Bubble Shape Oscillation Characteristic during Its Growth and Rising Process

Variation of bubble shape has a significant effect on twophase flow, heat and mass transfer process. In this paper, the bubble shape oscillation characteristics in growing and rising process were investigated experimentally using a highspeed video camera and particle image velocimetry (PIV) technique. The variation in the ratio of bubble height to width and its surrounding flow field at different gas injection rates were analyzed. Experimental results show that the gas injection rate has an obvious effect on the shape of departed bubbles. At low gas flow rate, the shape of the departed bubble changes from prolate spheroid to oblate spheroid gradually, while the coalescence of the departed bubble and the growing one leads to the drastic oscillation of bubble surface at high flow rate. In addition, the impact of the oscillated bubble on the shape of a growing bubble in its wake region cannot be neglected as well. The oscillated rising bubble will enhance the inertia effect on the growing bubble and leads to its shape fluctuation.