Effects of Door Opening Position on Cavity Flow Acoustics at Supersonic Speeds

A systematic experimental investigation is carried out to examine the dynamic response of the shear layer to the aircraft bay (represented by a rectangular cavity) door operation at supersonic speeds. The study examines the effects of various door opening positions on cavity resonance in terms of overall sound pressure levels and pressure spectra. Measurements were conducted on a rectangular cavity of aspect (length-to-width) ratio of 4.5, with and without doors at Mach 1.6 and 2 at the Florida State University polysonic wind tunnel. The results show that adding doors increases the overall sound pressure levels and amplifies mode 1 of the pressure spectra, except when the doors are 3/4th closed. The sound pressure levels at Mach 1.6 are much higher than at Mach 2. At Mach 1.6 for the cavity with doors, the pressure spectra measured ahead of the cavity leading edge indicate an upstream influence of the cavity resonance. The analysis of results involving probability density function and time-delay phase portraits suggests that the addition of doors to the cavity modifies the underlying mechanism and makes the system more or less unstable, depending on their opening positions.