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1
Lawson, D. A. "Combustion in porous media." Thesis, University of Oxford, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.354839.
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2
Ruthven, Douglas M. "Diffusion through porous media." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-188922.
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This paper considers permeation through microporous or nanoporous inorganic membranes under the influence of an applied pressure gradient. In general membrane permeation may be considered as a diffusive process, driven by the gradient of chemical potential (which depends on both composition and pressure). The relative importance of these two factors varies greatly for different types of system. The general features of such processes are reviewed and the diffusional behavior of selected systems is examined.
(membrane permeation, osmosis, diffusion, zeolite membrane, DDR-3, SAPO-34)
3
Little, Sylvia Bandy. "Multiphase flow through porous media." Thesis, Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/11779.
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Booth, Richard J. S. "Miscible flow through porous media." Thesis, University of Oxford, 2008. http://ora.ox.ac.uk/objects/uuid:542d3ec1-2894-4a34-9b93-94bc639720c9.
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This thesis is concerned with the modelling of miscible fluid flow through porous media, with the intended application being the displacement of oil from a reservoir by a solvent with which the oil is miscible. The primary difficulty that we encounter with such modelling is the existence of a fingering instability that arises from the viscosity and the density differences between the oil and solvent. We take as our basic model the Peaceman model, which we derive from first principles as the combination of Darcy’s law with the mass transport of solvent by advection and hydrodynamic dispersion. In the oil industry, advection is usually dominant, so that the Péclet number, Pe, is large. We begin by neglecting the effect of density differences between the two fluids and concentrate only on the viscous fingering instability. A stability analysis and numerical simulations are used to show that the wavelength of the instability is proportional to Pe^−1/2, and hence that a large number of fingers will be formed. We next apply homogenisation theory to investigate the evolution of the average concentration of solvent when the mean flow is one-dimensional, and discuss the rationale behind the Koval model. We then attempt to explain why the mixing zone in which fingering is present grows at the observed rate, which is different from that predicted by a naive version of the Koval model. We associate the shocks that appear in our homogenised model with the tips and roots of the fingers, the tip-regions being modelled by Saffman-Taylor finger solutions. We then extend our model to consider flow through porous media that are heterogeneous at the macroscopic scale, and where the mean flow is not one dimensional. We compare our model with that of Todd & Longstaff and also models for immiscible flow through porous media. Finally, we extend our work to consider miscible displacements in which both density and viscosity differences between the two fluids are relevant.
5
Mealey, Liam Robert. "Heat Transfer in Porous Media." Thesis, University of Leeds, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.494108.
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Murison, Julie Lynette. "Wetting heterogeneities in porous media." Doctoral thesis, Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2014. http://hdl.handle.net/11858/00-1735-0000-0022-5E9C-2.
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Dodgson, Emily. "Thermoconvective instability in porous media." Thesis, University of Bath, 2011. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.547618.
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This thesis investigates three problems relating to thermoconvective stability in porous media. These are (i) the stability of an inclined boundary layer flow to vortex type instability, (ii) front propagation in the Darcy-B´enard problem and (iii) the onset of Prantdl-Darcy convection in a horizontal porous layer subject to a horizontal pressure gradient. The nonlinear, elliptic governing equations for the inclined boundary layer flow are discretised using finite differences and solved using an implicit, MultiGrid Full Approximation Scheme. In addition to the basic steady state three configurations are examined: (i) unforced disturbances, (ii) global forced disturbances, and (iii) leading edge forced disturbances. The unforced inclined boundary layer is shown to be convectively unstable to vortex-type instabilities. The forced vortex system is found to produce critical distances in good agreement with parabolic simulations. The speed of propagation and the pattern formed behind a propagating front in the Darcy-B´enard problem are examined using weakly nonlinear analysis and through numerical solution of the fully nonlinear governing equations for both two and three dimensional flows. The unifying theory of Ebert and van Saarloos (Ebert and van Saarloos (1998)) for pulled fronts is found to describe the behaviour well in two dimensions, but the situation in three dimensions is more complex with combinations of transverse and longitudinal rolls occurring. A linear perturbation analysis of the onset of Prandtl-Darcy convection in a horizontal porous layer subject to a horizontal pressure gradient indicates that the flow becomes more stable as the underlying flow increases, and that the wavelength of the most dangerous disturbances also increases with the strength of the underlying flow. Asymptotic analyses for small and large underlying flow and large Prandtl number are carried out and results compared to those of the linear perturbation analysis.
8
Sommer, Jared Lee 1960. "Infiltration of deformable porous media." Thesis, Massachusetts Institute of Technology, 1992. http://hdl.handle.net/1721.1/13101.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1992.Vita.
Includes bibliographical references (leaves 179-188).
by Jared Lee Sommer.
Ph.D.
9
Ocko, Samuel Alan. "Studies in living porous media." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/103225.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 69-76).
Many biological systems need to control transport of nutrients and ventilation. Unlike many nonliving porous media, they modify themselves to meet these demands; they are active. Using a combination of experiment, theory, and computation, we investigate several living porous media. First we consider termite mounds, meter-sized structures built by insects nearly three orders of magnitude smaller than the mounds themselves. It is widely accepted that the purpose of these mounds is to give the colony a controlled microhabitat that buffers the organisms from strong environmental fluctuations while allowing them to exchange energy and matter with the outside world. However, previous work toward understanding their functions has led to conflicting models of ventilation mechanisms and little direct evidence to distinguish them. By directly measuring air flows inside mounds of the Indian termite Odontotermes obesus, we show that they use diurnal ambient temperature oscillations to drive cyclic flows inside the mound. These cyclic flows in the mound flush out CO2 from the nest and ventilate the colony, in a novel example of deriving useful work from thermal oscillations. We also observe the same diurnally-driven flows in mounds of the African termite Macrotermes michaelseni, evidence that this is likely a general mechanism. We then consider the problem of honeybee swarming, wherein thousands of bees cling onto each other to form a dense cluster that may be exposed to the environment for several days. During this period, the cluster has the ability to maintain its core temperature actively without a central controller. We suggest that the swarm cluster is akin to an active porous structure whose functional requirement is to adjust to outside conditions by varying its porosity to control its core temperature. Using a continuum model that takes the form of a set of advection-diffusion equations for heat transfer in a mobile porous medium, we show that the equalization of an effective "behavioral pressure", which propagates information about the ambient temperature through variations in density, leads to effective thermoregulation. Our model extends and generalizes previous models by focusing the question of mechanism on the form and role of the behavioral pressure, and allows us to explain the vertical asymmetry of the cluster (as a consequence of buoyancy driven flows), the ability of the cluster to overpack at low ambient temperatures without breaking up at high ambient temperatures, and the relative insensitivity to large variations in the ambient temperature. Our theory also makes testable hypotheses for the response of the cluster to external temperature inhomogeneities, and suggests strategies for biomimetic thermoregulation. Finally, we consider a generic model of an active porous medium where the conductance of the medium is modified by the flow and in turn modifies the flow, so that the classical linear laws relating current and resistance are modified over time as the system itself evolves. This feedback coupling is quantified in terms of two parameters that characterize the way in which addition or removal of matter follows a simple local (or non-local) feedback rule corresponding to either flow-seeking or flow-avoiding behavior. Using numerical simulations and a continuum mean field theory, we show that flow-avoiding feedback causes an initially uniform system to become strongly heterogeneous via a tunneling (channel-building) phase separation; flow-seeking feedback leads to an immuring(wall-building) phase separation. Our results provide a qualitative explanation for the patterning of active conducting media in natural systems, while suggesting ways to realize complex architectures using simple rules in engineered systems.
by Samuel Alan Ocko.
Ph. D.
10
Golding, Madeleine Jane. "Gravity currents in porous media." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.608091.
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Jing, Wen 1966. "Virus transport through porous media." Thesis, The University of Arizona, 1992. http://hdl.handle.net/10150/291550.
