Theoretical and experimental studies of the deformation of bubbles moving in quiescent newtonian and non-newtonian liquids

Abstract

Theoretical and experimental studies of the shapes and terminal velocities of bubbles rising in quiescent Newtonian and non-Newtonian liquids were carried out. For non-Newtonian liquids, the power law model was adopted as the constitutive model. Numerical analysis by use of the finite element method can predict well the observed shapes and velocities of such bubbles. It is found experimentally and theoretically that as bubble diameter increases, the bubble deforms from a sphere to one of three types of ellipsoids, depending on the viscosity of the continuous phase: (1) more deformed at the front than at the rear, (2) symmetrical front to rear, and (3) more deformed at the rear than at the front, in both Newtonian and non-Newtonian liquids. Shape regime maps are proposed on the basis of the numerical simulations. © 1990, The Society of Chemical Engineers, Japan. All rights reserved.