Behaviors of cavitation bubbles driven by high-intensity ultrasound

Abstract

Bubble behaviors are modulated by the primary and secondary acoustic fields in a multi-bubble system. To explore the translational motion of bubbles in cavitation liquids containing high-concentration cavitation nuclei, evolutions of bubbles were recorded by a high-speed camera, and translational trajectories of several representative bubbles were traced. It is found that translational movements of bubbles are always accompanied by the fragmentation and coalescence of bubbles, and for bubbles smaller than 10μm, the possibility of bubble coalescence is enhanced when the spacing of bubbles is less than 30μm. Measured signals and their spectra show the presence of strong negative pressure, broadband noise, and various harmonics, which imply that multiple interactions of bubbles appear in the region of high-intensity cavitation. Due to the strong coupling effect, the interaction between bubbles is random. A simplified triple-bubble model was developed to explore the interaction patterns of bubbles affected by the surrounding bubbles. Patterns of bubble interaction, such as attraction, repulsion, stable spacing, and rebound of bubbles, can be predicted by the theoretical analysis, which is in good agreement with experimental observations. Mass exchange between the liquid and bubbles as well as absorption in the cavitation nuclei also plays an important role in multi-bubble cavitation, which may account for the weakening of the radial oscillations of bubbles.