MAGNUM2D. Radionuclide Transport Porous Media
Langford, D.W.; Baca, R.G.
1989-03-01
MAGNUM2D was developed to analyze thermally driven fluid motion in the deep basalts below the Paco Basin at the Westinghouse Hanford Site. Has been used in the Basalt Waste Isolation Project to simulate nonisothermal groundwater flow in a heterogeneous anisotropic medium and heat transport in a water/rock system near a high level nuclear waste repository. Allows three representations of the hydrogeologic system: an equivalent porous continuum, a system of discrete, unfilled, and interconnecting fractures separated by impervious rock mass, and a low permeability porous continuum with several discrete, unfilled fractures traversing the medium. The calculations assume local thermodynamic equilibrium between the rock and groundwater, nonisothermal Darcian flow in the continuum portions of the rock, and nonisothermal Poiseuille flow in discrete unfilled fractures. In addition, the code accounts for thermal loading within the elements, zero normal gradient and fixed boundary conditions for both temperature and hydraulic head, and simulation of the temperature and flow independently. The Q2DGEOM preprocessor was developed to generate, modify, plot and verify quadratic two dimensional finite element geometries. The BCGEN preprocessor generates the boundary conditions for head and temperature and ICGEN generates the initial conditions. The GRIDDER postprocessor interpolates nonregularly spaced nodal flow and temperature data onto a regular rectangular grid. CONTOUR plots and labels contour lines for a function of two variables and PARAM plots cross sections and time histories for a function of time and one or two spatial variables. NPRINT generates data tables that display the data along horizontal or vertical cross sections. VELPLT differentiates the hydraulic head and buoyancy data and plots the velocity vectors. The PATH postprocessor plots flow paths and computes the corresponding travel times.
MAGNUM2D. Radionuclide Transport Porous Media
Langford, D.W.; Baca, R.G.
1988-08-01
MAGNUM2D was developed to analyze thermally driven fluid motion in the deep basalts below the Paco Basin at the Westinghouse Hanford Site. Has been used in the Basalt Waste Isolation Project to simulate nonisothermal groundwater flow in a heterogeneous anisotropic medium and heat transport in a water/rock system near a high level nuclear waste repository. Allows three representations of the hydrogeologic system: an equivalent porous continuum, a system of discrete, unfilled, and interconnecting fractures separated by impervious rock mass, and a low permeability porous continuum with several discrete, unfilled fractures traversing the medium. The calculation assumes local thermodynamic equilibrium between the rock and groundwater, nonisothermal Darcian flow in the continuum portions of the rock, and nonisothermal Poiseuille flow in discrete unfilled fractures. In addition, the code accounts for thermal loading within the elements, zero normal gradient and fixed boundary conditions for both temperature and hydraulic head, and simulation of the temperature and flow independently. The Q2DGEOM preprocessor was developed to generate, modify, plot and verify quadratic two dimensional finite element geometries. The BCGEN preprocessor generates the boundary conditions for head and temperature and ICGEN generates the initial conditions. The GRIDDER postprocessor interpolates nonregularly spaced nodal flow and temperature data onto a regular rectangular grid. CONTOUR plots and labels contour lines for a function of two variables and PARAM plots cross sections and time histories for a function of time and one or two spatial variables. NPRINT generates data tables that display the data along horizontal or vertical cross sections. VELPLT differentiates the hydraulic head and buoyancy data and plots the velocity vectors. The PATH postprocessor plots flow paths and computes the corresponding travel times.
Chaotic advection in 2D anisotropic porous media
NASA Astrophysics Data System (ADS)
Varghese, Stephen; Speetjens, Michel; Trieling, Ruben; Toschi, Federico
2015-11-01
Traditional methods for heat recovery from underground geothermal reservoirs employ a static system of injector-producer wells. Recent studies in literature have shown that using a well-devised pumping scheme, through actuation of multiple injector-producer wells, can dramatically enhance production rates due to the increased scalar / heat transport by means of chaotic advection. However the effect of reservoir anisotropy on kinematic mixing and heat transport is unknown and has to be incorporated and studied for practical deployment in the field. As a first step, we numerically investigate the effect of anisotropy (both magnitude and direction) on (chaotic) advection of passive tracers in a time-periodic Darcy flow within a 2D circular domain driven by periodically reoriented diametrically opposite source-sink pairs. Preliminary results indicate that anisotropy has a significant impact on the location, shape and size of coherent structures in the Poincare sections. This implies that the optimal operating parameters (well spacing, time period of well actuation) may vary strongly and must be carefully chosen so as to enhance subsurface transport. This work is part of the research program of the Foundation for Fundamental Research on Matter (FOM), which is part of Netherlands Organisation for Scientific Research (NWO). This research program is co-financed by Shell Global Solutions International B.V.
Representativeness of 2D models to simulate 3D unstable variable density flow in porous media
NASA Astrophysics Data System (ADS)
Knorr, Bastian; Xie, Yueqing; Stumpp, Christine; Maloszewski, Piotr; Simmons, Craig T.
2016-11-01
Variable density flow in porous media has been studied primarily using numerical models because it is a semi-chaotic and transient process. Most of these studies have been 2D, owing to the computational restrictions on 3D simulations, and the ability to observe variable density flow in 2D experimentation. However, it is recognised that variable density flow is a three-dimensional process. A 3D system may cause weaker variable density flow than a 2D system due to stronger dispersion, but may also result in bigger fingers and hence stronger variable density flow because of more space for fingers to coalesce. This study aimed to determine the representativeness of 2D modelling to simulate 3D variable density flow. 3D homogeneous sand column experiments were conducted at three different water flow velocities with three different bromide tracer solutions mixed with methanol resulting in different density ratios. Both 2D axisymmetric and 3D numerical simulations were performed to reproduce experimental data. Experimental results showed that the magnitude of variable density flow increases with decreasing flow rates and decreasing density ratios. The shapes of the observed breakthrough curves differed significantly from those produced by 2D axisymmetric and 3D simulations. Compared to 2D simulations, the onset of instabilities was delayed but the growth was more pronounced in 3D simulations. Despite this difference, both 2D axisymmetric and 3D models successfully simulated mass recovery with high efficiency (between 77% and 99%). This study indicates that 2D simulations are sufficient to understand integrated features of variable density flow in homogeneous sand column experiments.
Phenrat, Tanapon; Cihan, Abdullah; Kim, Hye-Jin; Mital, Menka; Illangasekare, Tissa; Lowry, Gregory V
2010-12-01
Concentrated suspensions of polymer-modified Fe(0) nanoparticles (NZVI) are injected into heterogeneous porous media for groundwater remediation. This study evaluated the effect of porous media heterogeneity and the dispersion properties including particle concentration, Fe(0) content, and adsorbed polymer mass and layer thickness which are expected to affect the delivery and emplacement of NZVI in heterogeneous porous media in a two-dimensional (2-D) cell. Heterogeneity in hydraulic conductivity had a significant impact on the deposition of NZVI. Polymer modified NZVI followed preferential flow paths and deposited in the regions where fluid shear is insufficient to prevent NZVI agglomeration and deposition. NZVI transported in heterogeneous porous media better at low particle concentration (0.3 g/L) than at high particle concentrations (3 and 6 g/L) due to greater particle agglomeration at high concentration. High Fe(0) content decreased transport during injection due to agglomeration promoted by magnetic attraction. NZVI with a flat adsorbed polymeric layer (thickness ∼30 nm) could not be transported effectively due to pore clogging and deposition near the inlet, while NZVI with a more extended adsorbed layer thickness (i.e., ∼70 nm) were mobile in porous media. This study indicates the importance of characterizing porous media heterogeneity and NZVI dispersion properties as part of the design of a robust delivery strategy for NZVI in the subsurface.
NASA Astrophysics Data System (ADS)
Lekmine, G.; Auradou, H.; Pessel, M.; Rayner, J. L.
2017-04-01
Cross-borehole ERT imaging was tested to quantify the average velocity and transport parameters of tracer plumes in saturated porous media. Seven tracer tests were performed at different flow rates and monitored by either a vertical or horizontal dipole-dipole ERT sequence. These sequences were tested to reconstruct the shape and temporally follow the spread of the tracer plumes through a background regularization procedure. Data sets were inverted with the same inversion parameters and 2D model sections of resistivity ratios were converted to tracer concentrations. Both array types provided an accurate estimation of the average pore velocity vz. The total mass Mtot recovered was always overestimated by the horizontal dipole-dipole and underestimated by the vertical dipole-dipole. The vertical dipole-dipole was however reliable to quantify the longitudinal dispersivity λz, while the horizontal dipole-dipole returned better estimation for the transverse component λx. λ and Mtot were mainly influenced by the 2D distribution of the cumulated electrical sensitivity and the Shadow Effects induced by the third dimension. The size reduction of the edge of the plume was also related to the inability of the inversion process to reconstruct sharp resistivity contrasts at the interface. Smoothing was counterbalanced by a non-realistic rise of the ERT concentrations around the centre of mass returning overpredicted total masses. A sensitivity analysis on the cementation factor m and the porosity ϕ demonstrated that a change in one of these parameters by 8% involved non negligible variations by 30 and 40% of the dispersion coefficients and mass recovery.
A 2-D Pore-Network Model of the Drying of Single-Component Liquids in Porous Media
Yortsos, Yanic C.; Yiotis, A.G.; Stubos, A.K.; Boundovis, A.G.
2000-01-20
The drying of liquid-saturated porous media is typically approaching using macroscopic continuum models involving phenomenological coefficients. Insight on these coefficients can be obtained by a more fundamental study at the pore- and pore-network levels. In this report, a model based on pore-network representation of porous media that accounts for various process at the pore-scale is presented. These include mass transfer by advection and diffusion in the gas phase, viscous flow in liquid and gas phases and capillary effects at the gas-liquid menisci in the pore throats.
Lappala, E.G.; Healy, R.W.; Weeks, E.P.
1987-01-01
This report documents FORTRAN computer code for solving problems involving variably saturated single-phase flow in porous media. The flow equation is written with total hydraulic potential as the dependent variable, which allows straightforward treatment of both saturated and unsaturated conditions. The spatial derivatives in the flow equation are approximated by central differences, and time derivatives are approximated either by a fully implicit backward or by a centered-difference scheme. Nonlinear conductance and storage terms may be linearized using either an explicit method or an implicit Newton-Raphson method. Relative hydraulic conductivity is evaluated at cell boundaries by using either full upstream weighting, the arithmetic mean, or the geometric mean of values from adjacent cells. Nonlinear boundary conditions treated by the code include infiltration, evaporation, and seepage faces. Extraction by plant roots that is caused by atmospheric demand is included as a nonlinear sink term. These nonlinear boundary and sink terms are linearized implicitly. The code has been verified for several one-dimensional linear problems for which analytical solutions exist and against two nonlinear problems that have been simulated with other numerical models. A complete listing of data-entry requirements and data entry and results for three example problems are provided. (USGS)
NASA Astrophysics Data System (ADS)
Blanc, Emilie; Chiavassa, Guillaume; Lombard, Bruno
2014-10-01
A time-domain numerical modeling of transversely isotropic Biot poroelastic waves is proposed in two dimensions. The viscous dissipation occurring in the pores is described using the dynamic permeability model developed by Johnson-Koplik-Dashen (JKD). Some of the coefficients in the Biot-JKD model are proportional to the square root of the frequency. In the time-domain, these coefficients introduce shifted fractional derivatives of order 1/2, involving a convolution product. Based on a diffusive representation, the convolution kernel is replaced by a finite number of memory variables that satisfy local-in-time ordinary differential equations, resulting in the Biot-DA (diffusive approximation) model. The properties of both the Biot-JKD and the Biot-DA models are analyzed: hyperbolicity, decrease of energy, dispersion. To determine the coefficients of the diffusive approximation, two approaches are analyzed: Gaussian quadratures and optimization methods in the frequency range of interest. The nonlinear optimization is shown to be the better way of determination. A splitting strategy is then applied to approximate numerically the Biot-DA equations. The propagative part is discretized using a fourth-order ADER scheme on a Cartesian grid, whereas the diffusive part is solved exactly. An immersed interface method is implemented to take into account heterogeneous media on a Cartesian grid and to discretize the jump conditions at interfaces. Numerical experiments are presented. Comparisons with analytical solutions show the efficiency and the accuracy of the approach, and some numerical experiments are performed to investigate wave phenomena in complex media, such as multiple scattering across a set of random scatterers.
NASA Astrophysics Data System (ADS)
Peters, C. A.; Crandell, L. E.; Um, W.; Jones, K. W.; Lindquist, W. B.
2011-12-01
Geochemical reactions in the subsurface can alter the porosity and permeability of a porous medium through mineral precipitation and dissolution. While effects on porosity are relatively well understood, changes in permeability are more difficult to estimate. In this work, pore-network modeling is used to estimate the permeability of a porous medium using pore and throat size distributions. These distributions can be determined from 2D Scanning Electron Microscopy (SEM) images of thin sections or from 3D X-ray Computed Tomography (CT) images of small cores. Each method has unique advantages as well as unique sources of error. 3D CT imaging has the advantage of reconstructing a 3D pore network without the inherent geometry-based biases of 2D images but is limited by resolutions around 1 μm. 2D SEM imaging has the advantage of higher resolution, and the ability to examine sub-grain scale variations in porosity and mineralogy, but is limited by the small size of the sample of pores that are quantified. A pore network model was created to estimate flow permeability in a sand-packed experimental column investigating reaction of sediments with caustic radioactive tank wastes in the context of the Hanford, WA site. Before, periodically during, and after reaction, 3D images of the porous medium in the column were produced using the X2B beam line facility at the National Synchrotron Light Source (NSLS) at Brookhaven National Lab. These images were interpreted using 3DMA-Rock to characterize the pore and throat size distributions. After completion of the experiment, the column was sectioned and imaged using 2D SEM in backscattered electron mode. The 2D images were interpreted using erosion-dilation to estimate the pore and throat size distributions. A bias correction was determined by comparison with the 3D image data. A special image processing method was developed to infer the pore space before reaction by digitally removing the precipitate. The different sets of pore
FLUID TRANSPORT THROUGH POROUS MEDIA
Fluid transport through porous media is a relevant topic to many scientific and engineering fields. Soil scientists, civil engineers, hydrologists and hydrogeologists are concerned with the transport of water, gases and nonaqueous phase liquid contaminants through porous earth m...
