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

Area of Science:

• Fluid Dynamics
• Nanoscale Transport Phenomena
• Computational Physics

Background:

• Understanding fluid behavior in nanoscale confinements is crucial for applications like separations and energy storage.
• Existing models often struggle to accurately capture complex interactions within binary mixtures at the nanoscale.

Purpose of the Study:

• To develop a robust one-dimensional isothermal hydrodynamic transport model for non-reacting binary mixtures in slit nanochannels.
• To incorporate key physical phenomena including viscous dissipation, interspecies friction, and species-specific wall slip.

Main Methods:

• A coupled species momentum equation framework based on the Maxwell-Stefan form for interspecies friction.
• Modeling of species partial viscosity using van der Waals one-fluid approximation and local average density.
• Implementation of species-specific macroscopic friction coefficient boundary conditions derived from a generalized Langevin formulation.

Main Results:

• The model demonstrates good quantitative agreement with non-equilibrium molecular dynamics simulations for methane-hydrogen and methane-argon mixtures.
• Binary mixtures exhibit pseudo-single-species fluid behavior, with interfacial friction linearly dependent on molar composition.
• Species-specific slip lengths were found to be independent of channel width.

Conclusions:

• The proposed hydrodynamic model provides an accurate and efficient tool for simulating binary mixture transport in nanochannels.
• The findings offer insights into the fundamental behavior of confined gas mixtures and the nature of interspecies interactions.
• The model's ability to predict species-specific slip lengths is critical for designing nanoscale devices and separation processes.