Scaling state of dry two-dimensional froths: universal angle-deviations and structure.

We characterize the late-time scaling state of dry, coarsening, two-dimensional froths using a detailed force-based dynamical model. We find that the slow evolution of bubbles leads to small and decreasing deviations from 120-degree angles at threefold vertices in the froth, but with a side-number dependence that is independent of time and apparently universal. We also find that a significant number of T1 side-switching processes occur for macroscopic bubbles in the scaling state, though most bubble annihilations involve four-sided bubbles at microscopic scales.