Aeroacoustic resonance in a rectangular cavity: Part 1 effect of mach number and reynolds number

An experimental study of flow over a generic cavity has been undertaken. Measurements of the fluctuating pressures within a cavity are presented. Cavity models having lengths of 200 and 250mm and a depth of 50mm were tested under freestream Mach numbers ranging between 0.3 to 1.3. Due to the coupling of the aerodynamic and acoustic fields, feedback loops can be established resulting in cavity resonance and on aircraft, these high-intensity acoustic tones may lead to noise radiation, structural fatigue, and interference with on-board avionic systems. The purpose of this experimental program is to understand the conditions leading to this resonance and the effect of a range of parameters on both the frequencies and intensities of the tones. In this paper we focus mostly on Mach number and Reynolds number dependency. There was found to be no observed dependency on the Reynolds number, across the Reynolds number range of 27106 to 81106 per metre. Both the (non-dimensional) frequencies and intensities varied with Mach number. The resonant frequencies observed were consistent with the semi-empirical feedback model of Rossiter.