Long-range dynamic correlations in confined suspensions

TL;DR

This paper reveals that in confined suspensions, hydrodynamic interactions exhibit long-range correlations due to diffusive compression modes, challenging the traditional view of screening beyond a certain distance.

Contribution

The study introduces an analytical theory and simulations showing that finite compressibility leads to unbounded velocity correlations in confined suspensions.

Findings

Hydrodynamic correlations decay as t^{-3/2} over time.

Finite compressibility causes long-range velocity correlations.

Traditional screening is qualitatively altered by compressibility effects.

Abstract

Hydrodynamic interactions between particles confined in a liquid-filled linear channel are known to be screened beyond a distance comparable to the channel width. Using a simple analytical theory and lattice-Boltzmann simulations, we show that the hydrodynamic screening is qualitatively modified when the time-dependent response and finite compressibility of the host liquid are taken into account. Diffusive compression modes in the confined liquid cause the particles to have velocity correlations of unbounded range, whose amplitude decays with time only as $t^{-3/2}$.