Структура течения и колебания давления при взаимодействии сверхзвуковой недорасширенной струи газа с трубной полостью

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.

Influence of Different Configurations of Microjet Injection on Structure and Acoustic Radiation of Supersonic Jet

The work is devoted to experimental study of the structure and acoustic radiation of a supersonic underexpanded jet Ma = 1, Npr = 5 with the presence of vortexgenerators in the form of small-sized jets injections. Ten different configurations were tested, in which following the gas-dynamic and geometrical parameters of the microjets were changed one by one: microjets pressure, the injection distance from the main nozzle section, azimuthal, tangential, and axial angles of micronozzles inclination. The flow visualization, azimuthal Pitot pressure profiles and characteristics of jet noise in the far field were obtained. It has been revealed that the injection of microjets in general leads to an increase in the jet long-range and a decrease in its mixing. The advantageous parameters of the microjets injection for reducing the jet acoustic emission are the injection point vicinity to the main nozzle section, micronozzles inclination to main jet axis and the small tangential angle of micronozzles. The micronozzles quantity effect is non-linearly in relation to the structure and the jet noise. The average pressure measuring distribution near artificial longitudinal vortices in a jet stream cannot predict the characteristics of its mixing and acoustic radiation.