The effects of bubble detachment shape on rising bubble hydrodynamics

Abstract

Local velocities and aspect ratios of rising bubbles were measured to investigate the effects of bubble detachment shape on rising bubble hydrodynamics. Two types of capillary were employed to generate bubbles of identical volume: one glassy nozzle aligned vertically and the other stainless steel needle aligned horizontally. Horizontally injected bubbles have a spherical initial shape, and their values of aspect ratio slightly fluctuate around unity. However, vertically injected bubbles have a surface-stretched initial shape, and their values of aspect ratios decrease sharply from 1.1 to 0.65. There is a notable correspondence between the variation of local velocities and aspect ratios that reects the relevance of the detachment shape of the bubbles to their surface energy. Correlations of Taylor & Acrivos and Vakhrushev & Efremov for aspect ratio were examined by experimental data.