Cavitation bubble collapse in a vicinity of a rigid wall with a gas entrapping hole

This paper aims to reveal the influence of a rigid wall with a gas entrapping hole on the characteristics of the dynamic behavior of a laser-induced bubble collapse. A high-speed camera system was used to record the oscillation process of the laser-induced bubble on a rigid wall with a gas entrapping hole. When a bubble is generated by a laser above the wall with a gas entrapping hole, the entire bubble collapse stays away from the wall or splits into two bubbles because of a radial jet induced by bubble contraction. These two distinctive collapse modes are dependent on the distance between the wall and the bubble. The focus of this study is the quantitative analysis of the jet formation, bubble migration, and oscillation period, and compared with the behavior of the bubble near a rigid wall. The results show that unlike the generation of the bubble near a rigid wall, a rigid wall with a gas entrapping hole affects the morphology of the jet and changes the direction of migration of the bubble and decreases the oscillation period. Thus, the rigid wall with a gas entrapping hole could be effective for reducing cavitation erosion on the wall surface, which is supported by our experiment results.