Yield drag in a two-dimensional foam flow around a circular obstacle: Effect of fluid fraction
Résumé
We study the two-dimensional flow of foams around a circular obstacle within a long channel. In experiments, we confine the foam between liquid and glass surfaces. In simulations, we use a deterministic software, the Surface Evolver, for bubble details; and a stochastic one, the extended Potts model, for statistics. We vary the fluid fraction in both experiments and simulations and determine the yield drag of the foam. We find that it is linear over a large range of the ratio of obstacle to bubble sizes, and is independent of the channel width over a large range. Fluid fraction, on the other hand, has a strong effect on the yield drag; at low fluid fraction the yield drag increases strongly with decreasing fluid fraction. We discuss and interpret this dependence on fluid fraction.