Experimental study of laser-induced bubble collapse near a rigid wall based on the double-exposure method

Capturing and studying the process of cavitation bubble collapse can help elucidate the mechanism of cavitation erosion. In this paper, a high-spatiotemporal-resolution double-exposure photographic method is used to investigate the collapse of laser-induced cavitation bubbles at two values of the dimensionless distance from the bubble to the wall, γ = d/Rmax = 0.9 and 1.25 (where d is the vertical distance between the bubble center and the wall and Rmax is the maximum radius of the bubble). Complete high-resolution evolution sequences of bubbles near a rigid wall are captured from optical breakdown to second collapse. The generation and development of microjets and shock waves during cavitation bubble collapse are described in detail. The oscillations of the bubble near the rigid wall and the microjets and shock waves generated by the collapse are analyzed. It is shown that the presence of the rigid wall affects the development of the bubble and microjets. The microjet velocity can reach up to 64 m/s. Multiple shock waves are found to be generated by bubble collapse.