Correlated particle dynamics in concentrated quasi-two-dimensional suspensions

TL;DR

This paper studies how particle motion correlations in concentrated quasi-two-dimensional suspensions are influenced by concentration, revealing that concentration effects are limited to short distances unlike in unconfined suspensions.

Contribution

It provides a combined theoretical and experimental analysis of hydrodynamic correlations in confined suspensions, highlighting differences from unconfined systems.

Findings

Correlations decay as 1/r^2 with distance

Concentration effects are prominent only at short inter-particle distances

Hydrodynamic screening differs from unconfined suspensions

Abstract

We investigate theoretically and experimentally how the hydrodynamically correlated lateral motion of particles in a suspension confined between two surfaces is affected by the suspension concentration. Despite the long range of the correlations (decaying as 1/r^2 with the inter-particle distance r), the concentration effect is present only at short inter-particle distances for which the static pair correlation is nonuniform. This is in sharp contrast with the effect of hydrodynamic screening present in unconfined suspensions, where increasing the concentration changes the prefactor of the large-distance correlation.