Unsteady dynamics of cavitating flows around a hydrofoil

The dynamics of cavitating flow around a hydrofoil were investigated experimentally. The experiments were carried out in a rectangular test section of a cavitation tunnel. A high-speed video camera was used to visualize the unsteady cavitating flows. The lift and drag forces around the hydrofoil have been measured. The time-frequency characteristics ofs lift signals at different cavitating regimes were obtained by using Choi-Williams transform and wavelet analysis technique. The results show that there is no remarkable frequency in time-frequency space for the forces when the cavitation is not generated. For sheet cavitation, the frequency of the lift oscillation decreases with cavitation number decreasing. At cloud cavitation stage, the frequency is relatively insensitive to changes in cavitation number. The joint time-frequency analysis can describe the characteristic of signals changing with time and frequency, which has been applied successfully to different aspects of cavitation.