PARTIAL CAVITIES - PRESSURE PULSE DISTRIBUTION AROUND CAVITY CLOSURE

Pressure pulse height spectra (PPHS) are measured in the case of partial cavitation attached to the leading edge of a hydrofoil. It is shown that the distributions of pressure pulses around cavity closure may significantly differ according to the type of cavity. In the case of a thin, well-closed and stable cavity, the pressure pulse distributions exhibit a strong maximum centered on the visible cavity termination. As the cavity becomes thicker and increasingly open and unsteady, the pressure pulse distribution widens. In the limit case of a cavity periodically shedding bubble clusters, no definite maximum in the pressure pulse distribution is observed. In addition, scaling of pressure pulse height spectra is approached from measurements at two different velocities. It is shown that the pressure pulse height spectra can be correctly transposed from a velocity to another one from two basic scaling rules concerning pulse heights and production rates of bubbles.