The influence of boundaries on shear banding in complex fluids

Friday, December 11, 2009 - 10:50am - 11:30am
EE/CS 3-180
Peter Olmsted (University of Leeds)
Keywords: shear banding,
boundary conditions,
flow instabilities,
wormlike micelles

Abstract: Shear banding fluids such as wormlike micelles, lamellar surfactant solutions, and emulsions, undergo transitions between fluids of different apparent viscosity as a function of applied flow conditions. This switching makes them appealing for use in microfluidic applications. Since their physics is controlled by the influence of flow on internal microstructure, which in turn is influenced by boundary effects, it is important to develop an understanding of how different kinds of boundary effects influence shear banding. In this talk I will discuss some of these issues, mainly using constitutive models inspired by experiments on wormlike micelles or polymer solutions. and explore the effects of different boundary conditions for the additional viscoelastic stress. These are needed because the equations of motion are inherently non-local and include “diffusive” or square-gradient terms. I will note some of the features expected to be important for microfluidic geometries.

[Work done in collaboration with JM Adams and SM Fielding]
MSC Code: