Get access

Experimental Investigation of Effects of Mach Number on the Flow Instability in a Supersonic Inlet


M.R. Soltani, Department of Aerospace Engineering, Sharif University of Technology and Engineering Research Institute, Tehran, Iran


An extensive wind tunnel tests were conducted on an axisymmetric supersonic inlet at Mach numbers from 1.8 to 2.2 and at different values of mass flow rates. Frequencies of the buzz were achieved from the pressure data as well as the high speed shadowgraph pictures. For each Mach number, two main frequencies for the buzz were obtained. The inlet at its design condition was stable, but when the mass flow rate was reduced, at first the shock wave started to oscillate with a small amplitude which is matched the Ferri criterion (little buzz). In this situation, both high- and low-frequency oscillations occurred; however, the high frequency one was dominant, but the oscillations seemed to be irregular. By further decreasing the inlet mass flow, the shock oscillations got a single low frequency and high amplitude, which in agreement with the Dailey criterion (big buzz). At a free stream Mach number of 2.2, the frequencies of these two kinds of instabilities are about 554 and 137 Hz, respectively. At this Mach number for moderate mass flow, an oscillation with high frequency/large amplitude and constant period was observed. The oscillation has the combined characteristics of the little buzz and the big buzz, which is named “added buzz” here. It is shown that at fairly constant mass flow, the frequency of the buzz is independent of the Mach number. It is further found that the buzz instability affects the external flow as well as the internal one with the same frequency.

Get access to the full text of this article