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Investigated in laboratory column experiments were the effects of 0.01 M and 0.001 M CaPO₄ concentrations and pH on the attachment-detachment of bacteriophages PRD-1 and MS-2. Bacteriophages PRD-1 and MS-2 exhibited attachment to the soil at concentrations of 0.01M CaPO₄ and 0.5M NaCl. Release of attached phage at 0.001 M CaPO₄ and without NaCl was observed. The pH was also found to affect the attachment-detachment of PRD-1 and MS-2. However, they attached at pH 5.5 and detached at pH 8.0 at a limited extent and over an extented long period of time. The effect of salt concentration on deattachment was greater than the effect of pH. Similar results were obtained when glass beads were used as the adsorbent. These results suggest that changes in pH and ionic strength (as might occur after a rainfall) can result in the rapid release of previously adsorbed virus. (Abstract shortened by UMI.)
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Kilchherr, Rudolf. "Transport phenomena in porous media." Thesis, Kingston University, 2003. http://eprints.kingston.ac.uk/20729/.
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Non-Newtonian flow in heterogeneous media is of enormous theoretical and industrial importance. This phenomenon is studied to reveal macroscopic effects that arise due to the interaction between the non-linear flow behaviour and the spatial variation of the medium through which it is forced to move. The heterogeneity is achieved by using porous granular media, which is naturally non-homogeneous. The non-Newtonian properties of the fluid may have many causes and is an intrinsic property of the fluid that is used: One way of achieving it is by studying dense slurries of neutral particles or naturally occurring magmatic flows. Another way is to study the case where the flow is dominated by its ionic content and where the double layer thickness (the effective size of the ionic entities) is of the order of magnitude of the pore size. All cases studied in this thesis pertain to slow flow (low Reynolds number), though the fluid may be compressible. The variations in the flow are calculated in first order and these turn out to be coupled to the spatial variations in the porous medium. In this way structure formation is predicted. The structures may be either aligned with or may be perpendicular to the mean flow direction. 'Experiments to decide on which regime is relevant have been conducted. The genesis of structure formation is studied as a temporal development by considering a compressible flow. The constitutive equation that is required to couple the compressibility to the flow parameters is investigated. Two possible mechanisms have been identified: compressibility coupled to the pressure field and compressibility associated with the fluctuations in the flow. Using linear analysis the structure formation patterns associated with these two mechanisms are established for the steady state. Flow of ionically laden fluids has also been studied. Experiments done at Loughborough University (Department of Chemical Engineering) on electrowashing of filter cakes has been used to prove a major macroscopic effect. This effect takes place when the ionic diameter (which is approximately twice the double layer thickness) is of the order of magnitude of the pore size. A phenomenological set of transport equations has been set up. These contain coefficients, such as transition probabilities and mean ionic flow rates, that can be obtained from experiments by doing a first order solution of the equations for short times. A more involved numerical solution is also supplied and confirms the initial analytical estimates.
13
Rhodes, Matthew Edward. "Transport in heterogeneous porous media." Thesis, Imperial College London, 2008. http://hdl.handle.net/10044/1/1296.
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We present a new algorithm for modelling single phase transport of a tracer in porous media which demonstrates that structure on all scales affects macroscopic transport behaviour. We marry the robustness of the continuous time random walk (CTRW) framework with the simplicity of a Monte Carlo approach to reservoir simulation. We simulate transport as a series of particles transitioning between nodes with probability (t).dt that a particle will first arrive at a nearest neighbor in a time t to t + dt. To this end we first determine the mixing rules and transition probability ADE(t) for transport governed by the advection-dispersion equation (ADE) (Rhodes and Blunt, 2006). We validate our algorithm by simulating advective transport in bond percolation clusters at the critical point. We compute the histogram of flow speeds using the velocities from the bonds on the backbone and find the multifractal spectrum for two-dimensional lattices with linear dimension L _ 2000 and in three dimensions for L _ 250. We demonstrate that in the limit of large systems all the negative moments of the velocity distribution become ill-defined. However, to model transport, the velocity histogram should be weighted by the flux to obtain a well-defined mean travel time. Finally, we use CTRWtheory to demonstrate that anomalous transport is observed whose characteristics can be related to the multifractal properties of the system. We next demonstrate a pore-to-reservoir simulation methodology which is consistent across all scales of interest. At the micron scale, we fit a truncated power law (t) for the distribution of particle transition times from pore to pore simulations. To do this we use our transport algorithm on a geologically representative network model of Berea sandstone and compare the results to the explicit modelling of advection and molecular diffusion by Bijeljic and Blunt (2006). We find that the results are similar. We then demonstrate the effect of increasing pore scale heterogeneity on the power law exponent (_) by stretching the distribution of throat radii in our network model. We show that by increasing the spread of velocities within the network we decrease _ making the transport more anomalous - in keeping with the consensus currently in the literature. This (t) is then used to calculate transport on the mm to cm scale. We can then move up to the metre/grid block scale by using the transit time distribution from the mm-cm simulation to model transport in an explicit, geologically representative model of heterogeneity found within a grid block of the reservoir. From these numerical experiments we determine the (t) appropriate for transport on grid block scale systems characterized by Peclet (Pe) number and the type of heterogeneity within the system. This allows us to account for small scale uncertainty by interpreting (t) probabilistically and running simulations for different possible realizations of the reservoir heterogeneity. At the field scale, we represent the reservoir as an unstructured network of nodes connected by links. For each node-to-node transition, we use our upscaled (t) from a simulation of transport at the smaller scale. We account for small-scale uncertainty by parameterising (t) in terms of sub-scale heterogeneity and Peclet number. We demonstrate the methodology by finding a (t) for each scale of interest taking into consideration the relevant physics at that scale and using the appropriate function in a million-cell reservoir model. We show that the macroscopic behaviour can be very different from that predicted by assuming that the ADE operates at the small scale. Small-scale structure dramatically retards the advance of the plume with the particles becoming trapped in the slow moving pores/regions increasing breakthrough times by an order of magnitude compared to those predicted by the ADE.
14
Hilbert, Thomas Adams 1961. "Bacterial attachment in porous media." Thesis, The University of Arizona, 1992. http://hdl.handle.net/10150/291433.
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Colloid filtration theory was utilized to estimate the sticking coefficient (α) of bacteria in filter media. Determination of bacterial cell numbers was facilitated by incorporation of [³H] leucine into cells prior to filtration. Large changes in retention of bacteria within porous material correlated with different stages in the bacterial growth cycle. This was due primarily to changes in cell size and not due to a change in α. The effects of ionic strength, pH, nutrient status, surfactant concentration and filter material on α were also evaluated. Various filtration models predicted similar trends in the magnitude of bacterial α with changes in experimental conditions. Experiments were performed with two gram negative and one gram positive bacterial species, Pseudomonas fluorescens, Pseudomonas JS6, and Bacillus pumilus. Small reductions in α were observed in cultures that were carbon-limited. Oxygen limitation produced no change in alpha. Bacterial α's were a function of ionic strength and filter material.
15
Webber, John Beausire Wyatt. "The characterisation of porous media." Thesis, University of Kent, 2000. https://kar.kent.ac.uk/13453/.
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This thesis describes the characterisation of a range of sol-gel silicas, mainly by the physical techniques of NMR cryoporometry, density and imbibation measurements and Small Angle Neutron Scattering. The developments made to these techniques as part of this work include Construction of the frst full cool/warm cycle automated NMR cryoporometer, with continual pore size distribution graphing. Calibration of melting point constants with respect to gas-adsorption and neutron scattering. Detailed characterisation of the thermal properties of the cryoporometer. Development and measurement of the rst multi-dimensionally resolved pore size maps by NMR cryoporometry. Demonstration that simple density and imbibation measurements can, when combined with models, provide a wealth of information concerning the silicas. Development of novel continuous medium Monte-Carlo integration methods to calculate the solid-solid density correlation function for porous media, showing excellent agreement with experimental SANS results. In particular, with the second point, there has been an attempt to use SANS to provide an absolute calibration scale for pore size, nominally given by gas-adsorption.
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Rimas, Zilvinas. "Sorption in disordered porous media." Thesis, University of Cambridge, 2017. https://www.repository.cam.ac.uk/handle/1810/268094.
