Multiple light scattering (MLS) techniques such as diffusing wave spectroscopy (DWS) and speckle visibility spectroscopy (SVS) allow the study of the dynamics of particles in dense particulate systems from nano to macroscopic length and timescales. We are using these class of methods in conjunction with colour video image analysis to probe the dynamics of particles in various fluidized bed configurations and determine the associated granular temperature distributions. Such information can underpin the correct formulation of models of fluidized beds and their validation.

In this presentation, I will outline the basis of MLS techniques and present results and analysis for air, liquid, dry-vibro and liquid-vibro fluidized beds. We will show that particle motion in weakly excited vibro-fluidized beds is in general sub-diffusive. We shall also provide spatial distributions of the granular temperature for the various bed configurations and the relationship between the granular temperature and bulk velocity. Comparison of a simple theory, a discrete element model and a Eulerian-Lagrangian model with the experimental data will also be presented.