Abstract
A flight test program was performed to gain further insight into the phenomenon of flow-induced pressure oscillations in cavities and to evaluate the effectiveness of various suppressure concepts. The cavity tested was rectangular with dimensions of 17 in. long, 8.5 in. deep, and 8.75 in. wide. It was instrumented with microphones, static pressure ports, and a thermocouple. The flight speeds ranged from Mach number 0.6 to 1.3 at pressure altitudes of 3000, 20 000, and 30 000 ft. The suppression devices tested included leading edge spoilers and deflectors and trailing edge ramps and deflectors. Several combinations of these were tested. The results indicate that the flow-induced pressure oscillations in a cavity, can be significantly reduced with leading edge spoilers in conjunction with a trailing edge ramp. A 20-dB reduction was achieved for the predominant modal frequency. Other combinations of the suppression devices afforded some reduction, but the spoiler–ramp combination proved most effective.
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