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The lattice-gas model of sorption in disordered porous media is studied for a variety of settings, using existing, updated and newly developed numerical techniques. Firstly, we construct an efficient algorithm to calculate the exact partition function for small lattice-gas systems. The exact partition function is used for detailed analysis of the core features exhibited by such systems. We proceed to develop an interactive Monte Carlo (MC) simulation engine, that simulates sorption in a porous media sample and provides real-time visual data of the state space projection and the 3d view of the sample among other parameters of interest, as the external fields are manipulated. The use of such tool provides a more intuitive understanding of the system behaviour. The MC simulations are employed to study sorption in several porous solids: silica aerogel, Vycor glass and soil. We investigate how the phenomena depend on the microstructure of the original samples, how the behaviour varies with the external conditions, and how it is reflected in the paths that the system takes across its state space. Secondly, we develop two methods for estimation of the relative degeneracy (the number of microstates that have the same value of some macroscopic variables) in the systems that are too large to be handled exactly. The methods, based on a restricted infinite temperature sampling, obtain equidegenerate surfaces and the degeneracy gradient across the state space. Combined with the knowledge of an internal energy of a microstate, it enables us to construct the free energy map and thus the equilibrium probability distribution for the studied projection of the state space. Thirdly, the jump-walking Monte-Carlo algorithm is revisited and updated to study the equilibrium properties of systems exhibiting quasi-ergodicity. It is designed for a single processing thread as opposed to currently predominant algorithms for large parallel processing systems. The updated algorithm is tested on the Ising model and applied to the lattice-gas model for sorption in aerogel and Vycor glass at low temperatures, when dynamics of the system is significantly slowed down. It is demonstrated that the updated jump-walking simulations are able to produce equilibrium isotherms which are typically hidden by the hysteresis effect characteristic of the standard single-flip simulations. As a result, we answer the long standing question about the existence of the first-order phase transitions in Vycor. Finally, we investigate sorption in several distinct topology network representations of soil and aerogel samples and demonstrate that the recently developed analytical techniques for random networks can be used to achieve a qualitative understanding of the phenomena in real materials.
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Ollivier-Triquet, Emma. "Dispersion in unsaturated porous media." Electronic Thesis or Diss., université Paris-Saclay, 2023. http://www.theses.fr/2023UPAST152.
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L'activité humaine a un impact significatif sur la vadose, une zone située au-dessus des nappes phréatiques, qui n'est que partiellement saturée en eau. La vadose peut être polluée par les activités agricoles ou industrielles, ce qui constitue une menace pour les ressources en eau. De plus, la saturation varie considérablement, notamment en raison des sécheresses plus fréquentes dues au changement climatique. Prévoir le transport de contaminants en milieux insaturées est donc essentiel. Cependant, la compréhension de la dispersion dans les milieux poreux insaturés reste limitée, en raison de l'interaction complexe des flux multiphasiques non miscibles avec le milieu poreux. Les modèles traditionnels tels que le modèle Fickien, décrit par l'équation d'Advection-Diffusion, ne parviennent pas à rendre compte avec précision de la dispersion dans les milieux poreux insaturés. L'objectif est d'aborder la question du transport dans les milieux poreux insaturés en identifiant les propriétés pertinentes à l'échelle du pore pour comprendre la dispersion à plus grande échelle. Il s'agit notamment de déterminer si la dispersion est fickienne ou non-fickienne, ce qui est crucial pour prédire la propagation des polluants. Une double approche est adoptée : des expériences de transport à l'échelle du pore et des simulations de Lattice Boltzmann. La visualisation directe des fluides dans les milieux poreux est un défi. Nous utilisons donc des micromodèles, réseaux poreux transparents interconnectés, pour permettre la visualisation optique à l'échelle du pore. Tout d'abord, un dispositif expérimental micromodèle a été établi et optimisé pour étudier l'écoulement et le transport multiphasiques. Des méthodes d'analyse ont été développées, ainsi que des techniques de caractérisation de la dispersion par l'analyse des moments spatiaux. Une première série d'expériences mène à des résultats préliminaires, l'évolution de la saturation et des distributions de phases avec le nombre capillaire a été caractérisée. Les expériences de transport réalisées pour toute la gamme de saturation montrent que la dispersion augmente à mesure que la saturation diminue. Cependant, l'analyse des faibles saturations s'est avérée difficile en raison de l'augmentation significative de la dispersion et des limites imposées par la taille du micromodèle, empêchant l'étude de la dispersion à long terme. Pour surmonter cette limitation, des simulations Lattice-Boltzmann ont été utilisées pour l'écoulement et le transport, car elles sont flexibles en taille et seulement limitées par le temps de calcul. Toutefois, simuler la distribution de deux phases après un écoulement multiphasique dans un milieu poreux complexe reste un défi. Générer des images à grande échelle de milieux poreux insaturés à partir de données expérimentales s'est donc avéré nécessaire pour observer la dispersion à temps long. Un algorithme de statistique multipoints (MPS) a été utilisé pour générer à la fois des images de milieux poreux non saturés plus larges et un grand ensemble de d'images plus petites pour augmenter la signification statistique de l'étude. Des simulations d'écoulement et de transport ont été réalisées sur l'ensemble des images générées afin d'explorer l'influence de la saturation sur l'écoulement et le transport. Cette étude révèle que la diminution de la saturation augmente de manière significative l'hétérogénéité de l'écoulement, ce qui entraîne une dispersion accrue. Notamment, la nature non fickienne de l'écoulement tend à être plus prononcée à faible saturation. De plus, la transition d'un transport fickien à un transport non fickien dépend du nombre de Peclet. Il existe une compétition entre l'advection et la diffusion dans des conditions saturées, ce qui entraîne un régime Fickien diffusif pour les faibles nombres de Peclet. Cependant, le transport en conditions non saturées est principalement advectif, même à faible nombre de Peclet, et présente donc un comportement non FickienHuman activity has a significant impact on the vadose zone, an area located below the land surface and above the water tables, only partially saturated with water. The vadose is susceptible to pollution from agricultural or industrial activities, posing a threat to water resources. Plus, saturation levels vary greatly, especially with the increasing frequency of droughts due to climate change. Hence, predicting contaminant transport in unsaturated conditions is crucial. However, the understanding of dispersion in unsaturated porous media remains limited, due to the complex interaction of multiphase non-miscible flows with the porous medium. Traditional models such as the Fickian model, described by the Advection-Diffusion Equation, fail to accurately capture dispersion in unsaturated porous media.The objective is to address the issue of transport in unsaturated porous media by identifying relevant properties at the pore scale to understand dispersion at a larger scale. One of the goals is to determine whether dispersion follows Fickian or non-Fickian behavior, as this understanding is crucial for predicting the spreading of pollutant in the vadose zone.To investigate transport in unsaturated porous media, a dual approach is being employed: pore scale transport experiments and Lattice Boltzmann simulations. Direct visualization of fluid structure in natural porous media is challenging. Thus, we use micromodels, transparent interconnected porous networks, to enable optical visualization at the pore scale. First, a micromodel experimental setup was established and optimized to study multiphase flow and transport. Analysis methods were developed, along with techniques for characterizing dispersion through spatial moment analysis.A series of experiments were conducted to obtain initial results on multiphase flow and dispersion. The evolution of saturation and phase distributions with the capillary number was characterized. Transport experiments were performed for the entire range of saturations, showing that dispersion increases as saturation decreases. However, analyzing low saturations was challenging due to the significant increase in dispersion and limitations imposed by the micromodel size, preventing the study of long-term dispersion.To overcome this limitation, Lattice Boltzmann simulations were used for flow and transport, as there is no size limitation except for computational time. However, simulating the distribution of two phases after a multiphase flow in a complex porous medium remains challenging. Generating large-scale images of unsaturated porous media based on experimental data was then crucial for observing late-time dispersion. Machine learning techniques, specifically the Multiple Point Statistic algorithm, were employed to generate images of wider unsaturated porous media and a large dataset of smaller images to increase the statistical significance of the study.Flow and transport simulations were conducted using the generated image dataset to explore the influence of saturation on flow and transport. This involved examining flow properties under saturated and unsaturated conditions. The nature of transport, specifically whether it exhibited Fickian or non-Fickian behavior was investigated. Furthermore, the effect of the Peclet number (a measure of the balance between advection and diffusion) on dispersion for different saturation levels was analyzed.This study revealed that decreasing saturation significantly increases flow heterogeneity, leading to increased dispersion. Notably, the non-Fickian nature of flow tends to be more pronounced with low saturations. Plus, the transition from Fickian to non-Fickian depends on the Peclet number. There is a competition between advection and diffusion in saturated conditions, resulting in a diffusive Fickian regime for low Peclet numbers. However, transport in unsaturated conditions is mainly advective, even at low Peclet, and thus displays a non-Fickian behavior
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Avesani, Diego. "A new Lagrangian method for transport in porous media (to model chemotaxis in porous media)." Doctoral thesis, Università degli studi di Trento, 2014. https://hdl.handle.net/11572/367738.
