Transient Shear Banding of Wormlike Micellar Solutions

We report experiments on a simple shear flow of a model shear banding wormlike micellar solution with a custom-built Taylor-Couette (TC) cell. The wormlike micellar solution contains cetyl trimethyl ammonium bromide (CTAB) and sodium salycilate (NaSal). Rheological measurements indicate formation of a shear stress plateau for 0.004 <shear rate< 1 (1/s) at 22 °C. Transient evolution of the velocity profile is investigated from rest using a step shear. Shear stress experiences an overshoot followed by an undershoot and finally steady state. Negative velocity is observed during the undershoot. The steady state velocity profile in θ-r plane of the TC cell confirmed formation of a shear banded velocity profile with no wall-slip at the moving boundary and the proportion of the high shear band compared well with the lever rule.