Experimental investigation into the effects of Mach number and boundary-layer bleed on flow stability of a supersonic air intake

A series of experiments were conducted to study impacts of the free stream Mach number, back pressure and bleed on the stability of a supersonic intake. The flow stability is related to the buzz phenomenon; oscillation of all shock waves of the intake and it may further occur during the time when the intake mass flow rate is decreasing. The present intake is an axisymmetric intake for Mach number of 2.0. The results showed that the stability margin of the intake decreases when the freestream Mach number increases for both bleed off and bleed on cases. For the configuration without bleed, the frequency of buzz oscillation is increased when the freestream Mach number is decreased or when the back pressure is increased. By applying the bleed and consequently preventing the flow separation, the intake is more stable and the shocks oscillate with a smaller amplitude during the buzz phenomenon. When the bleed is applied, the buzz triggering mechanism varied from the Dailey criterion to that of the Ferri one, a phenomenon that changes the stability characteristics of the intake considerably.