Model Studies of the Behavior of Underwater Explosion Bubbles in Contact with a Rigid Bottom
NAVAL ORDNANCE LAB WHITE OAK MD
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The behavior of the explosion bubble in contact with a rigid bottom was investigated on a small scale using high speed photography. The experiments were carried out in a vacuum tank with 0.2-gram charges fired above a 2-inch thick aluminum plate. Test conditions were varied by small increments so that a complex sequence of changing bubble behavior--from bubbles which remained intact on the bottom, to bubbles which split into two or more parts, to bubbles which separated from the bottom intact--was observed. A qualitative description of the bubble behavior along with its dimensions at maximum volume and--for strongly migrating bubbles--at minimum volume is presented in dimensionless form as a function of the inverse Froude number, the amplitude of oscillation, and the distance to the water surface. The qualitative behavior appears to be different from that observed with HE field tests on cratering bottoms. Other factors being equal, there appears to be a greater tendency for a bubble to stick to a cratering bottom.