were implemented on Ethernet based networks of engineering workstations and a large scale IBM SP2 distributed system using the Parallel Virtual Machine (PVM) software interface. It was found that the performance of the distributed solvers on the Ethernet based systems was heavily dependent on system load. However, effective load balancing procedures were shown to enable acceptable speedups over the baseline code. An implicit solution algorithm was also incorporated in the baseline explicit flow solver to enable efficient unsteady flow calculations. A series of steady were performed on the large scale distributed system to validate the implicit solver. The solver was then applied to solve the unsteady flow about the F5 wing oscillations in pitch. Results were found to correlate well with experiment. The effects of lagged boundary conditions imposed by the domain composition in the distributed solver were shown to have only a slight effect on solution accuracy. In addition, the performance of two communication strategies, a Manager/Worker and a Worker/Worker strategy, were compared for unsteady flows. The Worker/Worker scheme was shown to deliver superior performance with increasing numbers of processors.