Using Surface Evolver to measure pressures and energies of real 2D foams submitted to quasi-static deformations

International audience ; Static 2D foams have the interesting property that their energy is measurable by summing up the length of their films, so that a simple optical picture of a 2D foam should enable measurement of its energy and other quantities such as its bubbles’ pressures. This operation is of course unrealizable in most experiments since the optical resolution limits the accuracy of length measurements. Here we show that, using image analysis tools alongside an iterative procedure based on the Surface Evolver (Brakke, 1992) to analyze optical images of a 2D foam, we are able to measure accurately its energy and its bubbles’ pressures up to a single multiplying factor. We determine this factor, and validate this procedure, by comparing experimental measurements of the pressure and the work done on a 2D foam experiencing a quasi-static localized deformation with the energy and pressures computed using our procedure.