Nonequilibrium molecular dynamics simulations of nanoconfined fluids at solid-liquid interfaces

Abstract

We investigate the hydrodynamic properties of a Lennard-Jones fluid confined to a nanochannel using molecular dynamics simulations. For channels of different widths and hydrophilic-hydrophobic surface wetting properties, profiles of the fluid density, stress, and viscosity across the channel are obtained and analysed. In particular, we propose a linear relationship between the density and viscosity in confined and strongly inhomogeneous nanofluidic flows. The range of validity of this relationship is explored in the context of coarse grained models such as dynamic density functional-theory.

Macroscopic relations for microscopic properties at the interface between solid substrates and dense fluids

“…observed also by Morciano et al 36 by analyzing MD data correlations at a fixed temperature T = 1. Interestingly, Fig.…”

“…(31), which, under certain approximations, can be reduced to a local linear model (in terms of density), Eq. (36), which in turn can be further simplified to the linear model in Eq. (39).…”

“…We adopt two approaches. First, we propose a generalization of the relation for the viscosity profile that was recently proposed by Morciano et al 36 This generalized relation is validated for a range of interfacial conditions and temperatures. Second, we define a region in which wall effects are predominant and use this definition to calculate the average properties of the confined fluid.…”

Large effect of lateral box size in molecular dynamics simulations of liquid-solid friction

“…The shear velocity profiles are linear throughout almost all the liquid's thickness, except in the contact layer, where the shear rate slightly decreases, which can be understood as a small increase of the local viscosity due to the large local density [58,59]. In this work, we determined the slip velocity v s as the difference between the wall velocity and the liquid velocity at the position of the first adsorption peak.…”

Full characterization of the hydrodynamic boundary condition at the atomic scale using an oscillating channel: Identification of the viscoelastic interfacial friction and the hydrodynamic boundary position

“…For all wall cases, the bulk liquid velocity was well predicted by the present hydrodynamic BC. For the least wettable wall case, the velocity profile showed a small deviation from the linear profile in the first adsorption layer, which can be attributed to the local viscosity variation [49,50]. The right panel of the figure shows results for the Poiseuille flow problem.…”