Vibro-fluidized beds: A systematic dynamics study utilizing Diffusing Wave Spectroscopy

Abstract

Using a granular vibration fluidised bed, we demonstrate how our granular model system of polystyrene spheres becomes denser over time through different excitation amplitudes and how the heterogeneous dynamics of the system can be resolved with diffusing wave spectroscopy(DWS) measurements. We extract mean-square displacements from the DWS correlation functions of the sinusoidal excited system and model the excitation to extract the ballistic and diffusive time constants, as well as caging sizes, depending on applied acceleration and excitation time. At low excitations we observe a sub-diffusion power law behaviour of the MSD indicating potentially a glassy system.