Rising velocity and shape of single air bubbles in highly viscous liquids

Abstract

The shape and rising velocity of single air bubbles were investigated experimentally in quiescent, highly viscous liquids such as caster oil, glycerine and corn syrup. It was found that the bubble behavior in highly viscous liquids is very different from that in low viscosity liquids. The bubble rose rectilinearly and without oscillation. The terminal velocity was dependent mainly on the liquid viscosity and the surface tension showed only a minor effect. The Cd curve obtained experimentally agreed well, though no special caution of purification of liquids was taken, with Hadamard equation for gas sphere in the range of Re=about 10-3 to 10-1 and with Taylor-Acrivos equation for gas oblate spheroid in the range of Re up to about 2. The correlation proposed previously for low M systems, Cd/Cdf vs. ReM1/6, was found to be valid in the range of M<10-1. For the region M>10-1 the Cd/Cdf was a function of only Reynolds number and unity when Re<1. The bubble shape varied as the bubble diameter increased, from sphere to oblate spheroid whose bottom is convex, flat or concave depending on the size of bubble. At Reynolds number of about unity the bottom of the bubble became flat. The e curve obtained was a function of only Reynolds number in the high M systems, an empirical relationship being given by Eq.(4). The correlation, 1-e vs. We, proposed previously for the low M liquids was found applicable up to M=0.1. © 1968, The Society of Chemical Engineers, Japan. All rights reserved.