Higham, Jonathan E and Shahnam, Mehrdad and Vaidheeswaran, Avinash, Anomalous diffusion in a bench-scale pulsed fluidized bed, Physical Review E, Volume 103, Number 4, 043103, 2021, 10.1103/PhysRevE.103.043103, https://link.aps.org/doi/10.1103/PhysRevE.103.043103
Abstract: We present our analysis on microrheology of a bench-scale pulsed fluidized bed, which represents a weakly confined system. Nonlinear gas-particle and particle-particle interactions resulting from pulsed flow are associated with harmonic and subharmonic modes. While periodic structured bubble patterns are observed at the mesoscale, particle-scale measurements reveal anomalous diffusion in the driven granular medium. We use single-particle tracks to analyze ergodicity and ageing properties at two pulsing frequencies having remarkably different mesoscale features. The scaling of ensemble-averaged mean-squared displacement is not unique. The distribution of time-averaged mean-squared displacements is non-Gaussian, asymmetric, and has a finite trivial contribution from particles in crowded quasistatic surroundings. Results indicate weak ergodicity breaking, which along with ageing characterizes the nonstationary and out-of-equilibrium dynamics.