Relaxation and flow in linearly sheared two-dimensional foams

We probe the relation between rheology and shear-induced relaxation in experiments on two-dimensional foams at steady shear. The characteristic relaxation time t(r), which we extract from the non-affine part of the bubble displacements, scales non-linearly with the local strain rate. (gamma) over dot In particular, the relative strength of the non-affine part grows when (gamma) over dot -> 0 -hence the foam flow is not quasistatic down to the lowest experimentally accessible shear rate. Furthermore, we establish a direct connection between the relaxation time scaling and the macroscopic rheology. Copyright (C) EPLA, 2010