Strict equivalence between Maxwell-Stefan and fast-mode theory for multicomponent polymer mixtures
Abstract
The applicability of theories describing the kinetic evolution of fluid mixtures depends on the underlying physical assumptions. The Maxwell-Stefan equations, widely used for miscible fluids, express forces depending on coupled fluxes. They need to be inverted to recover a Fickian form which is generally impossible analytically. Moreover, the concentration dependence of the diffusivities has to be modelled, e.g. by the multicomponent Darken equation. Cahn-Hilliard type equations are preferred for immiscible mixtures, whereby different assumptions on the coupling of fluxes lead to the slow-mode and fast-mode theories. For two components, these were derived from the Maxwell-Stefan theory in the past. Here, we prove that the fast-mode theory and the generalized Maxwell-Stefan theory together with the multicomponent Darken equation are strictly equivalent even for multicomponent systems with very different molecular sizes. Our findings allow to reduce the choice of a suitable theory to the most efficient algorithm for solving the underlying equations.
Cite
@article{arxiv.1906.06201,
title = {Strict equivalence between Maxwell-Stefan and fast-mode theory for multicomponent polymer mixtures},
author = {Olivier J. J. Ronsin and Jens Harting},
journal= {arXiv preprint arXiv:1906.06201},
year = {2019}
}