Large two-dimensional clusters of equal-area bubbles: The influence of the boundary in determining the minimum-energy configuration

Finite monodisperse two-dimensional clusters of bubbles are shown to behave like a crystal rather than a liquid. They attain their lowest-energy configuration when they find an arrangement close to a hexagonal lattice, as predicted by the Wulff construction. The deviation from hexagonal shape of the bubbles in a cluster and the variation in bubble pressure throughout the structure are calculated. It is shown that the effect of reducing the length of the boundary is negligible, explaining why configurations retaining the structure of the lattice will give the lowest energy.