Surfactant Effects on Viscous Interactions of Drops and Bubbles
Department of Chemical Engineering
University of Minnesota-Duluth
Surfactants are important in a wide range of applications involving dispersions of drops and bubbles. In this talk, theoretical results will be presented concerning the impact of surfactants on viscous interactions of two drops or bubbles in various flows, including buoyancy, thermocapillary motion, and simple shear. Spherical and deformable drops are considered in the limit of negligible inertia. Bulk insoluble, nonionic surfactant is modeled with a linear equation of state for the dependence of interfacial tension on the surfactant surface concentration. Collision efficiencies are determined for spherical drops, while critical offsets for coalescence phenomena and breakup are studied for deformable drops. An interesting result for two contaminated deformable drops in buoyancy is the dominance of larger drop breakup over breakup of the smaller drop in certain regions of the parameter space.