Shepodd, Timothy J.
2002-01-01
Highly crosslinked monolithic porous polymer materials for chromatographic applications. By using solvent compositions that provide not only for polymerization of acrylate monomers in such a fashion that a porous polymer network is formed prior to phase separation but also for exchanging the polymerization solvent for a running buffer using electroosmotic flow, the need for high pressure purging is eliminated. The polymer materials have been shown to be an effective capillary electrochromatographic separations medium at lower field strengths than conventional polymer media. Further, because of their highly crosslinked nature these polymer materials are structurally stable in a wide range of organic and aqueous solvents and over a pH range of 2-12.
Eyler, L.L.; Budden, M.J.
1985-03-01
The objective of this work is to assess prediction capabilities and features of the MAGNUM-2D computer code in relation to its intended use in the Basalt Waste Isolation Project (BWIP). This objective is accomplished through a code verification and benchmarking task. Results are documented which support correctness of prediction capabilities in areas of intended model application. 10 references, 43 figures, 11 tables.
Natural thermal convection in fractured porous media
NASA Astrophysics Data System (ADS)
Adler, P. M.; Mezon, C.; Mourzenko, V.; Thovert, J. F.; Antoine, R.; Finizola, A.
2015-12-01
In the crust, fractures/faults can provide preferential pathways for fluid flow or act as barriers preventing the flow across these structures. In hydrothermal systems (usually found in fractured rock masses), these discontinuities may play a critical role at various scales, controlling fluid flows and heat transfer. The thermal convection is numerically computed in 3D fluid satured fractured porous media. Fractures are inserted as discrete objects, randomly distributed over a damaged volume, which is a fraction of the total volume. The fluid is assumed to satisfy Darcy's law in the fractures and in the porous medium with exchanges between them. All simulations were made for Rayleigh numbers (Ra) < 150 (hence, the fluid is in thermal equilibrium with the medium), cubic boxes and closed-top conditions. Checks were performed on an unfractured porous medium and the convection cells do start for the theoretical value of Ra, namely 4p². 2D convection was verified up to Ra=800. The influence of parameters such as fracture aperture (or fracture transmissivity), fracture density and fracture length is studied. Moreover, these models are compared to porous media with the same macroscopic permeability. Preliminary results show that the non-uniqueness associated with initial conditions which makes possible either 2D or 3D convection in porous media (Schubert & Straus 1979) is no longer true for fractured porous media (at least for 50
Deridder, Sander; Desmet, Gert
2012-03-02
Numerical calculations of the mobile zone mass transfer rate in a variety of ordered 2D and 3D structures are presented. These calculations are in line with earlier theoretical and experimental findings made in the field of chemical engineering and suggest that the Sherwood-number (Sh(m)) appearing in the mobile phase mass transfer term of the general plate height expression of liquid chromatography is not correctly predicted by the Wilson-Geankoplis--or the Kataoka--or the penetration model expression that have been used up to now to in the field of LC, and that at least more research is needed before these expressions can be continued to be used with confidence. The aforementioned expressions were obtained by neglecting the effect of axial dispersion on the mass transfer process, and it seems that they therefore underestimate the true Sh(m)-number by a factor of 2-5 around the minimum of the van Deemter-curve. New correlations describing the variation of the Sh(m)-coefficient as a function of the reduced velocity for a number of other packing geometries (tetrahedral monolith, 2D pillar array) are proposed. These correlations are in agreement with earlier theoretical and experimental studies showing that at low velocities the local-driving force-based Sh(m)-value is of the order of 10-20 in a packed bed column with an external porosity on the order of 35-40%.
Regeneratively Cooled Porous Media Jacket
NASA Technical Reports Server (NTRS)
Mungas, Greg (Inventor); Fisher, David J. (Inventor); London, Adam Pollok (Inventor); Fryer, Jack Merrill (Inventor)
2013-01-01
The fluid and heat transfer theory for regenerative cooling of a rocket combustion chamber with a porous media coolant jacket is presented. This model is used to design a regeneratively cooled rocket or other high temperature engine cooling jacket. Cooling jackets comprising impermeable inner and outer walls, and porous media channels are disclosed. Also disclosed are porous media coolant jackets with additional structures designed to transfer heat directly from the inner wall to the outer wall, and structures designed to direct movement of the coolant fluid from the inner wall to the outer wall. Methods of making such jackets are also disclosed.
Neeper, D.A.
1994-02-22
Methods are presented for distributing gases throughout the interstices of porous materials and removing volatile substances from the interstices of porous materials. Continuous oscillation of pressures and flows results in increased penetration of the interstices by flowing gases and increased transport of gaseous components out of the interstices. The invention is particularly useful in soil vapor extraction. 10 figures.
Neeper, Donald A.
1994-01-01
Methods for distributing gases throughout the interstices of porous materials and removing volatile substances from the interstices of porous materials. Continuous oscillation of pressures and flows results in increased penetration of the interstices by flowing gases and increased transport of gaseous components out of the interstices. The invention is particularly useful in soil vapor extraction.
Basser, Peter J.
2008-12-05
The fields of MR in Porous Media and Neuroradiology have largely developed separately during the past two decades with little appreciation of the problems, challenges and methodologies of the other. However, this trend is clearly changing and possibilities for significant cross-fertilization and synergies are now being realized.
Forced imbibition through model porous media
NASA Astrophysics Data System (ADS)
Odier, Celeste; Levache, Bertrand; Bartolo, Denis
2016-11-01
A number of industrial and natural process ultimately rely on two-phase flow in heterogeneous media. One of the most prominent example is oil recovery which has driven fundamental and applied research in this field for decades. Imbibition occurs when a wetting fluid displaces an immiscible fluid e.g. in a porous media. Using model microfluidic experiment we control both the geometry and wetting properties of the heterogenous media, and show that the typical front propagation picture fails when imbibition is forced and the displacing fluid is less viscous than the non-wetting fluid. We identify and quantitatively characterize four different flow regimes at the pore scale yielding markedly different imbibition patterns at large scales. In particular we will discuss the transition from a conventional 2D-front propagation scenario to a regime where the meniscus dynamics is an intrinsically 3D process.
Heterogeneous porous media in hydrology
NASA Astrophysics Data System (ADS)
Ababou, Rachid
In natural geologic formations, flow and transport-related processes are perturbed by multidimensional and anisotropic material heterogeneities of diverse sizes, shapes, and origins (bedding, layering, inclusions, fractures, grains, for example). Heterogeneity tends to disperse and mix transported quantities and may initiate new transfer mechanisms not seen in ideally homogeneous porous media. Effective properties such as conductivity and dispersivity may not be simple averages of locally measured quantities.The special session, “Effective Constitutive Laws for Heterogeneous Porous Media,” convened at AGU's 1992 Fall Meeting in San Francisco, addressed these issue. Over forty-five contributions, both oral and poster, covering a broad range of physical phenomena were presented. The common theme was the macroscale characterization and modeling of flow and flow-related processes in geologic media that are heterogeneous at various scales (from grain size or fracture aperture, up to regional scales). The processes analyzed in the session included coupled hydro-mechanical processes; Darcy-type flow in the saturated, unsaturated, or two-phase regimes; tracer transport, dilution, and dispersion. These processes were studied for either continuous (porous) or discontinuous (fractured) media.
Parametric study of boiling heat transfer in porous media
Shi, B.; Jones, B.G.; Pan, C.
1996-04-01
Detailed numerical modeling and parametric variation studies were conducted on boiling heat transfer processes in porous deposits with emphasis on applications associated with light water nuclear power reactor systems. The processes of boiling heat transfer in the porous corrosion deposits typically involve phase changes in finite volumetric regions in the porous media. The study examined such processes in two porous media configurations, without chimneys (homogeneous porous structures) and with chimneys (heterogeneous porous structures). A 1-D model and a 2-D model were developed to simulate two-phase flows with phase changes, without dry-out, inside the porous media for both structural configurations. For closure of the governing equations, an empirical correlation of the evaporation rate for phase changes inside the porous media was introduced. In addition, numerical algorithms were developed to solve the coupled nonlinear equations of mass, momentum, energy, capillary pressure, and evaporation rate. The distributions of temperature, thermodynamic saturation, liquid pressure, vapor pressure, liquid velocity, and vapor velocity were predicted. Furthermore, the effects of heat flux, system pressure, porosity, particle diameter, chimney population density, chimney radius, and crud thickness on the all superheat, critical heat flux, and minimum saturation were examined. The predictions were found to be in good agreement with the available experimental results.
Nonlinear flow in porous media
NASA Astrophysics Data System (ADS)
Rojas, Sergio Jesus
1998-07-01
Numerical solutions of the Navier-Stokes equations in two-dimensional quasi-periodic and quasi-isotropic random media were obtained to analyze the local and large scale aspects of finite Reynolds number flow. For Reynolds number less than one, the results show a first correction to Darcy's law which is cubic in the Darcy (averaged) velocity, while for Reynolds number greater than one, the results are in agreement with Forchheimer equation. That is, the correction to Darcy's law is quadratic in the average (Darcy) velocity. The cubic correction to Darcy's law support Mei and Auriault's (1991) theoretical study, based on homogenization theory. In addition, the results show support to a unifying empirical equation describing fluid flow in porous media of similar structure, first proposed by Beavers and Sparrow (1969). Also, the results show agreement, except by a multiplicative constant, with Sangani and Acrivos (1982) equation for the drag on dilute array of cylinders.
Multiphase flow in fractured porous media
Firoozabadi, A.
1995-02-01
The major goal of this research project was to improve the understanding of the gas-oil two-phase flow in fractured porous media. In addition, miscible displacement was studied to evaluate its promise for enhanced recovery.
Upscaling flow and transport properties in synthetic porous media
NASA Astrophysics Data System (ADS)
Jasinski, Lukasz; Dabrowski, Marcin
2015-04-01
Flow and transport through the porous media has instances in nature and industry: contaminant migration in geological formations, gas/oil extraction from proppant filled hydraulic fractures and surrounding porous matrix, underground carbon dioxide sequestration and many others. We would like to understand the behavior of propagating solute front in such medium, mainly flow preferential pathways and the solute dispersion due to the porous medium geometry. The motivation of our investigation is to find connection between the effective flow and transport properties and porous media geometry in 2D and 3D for large system sizes. The challenge is to discover a good way of upscaling flow and transport processes to obtain results comparable to these calculated on pore-scale in much faster way. We study synthetic porous media made of densely packed poly-disperse disk-or spherical-shaped grains in 2D and 3D, respectively. We use various protocols such as the random sequential addition (RSA) algorithm to generate densely packed grains. Imposed macroscopic pressure gradient invokes fluid flow through the pore space of generated porous medium samples. As the flow is considered in the low Reynolds number regime, a stationary velocity field is obtained by solving the Stokes equations by means of finite element method. Void space between the grains is accurately discretized by using body-fitting triangular or tetrahedral mesh. Finally, pure advection of a front carried by the velocity field is studied. Periodicity in all directions is applied to microstructure, flow and transport processes. Effective permeability of the media can be calculated by integrating the velocity field on cross sections, whereas effective dispersion coefficient is deduced by application of centered moment methods on the concentration field of transported solute in time. The effective parameters are investigated as a function of geometrical parameters of the media, such as porosity, specific surface area
Optimal implicit 2-D finite differences to model wave propagation in poroelastic media
NASA Astrophysics Data System (ADS)
Itzá, Reymundo; Iturrarán-Viveros, Ursula; Parra, Jorge O.
2016-08-01
Numerical modeling of seismic waves in heterogeneous porous reservoir rocks is an important tool for the interpretation of seismic surveys in reservoir engineering. We apply globally optimal implicit staggered-grid finite differences (FD) to model 2-D wave propagation in heterogeneous poroelastic media at a low-frequency range (<10 kHz). We validate the numerical solution by comparing it to an analytical-transient solution obtaining clear seismic wavefields including fast P and slow P and S waves (for a porous media saturated with fluid). The numerical dispersion and stability conditions are derived using von Neumann analysis, showing that over a wide range of porous materials the Courant condition governs the stability and this optimal implicit scheme improves the stability of explicit schemes. High-order explicit FD can be replaced by some lower order optimal implicit FD so computational cost will not be as expensive while maintaining the accuracy. Here, we compute weights for the optimal implicit FD scheme to attain an accuracy of γ = 10-8. The implicit spatial differentiation involves solving tridiagonal linear systems of equations through Thomas' algorithm.
NASA Astrophysics Data System (ADS)
Li, Y.; Kazemifar, F.; Blois, G.; Christensen, K. T.
2015-12-01
Multiphase flow of water and supercritical carbon dioxide (CO2) in porous media is central to geological sequestration of CO2 into saline aquifers. However, our fundamental understanding of the coupled flow dynamics of CO2 and water in complex geologic media still remains limited, especially at the pore scale. Recently, studies have been carried out in 2D homogeneous models with the micro-PIV technique, yielding very interesting observations of pore-scale flow transport. The primary aim of this work is to leverage this experimental protocol to quantify the pore-scale flow of water and liquid/supercritical CO2 in 2D heterogeneous porous micromodels under reservoir-relevant conditions. The goal is to capture the dynamics of this multi-phase flow in a porous matrix that mimics the heterogeneity of natural rock. Fluorescent microscopy and the micro-PIV technique are employed to simultaneously measure the spatially-resolved instantaneous velocity field in the water and quantify the instantaneous spatial configuration of both phases. The results for heterogeneous micromodels will be presented and compared with those for homogeneous micromodels, yielding valuable insight into flow processes at the pore scale in natural rock.
