Cavity flow oscillations and aeroacoustic characteristics at supersonic speeds

Cavity flow oscillations and aeroacoustic characteristics at supersonic speeds were investigated based on flow-fields of three types of cavity flow.The data presented herein was obtained over Mach number of 1.5 at a Reynolds number of 2.26×107 per meter with a boundary-layer thickness of approximately 0.024m.The length-to-depth ratios of the cavities were 15,12 and 6,respectively.The results indicate that the intense noise resulted from impingement of shear-layer and the cavity rear-face occurs in the cavities.Sound pressure level(SPL) in the region upstream of the cavity rear-face is more than that in the region downstream of the cavity front-face and in the middle of the cavity.The compressible or shock waves induced by impingement of shear-layer and the cavity floor disturb the sound feedback mechanism from the cavity rear-face to the front-face at supersonic speeds,causing self-sustained flow oscillations and peak frequencies of the cavity tone inside cavities for transitional and closed cavities with large length-depth ratios.However,the shear-layer bridges the open cavity,which has no influence on the mechanism.The self-sustained flow oscillations and some peak frequencies occur inside the open cavity.