# Soft Matter Seminar: Shear flows near jamming

Friday, May 20, 2011 - 1:15pm - 2:15pm

Reiss 261A

Brian Tighe

Leiden University

Many amorphous materials, from foams and emulsions to pastes and microgel suspensions, can be modeled as sphere packings interacting via repulsive contact forces. When the spheres are packed sufficiently closely they jam, forming a rigid material with weak shear resistance. I will describe how packings flow under two forms of driving: small amplitude oscillatory shear at finite frequency, a form of linear response, and steady shear at finite strain rate, a form of nonlinear response. Flows near the “jamming point,” a nonequilibrium critical point, are organized by the transition: they display qualitatively different regimes, in each of which stresses scale with distance to the transition and with deformation rate. Using analytical and numerical methods I will predict and verify these critical scaling relations, which capture ubiquitous features of complex fluid flow such as shear thinning and the emergence of a yield stress.

Host: Daniel Blair