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As recently shown in laboratory bench scale experiments, chemotaxis, i.e.the movement of microorganisms toward or away from the concentration gradient of a chemical species, could have a fundamental role in the transport of bacteria through saturated porous media. Chemotactic bacteria could enhance bioremediation by directing their own motions to residual contaminants in less conductive zones in aquifers. The aim of the present work is to develop a proper numerical scheme to define and to quantify the
magnitude and the role of chemotaxis in the complex groundwater system framework. We present a new class of meshless Lagrangian particle methods based on the Smooth
Particle Hydrodinamics (SPH) formulation of Vila & Ben Moussa, combined with a new Weighted Essentially Non-Oscillatory (WENO) reconstruction technique on moving point
clouds in multiple space dimensions. The purpose of this new scheme is to fully exploit the advantages of SPH among traditional meshbased and meshfree schemes and to overcome
its inapplicability for modeling chemotaxis in porous media.
The key idea is to produce for each particle first a set of high order accurate Moving Least Squares (MLS) reconstructions on a set of different reconstruction stencils. Then, these reconstructions are combined with each other using a nonlinear WENO technique in
order to capture at the same time discontinuities and to maintain accuracy and low numerical dissipation in smooth regions. The numerical fluxes between interacting particles are subsequently evaluated using this MLS-WENO reconstruction at the midpoint between two particles, in combination with a Riemann solver that provides the necessary stabilization of the scheme based on the underlying physics of the governing equations. We propose
the use of two different Riemann solvers: the Rusanov flux and an Osher-type flux. The use of monotone fluxes together with a WENO reconstruction ensures accuracy, stability,
robustness and an essentially non oscillatory solution without the artificial viscosity term usually employed in conventional SPH schemes. To our knowledge, this is the first time that the WENO method, which has originally been developed for mesh-based schemes in the Eulerian framework on fixed grids, is extended to meshfree Lagrangian particle
methods like SPH in multiple space dimensions.
In the first part, we test the new algorithm on two dimensional blast wave problems and on the classical one-dimensional Sod shock tube problem for the Euler equations of compressible gas dynamics. We obtain a good agreement with the exact or numerical reference solution in all cases and an improved accuracy and robustness compared to
existing standard SPH schemes. In the second part, the new SPH scheme is applied to advection-diffusion equation in
heterogeneous porous media with anisotropic diffusion tensor. Several numerical test case shows that the new scheme is accurate. Unlike standard SPH, it reduces the occurrence of negative concentration.
In the third part, we show the applicability of the new scheme for modeling chemotaxis in porous media. We test the new scheme against analytical reference solutions. Under the
assumption of complete mixing at the Darcy scale, we perform different two-dimensional conservative solute transport simulations under steady-state conditions with instant injection showing that chemotaxis significantly affect the quantification of field-scale mixing
processes.
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Avesani, Diego. "A new Lagrangian method for transport in porous media (to model chemotaxis in porous media)." Doctoral thesis, University of Trento, 2014. http://eprints-phd.biblio.unitn.it/1288/1/avesani_tesi.pdf.
Full textAbstract:
As recently shown in laboratory bench scale experiments, chemotaxis, i.e.the movement of microorganisms toward or away from the concentration gradient of a chemical species, could have a fundamental role in the transport of bacteria through saturated porous media. Chemotactic bacteria could enhance bioremediation by directing their own motions to residual contaminants in less conductive zones in aquifers. The aim of the present work is to develop a proper numerical scheme to define and to quantify the
magnitude and the role of chemotaxis in the complex groundwater system framework. We present a new class of meshless Lagrangian particle methods based on the Smooth
Particle Hydrodinamics (SPH) formulation of Vila & Ben Moussa, combined with a new Weighted Essentially Non-Oscillatory (WENO) reconstruction technique on moving point
clouds in multiple space dimensions. The purpose of this new scheme is to fully exploit the advantages of SPH among traditional meshbased and meshfree schemes and to overcome
its inapplicability for modeling chemotaxis in porous media.
The key idea is to produce for each particle first a set of high order accurate Moving Least Squares (MLS) reconstructions on a set of different reconstruction stencils. Then, these reconstructions are combined with each other using a nonlinear WENO technique in
order to capture at the same time discontinuities and to maintain accuracy and low numerical dissipation in smooth regions. The numerical fluxes between interacting particles are subsequently evaluated using this MLS-WENO reconstruction at the midpoint between two particles, in combination with a Riemann solver that provides the necessary stabilization of the scheme based on the underlying physics of the governing equations. We propose
the use of two different Riemann solvers: the Rusanov flux and an Osher-type flux. The use of monotone fluxes together with a WENO reconstruction ensures accuracy, stability,
robustness and an essentially non oscillatory solution without the artificial viscosity term usually employed in conventional SPH schemes. To our knowledge, this is the first time that the WENO method, which has originally been developed for mesh-based schemes in the Eulerian framework on fixed grids, is extended to meshfree Lagrangian particle
methods like SPH in multiple space dimensions.
In the first part, we test the new algorithm on two dimensional blast wave problems and on the classical one-dimensional Sod shock tube problem for the Euler equations of compressible gas dynamics. We obtain a good agreement with the exact or numerical reference solution in all cases and an improved accuracy and robustness compared to
existing standard SPH schemes. In the second part, the new SPH scheme is applied to advection-diffusion equation in
heterogeneous porous media with anisotropic diffusion tensor. Several numerical test case shows that the new scheme is accurate. Unlike standard SPH, it reduces the occurrence of negative concentration.
In the third part, we show the applicability of the new scheme for modeling chemotaxis in porous media. We test the new scheme against analytical reference solutions. Under the
assumption of complete mixing at the Darcy scale, we perform different two-dimensional conservative solute transport simulations under steady-state conditions with instant injection showing that chemotaxis significantly affect the quantification of field-scale mixing
processes.
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Satken, Bauyrzhan. "Adsorption/Retention of Polymer Solution in Porous Media." Thesis, Bordeaux, 2021. http://www.theses.fr/2021BORD0145.
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L'un des problèmes majeurs rencontré lors de l'injection de polymère pour l'EOR est la perte de polymère pendant l'injection due à la rétention / adsorption ainsi que le possible endommagement du réservoir du à des phénomènes mécaniques. Aussi, les compagnies pétrolières cherchent à minimiser cette perte de polymère.Pour comprendre la rétention des polymères dans les roches réservoirs, nous avons réalisé plusieurs études expérimentales « coreflood » en étudiant l'influence de la nature des polymères et de la perméabilité des roches (perméabilité élevée et intermédiaire pour des grès de Bentheimer et Berea), le poids moléculaire des polymères (faible et élevé) et la concentration de polymère (de diluée à semi-diluée).Dans des conditions monophasiques et à haute perméabilité, nous montrons que la rétention du polymère corrigée du volume de pore inaccessible (IPV) dépend du régime de concentration du polymère: la rétention augmente rapidement avec la concentration en polymère (Cp), en régime dilué et augmente plus faiblement dans le régime semi-dilué. De plus, l'utilisation d'un polymère de faible poids entraîne une perte de matière élevée et, dans le cas d'un poids moléculaire élevé et d'une faible perméabilité, un colmatage du milieu est mis en évidence.De plus, des expériences diphasiques en condition tertiaire ont été réalisées dans des conditions de mouillabilité à l’eau et intermédiaire. La première série d'expériences a été réalisée sur le milieu poreux natifs de Bentehimer mouillables à l'eau. La deuxième série d'expériences a été réalisée en modifiant d'abord la mouillabilité des mêmes milieux poreux, en les soumettant à un vieillissement en présence de pétrole brut pour altérer la mouillabilité initiale.Nos résultats montrent principalement que la rétention du polymère diminue lorsque l'huile est présente dans le système poreux en raison d'un volume poreux inaccessible occupé par l'huile résiduelle. Cependant, la rétention est encore plus faible dans les milieux poreux de mouillabilité intermédiaire car la surface des pores est partiellement couverte d'huile. Une explication phénoménologique est proposée qui soutient les comportements observésOne of the major issues of polymer flooding in EOR is the loss of polymer material during injection due to retention/adsorption and even the formation damage because of other mechanical phenomena. So, operating companies usually look for minimizing this polymer loss.To understand the retention of polymers in reservoir rocks, we carried out several coreflood experimental studies by investigating the influence of rock nature and permeability (high and intermediate permeability considering Bentheimer and Berea sandstones), polymer molecular weight (low and high), and concentration of polymer solutions (from dilute to semi-dilute).Under monophasic conditions and high permeability, we show that the polymer retention if corrected for inaccessible pore volume (IPV) depends on the polymer concentration regime: retention increases rapidly with polymer concentration (Cp), in the dilute regime and increases then very weakly in the semi-dilute regime. Moreover, the use of low polymer weight results in a high material loss, and in the case of high molecular weight and low permeability, plugging is evidenced.Besides, diphasic tertiary experiments were performed under water-wet and intermediate wet conditions. The first set of experiments was performed on the native water-wet Bentheimer porous medium. The second set of experiments was performed by altering first the wettability of the same porous media, by submitting them to ageing in presence of crude oil.Our results mainly show that the polymer retention decreases when the oil is present in the porous system due to additional inaccessible pore volume as added volume is now occupied by residual oil. However, the retention is even smaller in intermediate wet porous media because the pore surface is partially filled by oil. A phenomenological explanation is proposed that supports such observed behaviors
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Deng, Hailin. "Upscaling reactive transport parameters for porous and fractured porous media." Tallahassee, Florida : Florida State University, 2009. http://etd.lib.fsu.edu/theses/available/etd-10292009-103844/.
