AN ANALYSIS OF ELECTROHYDRODYNAMIC STABILITY AND DEFORMATION IN IMMISCIBLE FLUIDS

Abstract

OF THE DISSERTATION An Analysis of Electrohydrodynamic Stability and Deformation in Immiscible Fluids by Jia Zhang Dissertation Director: Professor Hao Lin The interactions between an electric field and fluid motion give rise to a class of complex and important phenomena known as electrohydrodynamics. In this work, we developed a set of analytical tools to provide basic understanding and quantitative prediction capabilities. Under this theme, three tasks have been accomplished. 1. A general solution approach for the electrohydrodynamic instability of stratified immiscible fluids is presented. The problems of two and three fluid layers subject to normal electric fields are analyzed. Analytical solutions are obtained by employing the transfer relations relating the disturbance stresses to the flow variables at the interface(s). The results assume a general format. Both new dispersion relations and those from various previous work are shown to be special cases when proper simplifications are considered. As a specific example, the stability behavior of a three-layer channel flow is investigated in details using this framework. This work provides a unifying method to treat a generic class of instability problems. 2. A transient analysis to quantify droplet deformation under DC electric fields is presented. The full Taylor-Melcher leaky dielectric model is employed where the charge relaxation time is considered to be finite. The droplet is assumed to be spheroidal in shape for all times. The main result is an ODE governing the evolution of the droplet aspect ratio. The model is validated by extensively comparing