Electrically-controlled self-similar evolution of viscous fingering patterns in radial Hele-Shaw flows

TL;DR

This paper introduces a novel electro-osmotic control method for viscous fingering in radial Hele-Shaw flows, enabling precise manipulation of finger number, timing of self-similar evolution, and pattern stability beyond traditional injection strategies.

Contribution

It develops a coupled electric and injection control strategy that surpasses traditional methods, allowing detailed regulation of interfacial pattern formation and evolution.

Findings

Electro-osmotic flow enhances control over finger patterns.

The method can tune the number and stability of fingers.

Control effectiveness confirmed beyond linear analysis.

Abstract

Time-dependent injection strategies are commonly employed to control the number of viscous fingers emerging at the interface separating two fluids during radial displacement in Hele-Shaw flows. Here we demonstrate theoretically that such a usual controlling method is significantly improved by taking advantage of an electro-osmotic flow generated by applying an external electric field. More specifically, under the coupled action of time-varying electric currents and injection rates, we design a strategy capable of controlling not only the number of fingers emerging at the interface but also when (and if) the self-similar evolution occurs. In addition, the level of instability of the $n$-fold fingered patterns can also be tuned. This improved control over the interfacial features cannot be realized by the sole consideration of a time-varying injection rate. Perturbative second-order mode-coupling analysis and boundary integral simulations confirm that the validity and effectiveness of the controlling protocol go beyond the linear regime.