A viscous froth model for dry foams in the Surface Evolver

An implementation of the recent viscous froth model of Kern et al. [N. Kern, D. Weaire, A. Martin, S. Hutzler, S.J. Cox, The two-dimensional viscous froth model for foam dynamics, Phys. Rev. E 70 (2004) 041411.] in the Surface Evolver is described, along with examples of the simulations that can be achieved. In particular, results are given for steady shear of both periodic and confined staircase structures, and contrasted with the quasi-static case. Also discussed are the case of Couette shear and the relaxation due to coarsening after an initial step-strain. It is shown how the viscous froth model allows the investigation of strain-rate dependent effects and that it gives improved resolution of the topological events which govern the foam's evolution, leading to structures that could not previously have been predicted.