Effects of Angle of Attack on Inlet Buzz

Anaxisymmetric supersonic inlet was tested to study the influence of angle of attack andmass flow rate on the inlet buzz phenomenon at a freestreamMach number of 2 and at various angles of attack 0–10 deg. For each angle of attack, two main frequencies for the buzz were seen in the data. For the moderate mass flow rates, small-amplitude and high-frequency oscillation occurred. In this operation stage, both highand low-frequency oscillations exist, but the higher one is dominant and is very close to the frequency of the second acoustic resonance mode. At lower mass flow, however, low-frequency and large-amplitude oscillation occurred that had a single frequency with a constant period. Increasing the angle of attack decreased the inlet performance and limited the stability margin. At intermediate values of themass flow, the buzz frequencywas seen to be independent of the angle of attack, but, for the lower mass flow rates and at high angles of attack, the frequency of the buzz at front portions of the inlet varied. However, the diffuser end still has a constant frequency. In addition, the total-pressure signal had behavior similar to that of the static data with approximately the same frequency.