High-Speed Observation of a Cavitating Jet in Air

The use of cavitation impact is a practical method for improving the fatigue strength of metals in the same way as shot peening. In the case of peening using cavitation impact, cavitation is produced by a high-speed submerged water jet with cavitation, i.e., a cavitating jet. A cavitating jet in air was successfully generated by injecting a high-speed water jet into a low-speed water jet injected into air using a concentric nozzle. In order to investigate the various appearances of cavitating jets in air, an observation was carried out using high-speed photography and high-speed video recording. In this study, periodical shading of the cavitation cloud was observed and the frequency of the shading was found to be a function of the injection pressure of the low-speed water jet. Unsteadiness of the low-speed water jet, which is related to the periodical shading of the cloud, was also observed.