Unsteady separated flow simulations using a cluster of workstations

The possibility of predicting the full three-dimensional, unsteady, separated flow around complex ship and helicopter geometries is explored using unstructured grids in a parallel flow solver. The flow solver used is a modified version of the Parallel Unstructured Maritime Aerodynamics (PUMA) software. The efficiency and accuracy of PUMA at resolving several steady state solutions and a fully three-dimensional unsteady separated flow around a sphere were studied. Since this requires immense computational resources, one has to often depend on expensive supercomputers to do the job. The COst effective COmputing Array (COCOA) is an inexpensive Beowulf-class supercomputer built and tested by the Aerospace Engineering Department at the Pennsylvania State University, as part of an effort to make this possible at a very economical cost. Various benchmarks were conducted on COCOA to study its performance at solving such problems. Unstructured grids were utilized in order to maximize the number of cells in the area of interest, while minimizing cells in the far field. A high level of clustering is required to solve viscous unsteady problems, and unstructured grids offer the least expensive method to ensure this. NASA's VGRID package was used to generate the unstructured grids.