Scaling of transient hydrodynamic interactions in concentrated suspensions

The mean-square displacement "r2() of particles in concentrated suspensions is measured at times sufficiently short to observe the transient nature of hydrodynamic interactions. For all volume fractions , the velocity autocorrelation function decays as a power law R()-3/2. A remarkable scaling with is observed for the time-dependent self-diffusion coefficient Ds()="r2()/6: If Ds() is scaled by its asymptotic value and if time is scaled by a viscous time inversely proportional to the shear viscosity of the suspension, all the data fall onto a single master curve.