Measurement of wall-slip-layer rheology in shear-thickening wormy micelle solutions

A microscope-mounted torsional shearing-flow cell is constructed and microscopic particle imaging velocimetry is employed to directly visualize and map the velocity slip layer in a shearing flow of dilute micellar surfactant solutions of cetyltriammonium bromide/sodium salicylate. It is shown that the thickness of the wall-slip layer is about 100 μm at low shear rates, decreasing to around 50–60 μm at high shear rates. Surprisingly, we find that the wall slip layer emerges only near the upper rotating plate of the flow cell, and not the lower surface. The rheological properties of the wormy micellar solutions are also measured by using a stress-controlled rheometer and the results are compared to the visualization results of wall-slip velocity in the shearing-flow cell. The rheometer measurements are consistent with literature reports [Hu et al. (1998a,1998b)] in that there is a critical shear rate at which the apparent shear viscosity increases drastically. Above the critical point, the shear viscosity r...

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