Jet-cavity interaction tones

A fundamental study of resonant tones produced by jet-cavity interaction over a wide range of flow conditions covering both subsonic and supersonic speeds is described. Two significant findings emerge. For the jet-cavity configurations investigated, a suitably defined reduced frequency parameter allows for a global classification of all jet-cavity tones into two main types. For the first type, the reduced frequency depends on the jet Mach number, whereas for the second type, the reduced frequency is independent of the jet Mach number. We propose simple correlations for the frequency of both types of tones. Based on earlier research, we had expected that the traditional classifications of cavity flows into the open, transitional, or closed variety would be insensitive to small changes in Mach number and would depend primarily on the cavity's LID ratio. However, use of the novel high-resolution photoluminescent pressure sensitive paint shows that these classifications are actually quite sensitive to the jet Mach number for jet-cavity interactions. However, these classifications provide no guidance for determining tone type, amplitude, or frequency.