  We describe a numerical model to predict the rheology of two-dimensional dry
foams. The model accurately describes soap film curvature, viscous friction
with the walls, and includes the transport of surfactant within the films and
across the vertices where films meet. It accommodates the changes in foam
topology that occur when a foam flows and, in particular, accurately represents
the relaxation of the foam following a topological change. The model is
validated against experimental data, allowing the prediction of elastic and
viscous parameters associated with different surfactant solutions.
