Spatio-temporal dynamics of wormlike micelles under shear

TL;DR

This study investigates the slow evolution and complex dynamics of wormlike micelles under shear, revealing long-term stress relaxation, interface oscillations, wall slip, and transient flow states through ultrasound measurements.

Contribution

It provides new insights into the spatio-temporal behavior and transient phenomena of wormlike micelles under shear, combining experimental observations with theoretical discussion.

Findings

Stress relaxation over six hours linked to high-shear band growth

Oscillations of interface position with 50 s period observed

Presence of wall slip and metastable flow states documented

Abstract

Velocity profiles in a wormlike micelle solution (CTAB in D2O) are recorded using ultrasound every 2 s after a step-like shear rate into the shear-banding regime. The stress relaxation occurs over more than six hours and corresponds to the very slow nucleation and growth of the high-shear band. Moreover, oscillations of the interface position with a period of about 50 s are observed during the growth process. Strong wall slip, metastable states and transient nucleation of three-band flows are also reported and discussed in light of previous experiments and theoretical models.