Experimental investigation on the cavitation modulation mechanism in submerged self-sustained oscillating jets

To investigate the cavitation evolution states in chamber and its modulation on the self-sustained oscillation, experimental research is conducted in the nozzles with three different chamber lengths using high-speed photography and high frequency sensors. The experiment results indicate that with the increase of the chamber length of Helmholtz nozzles utilized in this study, the intensity of cavitation gradually decreases and the complex congestion cavitation state will switch to the periodic shedding annular cavitation cloud and even discrete free cavitation. With the increase of inlet pressure, the self-maintenance of Helmholtz vortex ring in the jet shear layer enhances, making the random components in the shear layer and the chaotic degree of the flow field reduce. For the submerged self-sustained oscillating jets, the cavitation structure in the nozzle can be regarded as an accumulator, which shrinks and expands periodically to determine the release and aggregation of energy and modulates the pulsation frequency and intensity of the pulsed jet induced by Helmholtz nozzles. The amplitude of pressure pulsation is positively correlated with the cavitation intensity, which means that the pulsation performance of the self-sustained oscillating pulsed jet gets better with the increase of the cavitation intensity.