Fluid dynamics in porous media with Sailfish
NASA Astrophysics Data System (ADS)
Coelho, Rodrigo C. V.; Neumann, Rodrigo F.
2016-09-01
In this work we show the application of Sailfish to the study of fluid dynamics in porous media. Sailfish is an open-source software based on the lattice-Boltzmann method. This application of computational fluid dynamics is of particular interest to the oil and gas industry and the subject could be a starting point for an undergraduate or graduate student in physics or engineering. We built artificial samples of porous media with different porosities and used Sailfish to simulate the fluid flow through them in order to calculate their permeability and tortuosity. We also present a simple way to obtain the specific superficial area of porous media using Python libraries. To contextualise these concepts, we analyse the applicability of the Kozeny-Carman equation, which is a well-known permeability-porosity relation, to our artificial samples.
Explosion propagation in inert porous media.
Ciccarelli, G
2012-02-13
Porous media are often used in flame arresters because of the high surface area to volume ratio that is required for flame quenching. However, if the flame is not quenched, the flow obstruction within the porous media can promote explosion escalation, which is a well-known phenomenon in obstacle-laden channels. There are many parallels between explosion propagation through porous media and obstacle-laden channels. In both cases, the obstructions play a duel role. On the one hand, the obstruction enhances explosion propagation through an early shear-driven turbulence production mechanism and then later by shock-flame interactions that occur from lead shock reflections. On the other hand, the presence of an obstruction can suppress explosion propagation through momentum and heat losses, which both impede the unburned gas flow and extract energy from the expanding combustion products. In obstacle-laden channels, there are well-defined propagation regimes that are easily distinguished by abrupt changes in velocity. In porous media, the propagation regimes are not as distinguishable. In porous media the entire flamefront is affected, and the effects of heat loss, turbulence and compressibility are smoothly blended over most of the propagation velocity range. At low subsonic propagation speeds, heat loss to the porous media dominates, whereas at higher supersonic speeds turbulence and compressibility are important. This blending of the important phenomena results in no clear transition in propagation mechanism that is characterized by an abrupt change in propagation velocity. This is especially true for propagation velocities above the speed of sound where many experiments performed with fuel-air mixtures show a smooth increase in the propagation velocity with mixture reactivity up to the theoretical detonation wave velocity.
Transport of subsurface bacteria in porous media
Bales, R.C.; Arnold, R.G.; Gerba, C.P.
1995-02-01
The primary objective of this study was to develop tools with which to measure the advective transport of microorganisms through porous media. These tools were then applied to investigate the sorptive properties of representative microorganisms that were selected at random from the DOE`s deep subsurface collection of bacterial, maintained at Florida State University. The transport screening procedure that arose from this study was also used to investigate biological factors that affect the transport/sorption of biocolloids during their movement through porous media with the bulk advective flow.
2-D solution for drying with internal vaporization of anisotropic media
Perre, P.; Passard, J.
1999-01-01
A set of physical assumptions for a straightforward and efficient simulation of the drying of a porous medium submitted to a convective and/or radiative heating is proposed. All of the parameters used are physical (liquid migration coefficient, permeability values along the thickness and the length, thermal conductivity, and external changes), but the relevant geometrical properties (length and thickness of the slab) were also included in the analysis. The 2-D pressure field generated within the medium during the drying process is obtained by using an analytical expression. The treatment of the pressure field, especially for a strongly anisotropic medium, is an important feature of the model, which allows an analytical model for such a complicated porous medium as wood to be used across a wide range of drying conditions. The computer code developed from the proposed formulation permits a complete simulation of the drying process within a few seconds on a personal computer. Different configurations have been tested for both anisotropic (wood) and isotropic (light concrete) porous media. Agreement with the experimental results is reasonable in terms of the observed physical phenomena. For instance, the model highlights dependence of the duration of the first drying rate on both material properties and drying conditions. This new model can be used for a global physical characterization of products by curve fitting and the collated information for the design of dryers.
Full-waveform inversion in 2D VTI media
NASA Astrophysics Data System (ADS)
Kamath, Nishant
Full-waveform inversion (FWI) is a technique designed to produce a high-resolution model of the subsurface by using information contained in entire seismic waveforms. This thesis presents a methodology for FWI in elastic VTI (transversely isotropic with a vertical axis of symmetry) media and discusses synthetic results for heterogeneous VTI models. First, I develop FWI for multicomponent data from a horizontally layered VTI model. The reflectivity method, which permits computation of only PP reflections or a combination of PP and PSV events, is employed to model the data. The Gauss-Newton technique is used to invert for the interval Thomsen parameters, while keeping the densities fixed at the correct values. Eigenvalue/eigenvector decompostion of the Hessian matrix helps analyze the sensitivity of the objective function to the model parameters. Whereas PP data alone are generally sufficient to constrain all four Thomsen parameters even for conventional spreads, including PS reflections provides better constraints, especially for the deeper part of the model. Next, I derive the gradients of the FWI objective function with respect to the stiffness coefficients of arbitrarily anisotropic media by employing the adjoint-state method. From these expressions, it is straightforward to compute the gradients for parameters of 2D heterogeneous VTI media. FWI is implemented in the time domain with the steepest-descent method used to iteratively update the model. The algorithm is tested on transmitted multicomponent data generated for Gaussian anomalies in Thomsen parameters embedded in homogeneous VTI media. To test the sensitivity of the objective function to different model parameters, I derive an an- alytic expression for the Frechet kernel of FWI for arbitrary anisotropic symmetry by using the Born approximation and asymptotic Green's functions. The amplitude of the kernel, which represents the radiation pattern of a secondary source (that source describes a perturbation
Colloid straining within saturated heterogeneous porous media.
Porubcan, Alexis A; Xu, Shangping
2011-02-01
The transport of 0.46 μm, 2.94 μm, 5.1 μm and 6.06 μm latex particles in heterogeneous porous media prepared from the mixing of 0.78 mm, 0.46 mm and 0.23 mm quartz sands was investigated through column transport experiments. It was observed that the 0.46 μm particles traveled conservatively within the heterogeneous porous media, suggesting that under the experimental conditions employed in this research the strong repulsive interactions between the negatively charged latex particles and the clean quartz sands led to minimal colloid immobilization due to physicochemical filtration. The immobilization of the 2.94 μm, 5.1 μm and 6.06 μm latex particles was thus attributed to colloid straining. Experimental results showed that the straining of colloidal particles within heterogeneous sand mixtures increased when the fraction of finer sands increased. The mathematical model that was developed and tested based on results obtained using uniform sands (Xu et al., 2006) was found to be able to describe colloid straining within heterogeneous porous media. Examination of the relationship between the best-fit values of the clean-bed straining rate coefficients (k(0)) and the ratio of colloid diameter (d(p)) and sand grain size (d(g)) indicated that when number-average sizes were used to represent the size of the heterogeneous porous media, there existed a consistent relationship for both uniform sands and heterogeneous sand mixtures. Similarly, the use of the number-averaged sizes for the heterogeneous porous media produced a uniform relationship between the colloid straining capacity term (λ) and the ratio of d(p)/d(g) for all the sand treatments.
Statistical fusion of two-scale images of porous media
NASA Astrophysics Data System (ADS)
Mohebi, Azadeh; Fieguth, Paul; Ioannidis, Marios A.
2009-11-01
The reconstruction of the architecture of void space in porous media is a challenging task, since porous media contain pore structures at multiple scales. Whereas past methods have been limited to producing samples with matching statistical behavior, the patterns of grey-level values in a measured sample actually say something about the unresolved details, thus we propose a statistical fusion framework for reconstructing high-resolution porous media images from low-resolution measurements. The proposed framework is based on a posterior sampling approach in which information obtained by low-resolution (MRI or X-ray) measurements is combined with prior models inferred from high-resolution microscopic data, typically 2D. In this paper, we focus on two-scale reconstruction tasks in which the measurements resolve only the large scale structures, leaving the small-scale to be inferred. The evaluation of the results generated by the proposed method shows the strong ability of the proposed method in reconstructing fine-scale structures positively correlated with the underlying ground truth. Comparing our method with the recent method of Okabe and Blunt [12], in which the measurements are also used in the reconstruction, we conclude that our method is more robust to the resolution of the measurement, and more closely matches the underlying fine-scale field.
Heat transfer of laminar flow over a 2-D backward facing step with isotropic porous floor segments
Abu-Hijleh, B.A.K
1997-07-01
Forced convection due to fluid flow over a backward facing step has been studied extensively. Flow through porous media occurs in a wide range of engineering applications such as the flow through insulation material, grain storage, and water movement through a geothermal reservoir. Control of the heat transfer characteristics is desirable, and the control mechanism can be either active or passive. Here, the incompressible laminar (Re{sub H} = 100) reattaching flow over a 2-D backward facing step with different length porous floor segments was solved numerically using the finite element method. The focus of this study is the change in the forced convection heat transfer characteristics of the flow field due to the addition of porous floor segments. Several isotropic porous floor segment configurations with different lengths and depths were studied. The porosity of the segments was varied over a wide range by changing the value of the pressure loss coefficient (KP = 10{sup {minus}2}--10{sup 6}). The changes in the local and overall Nusselt number are reported and discussed. Depending on the configuration, axial variation of the local Nusselt number could be altered. For all configurations, the overall Nusselt number decreased by as much as 16% while the maximum local Nusselt number increased by as much as 170%, both relative to their respective values for the reference case of solid floor.
Finite volume hydromechanical simulation in porous media
Nordbotten, Jan Martin
2014-01-01
Cell-centered finite volume methods are prevailing in numerical simulation of flow in porous media. However, due to the lack of cell-centered finite volume methods for mechanics, coupled flow and deformation is usually treated either by coupled finite-volume-finite element discretizations, or within a finite element setting. The former approach is unfavorable as it introduces two separate grid structures, while the latter approach loses the advantages of finite volume methods for the flow equation. Recently, we proposed a cell-centered finite volume method for elasticity. Herein, we explore the applicability of this novel method to provide a compatible finite volume discretization for coupled hydromechanic flows in porous media. We detail in particular the issue of coupling terms, and show how this is naturally handled. Furthermore, we observe how the cell-centered finite volume framework naturally allows for modeling fractured and fracturing porous media through internal boundary conditions. We support the discussion with a set of numerical examples: the convergence properties of the coupled scheme are first investigated; second, we illustrate the practical applicability of the method both for fractured and heterogeneous media. PMID:25574061
Finite volume hydromechanical simulation in porous media.
Nordbotten, Jan Martin
2014-05-01
Cell-centered finite volume methods are prevailing in numerical simulation of flow in porous media. However, due to the lack of cell-centered finite volume methods for mechanics, coupled flow and deformation is usually treated either by coupled finite-volume-finite element discretizations, or within a finite element setting. The former approach is unfavorable as it introduces two separate grid structures, while the latter approach loses the advantages of finite volume methods for the flow equation. Recently, we proposed a cell-centered finite volume method for elasticity. Herein, we explore the applicability of this novel method to provide a compatible finite volume discretization for coupled hydromechanic flows in porous media. We detail in particular the issue of coupling terms, and show how this is naturally handled. Furthermore, we observe how the cell-centered finite volume framework naturally allows for modeling fractured and fracturing porous media through internal boundary conditions. We support the discussion with a set of numerical examples: the convergence properties of the coupled scheme are first investigated; second, we illustrate the practical applicability of the method both for fractured and heterogeneous media.
Capture of particles in soft porous media
NASA Astrophysics Data System (ADS)
Louvet, N.; Höhler, R.; Pitois, O.
2010-10-01
We investigate the capture of particles in soft porous media. Liquid foam constitutes a model system for such a study, allowing the radii of passage in the pore space to be tuned over several orders of magnitude by adjusting the liquid volume fraction. We show how particle capture is determined by the coupling of interstitial liquid flow and network deformation, and present a simple model of the capture process that shows good agreement with our experimental data.
Scaling theory of drying in porous media
Tsimpanogiannis, I.N.; Yortsos, Y.C.; Poulou, S.; Kanellopoulos, N.; Stubos, A.K.
1999-04-01
Concepts of immiscible displacements in porous media driven by mass transfer are utilized to model drying of porous media. Visualization experiments of drying in two-dimensional glass micromodels are conducted to identify pore-scale mechanisms. Then, a pore network approach is used to analyze the advancing drying front. It is shown that in a porous medium, capillarity induces a flow that effectively limits the extent of the front, which would otherwise be of the percolation type, to a finite width. In conjuction with the predictions of a macroscale stable front, obtained from a linear stability analysis, the process is shown to be equivalent to invasion percolation in a stabilizing gradient. A power-law scaling relation of the front width with a diffusion-based capillary number is also obtained. This capillary number reflects the fact that drying is controlled by diffusion in contrast to external drainage. The scaling exponent predicted is compatible with the experimental results of Shaw [Phys Rev. Lett. {bold 59}, 1671 (1987)]. A framework for a continuum description of the upstream drying regimes is also developed. {copyright} {ital 1999} {ital The American Physical Society}
Bacterial Trapping in Porous Media Flows
NASA Astrophysics Data System (ADS)
Dehkharghani, Amin; Waisbord, Nicolas; Dunkel, Jörn; Guasto, Jeffrey
2016-11-01
Swimming bacteria inhabit heterogeneous, microstructured environments that are often characterized by complex, ambient flows. Understanding the physical mechanisms underlying cell transport in these systems is key to controlling important processes such as bioremediation in porous soils and infections in human tissues. We study the transport of swimming bacteria (Bacillus subtilis) in quasi-two-dimensional porous microfluidic channels with a range of periodic microstructures and flow strengths. Measured cell trajectories and the local cell number density reveal the formation of filamentous cell concentration patterns within the porous structures. The local cell densification is maximized at shear rates in the range 1-10 s-1, but widely varies with pore geometry and flow topology. Experimental observations are complemented by Langevin simulations to demonstrate that the filamentous patterns result from a coupling of bacterial motility to the complex flow fields via Jeffery orbits, which effectively 'trap' the bacteria on streamlines. The resulting microscopic heterogeneity observed here suppresses bacterial transport and likely has implications for both mixing and cell nutrient uptake in porous media flows. NSF CBET-1511340.
