Bulletin of the American Physical Society
68th Annual Meeting of the APS Division of Fluid Dynamics
Volume 60, Number 21
Sunday–Tuesday, November 22–24, 2015; Boston, Massachusetts
Session G1: Porous Media Flows: Mixing, Transport and Reaction |
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Chair: Tanguy Le Borgne, Université de Rennes Room: Auditorium |
Monday, November 23, 2015 8:00AM - 8:13AM |
G1.00001: Reactive mixing in heterogeneous porous media flows: scalar gradient distribution, spatial intermittency and temporal scaling of effective reaction kinetics Tanguy Le Borgne, Marco Dentz, Emmanuel Villermaux Reactive mixing processes play a central role in a range of porous media systems, including CO2 sequestration operations, reactive geothermal dipoles, biofilms, or flow-through reactors. Many of these reactions are limited by fluid mixing processes that bring the reactants into contact. Hence, the temporal dynamics of effective global reactivity is determined by the creation of concentration gradients by fluid stretching and their dissipation by diffusion. From the analysis of the elongation and aggregation of lamellar structures formed in the transported scalar fields, we derive analytical predictions for the probability density functions of scalar gradients in heterogeneous Darcy flows over a large range of P\'{e}clet numbers and permeability field variances. In this framework, we show that heterogeneous Darcy fields generate highly intermittent concentration fields, as manifested by the spatial scaling of structure functions. The resulting effective reaction rates display a range of temporal behaviors that depend on the degree of heterogeneity. In the large Damk\"{o}hler limit, we derive analytical expressions for these temporal scalings in the different regimes that arise when exploring the P\'{e}clet number space. We generalize these results for different random flows. [Preview Abstract] |
Monday, November 23, 2015 8:13AM - 8:26AM |
G1.00002: Predicting anomalous diffusion rates of Stokes flow in porous media Bryan Quaife, Pietro de Anna, George Biros, Ruben Juanes Stokes flow in porous media finds many applications in hydrology, filtration, and groundwater flow. I will first describe an experimental setup that simulates two-dimensional Stokes flow in a porous media, and compare experimental and numerical results. Then, I will describe a technique where statistics of the geometry are used to predict statistics of the flow, including anomalous diffusion rates. This technique will be tested on several geometries. [Preview Abstract] |
Monday, November 23, 2015 8:26AM - 8:39AM |
G1.00003: Simulating Anomalous Dispersion and Multiphase Segregation in Porous Media with the Lattice Boltzmann Method Rastin Matin, Marek K. Misztal, Anier Hernandez-Garcia, Joachim Mathiesen Many hydrodynamic phenomena such as flows at micron scale in porous media, large Reynolds numbers flows, non-Newtonian and multiphase flows have been simulated numerically using the lattice Boltzmann method. By solving the Lattice Boltzmann Equation on three-dimensional unstructured meshes, we efficiently model single-phase fluid flow in real rock samples. We use the flow field to estimate the permeability and further investigate the anomalous dispersion of passive tracers in porous media. By extending our single-phase model with a free-energy based method, we are able to simulate binary systems with moderate density ratios in a thermodynamically consistent way. In this presentation we will present our recent results on both anomalous transport and multiphase segregation. [Preview Abstract] |
Monday, November 23, 2015 8:39AM - 8:52AM |
G1.00004: Dispersion properties in porous media: application to Redox Flow Battery electrodes Francesco Picano, Dario Maggiolo, Andrea Marion, Massimo Guarnieri Redox Flow Batteries (RFBs) represent a promising technology as a way to store energy. However, in order to improve RFBs performance, some conceptual and technological issues are still open. In particular, a properly designed geometry of flow channels and porous medium is still under investigation in order to uniformly distribute the reacting species all along the electrode. The ideal configuration aims to minimize the drag maximizing the mixing so to increase the overall performance and efficiency. In the present work a Lattice Boltzmann 3D model (LBM) has been used to better understand the dependence of mass and momentum transports on the porosity and carbon fiber preferential orientation. The LBM has been coupled with a Lagrangian particle tracking algorithm in order to investigate the dispersion mechanisms induced by the porous medium on the species flowing in a typical RFB. Results show that the drag is considerably reduced when the medium fibers are preferentially oriented along the streamwise direction. Surprisingly, this configuration shows also the highest transversal dispersion rate characterized by a super-diffusive behavior. Actually, the dispersion features are found to strongly depend on the porous media microstructure showing either anomalous or regular diffusion. [Preview Abstract] |
