DIRECT NUMERICAL SIMULATIONS OF ELECTROHYDRODYNAMICS OF LIQUID DROPS AND SUPERIMPOSED FLUIDS

Author

Alireza Razeghi, Southern Illinois University CarbondaleFollow

Date of Award

5-1-2023

Degree Name

Doctor of Philosophy

Department

Engineering Science

First Advisor

Esmaeeli, Asghar

Abstract

In this dissertation, the effect of the applying Direct Current (DC) electric field onthe interface deformation, and dynamics of the multiphase fluid systems have been investigated. The problems under study are grouped into two categories. In the first category the deformation and dynamics of superimposed fluids is investigated using direct numerical simulations. The second group of problems studied, consider the interface deformation, trajectory, and dynamics of single and binary drops using two dimensional, axisymmetric, and three-dimensional spaces. For superimposed fluids system, two fluids which are naturally stable regarding the Rayleigh-Taylor instability criteria, are exposed to uniform electric field. Depending on the fluid property ratio the interface of the fluids deforms into cone shape, or slender fluid jets with impinging drop at its tip. For the group of problems dealing with drop, first the dynamics of the drop positioned close to electrode is studied, and the drop deformation, trajectory, terminal velocity and related variables are quantified. It has been found that the drop based on the electrical property ratios can be attracted toward the wall or it can be repelled. This study is done in two frameworks. The first framework was a three-dimensional space, and the second one is done in an axisymmetric space. In addition to the drop electrical properties, the initial distance from the electrode significantly enhances the drop response to the electric field,such that the drop closer to the electrode gains higher acceleration to move toward or away from the electrode. Furthermore, the dynamics of a drop pair under the action of electric field is investigated using two dimensional, and three-dimensional space. An empirical analytical equation has been derived for the binary drops in two-dimensional space that can predict the relative trajectory of the drops. The analytical model is compared against the numerical results and good agreement is seen between them. It has been seen that the critical values changing the relative trajectory of drops in two dimensional and three-dimensional spaces are different, and hence the dynamics of the drops is investigated in three-dimensional space as well. It has been found that the drops may attract or repel each other based on their electrical properties or initial orientations. Furthermore, due to the existence of critical angle, the drop may experience repulsion at early times, and then attract each other under special circumstances.