Tetrahydrofuran hydrate decomposition characteristics in porous media
NASA Astrophysics Data System (ADS)
Song, Yongchen; Wang, Pengfei; Wang, Shenglong; Zhao, Jiafei; Yang, Mingjun
2016-12-01
Many tetrahydrofuran (THF) hydrate properties are similar to those of gas hydrates. In the present work THF hydrate dissociation in four types of porous media is studied. THF solution was cooled to 275.15 K with formation of the hydrate under ambient pressure, and then it dissociated under ambient conditions. THF hydrate dissociation experiments in each porous medium were conducted three times. Magnetic resonance imaging (MRI) was used to obtain images. Decomposition time, THF hydrate saturation and MRI mean intensity (MI) were measured and analyzed. The experimental results showed that the hydrate decomposition time in BZ-4 and BZ-3 was similar and longer than that in BZ-02. In each dissociation process, the hydrate decomposition time of the second and third cycles was shorter than that of the first cycle in BZ-4, BZ-3, and BZ-02. The relationship between THF hydrate saturation and time is almost linear.
Uncertainty quantification for porous media flows
Christie, Mike . E-mail: mike.christie@pet.hw.ac.uk; Demyanov, Vasily; Erbas, Demet
2006-09-01
Uncertainty quantification is an increasingly important aspect of many areas of computational science, where the challenge is to make reliable predictions about the performance of complex physical systems in the absence of complete or reliable data. Predicting flows of oil and water through oil reservoirs is an example of a complex system where accuracy in prediction is needed primarily for financial reasons. Simulation of fluid flow in oil reservoirs is usually carried out using large commercially written finite difference simulators solving conservation equations describing the multi-phase flow through the porous reservoir rocks. This paper examines a Bayesian Framework for uncertainty quantification in porous media flows that uses a stochastic sampling algorithm to generate models that match observed data. Machine learning algorithms are used to speed up the identification of regions in parameter space where good matches to observed data can be found.
Fluids in porous media: a morphometric approach
NASA Astrophysics Data System (ADS)
Mecke, Klaus; Arns, C. H.
2005-03-01
Predicting the relationship between the morphology of porous media and their physical properties, e.g, the conductivity, elasticity and permeability, is a long-standing problem and important to a range of applications from geophysics to materials science. Here, a set of four morphological measures, so-called Minkowski functionals, is defined which allows one to quantitatively characterize the shape of spatial structures, to optimally reconstruct porous media, and to accurately predict material properties. The method is based on integral geometry and Kac's theorem which relates the spectrum of the Laplace operator to the four Minkowski functionals. Analytic expressions for mean values of Minkowski functionals in Boolean models allow the definition of an effective shape of a grain in a system made up of a distribution of arbitrarily shaped constituents. Reconstructing the microstructure using this effective grain shape leads to an excellent match to the percolation thresholds and to the mechanical and transport properties across all phase fractions. Additionally, the use of the effective shape in effective medium formulations leads to good explicit predictions of bulk moduli. The method is verified for several model systems and sedimentary rock samples, demonstrating that a single tomographic image is sufficient to estimate the morphology and physical properties such as permeabilities and elastic moduli for a range of porosities. Also the thermodynamic behaviour of fluids in porous media, i.e., the shape dependence of the grand canonical potential and of surface energies of a fluid bounded by an arbitrarily shaped convex pore, can be calculated in the thermodynamic limit fully from the knowledge of the Minkowski functionals, i.e., of only four morphometric measures. This remarkable result is based on Hadwiger's theorem on the completeness of the additive Minkowski functionals and the assumption that a thermodynamic potential is an 'additive' functional which can be
Experiments with metallic and ceramic porous media
NASA Technical Reports Server (NTRS)
Frederking, T. H. K.; Abbassi, P.; Khandhar, P. K.; Luna, Jack
1988-01-01
Work in the area of mechano-caloric phenomena was initiated during 1988 with startup in the Summer 1988 period. The ideal system utilizing He-II super-phenomena is modeled readily, within the frame of thermodynamics energetics, using the concept of an ideal superleak. The real system however uses porous media of non-ideal pore-grain ingredients. The early phase of experimental and related modeling studies is outlined for the time period from Summer 1988 to the end of 1988.
Dynamics of clogging in drying porous media
NASA Astrophysics Data System (ADS)
Kaplan, C. Nadir; Mahadevan, L.
2014-11-01
Drying in porous media pervades a range of phenomena from brine evaporation arrested in porous bricks, causing efflorescence, i.e. salt aggregation on the surface where vapor leaves the medium, to clogging of reservoir rocks via salt precipitation when carbon dioxide is injected for geological storage. During the process of drying, the permeability and porosity of the medium may change due to the solute accumulation as a function of the particle concentration, in turn affecting the evaporation rate and the dynamics of the fluid flow imposed by it. To examine the dynamics of these coupled quantities, we develop a multiphase model of the particulate flow of a saline suspension in a porous medium, induced by evaporation. We further provide dimensional arguments as to how the salt concentration and the resulting change in permeability determine the transition between efflorescence and salt precipitation in the bulk. This research was supported by the Air Force Office of Scientific Research (AFOSR) under Award FA9550-09-1-0669-DOD35CAP and the Kavli Institute for Bionano Science and Technology at Harvard University.
Fundamentals of foam transport in porous media
Kovscek, A.R.; Radke, C.J.
1993-10-01
Foam in porous media is a fascinating fluid both because of its unique microstructure and because its dramatic influence on the flow of gas and liquid. A wealth of information is now compiled in the literature describing foam generation, destruction, and transport mechanisms. Yet there are conflicting views of these mechanisms and on the macroscopic results they produce. By critically reviewing how surfactant formulation and porous media topology conspire to control foam texture and flow resistance, we attempt to unify the disparate viewpoints. Evolution of texture during foam displacement is quantified by a population balance on bubble concentration, which is designed specifically for convenient incorporation into a standard reservoir simulator. Theories for the dominant bubble generation and coalescence mechanisms provide physically based rate expressions for the proposed population balance. Stone-type relative permeability functions along with the texture-sensitive and shear-thinning nature of confined foam complete the model. Quite good agreement is found between theory and new experiments for transient foam displacement in linear cores.
Modeling imbibition of liquids into rigid and swelling porous media
NASA Astrophysics Data System (ADS)
Masoodi, Reza
In porous media studies, imbibition is the spontaneous movement of a liquid into a porous medium under the influence of capillary forces. It is also known by the name wicking, and can sometimes be aided by an external pressure, as in the case of forced infiltration of liquid polymers into a bed of fibermats. In this study, the imbibition of liquids into porous media in important engineering applications is studied. A relatively new approach of using the single-phase flow behind a clearly-defined liquid front in a porous medium has been adopted in this work to model imbibition or wicking. Such an approach employs Darcy's law in conjunction with the continuity equation to model the liquid flow behind the front. First the modeling of liquid flow in polymer wicks is undertaken. A new formula to predict the capillary suction-pressure at the liquid fronts in commercial wicks made of sintering the polymer beads was proposed. Later, a more general formula was derived and verified for estimating the capillary suction pressure in any kind of porous substance. We compared the performance of the proposed Darcy's-law based approach with that of the Lucas-Washburn equation; some new methods were suggested to improve the accuracy of these two dominant methods for modeling the liquid transport in aforementioned wicks. Our Darcy's law based modeling approach is superior to the previous Washburn Equation based approaches as the former can be easily extended to 2-D and 3-D unlike the latter. The 3-D liquid flow in the wicks was studied numerically using PORE-FLOW(c), an in-house computer program to model porous-media flows. For the first time, the finite element/control volume (FE/CV) algorithm is employed to solve the moving- boundary problem encountered in wicking. A good validation is achieved against the 1-D wicking-flow analytical solution as well as a 3-D wicking experiment involving a wick with two different cross-sections. A special case of wicking, in which both the external
Modern hardware architectures accelerate porous media flow computations
NASA Astrophysics Data System (ADS)
Kulczewski, Michal; Kurowski, Krzysztof; Kierzynka, Michal; Dohnalik, Marek; Kaczmarczyk, Jan; Borujeni, Ali Takbiri
2012-05-01
Investigation of rock properties, porosity and permeability particularly, which determines transport media characteristic, is crucial to reservoir engineering. Nowadays, micro-tomography (micro-CT) methods allow to obtain vast of petro-physical properties. The micro-CT method facilitates visualization of pores structures and acquisition of total porosity factor, determined by sticking together 2D slices of scanned rock and applying proper absorption cut-off point. Proper segmentation of pores representation in 3D is important to solve the permeability of porous media. This factor is recently determined by the means of Computational Fluid Dynamics (CFD), a popular method to analyze problems related to fluid flows, taking advantage of numerical methods and constantly growing computing powers. The recent advent of novel multi-, many-core and graphics processing unit (GPU) hardware architectures allows scientists to benefit even more from parallel processing and built-in new features. The high level of parallel scalability offers both, the time-to-solution decrease and greater accuracy - top factors in reservoir engineering. This paper aims to present research results related to fluid flow simulations, particularly solving the total porosity and permeability of porous media, taking advantage of modern hardware architectures. In our approach total porosity is calculated by the means of general-purpose computing on multiple GPUs. This application sticks together 2D slices of scanned rock and by the means of a marching tetrahedra algorithm, creates a 3D representation of pores and calculates the total porosity. Experimental results are compared with data obtained via other popular methods, including Nuclear Magnetic Resonance (NMR), helium porosity and nitrogen permeability tests. Then CFD simulations are performed on a large-scale high performance hardware architecture to solve the flow and permeability of porous media. In our experiments we used Lattice Boltzmann
Electrochemical fabrication of 2D and 3D nickel nanowires using porous anodic alumina templates
NASA Astrophysics Data System (ADS)
Mebed, A. M.; Abd-Elnaiem, Alaa M.; Al-Hosiny, Najm M.
2016-06-01
Mechanically stable nickel (Ni) nanowires array and nanowires network were synthesized by pulse electrochemical deposition using 2D and 3D porous anodic alumina (PAA) templates. The structures and morphologies of as-prepared films were characterized by X-ray diffraction and scanning electron microscopy, respectively. The grown Ni nanowire using 3D PAA revealed more strength and larger surface area than has grown Ni use 2D PAA template. The prepared nanowires have a face-centered cubic crystal structure with average grain size 15 nm, and the preferred orientation of the nucleation of the nanowires is (111). The diameter of the nanowires is about 50-70 nm with length 3 µm. The resulting 3D Ni nanowire lattice, which provides enhanced mechanical stability and an increased surface area, benefits energy storage and many other applications which utilize the large surface area.
Review of enhanced vapor diffusion in porous media
Webb, S.W.; Ho, C.K.
1998-08-01
Vapor diffusion in porous media in the presence of its own liquid has often been treated similar to gas diffusion. The gas diffusion rate in porous media is much lower than in free space due to the presence of the porous medium and any liquid present. However, enhanced vapor diffusion has also been postulated such that the diffusion rate may approach free-space values. Existing data and models for enhanced vapor diffusion, including those in TOUGH2, are reviewed in this paper.
Utilization of Porous Media for Condensing Heat Exchangers
NASA Technical Reports Server (NTRS)
Tuan, George C.
2006-01-01
The use of porous media as a mean of separating liquid condensate from the air stream in condensing heat exchangers has been explored in the past inside small plant growth chambers and in the Apollo Command Module. Both applications used a cooled porous media made of sintered stainless steel to cool and separate condensation from the air stream. However, the main issues with the utilization of porous media in the past have been the deterioration of the porous media over long duration, such as clogging and changes in surface wetting characteristics. In addition, for long duration usage, biofilm growth from microorganisms on the porous medial would also be an issue. In developing Porous Media Condensing Heat Exchangers (PMCHX) for future space applications, different porous materials and microbial growth control methods will need to be explored. This paper explores the work performed at JSC and GRC to evaluate different porous materials and microbial control methods to support the development of a Porous Media Condensing Heat Exchanger. It outlines the basic principles for designing a PMCHX and issues that were encountered and ways to resolve those issues. The PMCHX has potential of mass, volume, and power savings over current CHX and water separator technology and would be beneficial for long duration space missions.
