Swelling of a single foam film under slipping

Aqueous foams are often used under flow, and one of the biggest challenges is to create predictive models of their rheology. Our investigations deal with the problem of slip at surfaces, and more precisely sliding bubbles inside a narrow horizontal tube. Using a new experimental procedure based on a Fabry–Perot interferometer, our first results underline some thickness variations for a vertical film separating two bubbles, and moving horizontally. The velocity-dependent thickness is quantitatively described by a power law. We discuss the possible origins of this effect, and the consistency with available models of bubble slipping. Our observations confirm that, under dynamical conditions, there can be complex liquid re-distribution between the different elements of the foam structure.