Electrocapillary flow in Melcher-Taylor experimental setup

TL;DR

This study investigates electrocapillary-driven two-phase flows in a classical Melcher-Taylor setup, revealing flow pattern changes with forcing, effects of Joule heating, and validating the Lippmann equation for surface tension and electric potential.

Contribution

It provides a detailed numerical analysis of electrocapillary flows, including non-isothermal effects and the validation of the Lippmann equation in such systems.

Findings

Flow pattern shifts with electrocapillary forcing.

Joule heating introduces buoyancy and thermocapillary effects.

Lippmann equation holds for both isothermal and non-isothermal cases.

Abstract

Electrocapillary-driven two-phase flows in a confined configuration of a classical experiment of Melcher and Taylor are studied. The computed streamlines of the flow of the heavier dielectric liquid (corn oil) qualitatively represents the corresponding experimental image. With the increase of electrocapillary forcing, the flow pattern changes, so that the main circulation localizes near boundary with a larger electric potential. When a dielectric liquid is replaced by a poorly conducting one, the system becomes non-isothermal owing to the Joule heating. Then the flow is driven also by buoyancy and thermocapillary convection, whose effect becomes noticeably stronger than the electrocapillary one. With the increase of electric conductivity, the electrocapillary effect is further weakened compared to the two others, while the electrocapillary and thermocapillary forces remain comparable at the central part of the interface, where the thermocapillary force changes its sign. The results show that consideration of the two-phase model is mandatory for obtaining correct flow patterns in the lower heavier fluid. The Lippmann equation, connecting electrically induced surface tension with non-uniform surface electric potential, is numerically verified for both isothermal and non-isothermal formulations and was found to hold in both of them.