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Title: Time scales of relaxation dynamics during transient conditions in two-phase flow: RELAXATION DYNAMICS

Abstract

The relaxation dynamics toward a hydrostatic equilibrium after a change in phase saturation in porous media is governed by fluid reconfiguration at the pore scale. Little is known whether a hydrostatic equilibrium in which all interfaces come to rest is ever reached and which microscopic processes govern the time scales of relaxation. Here we apply fast synchrotron-based X-ray tomography (X-ray CT) to measure the slow relaxation dynamics of fluid interfaces in a glass bead pack after fast drainage of the sample. The relaxation of interfaces triggers internal redistribution of fluids, reduces the surface energy stored in the fluid interfaces, and relaxes the contact angle toward the equilibrium value while the fluid topology remains unchanged. The equilibration of capillary pressures occurs in two stages: (i) a quick relaxation within seconds in which most of the pressure drop that built up during drainage is dissipated, a process that is to fast to be captured with fast X-ray CT, and (ii) a slow relaxation with characteristic time scales of 1–4 h which manifests itself as a spontaneous imbibition process that is well described by the Washburn equation for capillary rise in porous media. The slow relaxation implies that a hydrostatic equilibrium is hardlymore » ever attained in practice when conducting two-phase experiments in which a flux boundary condition is changed from flow to no-flow. Implications for experiments with pressure boundary conditions are discussed.« less

Authors:
ORCiD logo [1]; ORCiD logo [2];  [3]; ORCiD logo [4]; ORCiD logo [3]
  1. School of Chemical, Biological and Environmental Engineering, Oregon State University, Corvallis Oregon USA; Department Soil Physics, Helmholtz-Centre for Environmental Research-UFZ, Halle Germany
  2. Shell Global Solutions International B.V., Rijswijk Netherlands
  3. School of Chemical, Biological and Environmental Engineering, Oregon State University, Corvallis Oregon USA
  4. Department Soil Physics, Helmholtz-Centre for Environmental Research-UFZ, Halle Germany; Institut für Agrar- und Ernährungswissenschaften, Martin-Luther-Universität Halle-Wittenberg, Halle Germany
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org.:
NSFOTHER
OSTI Identifier:
1372226
Resource Type:
Journal Article
Resource Relation:
Journal Name: Water Resources Research; Journal Volume: 53; Journal Issue: 6
Country of Publication:
United States
Language:
ENGLISH
Subject:
54 ENVIRONMENTAL SCIENCES

Citation Formats

Schlüter, Steffen, Berg, Steffen, Li, Tianyi, Vogel, Hans-Jörg, and Wildenschild, Dorthe. Time scales of relaxation dynamics during transient conditions in two-phase flow: RELAXATION DYNAMICS. United States: N. p., 2017. Web. doi:10.1002/2016WR019815.
Schlüter, Steffen, Berg, Steffen, Li, Tianyi, Vogel, Hans-Jörg, & Wildenschild, Dorthe. Time scales of relaxation dynamics during transient conditions in two-phase flow: RELAXATION DYNAMICS. United States. doi:10.1002/2016WR019815.
Schlüter, Steffen, Berg, Steffen, Li, Tianyi, Vogel, Hans-Jörg, and Wildenschild, Dorthe. Thu . "Time scales of relaxation dynamics during transient conditions in two-phase flow: RELAXATION DYNAMICS". United States. doi:10.1002/2016WR019815.
@article{osti_1372226,
title = {Time scales of relaxation dynamics during transient conditions in two-phase flow: RELAXATION DYNAMICS},
author = {Schlüter, Steffen and Berg, Steffen and Li, Tianyi and Vogel, Hans-Jörg and Wildenschild, Dorthe},
abstractNote = {The relaxation dynamics toward a hydrostatic equilibrium after a change in phase saturation in porous media is governed by fluid reconfiguration at the pore scale. Little is known whether a hydrostatic equilibrium in which all interfaces come to rest is ever reached and which microscopic processes govern the time scales of relaxation. Here we apply fast synchrotron-based X-ray tomography (X-ray CT) to measure the slow relaxation dynamics of fluid interfaces in a glass bead pack after fast drainage of the sample. The relaxation of interfaces triggers internal redistribution of fluids, reduces the surface energy stored in the fluid interfaces, and relaxes the contact angle toward the equilibrium value while the fluid topology remains unchanged. The equilibration of capillary pressures occurs in two stages: (i) a quick relaxation within seconds in which most of the pressure drop that built up during drainage is dissipated, a process that is to fast to be captured with fast X-ray CT, and (ii) a slow relaxation with characteristic time scales of 1–4 h which manifests itself as a spontaneous imbibition process that is well described by the Washburn equation for capillary rise in porous media. The slow relaxation implies that a hydrostatic equilibrium is hardly ever attained in practice when conducting two-phase experiments in which a flux boundary condition is changed from flow to no-flow. Implications for experiments with pressure boundary conditions are discussed.},
doi = {10.1002/2016WR019815},
journal = {Water Resources Research},
number = 6,
volume = 53,
place = {United States},
year = {Thu Jun 01 00:00:00 EDT 2017},
month = {Thu Jun 01 00:00:00 EDT 2017}
}