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Thesis (Ph. D.)--Florida State University, 2009.Advisor: Ming Ye, Zhenxue Dai, Florida State University, College of Arts and Sciences, Dept. of Geological Sciences. Title and description from dissertation home page (viewed on Apr. 26, 2010). Document formatted into pages; contains xxii, 167 pages. Includes bibliographical references.
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Feng, Zhaoyong. "Stabilization of flows through porous media." [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=981904637.
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Ippisch, Olaf. "Coupled transport in natural porous media." [S.l. : s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=96376022X.
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Vlahou, Ioanna. "Freeze fracturing of elastic porous media." Thesis, University of Cambridge, 2012. https://www.repository.cam.ac.uk/handle/1810/244232.
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The physical motivation behind this thesis is the phenomenon of fracturing of rocks and other porous media due to ice growth inside pre-existing faults and large pores. My aim is to explain the basic physical processes taking place inside a freezing elastic porous medium and develop a mathematical model to describe the growth of ice and fracturing of ice-filled cavities. There are two physical processes that can potentially cause high pressures inside a cavity of a porous medium. The expansion of the water by 9% as it freezes causes flow away from the freezing front and through the porous medium, resulting in a water pressure rise inside the cavity. Flow of water towards freezing cavities can occur during the later stages of freezing, when cavities are almost ice-filled, with a thin premelted film separating the ice from the medium. The pressure rise in this case is due to the flux of water into the cavities, which then freezes and increases the overall ice mass. The special geometry of a spherical cavity is initially considered, as a means of comparing how the different processes can contribute to pressure rise inside a cavity. Having established that the expansion of water only contributes to the overall pressure rise in limited situations, I focus attention on the premelting regime and develop a model for the fracturing of a 3D penny-shaped cavity in a porous medium. Integral equations for the pressure and temperature fields are found using Green’s functions, and a boundary element method is used to solve the problem numerically. A similarity solution for a warming environment is discussed, as well as a fully time-dependent problem. I find that the fracture toughness of the medium, the size of pre-existing faults and the undercooling of the environment are the parameters determining the susceptibility of a medium to fracturing. I also explore the dependence of the growth rates on the permeability and elasticity of the medium. Thin and fast-fracturing cracks are found for many types of rocks. I consider how the growth rate can be limited by the existence of pore ice, which decreases the permeability of a medium, and propose an expression for the effective “frozen” permeability. An important further application of the theory developed here is the growth of ice lenses in saturated cohesive soils. I present results for typical soil parameters and find good agreement between our theory and experimental observations of growth rates and minimum undercoolings required for fracturing.
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Sheng, James Jiaping. "Foamy oil flow in porous media." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq21633.pdf.
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Dashti, Hameeda. "Miscible displacement in fractured porous media." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/mq64994.pdf.
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Byrne, Helen M. "Modelling combustion zones in porous media." Thesis, University of Oxford, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.291095.
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Carr, Magda. "Convection in fluid and porous media." Thesis, Durham University, 2003. http://etheses.dur.ac.uk/4049/.
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The subject of convection in fluid and porous media is investigated. Particular attention is paid to penetrative convection. The first two chapters are devoted to penetrative convection when fluid overlies and saturates a porous medium. Penetrative convection is described by a quadratic equation of state in the first instance and via internal heating in the second. Linear instability analyses are performed in both cases. A surprising and striking array of streamlines are presented at the onset of convection. The streamlines exhibit novel behaviour when physical parameters of the problem are varied. Penetrative convection in a horizontally isotropic porous layer is discussed next. Again penetrative convection is described by a quadratic equation of state and internal heating. The internally heated model is dealt with primarily as it yields a global nonlinear stability bound. The two models are shown to be mathematically adjoint and the nonlinear stability results compared with previously published linear ones. Good agreement between the two is seen. The effect of convection on the evolution of under-ice meltponds is investigated next. Linear and nonlinear analyses are employed to yield instability and global stability results respectively. Discrepancy between the two is found and the region of possible subcritical instabilities is presented. Finally convection in a porous medium is investigated via a cubic equation of state. It is found that unconditional nonlinear stability results can be established if Forchheimer theory is introduced. The results are compared to previously published linear ones and it is shown that the linear theory essentially captures the physics involved.
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Stower, G. X. M. "The permeability of regular porous media." Thesis, University of Essex, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355381.
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Schechter, David S. "Immiscible flow behaviour in porous media." Thesis, University of Bristol, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234777.
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GAMA, ROGERIO MARTINS SALDANHA DA. "MODELLING OF FLOW IN POROUS MEDIA." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1985. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=33487@1.
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CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOO presente trabalho tem como objetivo a modelagem de escoamentos através de meios porosos, sob o ponto de vista da Teoria Contínua de misturas. O fluido e o sólido, que compõe o meio poroso, são tratados como constituintes contínuos de uma mistura binária, onde não ocorrem reações químicas. Em todas as situações aqui tratadas o fluido é suposto Newtoniano e incompressível, enquanto o meio poroso é rígido, homogêneo e isotrópico. O trabalho pode ser dividido em duas partes principais. Na primeira são modelados escoamentos através de regiões contendo meios porosos saturados e regiões onde só existe o fluido. São discutidas condições de compatibilidade sobre as interfaces, que separam as regiões, e é estabelecido um modelo para escoamentos, nos quais não exista fluxo de massa através das interfaces. A segunda parte trata de escoamentos em meios porosos insaturados, onde é preciso se considerar o efeito de forças capilares. Nesta parte é estabelecido um modelo e são simuladas situações unidimensionais. São estudados vários casos entre eles o enchimento de uma placa porosa, com e sem efeitos de atrito e de forças gravitacionais. A obtenção de resultados, nestes casos, exige a solução numérica de um sistema hiperbólico não-linear de equações diferenciais.
This work aims to a modelling of flow through a porous media based upon the Continuum Theory of Mixtures. The fluid and the solid, which composes the porous media, are assumed as continuous constituent of a binary mixture where chemical reactions do not occur. In all situations here considered, the fluid is assuned Newtonian and incompressíble, while the porous media is rigid, homogeneus and isotropic. This work can be divided in two main parts. In the first one, flows are modelled through regions containing saturated porous media and regions where there is nothing but the fluid. Conditions of compatibility in the interfaces that divide the regions are discussed and a flow modelling is stablished where there are no crosaflow through the interfaces. The second part is concerned with flows in unsaturated porous media, where the effect of capillery pressure is considered. In this Part a model is stablished and unidimensíonal situations are simulated. Several cases are studied and the filling-up of a porous plate is among them, with and without frictíon effect and gravitational forces. The obtainment of results, in such cases, requires the numeric solution of a non-linear hyperbolíc system of differential equations.
