Flow‐Induced Coalescence Involving Attractive Interparticle Forces

Abstract

Coalescence is one of mechanisms of increasing average size of droplets dispersed in a matrix. Extensional‐flow‐induced coalescence where the motion can be described using two coordinates, distance and angle, and shear‐flow‐coalescence described in three dimensions have been studied. Unlike approaches in most of our previous papers where trajectories are solved as dependence of distance on angle or of distance and polar angle on azimuth, parallel integration of all spatial coordinates with respect to time is employed here, which allowed also more correct solution of coalescence including attractive forces. In contrast to previous studies, where interdroplet interaction is neglected till their close approach, this paper is based on the switch between equations describing hydrodynamic interactions between droplets at their moderate distance and equations for matrix drainage between close droplets. The results have been compared for zero and finite critical distance with and without considering van der Waals forces. For droplets keeping spherical shape during coalescence, non‐zero critical distance plays qualitatively the same role as attractive forces in calculation of collision. On the other hand, the critical distance cannot be omitted in models considering droplets flattening where the motion equations diverge for zero intersurface distance.