Partial Cavity Shedding Mechanisms on a Pitching Hydrofoil*

Unsteadiness in the incoming flow can affect the formation and dynamics of a partial cavity. On hydrofoils experiencing partial cavitation, either a liquid re-entrant flow or a propagating bubbly shock wave can cause periodic shedding of vapor clouds. In this study, cavitation dynamics on a plano-convex hydrofoil are studied at both stationary and pitching conditions at maximum pitching rates on the order of 10,000 deg/s^2. The effect of flow unsteadiness achieved by pitching the hydrofoil is examined using time resolved X-ray densitometry and high-speed cinematography. In addition, synchronized unsteady surface pressure and cavity static pressure measurements are also measured. The effect of pitching motion on the shedding mechanisms and cavity topology at various angular accelerations is discussed.