生长和浮升过程中气泡形状振荡特性研究

气泡形状变化对两相流动和热质传递过程有着重要影响。本文利用高速摄像仪和粒子图像测速（PIV）技术对生长和浮升过程中气泡的形状振荡特性进行了实验研究，分析了不同注气流量下气泡形状及其周围流场的变化规律。实验结果表明，气流量对脱离后气泡的形状有着明显影响，在低流量下，脱离气泡逐渐由长椭球形转变为扁椭球形，而在高流量下，脱离气泡与生长气泡的聚合将导致气液界面大幅振荡。此外，振荡气泡对其尾流区内生长气泡形状的影响同样不容忽视，其会引起生长气泡所受惯性作用增强，进而导致气泡形状波动。

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.