Experimental study on unsteady cavitating flow around hydrofoil with particle imaging velocimetry system

The unsteady cavitating flows around a Clark-Y hydromantic hydrofoil is studied by using particle imaging velocimetry (PIV) system. It is used to measure the cavity shapes and velocity and vorticity fields. The experiment results show that, firstly, with the decrease of the cavitation number, different flow structure characteristics can be observed in the cavitating flows, for unsteady cloud cavitating, a self-oscillation behavior of the whole sheet cavitation is obtained, with large length fluctuations and vapor cloud shedding; as the flow structure changes, there are obvious differences between the velocity distributions of cavitation flows, the high-fluctuating region with lower velocity gradually expands with the decrease of cavitation number, and the lower velocity area relates to the cavitation area. In various stages of cavitation, the vorticity concentrated in the rear vortex separation region. In cloud cavitation stage, more vortices structures can be seen in the cavitation area due to the frequently mass and momentum transformation, for vorticity gathering area, the original vortex changed into a large group of scattered distribution of vorticity, and also, the vortex regions expanded significantly.