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 . 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 , heterogeneous flows could be observed for as long as . These local dynamics account for the ultraslow stress relaxation observed at low shear rates.
- Received 17 February 2010
DOI:https://doi.org/10.1103/PhysRevLett.104.208301
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