Investigations on flow-sustained oscillations and aeroacoustic characterisitics induced by transonic and supersonic flow over open cavities

This paper presents flow-sustained oscillations and aeroacoustic characteristics within open rectangular cavities with length to depth ratios of 6 and 8 by analyzing flow-field structures and fluctuating pressure measurement inside the cavities in a wind-tunnel test. The free-stream Mach numbers were 0.8 and 1.5. The results indicate that a vortex inside the cavities vents the high pressures ahead of the rear face and the low pressures downstream of the front face, which has little influence on the sound-wave feedback mechanism from the cavity rear face to the cavity front face. Therefore, the self-sustained flow oscillations and some peak frequencies occur inside the open cavity. The simulated flow self-sustained oscillation frequencies inside the open cavities with length to depth ratio of 8 agree with Rossiter's and Heller's predicated results, which indicate their frequency characteristics. The results present that intensive noise exists inside open cavities.