Cavitation Bubble Behavior near Solid Boundaries

In the present study the bubble behavior in the narrow space are experimentally and numerically examined as the gap between two parallel walls and the position of bubble induction were changed. The main results are as follows. (1) The effects of two parallel walls can be classified by the ratio of the gap between the walls to the maximum bubble radius. If the ratio>5.0 the bubble shape is almost sphere. The wall effect remarkably appears for the ratio<3.0 and the bubble deforms to be dumbbellor cone-like shape. (2) When the gap between the walls is small, the single bubble is finally divided into two bubbles owing to the large lateral pressure. The rebound of each bubble causes impulsive pressure and damages the upper and lower wall surface. Especially, if the bubble is not created at the center between the walls, the collapse phase shift among the divided bubbles brings the further damage on the wall surface. (3) The computed motion of the bubble without non-condensable gases well explains the dumbbellor cone-shaped bubble deformation.