Effect of translational shear on interfacial structure in the viscous fingering instability

TL;DR

Applying oscillatory shear in a Hele-Shaw cell smooths the viscosity interface between miscible fluids, delaying the viscous fingering instability and providing a new method for controlling fluid displacement processes.

Contribution

This study introduces the use of oscillatory translational shear to control and delay viscous fingering in miscible fluids, combining experiments and simulations.

Findings

Shear smooths the viscosity profile at finger tips.

Increasing shear amplitude or velocity delays instability onset.

Shear stabilizes the interface against fingering.

Abstract

We introduce applied shear as a method to control viscous fingering by smoothing the interface between miscible fluids. In the viscous fingering instability, a less viscous fluid displaces a more viscous one through the formation of fingers. The instability, which requires a confined geometry, is often studied in the thin gap of a quasi-two-dimensional Hele-Shaw cell. When the two fluids are miscible, the structures that form in the dimension traversing the gap are important for determining the instability onset. We demonstrate with experiments and simulations that oscillatory translational shear of the confining plates changes the gap-averaged viscosity profile so that it becomes less abrupt at the finger tips. Increasing the amplitude or velocity of the shear delays the instability onset and decreases the finger growth rate. Shear can thus be used to stabilize a pair of miscible fluids against fingering. The results show a direct correlation between a smoother viscosity profile and delayed instability. TEASER: Oscillatory shear smooths fluid interfaces, stabilizing viscous fingering in miscible fluids.