Numerical simulation of the coalescence of two bubbles in an ultrasound field.

The coalescence of two bubbles under ultrasound irradiation is numerically investigated. The results indicate that ultrasound may accelerate the coalescence process, depending on the initial phase. The time-averaged nonzero Bjerknes force promotes bubble coalescence by dragging bubbles to nodes or antinodes, depending on their size. At the beginning of the coalescence process, a film forms between the two bubbles. The film drainage time first increases then decreases as a function of initial distance. This study contributes to an understanding of the effects of ultrasound on bubble coalescence.