Avalanches and diffusion in bubble rafts
CE Maloney, EPL, 111, 28001 (2015).
Energy dissipation distributions and particle displacement statistics are studied in the mean-field version of Durian's bubble model. A two- dimensional (2D) bi-disperse mixture is simulated at various strain rates, (gamma)over dot, and packing ratios, phi, above the rigidity onset at phi = phi(C). Well above phi(C), and at sufficiently low (gamma)over dot, the system responds in a highly bursty way, reminiscent of other dynamically critical systems with a power-law distribution of energy dissipation. As one increases (gamma)over dot at fixed phi or tunes phi -> phi(C) at fixed (gamma)over dot, the bursty behavior vanishes. Displacement distributions are non-Fickian at short times but cross to a Fickian regime at a universal strain, Delta gamma(*), independent of (gamma)over dot and phi. Despite the profound differences in short-time dynamics, at intermediate Delta gamma the systems exhibit qualitatively similar spatial patterns of deformation with lines of slip extending across large fractions of the simulation cell. These deformation patterns explain the observed diffusion constants and the universal crossover time to Fickian behavior. Copyright (C) EPLA, 2015
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