Electrically induced droplet ejection dynamics under shear flow

Abstract

Droplet nucleation, condensation, and transport is a ubiquitous phenomenon observed in various industrial applications involving power generation and energy conversion to enhance heat transfer. Recent studies have shown that electrowetting (EW) has emerged as a new tool to enhance pool boiling heat transfer. In these applications involving heat transfer through pool boiling, the interplay between the incoming air and an EW-induced jumping droplet is instrumental in determining the overall heat transfer enhancement. This study investigates the transport dynamics of EW-induced droplet ejection in shear flow. A high-density ratio based lattice Boltzmann method is employed to model the ejection dynamics, and a geometry-based contact angle formulation is used to capture the three-phase contact line. We observe a characteristic head vortex at the leading end of the droplet, the strength of which increases with an increase in the shear rate. The droplet angle of flight, aspect ratio, and surface energy are found to increase with an increase in the applied voltage. Variations in pulse width induce a phase shift in the temporal evolution of the angle of flight and aspect ratio. Due to an increase in drag forces, the droplet traverses a larger streamwise distance at higher gas densities.