Effects of a submerged particle on cavitation bubble–free surface interaction

The interaction between a cavitation bubble and a free surface is strongly altered when a submerged particle is present nearby. In this study, combined experiments and Kelvin-impulse-based theoretical analysis are performed to clarify how the particle modifies bubble collapse dynamics and the associated free surface response. An anisotropy parameter is introduced to characterize the boundary-induced asymmetry arising from the free surface and the particle. Within this framework, the influences of the bubble–free surface distance and particle–bubble distance on the bubble collapse morphology, oscillation period, centroid migration, and water spike dynamics are systematically examined. The principal findings are given as follows: (1) The particle suppresses bubble contraction, reduces the liquid velocity near the collapse-induced concave region, and prolongs the oscillation period. (2) An anisotropy-parameter-based predictive relation for bubble centroid migration velocity is established. The particle is found to enhance bubble migration, while the free surface exerts a stronger effect than the particle. (3) A predictive model for the peak height of the water spike is developed based on momentum conservation, and the peak height exhibits a quadratic dependence on the anisotropy parameter.