Numerical analysis of electrohydrodynamic (EHD) instability in dielectric liquid-gas flows subjected to unipolar injection

TL;DR

This paper extends the analysis of electrohydrodynamic instability from single-phase dielectric liquids to two-phase liquid-gas systems with a liquid-air interface, using a developed VOF model in OpenFOAM, revealing key effects of interface dynamics.

Contribution

It introduces a two-phase VOF-based numerical model for EHD instability analysis and explores the impact of interface effects on flow behavior and stability thresholds.

Findings

Critical stability value matches theoretical predictions

Lack of viscous effects increases flow intensity and reduces instability threshold

Interface presence alters flow structure and vortex positioning

Abstract

In this work, the electrohydrodynamic (EHD) instability induced by a unipolar charge injection is extended from a single-phase dielectric liquid to a two-phase system that consists of a liquid-air interface. A volume of fluid (VOF) model based two-phase solver was developed with simplified Maxwell equations implemented in the open-source platform OpenFOAM\textsuperscript. The numerically obtained critical value for the linear stability matches well with the theoretical values. To highlight the effect of the slip boundary at interface, the deformation of the interface is ignored. A bifurcation diagram with hysteresis loop linking the linear and finite amplitude criteria, which is Uf = 0.059, was obtained in this situation. It is concluded that the lack of viscous effect at interface leads to a significant increase in the flow intensity, which is the reason for the smaller instability threshold in two-phase system. The presence of interface also changes the flow structure and makes the flow vortices shift closer to the interface.