Monday, November 23, 2015 8:52AM - 9:05AM |
G1.00005: Diffusion in random networks Juan C. Padrino, Duan Z. Zhang The ensemble phase averaging technique is applied to model mass transport in a porous medium. The porous material is idealized as an ensemble of random networks, where each network consists of a set of junction points representing the pores and tortuous channels connecting them. Inside a channel, fluid transport is assumed to be governed by the one-dimensional diffusion equation. Mass balance leads to an integro-differential equation for the pores mass density. Instead of attempting to solve this equation, and equivalent set of partial differential equations is derived whose solution is sought numerically. As a test problem, we consider the one-dimensional diffusion of a substance from one end to the other in a bounded domain. For a statistically homogeneous and isotropic material, results show that for relatively large times the pore mass density evolution from the new theory is significantly delayed in comparison with the solution from the classical diffusion equation. In the short-time case, when the solution evolves with time as if the domain were semi-infinite, numerical results indicate that the pore mass density becomes a function of the similarity variable \textit{xt}$^{-1/4}$ rather than \textit{xt}$^{-1/2}$ characteristic of classical diffusion. This result was verified analytically. Possible applications of this framework include flow in gas shales. [Preview Abstract] |
Monday, November 23, 2015 9:05AM - 9:18AM |
G1.00006: Coupling micro-CT with computer simulations to analyze dispersion in porous media Sadaf Sobhani, Jared Dunnmon, Michael Werer In recent years, table-top X-ray Computed Tomography (XCT) systems have been utilized to analyze various samples with a resolution on the order of 1$ \mu m $-100$ \mu m $. In this study, we explore the use of these systems both in extracting high-resolution topologies of porous structures for use as inputs into computational simulations and in directly characterizing gas dispersion within such structures using fluoroscopic imaging of dense gaseous tracers. The opaque-solid environment and small pore-scale effects in porous media restrict the use of conventional imaging techniques, thereby making XCT a potentially useful diagnostic technique for understanding internal flows in porous and optically inaccessible structures. In the present work, we extract the topology of various reticulated porous foams from 3D XCT data and perform numerical simulations of the flow inside these structures. Permeability and tortuosity, which are key parameters in volume-averaged models are evaluated from the resulting flow fields and knowledge of the solid structure. [Preview Abstract] |
Monday, November 23, 2015 9:18AM - 9:31AM |
G1.00007: Particle dispersion and deposition in porous media: a computational perspective Gianluca Boccardo, Eleonora Crevacore, Rajandrea Sethi, Daniele Marchisio This work investigates particle dispersion in porous media, which is of central relevance in a number of applications ranging from groundwater remediation tochemical engineering. The challenge lies in studying the complex fluid dynamics behavior arising at the microscale (very difficult to observe experimentally) and obtaining transport models to be employed at the macroscopic scale of interest. While a wealth of studies have approached this problem, the case of particle transport with a concurrent heterogeneous chemical reaction (e.g.: particle deposition) still lacks a satisfactory description, especially when considering a polydisperse population of solid particles. Moreover, the oft-used simplified descriptions of the porous medium (via array of spheres or similar strategies) fail to fully take into account the effect of the packing structure. Our novel approach relies on an ``in-silico'' procedure where many 3-D realistic porous media models are constructed via rigid-body simulations and fluid flowand particle transport are then investigated through computational fluid dynamics. The results evidence the need for a deeper look, afforded by these methodology, into the influence of the features of realistic porous media on particle transport and deposition. [Preview Abstract] |
