Electrohydrodynamic interactions of drops

The interaction of fluids and electric fields is at the heart of natural phenomena such as the disintegration of raindrops in thunderstorms and many applications such as ink-jet printing, microfluidics, crude oil demulsification, and electrospray. Many of these processes involve droplets and there has been long-standing interest in understanding drop electrohydrodynamics. While an isolated drop in applied electric fields has been extensively studied, the behavior of many drops is virtually unexplored. Even the pair-wise drop interactions have received scant attention and existing models are limited to axisymmetric and two-dimensional geometries. Preliminary work by the PI found that in three dimensions the electrohydrodynamic interactions can be quite complex and non-trivial. For example, instead of chaining along the field direction, drops can initially attract in the direction of the field and move towards each other, but then separate in the transverse direction. However, systematic investigation, in particular when drops are near contact or surfactants are present, is lacking. To fill this void, the PI proposes a theoretical and computational study complemented with experiments that thoroughly explores the dynamics of a drop pair in an applied uniform electric field.