Bulletin of the American Physical Society
64th Annual Meeting of the APS Division of Fluid Dynamics
Volume 56, Number 18
Sunday–Tuesday, November 20–22, 2011; Baltimore, Maryland
Session E15: Porous Media I |
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Chair: Marc Hesse, University of Texas at Austin Room: 318 |
Sunday, November 20, 2011 4:40PM - 4:53PM |
E15.00001: Vapor transport through short hydrophobic nanopores for desalination Jongho Lee, Sean O'Hern, Tahar Laoui, Faizur Rahman, Rohit Karnik We propose a concept for desalination of water by reverse osmosis (RO) using a vapor-trapping membrane composed of short hydrophobic nanopores and separates the salt water (feed) and the fresh water (permeate) on each side. The feed water is vaporized by applied pressure and the water vapor condenses on the permeate side accompanied by recovery of latent heat. A probabilistic model based on rarified gas conditions predicted 3-5 times larger mass flux by the proposed membrane than conventional RO membranes at temperatures in the range of 30-50C. To realize the short hydrophobic nanopores, gold was deposited at the entrance of alumina pores followed by SAM formation. The fraction of leaking pores was confirmed to be less than 0.2{\%} using a calcium ion indicator (Fluo-4). Finally, a microfluidic flow cell was fabricated for characterizing the transport properties of the membranes. [Preview Abstract] |
Sunday, November 20, 2011 4:53PM - 5:06PM |
E15.00002: Wrinkling of wet paper Ho-Young Kim, Jungchul Kim, L. Mahadevan It is a mundane experience that paper stained with water wrinkles. It is because a wetted portion of paper, which swells due to the hygroexpansive nature of the cellulose fiber network, deforms out of its original plane. Here we quantify the dynamics of wrinkling of wet paper coupled to the capillary imbibition of water into paper using a combination of experiment and theory. While supplying water from a capillary tube that touches the center of a paper strip, we measure the spreading rate of the wet area, wait time for the out-of-plane buckling, and temporal growth of a wrinkling magnitude. Using a theoretical model assuming a linear increase of the strain and an exponential decay of the elastic modulus with the water concentration, we construct scaling laws to predict the simultaneous capillary imbibition and wrinkling rates. [Preview Abstract] |
Sunday, November 20, 2011 5:06PM - 5:19PM |
E15.00003: Permeability reduction of self-affine fractures explained by means of the critical barrier concept Laurent Talon, Harold Auradou, Alex Hansen In many low permeability geological formations, flow occurs primarily through fracture networks. There is therfore a need for reliable modeling of the hydromechanical behavior of fracture. We consider here fracture with self-affine correlation. Most of the models fails to predict the effective permeability of such fracture as soon as some contact area are present. We introduce a model based on the generalization of the concept of the bottle neck which allows the prediction of the permeability of self-affine rough channels (one-dimensional fracture) and two-dimensional fractures over the entire range of possible apertures. In one-dimensional rough fracture, when the two wall are brought to contact, the permeability is increasingly controlled by the region of minimum aperture. This is the bottle neck concept. In two-dimensionnal fracture, the position of the minimum aperture is not so crucial since the flow can easily by-pass regions of low permeability. To generalize this concept, we introduce the most restrictive barrier path defined as being the barrier that has the smallest average permeability. Using numerical simulation, we identify three permeability scaling regime that will be explained by the introduction of other critical barrier ordered by its criticality. [Preview Abstract] |
Sunday, November 20, 2011 5:19PM - 5:32PM |
E15.00004: Fluid Flow in Porous Media for Soil-Water Retention Cesare Mikhail Cejas, Bertrand Selva, Raphael Beaufret, Larry Hough, Christian Fretigny, Remi Dreyfus The study aims to understand the mechanisms that determine the behavior of water in soil. In developing a better comprehension of the coupling between the various fluxes (e.g. evaporation, drainage) in soil and the surrounding environment, we elaborate strategies that permit to understand and improve particularly the water absorption by the roots. Our first approach, through direct visualization, focuses on evaporation out of a 2D model soil consisting of monolayer glass beads. Evaporation from porous media exhibits an abrupt transition from capillary-supported regime 1 to diffusion-controlled regime 2. Varying the wettability of the model soil suggests that the duration of regime 1evaporation and drying front formation in hydrophobic media are shorter than in hydrophilic media due to the absence of hydraulic continuity towards the evaporating surface. We then study how evaporation couples in the presence of roots in the model soil while being subjected to various treatment conditions (e.g. physical additives, etc.). Through this study, we would be able to quantify how the physico-chemical soil treatments affect these phenomena and inspire solutions for improving soil water retention. [Preview Abstract] |
Sunday, November 20, 2011 5:32PM - 5:45PM |
