Criterion for purely elastic Taylor-Couette instability in the flows of shear-banding fluids

TL;DR

This paper develops a criterion to identify purely elastic Taylor-Couette instability in shear-banding fluids, explaining observed fluctuations and classifying flow stability in curved streamline flows.

Contribution

It adapts the elastic instability criterion to shear-banding flows, providing a new framework for understanding flow fluctuations in these complex fluids.

Findings

Three categories of shear-banding flows with curved streamlines are identified.

The criterion explains spatio-temporal fluctuations observed in experiments.

Flow stability depends on the flow configuration and elastic properties.

Abstract

In the past twenty years, shear-banding flows have been probed by various techniques, such as rheometry, velocimetry and flow birefringence. In micellar solutions, many of the data collected exhibit unexplained spatio-temporal fluctuations. Recently, it has been suggested that those fluctuations originate from a purely elastic instability of the flow. In cylindrical Couette geometry, the instability is reminiscent of the Taylor-like instability observed in viscoelastic polymer solutions. In this letter, we describe how the criterion for purely elastic Taylor-Couette instability should be adapted to shear-banding flows. We derive three categories of shear-banding flows with curved streamlines, depending on their stability.