title: The Role of Local Instabilities in Fluid Invasion into Permeable Media.
abstract: Wettability is an important factor which controls the displacement of immiscible fluids in permeable media, with far reaching implications for storage of CO2in deep saline aquifers, fuel cells, oil recovery, and for the remediation of oil contaminated soils. Considering the paradigmatic case of random piles of spherical beads, fluid front morphologies emerging during slow immiscible displacement are investigated in real time by X-ray micro-tomography and quantitatively compared with model predictions. Controlled by the wettability of the bead matrix two distinct displacement patterns are found. A compact front morphology emerges if the invading fluid wets the beads while a fingered morphology is found for non-wetting invading fluids, causing the residual amount of defending fluid to differ by one order of magnitude. The corresponding crossover between these two regimes in terms of the advancing contact angle is governed by an interplay of wettability and pore geometry and can be predicted on the basis of a purely quasi-static consideration of local instabilities that control the progression of the invading interface.
authors.affiliation: Saarland University, Experimental Physics, D-66123, Saarbrücken, Germany.|Max Planck Institute for Dynamics and Self-Organization, D-37077, Göttingen, Germany.|ESRF, The European Synchrotron, 71 avenue des Martyrs, 38000, Grenoble, France.|Imperial College London, SW7 2AZ, London, UK.
authors.forename: Kamaljit
authors.initials: K
authors.lastname: Singh
authors.affiliation: Saarland University, Experimental Physics, D-66123, Saarbrücken, Germany.|Max Planck Institute for Dynamics and Self-Organization, D-37077, Göttingen, Germany.
authors.forename: Hagen
authors.initials: H
authors.lastname: Scholl
authors.affiliation: Saarland University, Experimental Physics, D-66123, Saarbrücken, Germany.|Max Planck Institute for Dynamics and Self-Organization, D-37077, Göttingen, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Brinkmann
authors.affiliation: ESRF, The European Synchrotron, 71 avenue des Martyrs, 38000, Grenoble, France.
authors.forename: Marco Di
authors.initials: MD
authors.lastname: Michiel
authors.affiliation: ESRF, The European Synchrotron, 71 avenue des Martyrs, 38000, Grenoble, France.|Synchrotron Soleil, L'Orme des Merisiers, Saint-Aubin, 99190, Gif-sur-Yvette, France.
authors.forename: Mario
authors.initials: M
authors.lastname: Scheel
authors.affiliation: Max Planck Institute for Dynamics and Self-Organization, D-37077, Göttingen, Germany.
authors.forename: Stephan
authors.initials: S
authors.lastname: Herminghaus
authors.affiliation: Saarland University, Experimental Physics, D-66123, Saarbrücken, Germany. r.seemann@physik.uni-saarland.de.|Max Planck Institute for Dynamics and Self-Organization, D-37077, Göttingen, Germany. r.seemann@physik.uni-saarland.de.
authors.forename: Ralf
authors.initials: R
authors.lastname: Seemann