Interaction dynamics of a cavitation bubble and an air bubble entrapped in a cavity

• The interaction between cavitation bubble and air bubble confined in a cavity is studied. • The secondary Bjerknes force and Kelvin impulse on the cavitation bubble are investigated. • The influence of the cavity shape on the bubble collapse strength is investigated. In this study, a fully compressible, two-component, three-phase cavitation model was employed to investigate the interaction between cavitation bubbles and air bubbles confined within a finite-volume cavity. The focus was on understanding how an entrapped gas bubble influences cavitation dynamics, including bubble morphology, collapse intensity, the evolution of the secondary Bjerknes force, and the Kelvin impulse. Results show that at smaller wall-to-bubble distances ( L ), cavitation bubbles exhibit asymmetric growth due to interface intrusion into the air bubble, leading to earlier micro-jet formation and severe air bubble deformation. Rebound of the air bubble during collapse accelerates the micro-jet, enhancing jet velocity, though this effect weakens with increasing L . Larger cavity radius and depth reduce air bubble fragmentation and bottom pressure while maintaining collapse pressure. A power-law relationship was observed between the maximum collapse pressure and velocity and the dimensionless parameter ζ , highlighting the roles of cavity geometry and wall distance. Additionally, the secondary Bjerknes force exhibits significant fluctuations at smaller L , indicating strong mutual coupling between cavitation and air bubbles. These findings offer insights into optimizing gas-containing, cavitation-resistant structures through geometry control.