ABSTRACT
Bubble rise velocity is a complicated function of the bubble geometry, the physical properties of the medium, and the physicochemical properties of the gas-liquid interface. The shape that the bubble assumes is in tum a complex function of the hydrodynamic, viscous, and interfacial forces exerted. The drag force on small bubbles may be equal to the drag force on equivalent solid particles. The bubble surface may become mobile, in which case, the bubbles have, in contrast to solid particles, non-vanishing tangential velocities at the gas-liquid interface. The gas circulation inside a bubble also reduces the drag on it.
