Complex flows of viscoelastic wormlike micelle solutions

Abstract

Micelles are formed by the self-assembly of surfactants in solutions. Wormlike micelles or living polymers are a particularly interesting fluids because their long flexible cylindrical geometry can lead to entanglement even at relatively low concentrations. The non-linear rheological and flow response of wormlike micelles has proven to be incredibly rich and complex. In strong, steady-shear flows, some wormlike micelles have been shown to shear band. In uniaxial extensional flows, wormlike micelle solutions demonstrate enormous strain hardening of their extensional viscosity and under large extensional stresses, can break apart. This failure and the resulting morphological changes of the micelles in the flow have been linked to a number of interesting elastic instabilities that have been reported in flow of micelles past a falling sphere and/or a flexible cylinder. In this talk, we will primarily focus on flow of wormlike micelle solutions past a falling sphere and a flexible object, where both shear and extensional flow components are dominant. We will discuss how flow strength, detailed form of flow, micelle concentration, and micelle structure affect these complex flows.