Resistivity inversion in 2-D anisotropic media: numerical experiments
NASA Astrophysics Data System (ADS)
Wiese, Timothy; Greenhalgh, Stewart; Zhou, Bing; Greenhalgh, Mark; Marescot, Laurent
2015-04-01
Many rocks and layered/fractured sequences have a clearly expressed electrical anisotropy although it is rare in practice to incorporate anisotropy into resistivity inversion. In this contribution, we present a series of 2.5-D synthetic inversion experiments for various electrode configurations and 2-D anisotropic models. We examine and compare the image reconstructions obtained using the correct anisotropic inversion code with those obtained using the false but widely used isotropic assumption. Superior reconstruction in terms of reduced data misfit, true anomaly shape and position, and anisotropic background parameters were obtained when the correct anisotropic assumption was employed for medium to high coefficients of anisotropy. However, for low coefficient values the isotropic assumption produced better-quality results. When an erroneous isotropic inversion is performed on medium to high level anisotropic data, the images are dominated by patterns of banded artefacts and high data misfits. Various pole-pole, pole-dipole and dipole-dipole data sets were investigated and evaluated for the accuracy of the inversion result. The eigenvalue spectra of the pseudo-Hessian matrix and the formal resolution matrix were also computed to determine the information content and goodness of the results. We also present a data selection strategy based on high sensitivity measurements which drastically reduces the number of data to be inverted but still produces comparable results to that of the comprehensive data set. Inversion was carried out using transversely isotropic model parameters described in two different co-ordinate frames for the conductivity tensor, namely Cartesian versus natural or eigenframe. The Cartesian frame provided a more stable inversion product. This can be simply explained from inspection of the eigenspectra of the pseudo-Hessian matrix for the two model descriptions.
Miscible, porous media displacements with density stratification.
Riaz, Amir; Meiburg, Eckart
2004-11-01
High accuracy, three-dimensional numerical simulations of miscible displacements with gravity override, in both homogeneous and heterogeneous porous media, are discussed for the quarter five-spot configuration. The influence of viscous and gravitational effects on the overall displacement dynamics is described in terms of the vorticity variable. Density differences influence the flow primarily by establishing a narrow gravity layer, in which the effective Peclet number is enhanced due to the higher flow rate. Although this effect plays a dominant role in homogeneous flows, it is suppressed to some extent in heterogeneous displacements. This is a result of coupling between the viscous and permeability vorticity fields. When the viscous wavelength is much larger than the permeability wavelength, gravity override becomes more effective because coupling between the viscous and permeability vorticity fields is less pronounced. Buoyancy forces of a certain magnitude can lead to a pinch-off of the gravity layer, thereby slowing it down.
Convective mixing in homogeneous porous media flow
NASA Astrophysics Data System (ADS)
Ching, Jia-Hau; Chen, Peilong; Tsai, Peichun Amy
2017-01-01
Inspired by the flow processes in the technology of carbon dioxide (CO2) storage in saline formations, we modeled a homogeneous porous media flow in a Hele-Shaw cell to investigate density-driven convection due to dissolution. We used an analogy of the fluid system to mimic the diffusion and subsequent convection when CO2 dissolves in brine, which generates a heavier solution. By varying the permeability, we examined the onset of convection, the falling dynamics, the wavelengths of fingers, and the rate of dissolution, for the Rayleigh number Ra (a dimensionless forcing term which is the ratio of buoyancy to diffusivity) in the range of 2.0 ×104≤Ra≤8.26 ×105 . Our results reveal that the effect of permeability influences significantly the initial convective speed, as well as the later coarsening dynamics of the heavier fingering plumes. However, the total dissolved mass, characterized by a nondimensional Nusselt number Nu, has an insignificant dependence on Ra. This implies that the total dissolution rate of CO2 is nearly constant in high Ra geological porous structures.
Plume dynamics in heterogeneous porous media
NASA Astrophysics Data System (ADS)
Neufeld, Jerome A.; Huppert, Herbert E.
2008-11-01
Buoyancy driven flows in layered porous media are present in many geological settings and play an important role in the mixing of fluids, from the dispersal of pollutants in underground aquifers to enhanced oil recovery techniques and, of more recent importance, the sequestration of carbon dioxide (CO2). Seismic images of the rise of a buoyant CO2 plume at Sleipner in the North Sea indicate that these plumes are greatly influenced by a vertical array of thin lenses of relatively low permeability material. We model propagation of CO2 at each layer as a gravity current in a porous medium which propagates along, and drains through, a thin, low permeability seal. Drainage, driven both by hydrostatic pressure and the body force on the draining fluid, leads to an initial rapid advance followed by a gradual retreat of the current to a steady-state. By incorporating a vertical array of these single layer models we are able to capture the rise of the buoyant plume in layered reservoirs. We find that the plume is characterized by a broad head with a tail given by the steady state extent.
Helical swimming in viscoelastic and porous media
NASA Astrophysics Data System (ADS)
Liu, Bin
2012-02-01
Many bacteria swim by rotating helical flagella. These cells often live in polymer suspensions, which are viscoelastic. Recently there have been several theoretical and experimental studies showing that viscoelasticity can either enhance or suppress propulsion, depending on the details of the microswimmer. To help clarify this situation, we study experimentally the motility of the flagellum using a scaled-up model system - a motorized helical coil that rotates along its axial direction. A free-swimming speed is obtained when the net force on the helix is zero. When the helix is immersed in a viscoelastic (Boger) fluid, we find an increase in the force-free swimming speed as compared with the Newtonian case. The enhancement is maximized at a Deborah number of approximately one, and the magnitude depends not only on the elasticity of the fluid but also on the geometry of the helix. In the second part of my talk, I will discuss how spatial confinements, such as a porous medium, affect the flagellated swimming. For clarity, the porous media are modeled as cylindrical cavities with solid walls. A modified boundary element method allows us to investigate a situation that the helical flagella are very close to the wall, with high spatial resolution and relatively low computational cost. To our surprise, at fixed power consumption, a highly coiled flagellum swims faster in narrower confinements, while an elongated flagellum swims faster in a cavity with a wider opening. We try understanding these effects with simple physical pictures.
Motion of Deformable Drops Through Porous Media
NASA Astrophysics Data System (ADS)
Zinchenko, Alexander Z.; Davis, Robert H.
2017-01-01
This review describes recent progress in the fundamental understanding of deformable drop motion through porous media with well-defined microstructures, through rigorous first-principles hydrodynamical simulations and experiments. Tight squeezing conditions, when the drops are much larger than the pore throats, are particularly challenging numerically, as the drops nearly coat the porous material skeleton with small surface clearance, requiring very high surface resolution in the algorithms. Small-scale prototype problems for flow-induced drop motion through round capillaries and three-dimensional (3D) constrictions between solid particles, and for gravity-induced squeezing through round orifices and 3D constrictions, show how forcing above critical conditions is needed to overcome trapping. Scaling laws for the squeezing time are suggested. Large-scale multidrop/multiparticle simulations for emulsion flow through a random granular material with multiple drop breakup show that the drop phase generally moves faster than the carrier fluid; both phase velocities equilibrate much faster to the statistical steady state than does the drop-size distribution.
Macroscopic properties of fractured porous media
NASA Astrophysics Data System (ADS)
Thovert, J.; Mourzenko, V. V.; Adler, P. M.
2007-12-01
The determination of the local fields in fractured porous media is a challenging problem, because of the multiple scales that are involved and of the possible nonlinearity of the governing equations. The purpose of this paper is to provide an overall view of the numerical technique which has been used to solve numerous problems. It is based on a three-dimensional discrete description of the fracture network and of the embedding matrix. Any fracture network geometry, any type of boundary condition, and any distribution of the fracture and matrix properties can be addressed, without simplifying approximations. The first step is to mesh the fracture network as it is by triangles of a controlled size. This meshing by an advancing front technique is done successively for each fracture and the intersections between fractures are taken into account. Then, the space in between the fractures is meshed by tetrahedra by the advancing front technique again. The faces of the tetrahedra which are in contact with fractures, coincide with the corresponding triangles in these fractures. The performances of these meshing codes will be illustrated by a few examples. The second step consists in discretizing the conservation equations by the finite volume technique. Specific properties are given to each fracture such as a surface permeability or a joint rigidity. This general technique has been applied to the basic and most important properties of fracture networks and of fractured porous media (1). These properties are single and two phase flows, wether they are accompagnied or not by dispersion of a solute and mechanical properties possibly coupled with flow. These applications will be briefly illustrated by some examples, including when possible comparison with real data. Ref: (1) P.M. Adler, V.V. Mourzenko, J.-F. Thovert, I. Bogdanov, in Dynamics of fluids and transport in fractured rock, ed. B. Faybishenko, Geophysical Monograph Series, 162, 33, 2005.
Multiphase flow and transport in porous media
NASA Astrophysics Data System (ADS)
Parker, J. C.
1989-08-01
Multiphase flow and transport of compositionally complex fluids in geologic media is of importance in a number of applied problems which have major social and economic effects. In petroleum reservoir engineering, efficient recovery of energy reserves is the principal goal. Unfortunately, some of these hydrocarbons and other organic chemicals often find their way unwanted into the soils and groundwater supplies. Removal in the latter case is predicated on ensuring the public health and safety. In this paper, principles of modeling fluid flow in systems containing up to three fluid phases (namely, water, air, and organic liquid) are described. Solution of the governing equations for multiphase flow requires knowledge of functional relationships between fluid pressures, saturations, and permeabilities which may be formulated on the basis of conceptual models of fluid-porous media interactions. Mechanisms of transport in multicomponent multiphase systems in which species may partition between phases are also described, and the governing equations are presented for the case in which local phase equilibrium may be assumed. A number of hypothetical numerical problems are presented to illustrate the physical behavior of systems in which multiphase flow and transport arise.
Microbubble transport in water-saturated porous media
NASA Astrophysics Data System (ADS)
Ma, Y.; Kong, X.-Z.; Scheuermann, A.; Galindo-Torres, S. A.; Bringemeier, D.; Li, L.
2015-06-01
Laboratory experiments were conducted to investigate flow of discrete microbubbles through a water-saturated porous medium. During the experiments, bubbles, released from a diffuser, moved upward through a quasi-2-D flume filled with transparent water-based gelbeads and formed a distinct plume that could be well registered by a calibrated camera. Outflowing bubbles were collected on the top of the flume using volumetric burettes for flux measurements. We quantified the scaling behaviors between the gas (bubble) release rates and various characteristic parameters of the bubble plume, including plume tip velocity, plume width, and breakthrough time of the plume front. The experiments also revealed circulations of ambient pore water induced by the bubble flow. Based on a simple momentum exchange model, we showed that the relationship between the mean pore water velocity and gas release rate is consistent with the scaling solution for the bubble plume. These findings have important implications for studies of natural gas emission and air sparging, as well as fundamental research on bubble transport in porous media.
Foam Flows in Analog Porous Media
NASA Astrophysics Data System (ADS)
Meheust, Y.; Géraud, B.; Jones, S. A.; Cantat, I.; Dollet, B.
2015-12-01
Foams have been used for decades as displacing fluids for EOR and aquifer remediation, and more recently as carriers of chemical amendments for the remediation of the vadose zone. Apart from various interesting physico-chemical and biochemical properties, foams are better injection fluids due to their low sensitivity to gravity and their peculiar rheology: for foams with bubbles on the order of at least the typical pore size, viscous dissipation arises mostly from the contact zones between the soap films and the walls. In most experimental studies no local information of the foam structure is possible, and only global quantities such as the effective viscosity can be measured. We investigate foam flow through a two-dimensional porous medium consisting of circular obstacles positioned randomly in a horizontal transparent Hele-Shaw cell. The local foam structure is recorded in situ, which provides a measure of the spatial distribution of bubble velocities and sizes at regular time intervals. The flow exhibits a rich phenomenology including preferential flow paths and local flow intermittency/non-stationarity despite the imposed permanent global flow rate. Moreover, the medium selects the bubble size distribution through lamella division-triggered bubble fragmentation. Varying the mean bubble size of the injected foam, its water content, and mean velocity, we characterize those processes systematically and show that the distributions of bubble sizes and velocities are to some extent correlated. We furthermore measure the evolution, along the flow direction, of the distribution of bubble sizes, and measure the efficiency of bubble fragmentation as a function of the control parameters. The bubble fragmentation can be modeled numerically and to some extent analytically, based on statistical measures inferred from the experimental data. This study sheds new light on the local rheology of foams in porous media and opens the way towards quantitative characterization of the
Foam Transport in Porous Media - A Review
Zhang, Z. F.; Freedman, Vicky L.; Zhong, Lirong
2009-11-11
Amendment solutions with or without surfactants have been used to remove contaminants from soil. However, it has drawbacks such that the amendment solution often mobilizes the plume, and its movement is controlled by gravity and preferential flow paths. Foam is an emulsion-like, two-phase system in which gas cells are dispersed in a liquid and separated by thin liquid films called lamellae. Potential advantages of using foams in sub-surface remediation include providing better control on the volume of fluids injected, uniformity of contact, and the ability to contain the migration of contaminant laden liquids. It is expected that foam can serve as a carrier of amendments for vadose zone remediation, e.g., at the Hanford Site. As part of the U.S. Department of Energy’s EM-20 program, a numerical simulation capability will be added to the Subsurface Transport Over Multiple Phases (STOMP) flow simulator. The primary purpose of this document is to review the modeling approaches of foam transport in porous media. However, as an aid to understanding the simulation approaches, some experiments under unsaturated conditions and the processes of foam transport are also reviewed. Foam may be formed when the surfactant concentration is above the critical micelle concentration. There are two main types of foams – the ball foam (microfoam) and the polyhedral foam. The characteristics of bulk foam are described by the properties such as foam quality, texture, stability, density, surface tension, disjoining pressure, etc. Foam has been used to flush contaminants such as metals, organics, and nonaqueous phase liquids from unsaturated soil. Ball foam, or colloidal gas aphrons, reportedly have been used for soil flushing in contaminated site remediation and was found to be more efficient than surfactant solutions on the basis of weight of contaminant removed per gram of surfactant. Experiments also indicate that the polyhedral foam can be used to enhance soil remediation. The
Wave propagation in fluid-saturated porous media
NASA Astrophysics Data System (ADS)
Ren, Jiaxiang
The wave propagation in fluid-saturated porous media is studied by solving the Biot equations, the governing equations for the motion of the porous medium. Methods are devised to solve the Biot equations for different problems and medium models. The problem of the reflection and transmission at an interface is solved by using the eigen-analysis of the Biot equations. The displacement-stress vectors in the media on both sides of the interface are represented by corresponding upgoing and downgoing wave vectors which are then linked by the boundary conditions on the interface. The reflection and transmission coefficients are extracted from the proportionalities between the upgoing and downgoing waves. For an incident fast wave or shear wave, the reflection and transmission coefficients for the reflected and transmitted slow waves are very sensitive to frequency and interface permeability (kappasb{I}); while those for the reflected and transmitted fast waves and shear waves are not, except when incident angles are close to and greater than critical angles. For sandstones, the amplitudes of the reflected and transmitted slow waves could be several percent of the amplitude of the incident fast wave or shear wave. Higher interface permeabilities favor the generation of the slow wave. The slow waves generated at an open interface (kappasb{I}->infty) and a sealed interface (kappasb{I}=0) could be one-order different in amplitude. The reflection and transmission at an interface have been extended to the model composed of multi-layers of porous media. An algorithm based on the compact finite-difference method is developed for 2-D seismic modeling. The compact finite-difference method is used to estimate the spatial derivatives in the Biot equations, with a 6sp{th}-order accuracy. It needs fewer grid intervals to represent a mono-wavelength function than the traditional 2sp{nd}-order central-difference method. Therefore, the algorithm based on the compact finite
Influence of microbial biofilms on reactive transport in porous media
NASA Astrophysics Data System (ADS)
Gerlach, Robin; Cunningham, Al.
