AbstractThe shape of the cells in a foam is thought to be determined by the interplay between viscosity and surface tension. In order to assess the relative importance of the two, a simplified model is set up which considers only surface tension. It is assumed that the cells are of uniform cross section in one direction and are based on a regular hexagonal lattice in the other two. The resulting two‐dimensional problem is solved by means of the calculus of variations. For high density foams the voids take the form of circles centered within each hexagonal cell. For low densities (below about 9 solids) the solid part is concentrated at the vertices, between tangential circular areas, connected by straight segments of zero thickness. This illustrates the importance of viscosity, since in real foams the cell walls will break if too thin, while the thinner the walls become, the greater is the effect of viscosity in opposing further thinnin
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