Jet dynamics of two cavitation bubbles adjacent to a rigid wall

Cavitation bubbles in fluids frequently induce persistent cavitation erosion, which seriously impacts the service life and efficiency of hydraulic machinery. This study employed the multiple image method to analyze the jet behaviors induced by the collapse of two bubbles adjacent to the wall and conducted verification through high-speed photographic experiments. The variations of jet characteristics with the spacing of the two bubbles (L*) and the bubble-wall spacing (H*) were analyzed. Then, the parameter conditions for the jet directly colliding with the wall were quantitatively examined. Also, the dominant range and mechanisms of the bubble–bubble interaction and the bubble–wall interaction on the jet behaviors were discussed. The results are summarized as follows: (1) The phenomenon of a jet colliding with the wall non-vertically occurs within a wide parameter range of L*, which can exceed 10 times the maximum bubble radius. (2) As L* increases or H* decreases, there occurs a transition from jets colliding with each other to direct impact against the wall. For the critical situation, a quasi-linear relationship exists between L* and H*. (3) The L*-H* parameter space describing the dominant role of the bubble and the wall for jet behaviors is divided into three feature regions: the bubble-dominated region, the wall-dominated region, and the co-dominated region.