2012-05-01
Microbial biofilms form in natural and engineered systems and can significantly affect the hydrodynamics in porous media. Subsurface remediation, enhanced oil recovery, abatement of saltwater intrusion, filtration, deep-subsurface sequestration of supercritical carbon dioxide, and biofouling of injection or recovery wells are examples of proposed or implemented beneficial porous media biofilm applications. The thickness of the desired biofilm depends on a number of factors including desirable groundwater flow velocity and residence time of contaminated groundwater within the biofilm barrier as well as the prevailing hydraulic gradient. In order to better understand the influence of biofilms on reactive transport in porous media and ultimately improve biofilm-based porous media technologies, bench and mesoscale studies have been ongoing in our laboratories. This manuscript summarizes some of our past, current, and future efforts in this area and gives an outlook and overview of research and development needs.
NASA Astrophysics Data System (ADS)
Ziazi, R. M.; Liburdy, J.; Apte, S.; Wood, B. D.
2015-12-01
The sequential transient regime of the flow through randomly packed porous media has been observed experimentally from steady inertial to turbulent flow. Considering the inherent constraints in visualization and measurements in porous media, the characterization has been performed using time resolved PIV in a randomly packed ordered array of spheres with uniform size. The size of the spheres are 15 mm and the pore Reynolds numbers are set to be 300, 500, and 900. The test bed has a cross-section of 70×70 mm and a height of 15mm. In addition to the difficult accessibility to the interrogation window, the challenges of visualizing the flow in this porous structure is matching of refractive indices of the fluid and solid phase as slight mismatches have been shown to cause significant tracking errors. The 2-D velocity field has been captured at discrete planar locations along the optical axis through the test bed to study the physics and statistics of the flow. Variations occur in the imaging magnification, and if not taken into consideration may lead to increased error. This study addresses three forms of error in PIV as they pertain to porous media flow: tracking error, bias error due to displacement gradients and perspective error. The bias error due to displacement gradients was evaluated from correlation peak width. Direct Numerical Simulation is also being performed to investigate the transitional and turbulent flow in porous media in detail.
NASA Astrophysics Data System (ADS)
Jiang, Yuguang; Feng, Yu; Zhang, Silong; Qin, Jiang; Bao, Wen
2016-01-01
Hydrocarbon fuel has been widely used in air-breathing scramjets and liquid rocket engines as coolant and propellant. However, possible heat transfer deterioration and threats from local high heat flux area in scramjet make heat transfer enhancement essential. In this work, 2-D steady numerical simulation was carried out to study different schemes of heat transfer enhancement based on a partially filled porous media in a tube. Both boundary and central layouts were analyzed and effects of gradient porous media were also compared. The results show that heat transfer in the transcritical area is enhanced at least 3 times with the current configuration compared to the clear tube. Besides, the proper use of gradient porous media also enhances the heat transfer compared to homogenous porous media, which could help to avoid possible over-temperature in the thermal protection.
Development of correlations to predict biopolymer mobility in porous media
Hejri, S.; Willhite, G.P.; Green, D.W. )
1991-02-01
This paper describes the flow and rheological behavior of biopolymer solutions in sandpacks over a wide range of permeability and frontal advance rates. Empirical correlations were developed to estimate polymer mobility in porous media. The correlations are based on porous medium properties, polymer concentration, and rheological parameters for the polymer derived from steady-shear measurements.
Characterization of an impinging jet into porous media
NASA Astrophysics Data System (ADS)
Wang, Cong; Alhani, Salwan; Gharib, Morteza
2015-11-01
In this work, characteristic behavior of a liquid jet into porous hydrophobic / hydrophilic particle media is investigated. In porous media, the capillary effect becomes significant, especially when the jet Reynolds Number is low. To analyze the cavity creation phenomena, the effect of jet's diameter, speed and acceleration as well as particles' size are carefully studied. Such knowledge of fluid behavior will provide guidance for medicine injection process. This work is supported by Caltech GALCIT STEM program.
Note: Reconstruction of fluid flows in porous media using geometric a priori information
NASA Astrophysics Data System (ADS)
Maisl, Michael; Scholl, Hagen; Schorr, Christian; Seemann, Ralf
2016-12-01
X-ray tomography typically suffers from insufficient temporal resolution when imaging dynamic processes. Using the example of multiphase flow in solid porous media, we adapt an iterative algorithm to compute 3d tomograms from 2d projections, which allows for a significant reduction of scan time while maintaining a high level of reconstruction quality. To this end, a priori knowledge about the porous medium is incorporated into the reconstruction algorithm. This algorithm is universal when monitoring dynamic changes in any static matrix and allows for an at least five times decreased imaging time with respect to standard reconstruction algorithms.
Note: Reconstruction of fluid flows in porous media using geometric a priori information.
Maisl, Michael; Scholl, Hagen; Schorr, Christian; Seemann, Ralf
2016-12-01
X-ray tomography typically suffers from insufficient temporal resolution when imaging dynamic processes. Using the example of multiphase flow in solid porous media, we adapt an iterative algorithm to compute 3d tomograms from 2d projections, which allows for a significant reduction of scan time while maintaining a high level of reconstruction quality. To this end, a priori knowledge about the porous medium is incorporated into the reconstruction algorithm. This algorithm is universal when monitoring dynamic changes in any static matrix and allows for an at least five times decreased imaging time with respect to standard reconstruction algorithms.
Colloid Straining within Saturated Heterogeneous Porous Media
NASA Astrophysics Data System (ADS)
Porubcan, A.; Walczak, J.; Xu, S.
2008-12-01
A thorough understanding of colloid movement in the subsurface system is critical to the assessment of groundwater pollution by pathogenic bacteria and colloid-bound contaminants. It is increasingly recognized that straining, a process that occurs when the pore space is too small to allow for a particle's passage, represents an important process in colloid immobilization within groundwater systems. Previously published studies have focused on the kinetics of colloid straining within sand packs composed of uniform mineral grains. Natural aquifers, however, are usually characterized by physically heterogeneous sediments. In this study, we conducted column transport experiments with carboxylated latex particles and quartz sand to investigate the impact of sediment texture (i.e., the size distribution of mineral grains) on colloid straining kinetics. The quartz sands used in the experiment were thoroughly cleaned and the strong repulsive interactions between colloid particles and quartz sands resulted in minimal physicochemical deposition so the straining kinetics can be quantified unambiguously. Sand packs of different textures were prepared by mixing sands of various sizes (mesh sizes of 20-25, 35-40 and 60-70). Our results suggested that the ratio of colloid size and the median sand grain size was insufficient to predict colloid straining within heterogeneous sediments. Soil texture, which was related to the size distribution of the sand grains, must be considered. A relationship between colloid straining kinetics and the heterogeneity of porous media that can be useful for the prediction of colloid transport within heterogeneous sediments was presented.
Confined Impinging Jets in Porous Media
NASA Astrophysics Data System (ADS)
Buonomo, B.; Cirillo, L.; Manca, O.; Mansi, N.; Nardini, S.
2016-09-01
Impinging jets are adopted in drying of textiles, paper, cooling of gas turbine components, freezing of tissue in cryosurgery and manufacturing, electronic cooling. In this paper an experimental investigation is carried out on impinging jets in porous media with the wall heated from below with a uniform heat flux. The fluid is air. The experimental apparatus is made up of a fun systems, a test section, a tube, to reduce the section in a circular section. The tube is long 1.0 m and diameter of 0.012 m. The test section has a diameter of 0.10 m and it has the thickness of 10, 20 and 40 mm. In the test section the lower plate is in aluminum and is heated by an electrical resistance whereas the upper plate is in Plexiglas. The experiments are carried out employing a aluminum foam 40 PPI at three thickness as the test section. Results are obtained in a Reynolds number range from 5100 to 15300 and wall heat flux range from 510 W/m2 to 1400 W/m2. Results are given in terms of wall temperature profiles, local and average Nusselt numbers, pressure drops, friction factor and Richardson number.
Nanoparticle tracers in calcium carbonate porous media
NASA Astrophysics Data System (ADS)
Li, Yan Vivian; Cathles, Lawrence M.; Archer, Lynden A.
2014-08-01
Tracers are perhaps the most direct way of diagnosing subsurface fluid flow pathways for ground water decontamination and for natural gas and oil production. Nanoparticle tracers could be particularly effective because they do not diffuse away from the fractures or channels where flow occurs and thus take much less time to travel between two points. In combination with a chemical tracer they can measure the degree of flow concentration. A prerequisite for tracer applications is that the particles are not retained in the porous media as the result of aggregation or sticking to mineral surfaces. By screening eight nanoparticles (3-100 nm in diameter) for retention when passed through calcium carbonate packed laboratory columns in artificial oil field brine solutions of variable ionic strength we show that the nanoparticles with the least retention are 3 nm in diameter, nearly uncharged, and decorated with highly hydrophilic polymeric ligands. The details of these column experiments and the tri-modal distribution of zeta potential of the calcite sand particles in the brine used in our tests suggests that parts of the calcite surface have positive zeta potential and the retention of negatively charged nanoparticles occurs at these sites. Only neutral nanoparticles are immune to at least some retention.
2D quasi-ordered nitrogen-enriched porous carbon nanohybrids for high energy density supercapacitors
NASA Astrophysics Data System (ADS)
Kan, Kan; Wang, Lei; Yu, Peng; Jiang, Baojiang; Shi, Keying; Fu, Honggang
2016-05-01
Two-dimensional (2D) quasi-ordered nitrogen-enriched porous carbon (QNPC) nanohybrids, with the characteristics of an ultrathin graphite nanosheet framework and thick quasi-ordered nitrogen-doped carbon cladding with a porous texture, have been synthesized via an in situ polymerization assembly method. In the synthesis, the expandable graphite (EG) is enlarged by an intermittent microwave method, and then aniline monomers are intercalated into the interlayers of the expanded EG with the assistance of a vacuum. Subsequently, the intercalated aniline monomers could assemble on the interlayer surface of the expanded EG, accompanied by the in situ polymerization from aniline monomers to polyaniline. Meanwhile, the expanded EG could be exfoliated to graphite nanosheets. By subsequent pyrolysis and activation processes, the QNPC nanohybrids could be prepared. As supercapacitor electrodes, a typical QNPC12-700 sample derived from the precursor containing an EG content of 12%, with a high level of nitrogen doping of 5.22 at%, offers a high specific capacitance of 305.7 F g-1 (1 A g-1), excellent rate-capability and long-term stability. Notably, an extremely high energy density of 95.7 Wh kg-1 at a power density of 449.7 W kg-1 in an ionic liquid electrolyte can be achieved. The unique structural features and moderate heteroatom doping of the QNPC nanohybrids combines electrochemical double layer and faradaic capacitance contributions, which make these nanohybrids ideal candidates as electrode materials for high-performance energy storage devices.Two-dimensional (2D) quasi-ordered nitrogen-enriched porous carbon (QNPC) nanohybrids, with the characteristics of an ultrathin graphite nanosheet framework and thick quasi-ordered nitrogen-doped carbon cladding with a porous texture, have been synthesized via an in situ polymerization assembly method. In the synthesis, the expandable graphite (EG) is enlarged by an intermittent microwave method, and then aniline monomers are
Enhancing nZVI mobility in porous media using humate
NASA Astrophysics Data System (ADS)
Schmid, Doris; Micic Batka, Vesna; Gondikas, Andreas; Velimirovic, Milica; von der Kammer, Frank; Hofmann, Thilo
2016-04-01
The limited transport of nanoscale zero-valent iron (nZVI) particles in porous media is a major drawback for its use in groundwater remediation. Among other factors, transport of nZVI particles might be negatively affected by mineralogical and physical heterogeneities of the aquifer matrix. Carbonate minerals and iron oxides, for instance, provide positively charged patches which would further increase particle attachment to the sand grains. This study does assess the potential of sodium humate, a salt of humic acids, to enhance the mobility of nZVI particles. Humate is a non-toxic, inexpensive material extracted from natural oxidized lignite and obtained in commercial grade, which makes it advantageous for field applications. Humate is expected to shield the positively charged patches of the sand grains and consequently enhance nZVI mobility in porous media. In this study the humate was injected into an aquifer prior to injection of the nZVI particles. The potential of humate for enhancing the mobility of nZVI particles was tested in an array of columns packed with heterogeneous natural porous media of different mineralogical composition and sediment texture. The results demonstrated that without pre-injection of humates only limited mobility of nZVI particles can be obtained in all tested porous media. After the pre-injection of low concentration of humate (10 mg/L) the mobility of nZVI particles (1 g/L) was enhanced in all tested porous media. The magnitude of this enhancement was depended on the properties of the porous media. The largest improvement of nZVI mobility was observed for homogeneous quartz. This material had also the highest porosity (~ 40%), good sorting, and therefore a higher permeability compared to the other porous media tested. It is assumed that the higher permeability of this porous medium allowed an optimal distribution of humate, resulting in an approximately 6-fold enhancement of nZVI mobility. In carbonate-rich porous medium with a
Effects of Cognitive Styles on 2D Drafting and Design Performance in Digital Media
ERIC Educational Resources Information Center
Pektas, Sule Tasli
2010-01-01
This paper investigates the interactions between design students' cognitive styles, as measured by Riding's Cognitive Styles Analysis, and performance in 2D drafting and design tasks in digital media. An empirical research revealed that Imager students outperformed Verbalisers in both drafting and creativity scores. Wholist-Analytic cognitive…
Using TRINET for simulating flow and transport in porous media
Najita, J.; Doughty, C.
