Propagation of Chain-Reacting Bubble Collapse Generating at Cavitation Breakdown

In order to clarify the propagation phenomenon of the bubble collapse induced during cavitation breakdown generating around a circular cylinder, pressure measurement on the cylinder surface, high speed video camera and Particle and Bubble image velocimetry observation were carried out. The bubble collapse process is that, in first, the inflow yields toward into the cavity accompanying with the weak bubble collapse. In second, when the inflow is impinging against the cavity boundary, the strong bubble collapse pressure is induced. In finally, the surrounding bubbles collapse successively inducing new collapse pressures and this chain-reacting bubble collapse propagates toward the upstream cylinder along the cavity boundary. The propagation velocity of the chain-reaction is extremely low in the range from about 10 m/s to 20 m/s compared with the sound velocity of two phase fluid of gas and liquid.