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Batycky, Richard Panko. "Inhomogeneous Stokes flow through porous media." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/36640.
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Tran-Viet, Alexis. "Temperature-sensitive polymers in porous media." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610437.
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Krause, Andrew Leslie. "Network modelling of bioactive porous media." Thesis, University of Oxford, 2017. http://ora.ox.ac.uk/objects/uuid:980a0fd8-96a7-4818-904a-0842d4efbd41.
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In this thesis we consider several approaches to modelling interactions between fluid flow and cell proliferation in a bioactive porous medium. This is motivated by models of cell growth within tissue engineering scaffolds placed in perfusion bioreactors. These scaffolds are porous materials used to facilitate nutrient transport to cells placed within them. Recent modelling efforts have sought to understand the influence that cells have on the effective permeability of these tissue scaffolds, and hence on the capacity of the porous medium to facilitate fluid and nutrient transport, which enhances the overall growth of tissue within a scaffold. Contemporary experimental and theoretical studies have emphasized the importance of mechanical forcing on cells due to their environment. We therefore consider simple models of cell growth that assume cells are affected by the fluid itself, either via shear stress, hydrostatic pressure, or local flow rate, and that cell growth influences the local permeability of the scaffold at higher cell densities via pore-blocking. Hence, we are interested in the feedback between cell growth and fluid flow within a bioactive porous medium. It is within this simplified context of fluid-growth interaction that we explore different approaches to modelling the spatial structure of the pore network, and the influence that this has on the cell density distribution throughout the scaffold. Models in the literature are often spatially homogeneous (ODE) or spatially continuous (PDE), only implicitly accounting for the discrete pore network of the medium. The pore and scaffold length scales in typical experiments with perfusion bioreactors can lead to scaffolds with relatively few pores, and it is unclear that macroscopic spatially averaged (homogenized) continuous models will capture features present in small pore networks. We propose a suite of spatially continuous models, modified from existing PDE approaches in the literature, and compare these to discrete lattice (ODE) systems in order to elucidate differences between these modelling paradigms. We also use the structure of the lattice model to explore stochastic analogues that are computationally and theoretically amenable to analysis. We explore behaviours of these models via numerical simulations, bifurcation analyses, and asymptotic reductions to simpler systems. Our lattice modelling approach provides a 'mesoscopic' perspective, where the effective equations governing the cell growth and fluid flow are prescribed as ODEs at each pore. These capture the microscale dynamics at the pore scale, as opposed to homogenization approaches where the microscale is explicitly related to macroscale equations. This also allows us to use tools from dynamical systems theory which are substantially more tractable in the finite dimensional setting of ODEs (with algebraic conditions for the fluid flow), as opposed to the infinite dimensional setting of PDEs (consisting of coupled elliptic and parabolic equations). Additionally, we do not have to worry about issues of numerical convergence or existence of solutions that are important in the spatially continuous setting. Our emphasis on mesoscopic governing equations makes this network-based approach somewhat unique in the tissue engineering community. We demonstrate qualitative and quantitative differences between these continuum and network paradigms, and in particular show behaviours captured by explicitly accounting for the discrete pore network that are not captured in spatially continuous models. For each kind of fluid-cell interaction, we classify behaviours depending on nondimensional model parameters in order to elucidate in what regimes discrete models may provide useful insights into bioactive porous materials. We also discuss computational considerations for analyzing these kinds of models, and in particular suggest that stochastic and discrete models may be easier to simulate in some parameter regimes compared to typical spatially continuous models. Our results suggest several novel approaches to pursue in accounting for the finite discrete nature of bioactive porous media, and we highlight several useful further directions.
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Anna, Pietro de. "Mixing and reactions in porous media." Rennes 1, 2012. https://tel.archives-ouvertes.fr/tel-00822932.
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In this thesis we use a stochastic approach to address the modeling of mixing dominated reactions in flows within heterogeneous porous media. When the transport is represented only by diffusion fluctuations in spatial concentration distribution lead to segregation of chemicals and thus to anomalous kinetics. We show that the transition from mean field to this anomalous kinetics is intimately linked to the evolution of the concentration PDF from a Gaussian to non-Gaussian shape. Considering also advective transport processes, we studied the incomplete mixing on effective kinetics at the front between two solutes, one displacing the other. While classical Fickian models predict a scaling for the mass production as t1/2, we show that the kinetics follow 2 non-Fickian regime. At early times the invading reactant is organized in fingers and the mass production scales as t2. For later times the mass production slows down, but it is still faster then the Fickian prediction t1/2, does not depends on diffusion and is totally controlled by advective spreading. We propose a new general framework for upscaling dispersion in porous media, relating the temporal evolution of spreading to the small scale velocity field properties. The resulting effective transport model is a correlated Continuous Time Random Walk, whose predictions are in good agreement with the pore scale simulations. We finally carried out a laboratory experiment where a quasi 2d system is studied through an Hele-Shaw cell in which two reactive chemicals are injected, one displacing the other. The anomalous kinetics of the observed reactive front results to be consistent with our theoretical predictionsCette thèse porte sur l'étude théorique de la vitesse de réaction entre des produits chimiques qui se mélangent dans un milieu poreux. Si le transport est purement diffusif (pas d'advection), les fluctuations spatiales peuvent entraîner des séparations des reactifs et donc à des cinétiques anormales. Nous associons la transition de la pdf de la concentration d'une gaussienne vers une non-gaussienne à l'impact du mélange incomplet sur la vitesse de réaction. Nous considérons aussi le front de réaction entre deux produits chimiques injectés en continu, l'un déplaçant l'autre, dans un milieu poreux 2d. Lors du mélange des deux reactifs, une réaction bimoléculaire A + B --> C a lieu. Les modèles fickiens classiques considèrent un mélange parfait à l'échelle du pore et prédisent une évolution temporelle de la masse Mc produite proportionelle à t1/2. D'apres les simulations à l'échelle du pore l'évolution temporelle pour Mc suit deux régimes. Pour des temps faibles Mc est proportionelle à t2. Pour des temps plus longs, nous relions Mc à la dispersion longitudinale advective. Une observation clé dans ce régime est que la masse totale ne dépend pas du nombre de Peclet. La dernière étape de cette thèse est une expérience de laboratoire qui reproduit les conditions numériques simulées précédemment. Nous proposons une nouvelle technique pour observer et quantifier le transport, le mélange et les réactions à l'échelle du pore. L'évolution temporelle de la masse produite au niveau du front de la réaction est cohérente avec les prédictions données par notre modèle théorique
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Nguyen, Kim Thang. "Direct Sampling applied to porous media." Paris 6, 2013. http://www.theses.fr/2013PA066686.