1998-08-01
The finite element model TRINET calculates transient or steady-state fluid flow and solute transport on a lattice composed of one-dimensional finite elements (i.e., pipes) of porous medium. TRINET incorporates an adaptive gridding algorithm to minimize numerical dispersion for transport calculations. Although TRINET was originally developed to study fracture networks, the primary interest here is in applying TRINET more generally to simulate transport in porous media (or a fractured medium being treated as an effective continuum). This requires developing expressions to relate TRINET inputs to equivalent parameters used to describe flow and transport in homogeneous porous media. In this report, the authors briefly describe the basic TRINET formulation for flow and transport, present TRINET equivalences for porous medium parameters, and compare TRINET to analytical solutions using the proposed porous medium equivalents.
Homogenization of two fluid flow in porous media
Daly, K. R.; Roose, T.
2015-01-01
The macroscopic behaviour of air and water in porous media is often approximated using Richards' equation for the fluid saturation and pressure. This equation is parametrized by the hydraulic conductivity and water release curve. In this paper, we use homogenization to derive a general model for saturation and pressure in porous media based on an underlying periodic porous structure. Under an appropriate set of assumptions, i.e. constant gas pressure, this model is shown to reduce to the simpler form of Richards' equation. The starting point for this derivation is the Cahn–Hilliard phase field equation coupled with Stokes equations for fluid flow. This approach allows us, for the first time, to rigorously derive the water release curve and hydraulic conductivities through a series of cell problems. The method captures the hysteresis in the water release curve and ties the macroscopic properties of the porous media with the underlying geometrical and material properties. PMID:27547073
Porous media heat transfer for injection molding
Beer, Neil Reginald
2016-05-31
The cooling of injection molded plastic is targeted. Coolant flows into a porous medium disposed within an injection molding component via a porous medium inlet. The porous medium is thermally coupled to a mold cavity configured to receive injected liquid plastic. The porous medium beneficially allows for an increased rate of heat transfer from the injected liquid plastic to the coolant and provides additional structural support over a hollow cooling well. When the temperature of the injected liquid plastic falls below a solidifying temperature threshold, the molded component is ejected and collected.
Simulation of foam displacement in porous media
Kovscek, A.R.; Patzek, T.W.; Radke, C.J.
1993-08-01
Foam is an excellent fluid for achieving mobility control of gas in porous media. Practical application of foams for EOR processes, however requires a predictive model of foam displacement. Further, quantitative information on foam-flow behavior at reservoir flow rates and pressures is required as input to any field-scale modeling. An experimental and mechanistic-modeling study is reported for the transient flow of foam through 1.3 {mu}m{sup 2} (1.3 D) Boise sandstone at backpressures in excess of 5 MPa (700 psi) over a quality range from 0.80 to 0.99. Total superficial velocities range from as little as 0.42 to 2.20 m/day (1.4 ft/day to 7 ft/day). Sequential pressure taps and gamma-ray densitometry measure flow resistance and in-situ liquid saturations, respectively. We garner experimental pressure and saturation profiles in both the transient and steady states. Adoption of a mean-size foam-bubble conservation equation along with the traditional reservoir simulation equations allows mechanistic foam simulation. Since foam mobility depends heavily upon its texture, the bubble population balance is both useful and necessary as the role of foam texture must be incorporated into any model which seeks accurate prediction of flow properties. Our model employs capillary-pressure-dependent kinetic expressions for lamellae generation and coalescence and also a term for trapping of lamellae. Additionally, the effects of surfactant chemical transport are included. We find quantitative agreement between experimental and theoretical saturation and pressure profiles in both the transient and steady states.
Transport of human adenoviruses in porous media
NASA Astrophysics Data System (ADS)
Kokkinos, Petros; Syngouna, Vasiliki I.; Tselepi, Maria A.; Bellou, Maria; Chrysikopoulos, Constantinos V.; Vantarakis, Apostolos
2015-04-01
Groundwater may be contaminated with infective human enteric viruses from various wastewater discharges, sanitary landfills, septic tanks, agricultural practices, and artificial groundwater recharge. Coliphages have been widely used as surrogates of enteric viruses, because they share many fundamental properties and features. Although a large number of studies focusing on various factors (i.e. pore water solution chemistry, fluid velocity, moisture content, temperature, and grain size) that affect biocolloid (bacteria, viruses) transport have been published over the past two decades, little attention has been given toward human adenoviruses (hAdVs). The main objective of this study was to evaluate the effect of pore water velocity on hAdV transport in water saturated laboratory-scale columns packed with glass beads. The effects of pore water velocity on virus transport and retention in porous media was examined at three pore water velocities (0.39, 0.75, and 1.22 cm/min). The results indicated that all estimated average mass recovery values for hAdV were lower than those of coliphages, which were previously reported in the literature by others for experiments conducted under similar experimental conditions. However, no obvious relationship between hAdV mass recovery and water velocity could be established from the experimental results. The collision efficiencies were quantified using the classical colloid filtration theory. Average collision efficiency, α, values decreased with decreasing flow rate, Q, and pore water velocity, U, but no significant effect of U on α was observed. Furthermore, the surface properties of viruses and glass beads were used to construct classical DLVO potential energy profiles. The results revealed that the experimental conditions of this study were unfavorable to deposition and that no aggregation between virus particles is expected to occur. A thorough understanding of the key processes governing virus transport is pivotal for public
Transport of Graphene Oxide through Porous Media
NASA Astrophysics Data System (ADS)
Duster, T. A.; Na, C.; Bolster, D.; Fein, J. B.
2012-12-01
Graphene oxide (GO) is comprised of anisotropic nanosheets decorated with covalently-bonded epoxide, ketone, and hydroxyl functional groups on the basal planes, and carboxylic and phenolic functional groups at the edges. Individual GO nanosheets are generally two to three micrometers in width, with thicknesses depending on the degree of exfoliation and typically ranging from one to approximately 100 nanometers. As a result of this extraordinarily large surface area-to-mass ratio and the presence of numerous proton-active functional groups, GO nanosheets exhibit a tremendous capacity to adsorb metals and other contaminants from aqueous solutions and are thus often suggested for use in in situ remediation efforts. The potential importance of GO nanosheets as an adsorbent in soil and groundwater necessitates a detailed understanding of their mobility in environmental systems, but this topic remains largely unexplored. Hence, the objective of this study was to investigate the transport behavior of GO nanosheets through well-characterized saturated porous media. In this study, we used replicate glass columns packed with two different sand grain sizes, and within each treatment we varied pH (5.5 to 8.5), ionic strength (<0.01 M to 0.1 M), electrolyte composition (Na+ and Ca2+ salts), and GO nanosheet exfoliation extent (few-layered and many-layered) to determine the relative influence of both physical and electrochemical properties on GO nanosheet transport in these systems. The break-through of GO nanosheets from each treatment was continuously monitored using a flow-through quartz cuvette and UV-Vis absorbance at 230 nm. GO nanosheet transport through these systems was then modeled using distinct advection-dispersion equations to establish the relative influence of attachment, deposition, and detachment in the overall transport behavior, and a corresponding retardation coefficient was calculated for each treatment. Break-through curves displayed anomalous transport
A 2D spring model for the simulation of ultrasonic wave propagation in nonlinear hysteretic media.
Delsanto, P P; Gliozzi, A S; Hirsekorn, M; Nobili, M
2006-07-01
A two-dimensional (2D) approach to the simulation of ultrasonic wave propagation in nonclassical nonlinear (NCNL) media is presented. The approach represents the extension to 2D of a previously proposed one dimensional (1D) Spring Model, with the inclusion of a PM space treatment of the intersticial regions between grains. The extension to 2D is of great practical relevance for its potential applications in the field of quantitative nondestructive evaluation and material characterization, but it is also useful, from a theoretical point of view, to gain a better insight of the interaction mechanisms involved. The model is tested by means of virtual 2D experiments. The expected NCNL behaviors are qualitatively well reproduced.
Is Chaotic Advection Inherent to Porous Media Flow?
NASA Astrophysics Data System (ADS)
Lester, Daniel; Metcalfe, Guy; Trefry, Mike
2013-11-01
All porous media, including granular and packed media, fractured and open networks, are typified by the inherent topological complexity of the pore-space. This topological complexity admits a large number density of stagnation points under steady Stokes flow, which in turn generates a 3D fluid mechanical analouge of the Bakers map, termed the Baker's flow. We demonstrate that via this mechanism, chaotic advection at the pore-scale is inherent to almost all porous media under reasonable conditions, and such dynamics have significant implications for a range of fluid-borne processes including transport and mixing, chemical reactions and biological activity.
Liquid flow and distribution in unsaturated porous media
NASA Technical Reports Server (NTRS)
Alexander, J. Iwan
2004-01-01
Flow and transport in permeable or porous media and microchannels occurs in a variety of situations in micro- and reduced-gravity environments, many of them associated with environmental control and life support systems. While the role of gravity is limited, due to the typically small size scales associated permeable media, gravity, at the very least, affects the overall disposition of fluid in a macroscopic system. This presentation will discuss examples where the absence of gravity affects flow and phase distribution in selected examples of unsaturated flow and transport of heat and mass in porous media and microchannels that are pertinent to spacecraft systems.
FID-SPI pulse sequence for quantitative MRI of fluids in porous media
NASA Astrophysics Data System (ADS)
Marica, Florea; Goora, Frédéric G.; Balcom, Bruce J.
2014-03-01
MRI has great potential for providing quantitative, spatially resolved information about fluids imbibed in porous media. The pure phase encode SPRITE technique has proven to be a very general method for the generation of density images in porous media; however, low flip-angle RF pulses and broad filter widths, required by short encoding times, yield sub-optimal S/N images. A 1-D phase-encoding sequence for T2∗ mapping, named FID-SPI, is presented and analyzed in terms of image quality and accuracy of fluid content distribution in porous media. Extension to 2-D and 3-D imaging was straightforward and images of heterogeneous samples are presented. The FID-SPI measurement results in a series of individual T2∗ weighted images acquired following RF excitation and pulsed phase-encoding gradients. Key to the performance of the FID-SPI method is high quality control of the magnetic field gradient pulse to ensure each FID point has identical spatial encoding. FID-SPI is intended for a quantitative determination of the spatially resolved fluid content in heterogeneous porous media, having the ability to determine the T2∗ decay for each image pixel. T2∗ mapping aids in estimation of the local fluid content.
Viscous flow in three-dimensional reconstructed porous media
NASA Astrophysics Data System (ADS)
Pilotti, Marco
2003-07-01
In a recent paper Masad et al. (Int. J. Numer. Methods Eng. 2000; 26: 53-74) have shown the possibility of numerically studying fluid flow within two-dimensional microscopic images of granular materials. In this paper we investigate the possibility of computing the flow field at the pore scale within numerically reconstructed three dimensional porous media, by coupling a physically based sedimentation algorithm for porous media generation and a Lattice Boltzmann Technique for solving Navier equations for the monophasic flow of a newtonian fluid inside the intergranular space. Since the adopted sedimentation algorithm can produce porous media with a controlled level of complexity, we believe that this type of approach provides an ideal numerical laboratory to probe the effect of void space topology and geometry on the flow field. This should allow to understand the fluid-dynamic implications of processes such as compaction and cementation. After showing that the Lattice Boltzmann Technique is effective in solving Navier equations in porous media also at moderately high Reynolds, where Darcy's flow does not strictly hold anymore, we investigate the distribution of velocity components within porous media of growing complexity, starting from two different periodic arrangements of spheres up to a mixture of log-normally distributed spheres. We observe that the distribution of velocity components is conditioned by the medium complexity and tends to an exponential pattern.
a Fractal Network Model for Fractured Porous Media
NASA Astrophysics Data System (ADS)
Xu, Peng; Li, Cuihong; Qiu, Shuxia; Sasmito, Agus Pulung
2016-04-01
The transport properties and mechanisms of fractured porous media are very important for oil and gas reservoir engineering, hydraulics, environmental science, chemical engineering, etc. In this paper, a fractal dual-porosity model is developed to estimate the equivalent hydraulic properties of fractured porous media, where a fractal tree-like network model is used to characterize the fracture system according to its fractal scaling laws and topological structures. The analytical expressions for the effective permeability of fracture system and fractured porous media, tortuosity, fracture density and fraction are derived. The proposed fractal model has been validated by comparisons with available experimental data and numerical simulation. It has been shown that fractal dimensions for fracture length and aperture have significant effect on the equivalent hydraulic properties of fractured porous media. The effective permeability of fracture system can be increased with the increase of fractal dimensions for fracture length and aperture, while it can be remarkably lowered by introducing tortuosity at large branching angle. Also, a scaling law between the fracture density and fractal dimension for fracture length has been found, where the scaling exponent depends on the fracture number. The present fractal dual-porosity model may shed light on the transport physics of fractured porous media and provide theoretical basis for oil and gas exploitation, underground water, nuclear waste disposal and geothermal energy extraction as well as chemical engineering, etc.
