Flow of wormlike micelles: From shear banding to elastic turbulence

Shear banding is a ubiquitous phenomenon in complex fluids flows. Most often it corresponds to a flow state in which a fluid splits into layers of differing apparent viscosities supporting different local shear rates. Shear banding has been observed, either transiently or at steady state, in different classes of complex systems including polymeric fluids and soft glassy materials. Its description and understanding is particularly advanced in surfactant wormlike micelles, for which the experimental evidence of its mechanical signature dates back to the 1990s. Over the past 10 years a strong effort was made to combine global rheology with local time-resolved techniques to probe both the velocity field and the structural properties in various macro- and micro-fluidic geometries. Overall, complex flows have been observed to emerge on top of the shear-banding flow and have been connected to the development of viscoelastic instabilities.