An experimental investigation of flat plates with shallow cavities.

摘要

The overall drag influence of cavities located on the surface of a flat plate was experimentally studied for twelve different cavity configurations. Velocity profiles were experimentally acquired using Laser Doppler Velocimetry. A data analysis procedure to characterize flows over cavities was developed---expressing velocity data in terms of outer variables and determining the optimal friction velocity and cavity induced displacement that produced defect profiles acquired near the cavity consistent with those for an identical streamwise position over a smooth flat plate. Computational Fluid Dynamics software was used to model the flow and a flow visualization study was completed to help identify those flow mechanisms responsible for the increased drag. This confirmed that those cavities that exhibit well-defined internal vortical structures typically exhibit more drag. The velocity results are ultimately presented as a drag increase scaled by the free-stream stagnation pressure and cavity area, and range from 0.0084 for a circular-cylinder cavity to -0.0022 for a spherical cavity.