Experimental investigation on the effect of fluid–structure interaction on unsteady cavitating flows around flexible and stiff hydrofoils

We experimentally investigated the effect of fluid–structure interaction on unsteady cavitating flows around flexible and stiff National Advisory Committee for Aeronautics 0015 hydrofoils in a low-pressure cavitation tunnel. We analyzed the cavitating dynamics by capturing the cavitation dynamics using two high-speed cameras at different cavitating regimes on the surface of the hydrofoils, made of polyvinyl chloride, brass, and aluminum. We then measured the associated structural deformations in specific cavitation regime such as cloud and partial cavitation dynamics, using a digital image correlation technique. The hydrofoil's angle of attack was set to 10°, and the flow's Reynolds number was adjusted to 0.6 × 106. Results showed that the cavity's shedding frequency on the flexible hydrofoil shifted faster to a higher frequency than on the stiff hydrofoils under similar cavitating conditions. The flexible hydrofoil underwent strong structural oscillations at the low cavitation number for the cloud cavitation regime. The associated amplitudes of the vibration were about 20 times higher than those of the hydrofoil made of brass. It was observed that the fluid–structure interaction can significantly affect the cavitation-induced vibration of the flexible hydrofoil.