Flow Structure and Pressure Oscillations during the Interaction of a Supersonic Underexpanded Gas Jet with a Tubular Cavity

Supersonic jets are widely used in devices based on a self-oscillation process emerging during the interaction of a gas flow with tubular cavities (gas-jet acoustic emitters). We analyze the mechanisms for sustaining undamped pulsations of pressure and determine the flow field in a tubular cavity during the interaction of an underexpanded supersonic jet with it. We consider the physical pattern of the flow in the cavity of a gas-jet emitter, demonstrate the existence of odd longitudinal modes, and propose wave diagrams for describing the flow in odd longitudinal modes. Wave diagrams are constructed based on analysis of signals from piezoelectric sensors detecting pressure pulsations in a tubular cavity. The flow parameters in the tubular cavity in the longitudinal modes are calculated using the flow velocity-velocity of sound diagram.