Experimental research on the hydrodynamic processes of water exit and entry

Using a pneumatic gun and a single stage light gas gun, the supercavitation phenomena during water entry and exit of high-speed bodies (slender bodies) were investigated experimentally. The flow fields were visualized by a high speed camera. The study shows that the trailing vortices consisting of small bubbles shed periodically behind a supercavity. During water exit, the bodies velocities decrease generally, but a short acceleration may occur when the water splash impacts on the bottom of the body. During water entry, the hydroballistics of the underwater body may change due to the asymmetric bubble shedding behind the body and the collision between the body and the cavitys wall. According to experimental results, the drag coefficient in water Cd was measured, and Cd≈07~12.