Monday, November 23, 2015 9:31AM - 9:44AM |
G1.00008: Effective reaction rates for transport of particles to heterogeneous reactive (or porous) surfaces under shear. Preyas Shah, Eric S. G. Shaqfeh Mass transfer to heterogeneous reactive (or porous) surfaces is common in applications like heterogeneous catalysis, and biological porous media transport like drug delivery. This is modeled as advection-diffusion in a shear flow to an inert surface with first order reactive patches. We study transport of point particles using boundary element simulations. We show that the heterogeneous surface can be replaced with a uniform-flux boundary condition related to the Sherwood number (S), aka, the dimensionless flux to the reactive region. In the dilute limit of reactive regions, large-scale interaction between the reactive patches is important. In the dilute limit of inert regions, [S] grows as the reciprocal of the inert area fraction. Based on the method of resistances and numerical results, we provide correlations for [S] for general reactive surfaces and flow conditions. We model finite sized particles as general spheroids, specifically for biological applications. We do Brownian Dynamics simulations to account for hydrodynamic and steric interactions with the flow field and the domain geometry, and compare to the point particle results. We observe that anisotropic particles gave a higher pore transport flux compared to spherical particles at all flow conditions. [Preview Abstract] |
Monday, November 23, 2015 9:44AM - 9:57AM |
G1.00009: Targeted delivery by smart capsules for controlling two-phase flow in porous media Jing Fan, Alireza Abbaspourrad, David Weitz Two-phase flow in porous media is significantly influenced by the physical properties of the fluids and the geometry of the medium. We develop a variety of smart microcapsules that can deliver and release specific substances to the target location in the porous medium, and therefore change the fluid property or medium geometry at certain locations. In this talk, I will present two types of smart capsules for targeted surfactant delivery to the vicinity of oil-water interface and targeted microgel delivery for improving the homogeneity of the porous medium, respectively. We further prove the concept by monitoring the capsule location and the fluid structure in the porous media by micro-CT and confocal microscopy. This technique not only is of particular importance to the relevant industry applications especially in the oil industry but also opens a new window to study the mechanism of two-phase flow in porous media. [Preview Abstract] |
Monday, November 23, 2015 9:57AM - 10:10AM |
G1.00010: Transport and Aggregation of Nanoparticles in Packed Beds: Effects of Pore Velocity and Initially-Fed Particle Size on Transient Particle Size Distributions Ngoc Pham, Dimitrios Papavassiliou Aggregation of colloidal particles in flow through porous media has received careful consideration, as it reduces particle breakthrough due to pore clogging and sedimentation. Additionally, in unstable colloidal systems, deposition of colloidal aggregates on the pore surfaces can create sub-surfaces for further colloidal attachment. This phenomenon is known as ripening effect. In this study, transient particle size distributions of nano-particle systems, propagating in a bed packed with spheres are numerically investigated. In our simulation, only pair interactions are considered, and the aggregation rate is varied with the relative position of two particles in a pair. The packed bed consists of spheres of known size, randomly packed in a simulation box. To generate the velocity field of water inside the porous medium, the lattice Boltzmann method (LBM) is used. In conjunction with that, the trajectories of thousands of massless particles moving with the flow under convection and diffusion are recorded employing a Lagrangian framework [1, 2]. While pore clogging is neglected, we draw attention to the change of the distribution of particle size under different pore velocities and different initially-fed particle sizes.\\[4pt] [1] R. S. Voronov, S. VanGordon, V. I. Sikavitsas, and D. V. Papavassiliou, International Journal for Numerical Methods in Fluids, 67, 501-517, 2011\\[0pt] [2] N.H. Pham, D.P. Swatske, J.H. Harwell, B-J Shiau, D.V. Papavassiliou, International Journal of Heat {\&} Mass Transfer, 72, 319-328, 2014 [Preview Abstract] |
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