Spring 2016
Seminars are held on Mondays from 2:30 - 3:30PM in Cullimore Hall, Room 611, unless noted otherwise. For questions about the seminar schedule, please contact David Shirokoff.
Date: May 2, 2016
Speaker: Aditya Khair
Chemical Engineering,
Carnegie Mellon University
Title: "Transient Electrohydrodynamics of Low-Conductivity Drops"
Abstract:
Deformable interfaces are exposed to electric fields in electro-coalescence, electro-poration, electro-emulsification, and electro-wetting, for instance. In each application, knowledge of the pertinent transport mechanisms and their associated time scales is essential to accurately predict interface deformation and accompanying fluid flow. In this talk, we consider the paradigmatic case of a weakly conducting (oil) drop subject to a spatially uniform DC electric field. We first demonstrate via numerical (boundary integral) computations that charge relaxation and charge convection play a critical role in the transient oblate deformation of a drop. These predictions are verified against experiments. We proceed to quantify the dynamics of a low conductivity prolate drop upon removal of an electric field, again via computation and experiment. Counterintuitively, here a large charge relaxation timescale yields a fast drop relaxation due to the cooperative action of the interfacial electrical stress and the capillary stress after the field is switched off. Finally, we examine the electric-field-induced breakup of an oil drop containing a colloidal suspension of carbon black particles and varying amounts of surfactant. Depending on the amount of added surfactant, and hence the suspension stability, the drop achieves radically different breakup conformations under the applied field.