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Research Abstracts Online
January - December 2011

Main TOC

University of Minnesota Duluth
Swenson College of Science and Engineering
Department of Chemical Engineering

PI: Michael A. Rother

Surfactant Effects on Viscous Interactions of Drops

Surfactants (“surface-active agents,” e.g., soap) reside at the interface between two liquids, or a liquid and a gas, and modify the interfacial tension between the phases. The presence of surfactant affects the interactions between drops in an immiscible medium, including whether or not the drops coalesce. These interactions are important in emulsion stability, sedimentation and creaming, polymer blending, rheology, liquid-liquid extraction, and geophysical flows. Thus, understanding how surfactants work is important to many industries, including food, pesticides, paints, ore flotation, and detergents.

The primary objective is to develop a fundamental understanding of the role of surfactants in dilute dispersions of spherical and deformable drops in a variety of flows. Analytical and semi-analytical methods are used for two spherical drops in the presence of surfactant, while boundary-integral methods are employed for two moderately deformable drops. In general, the goal is to predict the behavior of dilute dispersions by trajectory analysis, which provides collision or breakup efficiencies, and population dynamics simulations. Past work includes research on gravitational interactions of spherical drops covered with compressible surfactant. Other work includes investigations on the effects of surfactant redistribution on interactions of deformable drops in combined gravitational and thermocapillary motion and on clean spherical drops interacting at finite Stokes numbers and low Reynolds numbers.