Influence of hydrodynamics on many-particle diffusion in 2D colloidal suspensions

Abstract.

We study many-particle diffusion in 2D colloidal suspensions with full hydrodynamic interactions through a novel mesoscopic simulation technique. We focus on the behaviour of the effective scaled tracer and collective-diffusion coefficients $D_{\rm T}(\rho) / D_0$ and $D_{\rm C}(\rho) / D_0$, respectively, where D ₀ is the single-particle diffusion coefficient, as a function of the density of the colloids $\rho$. At low Schmidt numbers $Sc \sim 1$, we find that hydrodynamics has essentially no effect on the behaviour of $D_{\rm T}(\rho) / D_0$. At larger Sc, $D_{\rm T}(\rho) / D_0$ seems to be enhanced at all densities, although the differences compared to the case without hydrodynamics are rather minor. The collective-diffusion coefficient, on the other hand, is much more strongly coupled to hydrodynamical conservation laws and is distinctly different from the purely dissipative case without hydrodynamic interactions.