Deformation and Breakup of Liquid Drop in Simple Shear Field

Abstract

Process of deformation and breakup of droplets, which plays an important role in mass transfer and chemical reaction in a dispersed liquid system, was studied experimentally in steady and unsteady shear fields generated in the annular space between two coaxial rotating cylinders. In steady shear field, four patterns of deformation and breakup are characterized according to the viscosity ratio of dispersed and continuous liquids, and the critical shear rate required for breaking up a droplet and its deformation vary with viscosity ratio. The orientation of deformed droplet was correlated with the viscosity ratio and the degree of stationary deformation. In a step change of shear field, two patterns of unsteady deformation process were observed. In a system of low viscosity ratio, the unsteady deformation process does not oscillate with time and the time dependence of deformation can be estimated by a equation derived semi-theoretically. On the other hand, the unsteady deformation process oscillates with time in a system of high viscosity ratio and the periodic time has been correlated with the Weber number. The necessary and sufficient conditions of shear rate and loaded time required for breaking up droplets have been determined under the step change of shear field and the numbers of broken droplets have been correlated with excess shear rate and the loaded shearing time. © 1976, The Society of Chemical Engineers, Japan. All rights reserved.