Supersonic jets are widely used in devices based on the phenomenon of a self-oscillating process that occurs when a gas flow interacts with circular cavities (gas-jet sound emitters). The mechanisms of maintaining undamped pressure oscillations and determining the flow field in the tube cavity during the interaction of a supersonic underexpanded jet with cavity are considered. The physical pattern of the flow in the cavity of a gas-jet emitter is discussed, the existence of odd longitudinal modes is shown, and wave diagrams are proposed for describing the flow in odd longitudinal modes. The wave diagrams are based on the analysis of the signals of piezoelectric sensors, recording pressure oscillations in the tube cavity. The calculation of the flow parameters in the tube cavity in longitudinal modes is based on the flow velocity and speed of sound diagram.

In high-pressure gas-jet emitters, the source of sound energy is kinetic energy of gas jet at supercritical pressure ratios between the working pressure and the atmospheric pressure. Under certain conditions, interaction of a supersonic jet with the resonator is accompanied by powerful self-excited oscillating process with the generation of acoustic waves into the environment and cavity resonator. A model of a self-excited oscillating process arising from the interaction of non-isobaric jet with semi-closed cylindrical cavities, allowing to distinguish typical elements of gas-dynamic structure of the forming flow, is considered. The physical pattern of the flow in the cavity of gas-jet emitter is discussed, and a study of the dependence of the characteristics of the self-excited oscillating process on the gas-dynamic and geometric parameters is performed.