The movement of single large bubbles in closed vertical tubes

Abstract

The flow and deformation of single large air and liquid bubbles suspended in wetting liquids when moving under gravity in closed vertical tubes have been studied. The flow patterns in both phases and thickness of the liquid film surrounding the bubbles and the shape of the bubble ends were determined by direct observation through a microscope. Quantitative agreement with a theory relating bubble velocity to film thickness in viscous flow, and to the tube radius in inertial flow was obtained. In viscous flow the deformation at a given interfacial tension was independent of bubble length and of the viscosity of the suspending liquid. In viscous flow the end of the sedimenting bubbles were spheroidal, with the leading ends prolate and the trailing ends generally oblate. The axis ratio of the leading ends increased with increasing interfacial tension. Wave disturbances occurred at the trailing ends of the bubbles. In inertial flow the leading ends of rising air bubbles were hemispherical.