Electromagnetic field orientation and dynamics governs advection characteristics within pendent droplets

TL;DR

This study investigates how electric and magnetic field orientations influence internal flow patterns and velocities within pendant salt solution droplets, revealing magnetic fields enhance while electric fields diminish circulation speed.

Contribution

It introduces a mathematical model based on electro and magnetohydrodynamics that predicts field-dependent internal flow velocities in pendant droplets, validated by experimental data.

Findings

Magnetic fields increase circulation velocity.

Electric fields decrease circulation velocity.

Flow direction and strength are governed by field orientation.

Abstract

The article reports the domineering governing role played by the direction of electric and magnetic fields on the internal advection pattern and strength within salt solution pendant droplets. Literature shows that solutal advection drives circulation cells within salt based droplets. Flow visualization and velocimetry reveals that the direction of the applied field governs the enhancement/reduction in circulation velocity and the directionality of circulation inside the droplet. Further, it is noted that while magnetic fields augment the circulation velocity, the electric field leads to deterioration of the same. The concepts of electro andmagnetohydrodynamics are appealed to and a Stokesian stream function based mathematical model to deduce the field mediated velocities has been proposed. The model is found to reveal the roles of and degree of dependence on the governing Hartmann, Stuart, Reynolds and Masuda numbers. The theoretical predictions are observed to be in good agreement with experimental average spatio-temporal velocities. The present findings may have strong implications in microscale electro and/or magnetohydrodynamics.