Impact of nozzle lip on the cavitation cloud characteristics of self-excited cavitating waterjets

The impact of the nozzle lip geometry on the cavitation cloud characteristics induced by self-excited cavitating waterjets, SECJ, is explored experimentally using high-speed imaging under uniform flow conditions and ambient pressure. Complementary inspection of the erosion behavior and resonant state is carried out with erosive tests and high-frequency pressure detection. The nozzle lips inspected include relatively short and long throats with and without a whistle. The temporal and spatial distributions of the cavitation cloud are analyzed using Proper Orthogonal Decomposition, whereas the morphology of eroded specimens is assessed using macroscopic and microcosmic imaging. The results show that the cavitation cloud modulated by a nozzle lip with a short throat and a whistle has a larger volume, lower shedding frequency, longer effective standoff distance, and more intense cavitation erosive ability. Spectral analysis shows that the whistle can promote self-excitation feedback and lower the shedding frequency, improving the cavitation cloud's structuring process.