Oscillatory Characteristics of Shallow Open Cavities in Supersonic Flow

摘要

Numerical simulations and experiments were carried out to investigate the unsteady flow in a two-dimensional rectangular open cavity with emphasis on the effects of length-to-depth ratio on the shear-layer development and cavity drag. The cavity was exposed to a supersonic flow of Mach 2. The results of the simulations were compared and analyzed with experimental data. Detailed predictions of flow features and frequencies showed a good agreement with the experiments. Particularly, the results indicated how the cavity flowfield changes when the length-to-depth ratio of the cavity is changed. Below a certain value of length-to-depth ratio, self-sustained periodic oscillations are strong and coherent, and the cavity drag is low. Beyond this value, the oscillations are weak, frequencies are mostly broadband, and the drag is high. This transition was found to occur for a cavity of length-to-depth ratio of 5. The investigation has also explored features of cavity shear-layer development, hitherto unexplained, and these are elucidated.