AUTHOR=Winkler Mathias , Gjennestad Magnus Aa. , Bedeaux Dick , Kjelstrup Signe , Cabriolu Raffaela , Hansen Alex 

TITLE=Onsager-Symmetry Obeyed in Athermal Mesoscopic Systems: Two-Phase Flow in Porous Media

JOURNAL=Frontiers in Physics

VOLUME=8

YEAR=2020

URL=https://www.frontiersin.org/journals/physics/articles/10.3389/fphy.2020.00060

DOI=10.3389/fphy.2020.00060

ISSN=2296-424X

ABSTRACT=<p>We compute the fluid flow time correlation functions of incompressible, immiscible two-phase flow in porous media using a 2D network model. Given a properly chosen representative elementary volume, the flow rate distributions are Gaussian, and the integrals of time correlation functions of the flows are found to converge to a finite value. The integrated cross-correlations become symmetric, obeying Onsager's reciprocal relations. These findings support the proposal of a non-equilibrium thermodynamic description for two-phase flow in porous media.</p>