Experimental/Numerical Study on Cavitating Flow around Clark Y 11.7% Hydrofoil

Cavitating flow around a Clark Y 11.7% hydrofoil in water tunnel is studied both experimentally and numerically in order to acquire the knowledge about the cavitating flow field and its relation to hydrofoil performances. In the experiment, timeaveraged pressure and velocity distributions around the hydrofoil are measured in cavitating conditions to evaluate the cavitation performance of hydrofoil. In addition, the unsteady cavitating flows are visually observed using high-speed video camera. Numerical simulation of cavitating flow is also carried out for the same test apparatus (but two-dimensional). The angle of attack of 8 degrees is chosen for the present investigation. It is confirmed experimentally that, as the cavitation number is decreased, the estimated lift slightly increases from that in the non-cavitating condition just before the sudden breakdown, which has been reported by the past literatures. However, this is not observed in numerical simulations, and the critical cavitation number, at which the breakdown starts to occur, is seen to be different between the experiment and the numerical simulation, revealing the insufficient prediction ability of present numerical simulation. In the experiment, the oscillating sheet cavity with cloud cavities shed from its trailing edge seems to sustain the low pressure downstream of the partial cavity, which keeps the lift unchanged from that in noncavitating conditions. On the other hand, the simulated sheet cavity with short length is rather stable, and pressure behind the cavity increases. As a result, the lift starts to decrease with the formation of short partial cavity in the numerical simulation.