Experimental study on unsteady cavitation flows around three-dimensional hydrofoil

In order to study the mechanism of the cavity generation, shedding in cloud cavitation regime, the characteristics of unsteady cavitating flows around a three-dimensional hydrofoil are investigated by experimental methods. Experiments on a hydrofoil are carried out in a rectangular test section of a cavitation tunnel, a high-speed video camera is used to visualize the cavitating flows, the drag and lift forces under different cavitation conditions are measured and the spectral analysis for the measured data is conducted. The results show that in unsteady cavitation a quasi-periodic process corresponding to the occurrence-development-shedding-seasing of cavity is observed and the U-shaped cloud cavity and different intensity reentrant jet in spanwise direction towards the mid-span region are captured, the cavities are broken off from the mid-span region near the leading edge of the hydrofoil and become the vortical cloud cavities with the large-scale U-shaped structure. The spectral analysis for the lift and drag forces is conducted through Choi-Williams transformation, and the shedding frequency is 24.3Hz.