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arXiv · 2005.00170

Effects of Surfactant Solubility on the Hydrodynamics of a Viscous Drop in a DC Electric Field

H. Nganguia·W. -F. Hu·M. -C. Lai·Y. -N. Young
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Abstract

The physico-chemistry of surfactants (amphiphilic surface active agents) is often used to control the dynamics of viscous drops and bubbles. Surfactant sorption kinetics has been shown to play a critical role in the deformation of drops in extensional and shear flows, yet to the best of our knowledge these kinetics effects on a viscous drop in an electric fieldhave not been accounted for. In this paper we numerically investigate the effects of sorption kinetics on a surfactant-covered viscous drop in an electric field. Over a range of electric conductivity and permittivity ratios between the interior and exterior fluids, we focus on the dependence of deformation and flow on the transfer parameter $J$, and Biot number $\text{Bi}$ that characterize the extent of surfactant exchange between the drop surface and the bulk. Our findings suggest solubility affects the electrohydrodynamics of a viscous drop in distinct ways as we identify parameter regions where (1) surfactant solubility may alter both the drop deformation and circulation of fluid around a drop, and (2) surfactant solubility affects mainly the flow and not the deformation.

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H. Nganguia, W. -F. Hu, M. -C. Lai, Y. -N. Young. 2020-05-01. Effects of Surfactant Solubility on the Hydrodynamics of a Viscous Drop in a DC Electric Field. https://doi.org/10.1103/physrevfluids.6.064004

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