Parallel discrete vortex methods on commodity supercomputers; an investigation into bluff body far wake behaviour

¹ Department of Aeronautics and Astronautics, and High Performance Computing Centre Department of Electronics and Computer Science University of Southampton SO17 1BJ, UK
² Department of Aeronautics and Astronautics Department of Electronics and Computer Science University of Southampton SO17 1BJ, UK

Abstract

Parallel discrete vortex methods are ideally suited for studying the behaviour of bluff body wakes due to their ability to capture the motion of vortex structures and lack of downstream grid boundaries. However, the availability of suitable parallel computers to run long simulations is always an issue. The convergence of the high-end workstation and commodity PC markets means that it is now possible to build cheap, powerful supercomputer-level machines at a fraction of the cost of proprietary systems. The characteristics, programming methodology and performance of such systems are discussed in this paper. We also present results showing vortex merging behaviour in the far-wake of a circular cylinder. Previous simulations using the random walk method have shown a doubling of the shedding wavelength in the far wake compared with the near wake. New results using a deterministic vortex method are presented. The parallel vortex method used incorporates an O(NlogN) fast multipole method and vortex panel method to satisfy solid body boundary conditions. In order to account for viscous effects, both near the body and in the far wake, the vorticity redistribution method is used. This is considerably more accurate than stochastic methods The aim of this paper is twofold. To present our findings on the behaviour of fully viscous, far wakes behind bluff bodies and to demonstrate that sufficient resource can be obtained on a cost-effective commodity supercomputer.