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• Mass transfer across a gas–liquid interface of acoustic cavitation is investigated. • Time-averaged Sherwood number is decreased with sound pressure amplitude. • Time-averaged Sherwood number can be negative value due to area and shell effect. • The instantaneous Sherwood number is varied in the range of O (101) ∼ O (102). In the present study, mass transfer across a gas–liquid interface of acoustic cavitation bubble is numerically investigated. The volume of fluid (VOF) method coupled with a continuous species transfer model is used to simulate the bubble dynamic behavior and mass transfer across the gas–liquid interface. Chemical species are transferred repeatedly between the liquid and gas phases in accordance with the bubble oscillation, and the chemical species are transferred into the bubble during an expansion phase, and to the outside of bubble during a compression phase. Time-averaged Sherwood number is decreased with an amplitude of sound pressure due to area effect and shell effect , and its value becomes negative at high pressure amplitude. Meanwhile, the instantaneous Sherwood number is largely varied in accordance with the bubble oscillation, and its magnitude becomes O (101) ∼ O (102). [ABSTRACT FROM AUTHOR]

Acoustic cavitation occurs in ultrasonic treatment causing various phenomena such as chemical synthesis, chemical decomposition, and emulsification. Nonlinear oscillations of cavitation bubbles are assumed to be responsible for these phenomena, and the neighboring bubbles may interact each other. In the present study, we numerically investigated the dynamic behavior of cavitation bubbles in multi-bubble systems. The results reveal that the oscillation amplitude of a cavitation bubble surrounded by other bubbles in a multi-bubble system becomes larger compared with that in the single-bubble case. It is found that this is caused by an acoustic wake effect, which reduces the pressure near a bubble surrounded by other bubbles and increases the time delay between the bubble contraction/expansion cycles and sound pressure oscillations. A new parameter, called "cover ratio" is introduced to quantitatively evaluate the variation in the bubble oscillation amplitude, the time delay, and the maximum bubble radius. [ABSTRACT FROM AUTHOR]