Experimental study on the ventilated two-dimensional supercavity beneath a moving flat plate near the free surface in a still fluid

A flat plate moves with a constant speed near the free surface in a still fluid. Beneath the moving plate and near the leading edge, a rectangular cavitator is perpendicularly attached and compressed air is injected behind the cavitator. Resultant cavity-flow patterns are observed according to the speed of the moving plate (0.5 to 2 m/s) and the volume flow rate of the compressed air (20 to 100 liter/min). When the speed of the plate is relatively small (0.5m/s and 1m/s), the plate bottom is partially covered by a two-dimensional supercavity; at 0.5 m/s, for all flow rates, the cavity length is time-periodically changed and a thin air film is generated behind the cavity wake and, at 1m/s, as the air flow rate increases, the length of a steady cavity increases and bubble-shedding occurs at the cavity wake. When the speed of the plate is relatively high (1.5m/s and 2m/s), the plate bottom is fully covered by a two-dimensional supercavity; for specific air flow rates, the length of a steady cavity becomes larger than the plate length and, beyond the trailing edge of the plate, reaches the free surface with a re-entrant jet closure.

This work was supported by the National Research Foundation of Korea (NRF-2020R1F1A1058357).