Foam drainage in two dimensions

A two-dimensional foam between glass plates is subjected to a forced drainage experiment. The propagation of the surfactant solution into the foam is measured and compared with computer simulations of a foam drainage equation. The spread of liquid both vertically, due to gravity, and horizontally, due to capillary suction, is tracked over time. Finally, the effect of varying the width of the input pipe is investigated: the velocities of the wetting fronts are shown to strongly depend on the ratio of the width of the input to the width of the cell.