Macroscopic Flow Potentials in Swelling Porous Media

TL;DR

This paper demonstrates that flow potentials in swelling porous media are electro-chemical potentials and clarifies how different flow equations relate to chemical potential forms, highlighting the role of pressure gradients and equilibrium conditions.

Contribution

It establishes the electro-chemical potential as the fundamental macroscopic flow potential in swelling porous media and links various flow equations to specific chemical potential forms.

Findings

Flow potentials are electro-chemical potentials.

Different flow equations correspond to different chemical potential forms.

A critical pressure gradient exists depending on equilibrium conditions.

Abstract

In swelling porous media, the potential for flow is much more than pressure, and derivations for flow equations have yielded a variety of equations. In this paper we show that the macroscopic flow potentials are the electro-chemical potentials of the components of the fluid and that other forms of flow equations, such as those derived through mixture theory or homogenization, are a result of particular forms of the chemical potentials of the species. It is also shown that depending upon whether one is considering the pressure of a liquid in a reservoir in electro-chemical equilibrium with the swelling porous media, or the pressure of the vicinal liquid within the swelling porous media, a critical pressure gradient threshold exists or does not.