Simulations of two-dimensional foam rheology: localization in linear Couette flow and the interaction of settling discs.

Surface Evolver simulations of flowing two-dimensional foams are described. These are used for two purposes. Firstly, to extract the location of the T 1s, the changes in bubble topology that occur during plastic flow. It is shown that in linear Couette flow the T1 s are localized in space, becoming more so as the polydispersity of the foam decreases. Secondly, the sedimentation of two circular discs through a foam under gravity is studied. If the discs are sufficiently close, they begin to interact and one moves behind the other during their descent.