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Le problème de la simulation des milieux poreux qui partagent les propriétés d'un milieu réel a une grande importance théorique et pratique. L'objectif général de la reconstruction des milieux poreux est de créer des échantillons numériques avec les propriétés géométriques et les propriétés de transport du milieu réel. Par exemple, la méthode de corrélation à deux-points est très populaire [1]. Ici, notre objectif est de développer un algorithme qui simule une fonction aléatoire de phase Z(x) par la méthode appelée Direct Sampling basée sur les recherches dans la Training Image (TI) de façon aléatoire, mais conditionnelle [2]. Chaque noeud à simuler x a sa configuration qui comprend les valeurs et positions relatives de ses Ncd voisinages les plus proches. La TI est balayée pour calculer la distance d{dNcd(x), dNcd(y)} entre chaque y TI et noeud x. La valeur du point y telle que d{dNcd(x), dNcd(y)} soit inférieure ou égale au seuil d'acceptation est donnée au point x. S'il n'y a pas de y satisfaisant la condition de seuil, le noeud y qui donne la distance de configuration minimale parmi ceux balayés dans TI est pris. L'algorithme est détaillé. Cette procédure est appliquée jusqu'à ce que tous les points dans le milieu simulé soient remplis. La notion de distance entre les configurations est très puissante car souple. Plusieurs types de milieu réel sont utilisés comme TI : milieu binarisé avec seulement deux sortes de voxels ou plus (tels que des cartes minéralogiques). Les paramètres de l'algorithme sont optimisés. La comparaison de fonctions de corrélation à plusieurs points (jusqu'à quatre) [3] est bonne. La perméabilité des simulations et de la TI sont en bon accord. Le milieu simulé peut avoir soit la même dimension que les TI (de 2D à 2D ou de 3D à 3D) ou pas (de 2D à 3D); il peut être simulé avec ou sans les conditions périodiques. Malgré les avantages de cette méthode, telle que sa simplicité, la diversité d'application, l'utilisation limitée de mémoire ; il existe certains problèmes tels que l'apparition des noeuds isolés qui peuvent être supprimés dans la simulation et la sensibilité des composants dont la proportion est très faible dans la TI. Enfin, le temps de calcul est relativement important car un milieu 3D 128x128x128 est généré après 76 heures sur un mono-processeur avec une horloge de 3GhzThe problem of simulating porous media which share the properties of real media has considerable theoretical and practical importance. The general objective of reconstructed porous media is to create numerical samples with the geometrical properties and the transport properties of real media. For instance, the two-point method is very popular [1]. Here, our objective is to develop an algorithm that simulates a random phase function Z(x) by the method called Direct Sampling which is based on research in the Training Image (TI), but in a conditional random way [2]. Each node x to be simulated has its data event which includes the values and relative positions of its Ncd nearest neighbourhoods. TI is scanned to determine the distance d{dNcd(x), dNcd(y)} between each node y TI and node x. The value of node y such that d{dNcd(x), dNcd(y)} is less than or equal to the acceptance threshold is given to the point x. If there is no node y satisfying the threshold condition, the node y that gives the minimum distance among these scanned nodes in TI is taken. The algorithm will be detailed. This procedure is repeatedly applied until all the voxels of the simulated medium are filled. The concept of distance between the data events is very powerful because flexible. Several types of real medium are used as training images: binarized media with only two kinds of voxels or more (such as mineralogical maps). The parameters of the algorithm are optimized. The comparison of the multi-point correlation functions (up to four) [3] is good. The permeabilities of the reconstructed media and of the TI are in good agreement. The simulated medium may have either the same dimension as the TI (from 2D to 2D or from 3D to 3D) or not (from 2D to 3D); it may be simulated with or without periodic boundary conditions. Despite the advantages of this method such as its simplicity, diversity of applications, limited memory, there are some minor problems such as the occurrence of isolated nodes which have to be deleted and the sensitivity of components whose proportion is very small in the TI. Finally, the calculation time is relatively large since a 3D medium 128x128x128 is generated in 76 hours on a 3 GHz mono processor
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Sheng, Jopan. "Multiphase immiscible flow through porous media." Diss., Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/53630.
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A finite element model is developed for multiphase flow through soil involving three immiscible fluids: namely air, water, and an organic fluid. A variational method is employed for the finite element formulation corresponding to the coupled differential equations governing the flow of the three fluid phase porous medium system with constant air phase pressure. Constitutive relationships for fluid conductivities and saturations as functions of fluid pressures which may be calibrated from two-phase laboratory measurements, are employed in the finite element program. The solution procedure uses iteration by a modified Picard method to handle the nonlinear properties and the backward method for a stable time integration. Laboratory experiments involving soil columns initially saturated with water and displaced by p-cymene (benzene-derivative hydrocarbon) under constant pressure were simulated by the finite element model to validate the numerical model and formulation for constitutive properties. Transient water outflow predicted using independently measured capillary head-saturation data agreed well with observed outflow data. Two-dimensional simulations are presented for eleven hypothetical field cases involving introduction of an organic fluid near the soil surface due to leakage from an underground storage tank. The subsequent transport of the organic fluid in the variably saturated vadose and ground water zones is analysed.Ph. D.
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Pazdniakou, Aliaksei. "Lattice models in porous media studies." Paris 6, 2012. http://www.theses.fr/2012PA066116.
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La thèse est consacrée à l'étude des ondes acoustiques et des écoulements à plusieurs phases en milieux poreux. Pour la simulation des écoulements, la méthode de Boltzmann sur réseau a été choisie. On utilise cette méthode pour simuler des écoulements à plusieurs phases ainsi que des ondes acoustiques dans un fluide. Cette méthode représente une approche alternative à la description du mouvement de fluide basée sur la théorie cinétique des gaz. Pour simuler les ondes acoustiques en solide élastique, le modèle LSM (Lattice spring model) a été choisi. Dans le cadre du LSM, le milieu solide est remplacé par un réseau cubique. Les noeuds de réseau sont liés par des ressorts de deux types. Les équations dynamiques obtenues correspondent à celles de la théorie élastique. La méthode a été appliquée pour calculer les célérités des ondes de compression et de cisaillement dans des milieux poreux reconstruits pour différentes fréquences et différentes valeurs de porosité. Les deux modèles (LBM et LSM) ont été couplés par les conditions aux limites pour l'étude des ondes acoustiques en milieu poreux saturé de liquide. Il existe deux approches principales pour simuler des ondes acoustiques en milieu poreux saturé de liquide en utilisant notre modèle (LBM+LSM). La première est basée sur la théorie d’homogénéisation et la deuxième sur la modélisation des ondes acoustiques en temps réel. Les deux méthodes ont été appliquées pour calculer les célérités des ondes acoustiques dans des milieux poreux reconstruits saturés. Les résultats ont été analysés. Les codes ont été systématiquement parallélisés sous OpenMP de manière à réduire significativement les temps de restitutionThe thesis adresses the study of acoustic waves and multiphase flows in porous media. For the simulation of fluid flows, the lattice Boltzmann method is selected. The method is used for simulation of multiphase flows as well as for acoustic waves in a fluid. The method represents an alternative approach to the description of the fluid dynamics based on the kinetic theory of gases. In order to simulate acoustic waves in an elastic solid, the LSM (Lattice Spring model) is selected. In the framework of the LSM, the medium is replaced by a cubic lattice. The nodes of the lattice are connected by springs of two types. The obtained dynamic equations correspond to those of the theory of elasticity. The method is applied to calculate the compressional and shear wave velocities in reconstructed porous media for various frequencies and porosity values. The two models (LBM and LSM) are coupled by the boundary conditions in order to study acoustic waves in saturated porous media. Two principal approaches exist to simulate acoustic waves in saturated porous media using our coupled (LBM+LSM) model. The first is based on the homogenization theory and the second on the real time simulation of acoustic waves. The two methods are applied for calculation of the acoustic waves velocities in saturated reconstructed porous media. The results are systematically analysed. The codes are parallelized by using OpenMP in order to reduce significantly the program run time
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Ippisch, Olaf. "Coupled transport in natural porous media." [S.l. : s.n.], 2003. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB10605053.
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Fukumura, Kazunari 1956. "Electrokinetic nitrate removal from porous media." Diss., The University of Arizona, 1996. http://hdl.handle.net/10150/290595.
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Nitrate movement under simultaneous influence of hydraulic, electric and chemical gradients was investigated. A one-dimensional ion migration model was developed and compared with laboratory column experiments. Operation of subsurface drainage with an electrode was discussed as an application. The ion transport equation was developed utilizing non-equilibrium thermodynamics. Onsager's reciprocal relations were applied to reduce the number of linear phenomenological coefficients that relate flux to driving forces. Then phenomenological coefficients were expressed using known or measurable physical, chemical and electrical properties of solute and porous media. Developed equations were numerically solved by the Integral Finite Difference Method in one dimension. The numerical results were validated with analytical solutions of simple boundary conditions as well as the results obtained from laboratory column experiments for two or three applied gradients. Without water flow, nitrate concentration increased at the anode by 2.5 times after 100 hrs of 30 V application. Three initial concentrations, 10, 100 and 500 ppm NO₃-N, were tested. A log normal relation between elapsed time and relative concentration increase at the anode was obtained. Two flux rates (0.112 and 0.225 cm min⁻¹), and three inflow concentrations (100, 500 and 1000 ppm NO₃-N) were used to evaluate nitrate transport in the column. Nitrate concentration at the anode increased by 10 to 20% at the end of all experiments. However, the concentration in the column was same as inflow concentration. The application of electrokinetic nitrate removal by installed subsurface drainage with on-off (no flow then flush out) operation is recommended over a continuous flow approach. The numerical model results showed very low flux rates (i.e. 2.68 x 10⁻³ cm min⁻¹) are required for nitrate accumulation in a sand column, and the experimental results confirmed no accumulation at a flux rate of 0.112 cm min⁻¹.
