Interfacially driven instability in the microchannel flow of a shear-banding fluid.
Using microparticle image velocimetry, we resolve the spatial structure of the shear-banding flow of a wormlike micellar surfactant solution in a straight microchannel. We reveal an instability of the interface between the shear bands, associated with velocity modulations along the vorticity direction. We compare our results with a detailed theoretical study of the diffusive Johnson-Segalman model. The quantitative agreement obtained favors an instability scenario previously predicted theoretically but hitherto unobserved experimentally, driven by a normal stress jump across the interface between the bands.
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Laboratoire Microfluidique, MEMS et Nanostructures, UMR Gulliver CNRS-ESPCI 7083, France.
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