Structure stability of cyclic chain-like cavitation cloud in thin liquid layer

Abstract

In this paper, the evolution of the cavitation bubbles is investigated. A model is developed to describe the cyclic chain-like cavitation cloud and analyze its structure stability in a thin liquid layer. By considering the effect of secondary acoustic radiation of bubbles, the dynamic equations of the bubbles in three zones of the cyclic chain are obtained. The secondary Bjerknes force is selected and used to explore the interaction between the bubbles in different regions. Numerical results show that the newborn bubbles inside the pure liquid zone of the thin layer can be attracted by the bubbles at the cyclic chain-like bubble chain. The bubble number density can affect the coupling strength between bubbles, and it is closely related to the driving pressure. Therefore, the structure stability of cyclic chain-like cavitation cloud can be disrupted by the perturbations of the acoustic pressure. To verify our analysis, we observe the structure of cavitation cloud in a thin liquid layer in a strong acoustic field by using a high speed camera. It is observed that the simultaneous collapse of local bubbles occurs, and pure liquid-like thin layers are distributed in the bubble cloud randomly. The boundary of the pure liquid-like thin layers oscillates with the acoustic field, and these liquid zones sustain about 4 acoustic cycles. The experimental results accord well with theoretical results.