Abstract
It is known that the cloud cavitation shows periodic unsteady behavior but there remain some points to be solved on the cavitation instability. In order to make clear a mechanism of cavitation instability on the role of the nozzle divergent part, we experimentally examined the cloud cavitation using a high speed video camera and an image analysis based on the frame difference method to quantitatively estimate the unsteady cloud behavior. As a result, we found that the generation mechanism of reentrant motion is dependent on the difference in the upstream pressure of nozzle as well as the shape of nozzle divergent part. In addition we indicated that for nozzles with a divergent part the pressure wave issued at cloud collapse may hardly affect the reentrant behavior of cloud cavitation.
