Self-Oscillations in an Axisymmetric Generator of Pulsed Jets and High-Frequency Regime Associated with Cavity Boundary Instability

Liquid jet flows in the presence of a ventilated cavity with a negative cavitation number are investigated. The studies carried out in the Institute of Mechanics of Moscow State University show that under certain conditions cavitation-induced self-oscillations can occur in the hydraulic system with highly intense pressure fluctuations. The results of an investigation of the axisymmetric model of a pulsed jet generator with liquid jet outflow through a central orifice in a diaphragm and gas blow from the periphery beyond the diaphragm are presented. The two-phase medium outflow was realized through a convergent conical nozzle. The influence of the generator parameters and the distance to a wall (screen) on the efficiency of its operation is investigated. A narrow range of comparatively small blowing, in which high-frequency pressure oscillations are recorded, while the amplitude of impact pressure pulses on the screen is considerably higher than the amplitude of pulses in high-frequency generation regimes, is revealed. This flow regime can be due to the development of two-phase structures on the unstable jet boundary interactioning with the convergent nozzle walls. The evidence for the possible existence of this flow regime has been given by the solution of the plane problem of interaction between a finite jet and an inclined plate for different pressures on the jet surfaces. The problem was solved exactly using the methods of theory of functions of a complex variable for quasi-doubly-periodic theta functions.

jet flows, cavities, negative cavitation number, cavitation-induced self-oscillations, pulsation technologies