Flows of Foams
Martin van Hecke
Leiden Institute of Physics
Leiden University
Abstract:
We will show the surprising and non-trivial role of disorder for foam flows in experiments on the rheology of 2D foams. Our central finding is that for disordered foams the effective viscosity scales differently with flow rate than the local bubble-bubble drag does. Monodisperse foams do not exhibit this anomalous behavior, which points to the role of non-affine, swirling motion in setting the coarse grained flow features. The effective viscosity also exhibits nontrivial scaling with wetness --- both anomalous scaling laws are reminiscent of the behavior of the shear modulus near jamming.
We will argue that since bubble interactions are probably simpler than those of, e.g., frictional grains, and are similar to those of the soft spheres without static friction that have been studied extensively in the context of jamming, foams are eminently suited for fundamental studies of the flow of disordered media.