Formation process of vortex ring cavitation in high-speed submerged water jets

In order to clarify the breakdown of cavitation bubble clouds around a high-speed submerged water jet, flow visualizations were conducted to observe the vortex structure around the jet boundary by the shadowgraph technique, and by the laser light sheet method. The cloud shedding frequency with respect to the cavitation number was measured by means of a digital image processing technique, because such an unsteady behavior is closely related to the impinging erosion. Clearly, the vortex ring cavitation markedly changes with the ambient pressure, and the size and the position at which it maximally develops correspond well to results of our previous erosion tests on the impinging erosion characteristics of maximum peak. It is also quantitatively shown that the breakdown frequency of the clouds increases with increasing cavitation number.