Critical condition for inhibition effect of two cavitation bubbles with similar sizes near a rigid wall

Cavitation often occurs in the form of bubble clusters or cavitation clouds. To explore the interaction among cavitation bubbles within clusters or clouds, the corona underwater discharge technology was used to induce two cavitation bubbles with similar sizes and synchronized initial formation near a rigid wall. It was found that the direction and velocity of the micro-jet of the near-wall cavitation bubble are significantly influenced by the other cavitation bubble. Specifically, as the bubble-bubble distance and the bubble-bubble-wall angle increase, the micro-jet of the near-wall cavitation bubble gradually shifts from mutual attraction to direct impact on the wall. As the micro-jet direction changes, the forms of shock waves generated by two cavitation bubbles near the rigid wall also change accordingly. Specifically, shock waves exhibit varying forms of stratification as the bubble-bubble distance increases. Accordingly, the shock wave intensity of the near-wall cavitation bubble can be either higher or lower than that of a single cavitation bubble near a rigid wall. By analyzing the influence patterns of micro-jets and shock waves, the critical condition for inhibition and enhancement effects of two cavitation bubbles with similar sizes near a rigid wall was further identified based on the impact intensity on the rigid wall. The characteristics of micro-jets and shock waves caused by two cavitation bubbles near a rigid wall have significant theoretical implications for the quantitative study of bubble clusters and cavitation clouds, as well as for the prediction of cavitation erosion models.