Diffusion, dispersion, and settling of hard spheres

Using a multiple light scattering technique and a stabilizing counterflow (i.e., a fluidized bed), we measured the average sedimentation velocity, its variance, and the short-time self-diffusion coefficient in a concentrated hard-sphere suspension. Many-body hydrodynamic interactions slow both the Brownian diffusion and mean sedimentation and provide a novel mechanism for long time dispersion.