Unified drift velocity closure relationship for large bubbles rising in stagnant viscous fluids in pipes

This study investigates the effects of oil viscosity, pipe diameter, and pipe inclination angle on drift velocity. Experiments were conducted for medium viscosity oils using a 0.0508-m ID pipe for inclination angles between 0° and 90°. In these experiments, it was observed that as the liquid viscosity increased, the drift velocity decreased. Drift velocity displayed a convex parabolic behavior with respect to the inclination angle. For all liquid viscosities, a maximum velocity value was observed between 30° and 50° inclinations from horizontal. A unified dimensionless closure relationship for drift velocity is proposed. It was developed using data acquired in this study and available data from literature with a pipe diameter range of 0.0373–0.178 m.