An Investigation of the Motion of a Bubble near a Free Surface

An investigation was made of the motion of a cavitation bubble in the vicinity of a free surface experimentally as well as theoretically. A bubble was produced by focusing a ruby laser into water, and subsequent behavior was observed with a high speed camera. The deformable nature of both a bubble and a free surface becomes significant when a bubble behaves relatively close to the surface. Immediately after the bubble rebound a secondary cavitation occurs, at around zero dynamic pressure region, which was developed in water between a rising free surface and a re-expanding bubble due to lower pressure caused by the interaction of reflected expansion waves from the surface. Some aspects of the bubble motion were compared with image theory with good agreement.