(503h) Transient Evolution of Shear Bands in a Model 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 cetyltrimethyl ammonium bromide (CTAB) and sodium salycilate (NaSal). Rheological measurements indicate formation of a shear stress plateau for 0.004 <shear rate< 0.9 (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. An elastic recoil with negative velocities is observed during the stress 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. However, we report formation of a significant wall-slip at the stationary outer wall.