PASSIVE PRESSURE-DRAG CONTROL IN A PLANE WAKE

We report results of a study of the transition region of a compressible (subsonic) plane wake at moderately high Reynolds numbers, based on the numerical solution of the inviscid time-dependent flow equations. The focus is placed on the flow dynamics in the region of vortex formation and the near wake. A thin interference plate along the wake centerline, which can either be attached or detached from the bluff-body base, is used as a means for passive pressure-drag control by affecting the vortex formation process directly. The results show that the inclusion of an interference plate in the flow configuration can significantly decrease the magnitude of the base pressure coefficient by factors of up to 3, depending on the length of the plate and its separation from the base. The calculated results are in good agreement with the available experimental data and include the detached case for which little or no data exists. The observed self-sustained (global) instabilities in the present simulations were found to be intrinsic features of the flows investigated and are consistent with the local absolute/global instability picture currently favored.