Transient Shear Banding in a Simple Yield Stress Fluid
Abstract
We report a large set of experimental data which demonstrates that a simple yield stress fluid, i.e. which does not present aging or thixotropy, exhibits transient shear banding before reaching a steady state characterized by a homogeneous, linear velocity profile. The duration of the transient regime decreases as a power law with the applied shear rate γ. This power law behavior, observed here in carbopol dispersions, does not depend on the gap width and on the boundary conditions for a given sample preparation. For γ 0.1 s-1, heterogeneous flows could be observed for as long as 105 s. These local dynamics account for the ultraslow stress relaxation observed at low shear rates.
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