Cavity separations and the associated impulsive pressures around a cavitating cylinder. (1st Report, Vortex-type cavitation in the wake and in attached cavitation).

Abstract

The flow patterns and the fluctuating pressures around a cavitating circular cylinder, especially about the wake and the attached cavity separation, have been systematically studied by high-speed photography and by the wave analysis for several Reynolds numbers for Re=4×105 to 7×105, in the cavitation tunnel at Tokyo Metropolitan Institute of Technology. The impulsive pressure originated in the core of vortex-type cavitation, which occurs frequently in the turbulent wake, is about -70 kPa in amplitude and 4 ms in half-width duration. The attached cavitation occurs intermittently according to the fluctuating pressure cycles of the Karman vortices and its inception point is located within the turbulent transition region where the high-frequency fluctuating pressures of about 7 kHz are occurring. In the attached cavitation, the transitional waves appear at he boundary of the clear and the cloud cavity. From this boundary, a lump of bubbles separates leaving the clear cavity. The impulsive pressures have a violent spike pulse of about 260 kPa in amplitude, 2 ms in period and 500 μs in pulse half width at Re=7.2×105.