Mapping molecular models to continuum theories for partially miscible fluids

Abstract

We map molecular dynamics simulations of fluid-fluid interfaces onto mesoscale continuum theories for partially miscible fluids. Unlike most previous work, we examine not only the interface order parameter and density profiles, but also the stress. This allows a complete mapping from the length scales of molecular dynamics simulations onto a mesoscale model suitable for a lattice Boltzmann or other mesoscale simulation method. Typical assumptions of mesoscale models, such as incompressibility, are found to fail at the interface, and this has a significant impact on the surface tension. Spurious velocities, found in a number of discrete models of curved interfaces, are found to be minimized when the parameters of the mesoscopic model are made consistent with molecular dynamics results. An improved mesoscale model is given and demonstrated to produce results consistent with molecular dynamics simulations for interfaces with widths down to near molecular size.

43 pages, 17 figures, RevTex4

References in corpus (4)

• Spurious velocities in lattice Boltzmann
• On molecular and continuum boundary conditions for a miscible binary fluid
• Simulations of liquid crystals in Poiseuille flow
• Bulk and Interfacial Shear Thinning of Immiscible Polymers

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• Finite-Difference Lattice Boltzmann Methods for binary fluids
• Capillary Adhesion at the Nanometer Scale
• Nanocapillary adhesion between parallel plates
• Continuum balances from extended Hamiltonian dynamics
• Molecular dynamics perspectives on nonideal fluid models for the lattice Boltzmann method