Hydrodynamics of confined colloidal fluids in two dimensions

TL;DR

This study investigates the hydrodynamic behavior of two-dimensional confined colloidal fluids using hybrid simulation methods, revealing long-time tails, oscillations, and size-dependent diffusion characteristics.

Contribution

It introduces a hybrid simulation approach to analyze confined colloidal fluids and characterizes their unique hydrodynamic tail behaviors and size-dependent diffusion properties.

Findings

Observed the $t^{-1}$ hydrodynamic tail in unconfined fluids.

Identified oscillating and negative tails in confined geometries.

Showed diffusion coefficient depends logarithmically on system size.

Abstract

We apply a hybrid Molecular Dynamics and mesoscopic simulation technique to study the dynamics of two dimensional colloidal discs in confined geometries. We calculate the velocity autocorrelation functions, and observe the predicted $t^{-1}$ long time hydrodynamic tail that characterizes unconfined fluids, as well as more complex oscillating behavior and negative tails for strongly confined geometries. Because the $t^{-1}$ tail of the velocity autocorrelation function is cut off for longer times in finite systems, the related diffusion coefficient does not diverge, but instead depends logarithmically on the overall size of the system.