Details zur Publikation

Kategorie Textpublikation
Referenztyp Zeitschriften
DOI 10.1002/2016WR019815
Titel (primär) Time scales of relaxation dynamics during transient conditions in two-phase flow
Autor Schlüter, S.; Berg, T.; Li, T.; Vogel, H.-J.; Wildenschild, D.
Quelle Water Resources Research
Erscheinungsjahr 2017
Department BOPHY
Band/Volume 53
Heft 6
Seite von 4709
Seite bis 4724
Sprache englisch
UFZ Querschnittsthemen RU1

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.

dauerhafte UFZ-Verlinkung
Schlüter, S., Berg, T., Li, T., Vogel, H.-J., Wildenschild, D. (2017):
Time scales of relaxation dynamics during transient conditions in two-phase flow
Water Resour. Res. 53 (6), 4709 - 4724 10.1002/2016WR019815