Hydrodynamic correlations in shear flow: A Multiparticle--Collision--Dynamics simulation study

TL;DR

This study combines analytical calculations and simulations to explore how shear flow influences hydrodynamic correlations in a multiparticle collision dynamics fluid, revealing anisotropic behaviors and directional dependencies.

Contribution

It provides a detailed theoretical and simulation-based analysis of anisotropic hydrodynamic correlations in shear flow using MPC fluid models, which was not previously characterized.

Findings

Hydrodynamic correlations are anisotropic under shear flow.

Transverse velocity modes differ in shear flow.

Velocity autocorrelations depend on flow direction.

Abstract

The nonequilibrium hydrodynamic correlations of a Multiparticle-Collision-Dynamics (MPC) fluid in shear flow are studied by analytical calculations and simulations. The Navier-Stokes equations for a MPC fluid are linearized about the shear flow and the hydrodynamic modes are evaluated as an expansion in the momentum vector. The shear-rate dependence and anisotropy of the transverse and longitudinal velocity correlations are analyzed. We demonstrate that hydrodynamic correlations in shear flow are anisotropic, specifically, the two transverse modes are no longer identical. In addition, our simulations reveal the directional dependence of the frequency and attenuation of the longitudinal velocity correlation function. Furthermore, the velocity autocorrelation functions of a tagged fluid particle in shear flow are determined. The simulations results for various hydrodynamic correlations agree very well with the theoretical predictions.