Dynamics of hard-sphere suspensions

A systematic theory for the dynamics of concentrated hard-sphere suspensions of interacting Brownian particles with both hydrodynamic and direct interactions is presented. An alternative equation for the number density of particles is derived. The volume-fraction dependence of the short- and long-time self-diffusion coefficients is thus explored from a new point of view. Both the short-range and the long-range hydrodynamic interactions are shown to play an important role in both coefficients, while the direct interactions are reduced drastically by the hydrodynamic interactions.