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Rioux, Ran Wei. "The Rate of Fluid Absorption in Porous Media." Fogler Library, University of Maine, 2003. http://www.library.umaine.edu/theses/pdf/RiouxRW2003.pdf.
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Breitmeyer, Ronald J. "Thermal convection in laboratory-scale porous media." abstract and full text PDF (free order & download UNR users only), 2006. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1438927.
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Kumar, Nadupuri Suresh. "Numerical study of drying in porous media." [S.l.] : [s.n.], 2007. http://deposit.ddb.de/cgi-bin/dokserv?idn=983595720.
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Shao, Haibing. "Modelling reactive transport processes in porous media." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-61738.
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Reactive transport modelling has wide applications in geosciences. In the field of hydrogeology, it has been utilised to simulate the biogeochemical processes that disperse and degrade contaminants in the aquifer. For geotechnical applications, such as geological CO2 sequestration, the reaction of CO2 with the ambient saline aquifer determines the final success of storage. In a radioactive waste repository, scientists rely on reactive transport models to predict the mobilisation of hazardous radionuclides within space and time.
In this work, the multi-component mass transport code OpenGeoSys, was coupled with two geochemical solvers, the Gibbs Energy Minimization Selektor (GEM) and the Biogeochemical Reaction Network Simulator (BRNS). Both coupled codes were verified against analytical solutions and simulation results from other numerical models. Moreover, the coupling interface was developed for parallel simulation. Test runs showed that the speed-up of reaction part had a very good linearity with number of nodes in the mesh. However, for three dimensional problems with complex geochemical reactions, the model performance was dominated by solving transport equations of mobile chemical components.
OpenGeoSys-BRNS was applied to a two dimensional groundwater remediation problem. Its calculated concentration profiles fitted very well with analytical solutions and numerical results from TBC. The model revealed that natural attenuation of groundwater contaminants is mainly controlled by the mixing of carbon source and electron donor. OpenGeoSys-GEM was employed to investigate the retardation mechanism of radionuclides in the near field of a nuclear waste repository. Radium profiles in an idealised bentonite column was modelled with varying clay/water ratios. When clay content is limited, Ba-Sr-Ra sulfate solid solutions have a very strong retardation effect on the aqueous radium. Nevertheless, when clay mineral is abundant, cation exchange sites also attract Sr and Ba, thus dominates the transport of Ra.
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Khayamyan, Shervin. "Transitional and turbulent flow in porous media." Licentiate thesis, Luleå tekniska universitet, Strömningslära och experimentell mekanik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-26476.
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Fluid flow through porous media takes place in many natural processes such as ground water flows, capillary flows in plants and flow in human organs and muscles. It is also of outmost importance to have knowledge of this flow in a number of industrial processes such as paper making, making of fibre boards, composites manufacturing, filtering, forming and sintering of iron ore pellets and drying and impregnation of wood. Despite the significance of porous media flow and the vast amount of work that has been performed to investigate it, knowledge of some fundamentals is missing. Little is, for instance, known about transitional and turbulent flow in porous media on the microscopic level. On a macroscopic level Darcy law is extended to the so called Ergun or Forchheimer Equations when Re becomes larger than about 10 to fit experimental. The actual value depends both on the porous media and how Re is defined. The deviation from Darcy flow can for modest Re be explained by inertia but may, as Re increases, also be attributed to turbulence. The macroscopic way of modelling the transition from inertia dominated to turbulent flow is just to continue with the Forchheimer Equation or possibly some version of it. In any case experimental data yields that, on a macroscopic level, the transition from Darcy flow to inertia dominated and turbulent flow is smooth. To get a better understanding of this process the transition from laminar to turbulent flow in porous media is here studied with a new method. To mimic inter-connected pores, a simplified geometry is studied consisting of a pipe with a relatively large diameter that is split into two parallel pipes with different diameters. This is a pore-doublet set-up and the pressure drop over all pipes is recorded by pressure transducers for different flow rates. Statistical method and frequency analysis are performed to investigate collected data (Papers A and B). Positive skewness of pressure drop fluctuations indicates early stage of presence of turbulent patches in the flow for each pipe. The measured flow distribution and pressure drop fluctuations highlights six distinct flow patterns in the pipe network based on variation in flow regime of each pipe and the level of pressure fluctuations (Paper B). Correlation between the pressure drop between two pipes shows that two parallel pipes follow each other fluctuations much better before both of them become fully turbulent. Some detailed results are that the frequency analysis reveals two different frequency band events in the pipes. The gain factor shows that both frequency band events originate from the larger pipe until the early presence of turbulent patches in the smaller pipe (Paper B). The low frequency fluctuations makes the flow in the pipes to be out of phase while the high frequency band fluctuations try to bring the flow in the pipes back to equilibrium state.Godkänd; 2013; 20130521 (shekha); Tillkännagivande licentiatseminarium 2013-05-29 Nedanstående person kommer att hålla licentiatseminarium för avläggande av teknologie licentiatexamen. Namn: Shervin Khayamyan Ämne: Strömningslära/Fluid Mechanics Uppsats: Transitional and Turbulent Flow in Porous Media Examinator: Professor Staffan Lundström, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet Diskutant: Professor Carl-Erik Grip, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet Tid: Onsdag den 19 juni 2013 kl 09.00 Plats: E231, Luleå tekniska universitet
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Shin, Youn-Ok. "Vapor and liquid equilibria in porous media." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0022/MQ50659.pdf.
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Woudberg, Sonia. "Laminar flow through isotropic granular porous media." Thesis, Link to the online version, 2006. http://hdl.handle.net/10019/1320.
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Shin, Youn-Ok 1971. "Vapor and liquid equilibria in porous media." Thesis, McGill University, 1999. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=21323.
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The alteration of the vapor and liquid equilibrium (VLE) of volatile organic mixtures by using porous media at the liquid-vapor interface was studied. Kelvin, assuming ideal behavior of fluids, first introduced the vapor pressure of liquid over a meniscus as a function of its surface tension and the radius of the curvature. A thermodynamic model (SSmod model) predicting the VLE of non-ideal organic mixtures in porous media was developed as a function of pore sizes based on the pressure equations available in literature. The model was used to predict the VLE of two aqueous alcohol solutions, ethanol-water and propanol-water, and two binary alcohol solutions, methanol-isopropanol and ethanol-octane. Experiments were conducted using sintered metal and fritted glass plates as porous media and compared with the model predictions. The model predictions for the actual pore diameters tested showed good agreement with the experimental results.
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Khan, Zafar Hayat. "Modelling moving evaporation fronts in porous media." Thesis, University of Strathclyde, 2011. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=16850.
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Understanding vertical heat transfer and through flow in porous media such as geothermal reservoirs is of great interest. In a geothermal system, a denser layer of liquid water may overlie a less dense layer of water vapour. Vertical and horizontal thermal diffusion stabilises such configurations, but the buoyancy contrast can cause instability. In this study, the mechanisms contributing to the stability and instability of such systems are analysed using a separate-phase model with a sharp interface be- tween liquid and vapour. The governing equations representing incompressibility, Darcy’s law and energy conservation for each phase are linearised about suitable base states and the stability of these states is investigated. We have considered two different thermal boundary conditions, both with and without a vertical through- flow. In the first case, the boundaries above and below the layer of interest are assumed to be isothermal. We found that due to the competition between thermal and hydrostatic effects, the liquid–vapour interface may have multiple positions. A two-dimensional linear stability analysis of these basic states shows that the Rayleigh–Taylor mechanism is the dominant contributor to instability, but that there are circumstances under which the basic state may be stable, especially when the front is close to one of the boundaries. In the second case, a constant heat flux is imposed at the liquid boundary and a fixed temperature at the vapour boundary. We have shown that competition between the effects of cooling and the viscosity difference between the fluid phases causes multiple liquid-vapour front positions, whether or not gravity is considered. The stability analysis has shown that along with the Rayleigh-Taylor (buoyancy- driven) mechanism, a Saffman-Taylor viscous fingering mechanism can also play an important rule in the transition to instability.
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Ochi, Fumihiro, and Kazuhiro Yamamoto. "Soot accumulation and combustion in porous media." Maney Publishing, 2006. http://hdl.handle.net/2237/20054.
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