Experimental research of the cavitation bubble dynamics during the second oscillation period near a spherical particle

In this paper, the dynamic behaviors of the cavitation bubble near a fixed spherical particle during the second oscillation period are analyzed based on the high-speed photographic system. The deformation and motion of the bubble during the second period are investigated by changing the distance between the particle and the bubble and the maximum radius of the bubble. Meanwhile, the variation of the equivalent radius and the centroid motions are analyzed, and the dynamic behaviors of the bubble are categorized according to the bubble morphological characteristics during the second period. Through this research, it is found that (1) The dynamic behaviors of the bubble during the second oscillation period could be divided into three typical cases: For case 1, a bulge would exist on the bubble interface away from the particle, and for case 2, a bulge would appear on the bubble interface and evolve towards the particle, while for case 3, the bubble would be divided into two parts. (2) The larger the dimensionless distance between the particle and the bubble, the smaller the maximum bubble equivalent radius in the second period, and the shorter the second oscillation period. (3) When the bubble is close to the particle, a counter-jet appears at the bubble interface away from the particle during the rebound stage.