A multiscale transport model for Lennard-Jones binary mixtures based on interfacial friction

Abstract

We propose a one-dimensional isothermal hydrodynamic transport model for non-reacting binary mixtures in slit shaped nanochannels. The coupled species momentum equations contain viscous dissipation and interspecies friction term of Maxwell-Stefan form. Species partial viscosity variations in the confinement are modeled using the van der Waals one fluid approximation and the local average density method. Species specific macroscopic friction coefficient based Robin boundary conditions are provided to capture the species wall slip effects. The value of this friction coefficient is computed using a species specific generalized Langevin formulation. Gravity driven flow of methane-hydrogen and methane-argon mixtures confined between graphene slit shaped nanochannels are considered as examples. The proposed model yields good quantitative agreement with the velocity profiles obtained from the non-equilibrium molecular dynamics simulations. The mixtures considered are observed to behave as single species pseudo fluid, with the interfacial friction displaying linear dependence on molar composition of the mixture. The results also indicate that the different species have different slip lengths, which remain unchanged with the channel width.

Multiscale modeling of electroosmotic flow: Effects of discrete ion, enhanced viscosity, and surface friction

“…We begin with the analysis first presented by Huang and Szlufarska 26 that was later adapted for SPC/E water near an uncharged wall 24 and binary mixtures. 25 The friction contribution ζ j 0 from a single solvent particle j in the interfacial region can be expressed as…”

“…The trajectory of the representative solvent particle j is generated using the coarse-grained phenomenological dynamical framework of GLE. 24,25 The relevant equations of motion of the representative particle include a dissipative, non-Markovian friction force and its corresponding random force that is orthogonal to the particle velocity, as explained in the Mori-Zwanzig projection operator formalism. [44][45][46] The equations of motion can be written as…”

“…22 The contact-adsorption of ions at the wall has also been linked to the increase in the solvent viscosity. 23 In our previous work, 24,25 we have characterized the slip of a single component fluid and binary mixtures using a multiscale, phenomenological Generalized Langevin Equation (GLE) based slip model. In these friction based models, we evolve the trajectories of the interfacial particles using GLE, while also accounting for the total PMF of the fluid.…”

A multiscale transport model for non-classical nanochannel electroosmosis

“…20 The no-slip condition was replaced by a slip velocity that is dependent on the system specific solvent interfacial friction, which in turn can be readily obtained using a Generalized Langevin Equation (GLE) based interfacial particle dynamics framework developed previously in our laboratory. 19,21,22 However, the accuracy of the model, as we will demonstrate later in the text, was limited to low to moderate wall-charge density cases as it did not account for viscous enhancement due to ion-solvent interactions.…”

Molecular Dynamics Simulation Study of Colloidal Suspensions under Confinement

“…The phenomena of drying [25] and freezing [26] transitions in confinement have created interest to study the behaviour of colloids in spatial two-dimension [27][28][29]. Also, the diffusion coefficient of the binary colloidal mixtures have been studied in confined geometries [30], slit shaped nanochannels [31,32], cylindrical pores [33], rectangular nanotubes [34,35] and within spherical cavity [36].…”