E15.00005: Impact of wettability correlations on multiphase flow through porous media Marta Sanchez de La Lama, Martin Brinkmann, Stephan Herminghaus In the last decades, significant progress has been made toward understanding the multiphase displacement through porous media and the role of substrate properties like homogeneous wettability or pore geometry. However, the effect of heterogeneous wettability at microscopic scales and its relation to large-scale properties, like relative permeability or capillary pressure, remains still little understood. In the present study forced imbibition through a two-dimensional porous medium is simulated at the pore scale by means of a mesoscopic particle approach [1,2]. The substrate is described as an assembly of non-overlapping circular disks whose preferential wettability is distributed according to prescribed correlations, i.e., from pore scale in terms of Janus beads up to domains at system scale. We analyze how this well-defined heterogeneous wettability affects the dynamics and try to establish a relationship among wettability-correlations and large-scales properties of the multiphase flow. References [1] Y. Inoue et al., J. Comp. Phys. 201, 191 (2004) [2] G. Gompper et al., Adv. Polym. Sci. 221, 1 (2009) [Preview Abstract] |
Sunday, November 20, 2011 5:45PM - 5:58PM |
E15.00006: Analytical model of wetting liquid unsaturated climb in a porous medium B. Markicevic, B. Bijeljic, H.K. Navaz The analysis of the dynamics and stability of the wetting liquid capillary climb flow in the porous medium, which is opposed by gravity force, suggests that there may be a unique analytical correlation between the capillary and Bond number given in the exponential form. Starting from this exponential expression, the analytical model for the climbing height as a function of time is obtained. The model accounts for two-step climbing dynamics, where for smaller climbing height, the height of single-phase displacement flow is identified. For larger climbing heights closer to the point in which the capillary and gravity forces equilibrate, the height of the developing multiphase flow front and interface position between partially wet and dry fraction of porous medium is defined. It turns out that the analytical solution predicts the climbing height for short and longer times. To use this approach, one needs the capillary versus Bond number correlation only, which is completely measureable from the experiments. In calculating both numbers, the average pore radius is used as the geometrical scale. There is an excellent agreement between the analytical model predictions and the set of experimental results in which the permeability varies for two orders of magnitude, and where both single-phase and multiphase climbing dynamics is observed. Finally, the generality of analytical model needs to be examined further. [Preview Abstract] |
Sunday, November 20, 2011 5:58PM - 6:11PM |
E15.00007: Effect of hydrophobicity on the flow through a porous media O. Chavez, R. Zenit, D. Chehata We have experimentally studied the effect of hydrophobic conditions on the flow in a porous medium; our motivation arises from the flow of petroleum at well conditions, where the wettability can change drastically. A porous media made with glass beads was considered as reference to obtain the permeability. Subsequently the glass beads were coated with a hydrophobic agent in order to observe the effect on the coefficient of permeability of the porous medium, in the Darcy flow regime. Many experiments were conducted considering mixtures of sizes of beads and wettability conditions. Preliminary results will be presented and discussed. As expected, variations of the wettability of the grains affect the permeability in a significant manner. [Preview Abstract] |
Sunday, November 20, 2011 6:11PM - 6:24PM |
E15.00008: Capillary effects in buoyancy-driven spreading within a porous medium Jerome Neufeld, Olivier Dubourdieu, Herbert Huppert Patterns driven by the imbibition and spread of fluids in porous media due to gravity and capillarity can be found in a host of industrial and environmental settings. We show experimentally that for small, constant fluid volumes, gravity and capillarity can lead to static fluid configurations. In contrast, when the fluid exceeds a critical depth it can flow under gravity before finding a new static configuration. We show that the evolution can be modeled as a gravity current in which capillarity, manifest as hysteresis between advancing and receding interfaces, plays a key role. Model predictions of the ultimate extent of such currents are compared to our experimental results. [Preview Abstract] |
Sunday, November 20, 2011 6:24PM - 6:37PM |
E15.00009: Stable and unstable waves in two-phase porous media flow Kimberly Spayd, Michael Shearer, Zhengzheng Hu Plane waves for two phase flow in a porous medium are modeled by the one-dimensional Buckley-Leverett equation, a {\em scalar} conservation law. We analyze stability of sharp planar interfaces to two-dimensional perturbations, which involves a {\em system} of partial differential equations. Linear stability analysis, in a more general regime than the classical Saffman-Taylor analysis, results in a description of the dispersion relation to leading order in the wave number, providing a criterion that distinguishes between interfaces that are long-wave stable and those that are not. Numerical simulations of the full nonlinear system of equations, including dissipation and dispersion, illustrate the analytical results. [Preview Abstract] |
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