Unsteady Performance of a Cavitating Hydrofoil in Stall Conditions.

To improve the reliability on the performance of hydraulic machinery, especially at large angles of attack near stall conditions, the lift-and-drag performance of a symmetric hydrofoil was measured in the wide region from a noncavitating state to a supercavitating state in relation to the corresponding cavitation aspects. The noncavitating flow around the hydrofoil in the stall condition was also computed by directly solving the N-S equation. The spectra of lift fluctuation in noncavitating states are similar to those in states of the cavitation violent vibration. This means that the shedding of large-scaled coherent vortices corresponds well to the shedding of bubble clouds in the cavitation violent vibration.