Numerical Investigation on Mechanism Analysis of Bubble Pinch-off

The studies on bubble pinch-off deviates to some degree from the actual situation due to limitations in theoretical assumptions and experimental conditions, and physical details such as satellite bubbles inside the bubble cannot be observed. Even some of the published experimental results are divergent. To fully understand the dynamics of bubble pinch-off, the authors applied the volume of fluid (VOF) method to investigate the effect of liquid-phase viscosity on bubble pinch-off, and analyzed the pinch-off process and the surrounding flow field. It was found that in low-viscosity liquids, the process of bubble pinch-off is relatively fast and the position corresponding to R_min varies only in the axial direction; and satellite bubbles during pinch-off shows vertical distribution, which enter the upper and lower parts with the jet after bubble pinch-off. In intermediate and high viscosity liquids, a gas line is formed after bubble pinch-off, and the length and duration of the gas line increase with an increase in liquid-phase viscosity; and the position corresponding to R_min moves not only radially inward, but also axially upward. In liquids of different viscosities, the strength of annular flow and the radial pressure drop are different, which leads to different phenomena of bubble pinch-off.