Velocity profiles in shear-banding wormlike micelles

TL;DR

This study uses Dynamic Light Scattering to measure velocity profiles in wormlike micelles, revealing a simple shear-banding scenario where a highly sheared band nucleates and grows with increasing shear rate, highlighting complex flow behavior.

Contribution

First direct measurement of velocity profiles in shear-banding wormlike micelles confirming a simple nucleation and growth model of shear bands.

Findings

Effective viscosity drop due to shear band nucleation

Linear growth of shear band thickness with shear rate

Complex non-Newtonian flow in the highly sheared band

Abstract

Using Dynamic Light Scattering in heterodyne mode, we measure velocity profiles in a much studied system of wormlike micelles (CPCl/NaSal) known to exhibit both shear-banding and stress plateau behavior. Our data provide evidence for the simplest shear-banding scenario, according to which the effective viscosity drop in the system is due to the nucleation and growth of a highly sheared band in the gap, whose thickness linearly increases with the imposed shear rate. We discuss various details of the velocity profiles in all the regions of the flow curve and emphasize on the complex, non-Newtonian nature of the flow in the highly sheared band.