2007-09-12
10:15 at HCI J 574

Shear banding in complex fluids

Suzanne M. Fielding

School of Mathematics, University of Manchester, UK

Complex fluids commonly undergo flow instabilities and flow-induced transitions that result in spatially heterogeneous "shear banded" states. Often, these banded states display oscillatory or chaotic dynamics, measured in the bulk rheological signals and in the motion of the interface between the bands. Until recently, however, theory predicted a steady state comprising stationary bands separated by a flat interface. I will discuss recent theoretical progress in capturing complex dynamics of the banded state: first in a model in which the interface (or interfaces) remains flat but moves in a chaotic way; second in a model that explicitly allows for undulations along the interface. I will also discuss the formation of vorticity structuring, as a secondary instability to ordinary shear bands. Time permitting, I will finally discuss some recent results on temperature-induced fluid-fluid demixing, subject to an applied shear flow.