A Multiscale Lattice Boltzmann Model for Simulating Drainage in Wet and Dry Foams

We use a systematic, two-component, 2D, Lattice Boltzmann Model (LBM) with frustrated short range attractive and mid/long-range repulsive-interactions to simulate the capillary and gravity-driven drainage of wet and dry foams in a confined geometry. From the assigned LBM interactions, the gas/liquid surface tension, film elasticity and capillary disjoining pressure are computed to characterize the simulated foam. First, LBM simulations of a Poiseuille flow of the foam are performed as a verification of our model, and these demonstrate a reduction in the maximum velocity with increase in the air area fraction of the foam, and a Non-Newtonian rheology. In the drainage simulations, as gas separates from the foam in the computational domain, the temporal evolution of the foam height shows a rapid collapse followed by a regime in which the foam is more stable. These results compare favorably with experiments on SDS stabilized glycerol/water foams, demonstrating the ability of the LBM method to capture the realistic behavior of foams.