Structure of random bidisperse foam

The Surface Evolver was used to compute the equilibrium microstructure of random soap foams with bidisperse cell-size distributions and to evaluate topological and geometric properties of the foams and individual cells. The simulations agree with the experimental data of Matzke and Nestler for the probability ρ ( F ) of finding cells with F faces and its dependence on the fraction of large cells. The simulations also agree with the theory for isotropic Plateau polyhedra (IPP), which describes the F-dependence of cell geometric properties, such as surface area, edge length, and mean curvature (diffusive growth rate); this is consistent with results for polydisperse foams. Cell surface areas are about 10% greater than spheres of equal volume, which leads to a simple but accurate relation for the surface free energy density of foams. The Aboav–Weaire law is not valid for bidisperse foams.