Modeling isothermal and non-isothermal flows in porous media
NASA Astrophysics Data System (ADS)
Mohseni Languri, Ehsan
2011-12-01
A complete understanding of the physics of flow and heat transfer phenomena in porous media is vital for accurate simulation of flow processes in industrial applications. In one such application pertaining to liquid composite molding (LCM) for manufacturing polymer composites, the fiber preforms used in LCM as reinforcements are limited not only to the single-scale porous media in the form of random fiber-mats, but also include dual-scale porous media in the form of woven or stitched fiber-mats. The conventional flow physics is not able to model the resin filling process in LCM involving the dual-scale porous media. In this study, the flow in dual-scale porous media is studied in order to predict the permeability of these fiber mats. The effect of aspect ratio of the fiber preform on the accuracy and flow during permeability estimation in single- and dual-scale porous media is analyzed experimentally and numerically. Flow of liquid in a free channel bounded on one side by porous medium is studied next, and two well-known boundary conditions of stress continuity and stress jump at the interface of the two regions are evaluated numerically. A point-wise solution for Stokes flow through periodic and non periodic porous media (made of cylindrical particles) adjacent to the free channel is presented using the Imite element based CFD software COMSOL. The efficacy of the two interfacial conditions is evaluated after volume averaging the point-wise velocity using a long averaging volume, also called the representative elementary volume or REV, and then comparing such a volume-averaged velocity profile with the available analytical solution. The investigation is carried out for five different porosities at three different Reynolds numbers to cover a wide range of applications. The presence of randomly-placed cylinders during the creation of non-periodic porous media damps out spatial fluctuations in the averaged velocity observed in periodic porous media. The analytical
Discrete Particle Model for Porous Media Flow using OpenFOAM at Intel Xeon Phi Coprocessors
NASA Astrophysics Data System (ADS)
Shang, Zhi; Nandakumar, Krishnaswamy; Liu, Honggao; Tyagi, Mayank; Lupo, James A.; Thompson, Karten
2015-11-01
The discrete particle model (DPM) in OpenFOAM was used to study the turbulent solid particle suspension flows through the porous media of a natural dual-permeability rock. The 2D and 3D pore geometries of the porous media were generated by sphere packing with the radius ratio of 3. The porosity is about 38% same as the natural dual-permeability rock. In the 2D case, the mesh cells reach 5 million with 1 million solid particles and in the 3D case, the mesh cells are above 10 million with 5 million solid particles. The solid particles are distributed by Gaussian distribution from 20 μm to 180 μm with expectation as 100 μm. Through the numerical simulations, not only was the HPC studied using Intel Xeon Phi Coprocessors but also the flow behaviors of large scale solid suspension flows in porous media were studied. The authors would like to thank the support by IPCC@LSU-Intel Parallel Computing Center (LSU # Y1SY1-1) and the HPC resources at Louisiana State University (http://www.hpc.lsu.edu).
Modeling microbial processes in porous media
NASA Astrophysics Data System (ADS)
Murphy, Ellyn M.; Ginn, Timothy R.
The incorporation of microbial processes into reactive transport models has generally proceeded along two separate lines of investigation: (1) transport of bacteria as inert colloids in porous media, and (2) the biodegradation of dissolved contaminants by a stationary phase of bacteria. Research over the last decade has indicated that these processes are closely linked. This linkage may occur when a change in metabolic activity alters the attachment/detachment rates of bacteria to surfaces, either promoting or retarding bacterial transport in a groundwater-contaminant plume. Changes in metabolic activity, in turn, are controlled by the time of exposure of the microbes to electron acceptors/donor and other components affecting activity. Similarly, metabolic activity can affect the reversibility of attachment, depending on the residence time of active microbes. Thus, improvements in quantitative analysis of active subsurface biota necessitate direct linkages between substrate availability, metabolic activity, growth, and attachment/detachment rates. This linkage requires both a detailed understanding of the biological processes and robust quantitative representations of these processes that can be tested experimentally. This paper presents an overview of current approaches used to represent physicochemical and biological processes in porous media, along with new conceptual approaches that link metabolic activity with partitioning of the microorganism between the aqueous and solid phases. Résumé L'introduction des processus microbiologiques dans des modèles de transport réactif a généralement suivi deux voies différentes de recherches: (1) le transport de bactéries sous forme de colloïdes inertes en milieu poreux, et (2) la biodégradation de polluants dissous par une phase stationnaire de bactéries. Les recherches conduites au cours des dix dernières années indiquent que ces processus sont intimement liés. Cette liaison peut intervenir lorsqu
Examining Asphaltene Solubility on Deposition in Model Porous Media.
Lin, Yu-Jiun; He, Peng; Tavakkoli, Mohammad; Mathew, Nevin Thunduvila; Fatt, Yap Yit; Chai, John C; Goharzadeh, Afshin; Vargas, Francisco M; Biswal, Sibani Lisa
2016-08-30
Asphaltenes are known to cause severe flow assurance problems in the near-wellbore region of oil reservoirs. Understanding the mechanism of asphaltene deposition in porous media is of great significance for the development of accurate numerical simulators and effective chemical remediation treatments. Here, we present a study of the dynamics of asphaltene deposition in porous media using microfluidic devices. A model oil containing 5 wt % dissolved asphaltenes was mixed with n-heptane, a known asphaltene precipitant, and flowed through a representative porous media microfluidic chip. Asphaltene deposition was recorded and analyzed as a function of solubility, which was directly correlated to particle size and Péclet number. In particular, pore-scale visualization and velocity profiles, as well as three stages of deposition, were identified and examined to determine the important convection-diffusion effects on deposition.
A volume-balance model for flow on porous media
NASA Astrophysics Data System (ADS)
Malaga, Carlos; Mandujano, Francisco; Becerra, Julian
2015-11-01
Volume-balance models are used by petroleum engineers for simulating multiphase and multicomponent flow phenomena in porous media and the extraction process in oil reservoirs. In these models, mass conservation equations and Darcy's law are supplemented by a balance condition for the pore and fluid volumes. This provides a pressure equation suitable for simulating a compressible flow within a compressible solid matrix. Here we present an alternative interpretation of the volume-balance condition that includes the advective transport within a consolidated porous media. We obtain a modified equation for the time evolution of the pressure field. Numerical tests for phase separation under gravity are presented for multiphase three dimensional flow in heterogeneous porous media. The authors acknowledge funding from Fondo Sectorial CONACYT-SENER grant number 42536 (DGAJ-SPI-34-170412-217).
Transport of Polycyclic Aromatic Hydrocarbons in Unsaturated Porous Media
NASA Astrophysics Data System (ADS)
Chahal, Maninder; Flury, Markus
2016-04-01
Polycyclic aromatic hydrocarbons (PAHs) are complex organic molecules containing 2 or more fused benzene rings. Being hydrophobic and non-polar, PAHs tend to partition to the organic matter in the soil from bulk aqueous phase. Though transport of these contaminants has been well studied in saturated environment, interactive mechanisms of these fluorescent compounds in unsaturated (identified by presence of air-water interface) porous media is still not well understood. We studied is the transport of fluoranthene in unsaturated porous media as facilitated by moving air-water interfaces. Confocal microscopy was used to visualize the interactions of fluoranthene particles in a glass channel packed with quartz glass beads. The packed glass channel was used to mimic a porous media and effects of an advancing and receding capillary fringe on the detachment of fluoranthene.
Permeability modification of porous media by surfactant solutions
Kalpakci, B.; Klaus, E.E.; Duda, J.L.; Nagarajan, R.
1981-01-01
Results are presented of a study on the flow properties of surfactant solutions in porous media, using the Penn State Porous Media Viscometer. The effects of permeability, shear rate, and surface characteristics of the porous media on the flow of oil-external, and water-external type microemulsions as well as surfactant solutions with lamellar structures have been examined. Flow studies have been carried out in untreated Bradford and Berea sandstones, oil-wet and water-wet treated sandstones, and filter papers. This study shows that the flow of surfactant solutions causes a decrease in permeability which reaches a stable value after the flow of several hundred pore volumes of the surfactant solution. This work is pertinent to flooding with surfactants. 33 refs.
Channelization in porous media driven by erosion and deposition
NASA Astrophysics Data System (ADS)
Jäger, R.; Mendoza, M.; Herrmann, H. J.
2017-01-01
We develop and validate a new model to study simultaneous erosion and deposition in three-dimensional porous media. We study the changes of the porous structure induced by the deposition and erosion of matter on the solid surface and find that when both processes are active, channelization in the porous structure always occurs. The channels can be stable or only temporary depending mainly on the driving mechanism. Whereas a fluid driven by a constant pressure drop in general does not form steady channels, imposing a constant flux always produces stable channels within the porous structure. Furthermore we investigate how changes of the local deposition and erosion properties affect the final state of the porous structure, finding that the larger the range of wall shear stress for which there is neither erosion nor deposition, the more steady channels are formed in the structure.
Biomass plug development and propagation in porous media.
Stewart, T L; Fogler, H S
2001-02-05
Exopolymer-producing bacteria can be used to modify soil profiles for enhanced oil recovery or bioremediation. Understanding the mechanisms associated with biomass plug development and propagation is needed for successful application of this technology. These mechanisms were determined from packed-bed and micromodel experiments that simulate plugging in porous media. Leuconostoc mesenteroides was used, because production of dextran, a water-insoluble exopolymer, can be controlled by using different carbon sources. As dextran was produced, the pressure drop across the porous media increased and began to oscillate. Three pressure phases were identified under exopolymer-producing conditions: the exopolymer-induction phase, the plugging phase, and the plug-propagation phase. The exopolymer-induction phase extended from the time that exopolymer-producing conditions were induced until there was a measurable increase in pressure drop across the porous media. The plugging phase extended from the first increase in pressure drop until a maximum pressure drop was reached. Changes in pressure drop in these two phases were directly related to biomass distribution. Specifically, flow channels within the porous media filled with biomass creating a plugged region where convective flow occurred only in water channels within the biofilm. These water channels were more restrictive to flow causing the pressure drop to increase. At a maximum pressure drop across the porous media, the biomass yielded much like a Bingham plastic, and a flow channel was formed. This behavior marked the onset of the plug-propagation phase which was characterized by sequential development and breakthrough of biomass plugs. This development and breakthrough propagated the biomass plug in the direction of nutrient flow. The dominant mechanism associated with all three phases of plugging in porous media was exopolymer production; yield stress is an additional mechanism in the plug-propagation phase.
Linking Colloid Deposit Morphology and Clogging in Porous Media
NASA Astrophysics Data System (ADS)
Roth, E. J.; Mont-eton, M. E.; Mays, D. C.
2012-12-01
Innovations in the field of groundwater remediation have been hampered by delivery limitations in the porous media. For example, colloid deposits (comprising clays or silts) can cause a detrimental reduction in permeability, or clogging, which is problematic for groundwater remediation as well as granular media filtration and aquifer storage and recovery. During remediation, clogging creates preferential pathways in the media, leading to localized rather than spatially extensive contaminant treatment. Consequentially, remediation efforts become more expensive, less effective, and take a very long time. This presentation describes ongoing research investigating the link between colloid deposit morphology and clogging in porous media. As described by Darcy's Law, the velocity of fluid flow through porous media is proportional to permeability, which depends, in part, on porosity. However, changes in permeability are not in accord with changes in porosity as predicted by the Kozeny-Carman equation. It is hypothesized that unmeasured aspects of colloid deposit morphology could be the cause of this anomaly. Colloidal phenomena have important and dynamic effects on the permeability of natural porous media, and several lines of evidence suggest a correlation between clogging in porous media and the fractal dimension of colloid deposits. Here, a custom-built static light scattering apparatus is used to measure the fractal dimension of colloid deposits in refractive index matched porous media within a flow column. The media in our flow column is Nafion, which becomes essentially invisible when saturated by a solution of isopropanol and water. Polystyrene microspheres are then added to the influent through the column as a surrogate for natural colloids. Light from a laser is passed through the column, scattering from the deposited colloids, but not from the index matched Nafion. The resulting intensity of scattered light is measured as a function of scattering angle, and then
Combustion and heat transfer in porous media
Sathe, S.B.; Peck, R.E.; Tong, T.W.
1990-06-01
The objective of the present study is to generate fundamental knowledge about heat transfer and combustion in porous radiant burners (PRBs) in order to improve their performance. A theoretical heat transfer and combustion model is developed to study the characteristics of PRBs. The model accounts for non-local thermal equilibrium between the solid and gas phases. The solid is assumed to absorb, emit and scatter radiant energy. Combustion is modeled as a one-step global reaction. It is revealed that the flame speed inside the porous medium is enhanced compared to the adiabatic flame speeds due to the higher conductivity of the solid compared to the gas as well as due to radiative preheating of the reactants. The effects of the properties of the porous material on the flame speeds, radiative outputs and efficiencies were investigated. To improve the radiative output from the burner, it is desirable that the porous layer has an optical thickness of about ten. The radiative output and the efficiency is higher for lower scattering albedo. The heat transfer coupling between the solid and gas phases should be high enough to ensure local thermal equilibrium, by choosing a fine porous matrix. Higher solid phase conduction enhances the flame speed and the radiative output. Experiments are performed on a ceramic foam to verify the theoretical findings. The existence of the two stability regions was verified experimentally.
Liquid imbibition in particulate porous media in microgravity
NASA Astrophysics Data System (ADS)
Jones, Scott; Tuller, Markus; Or, Dani
Porous media liquid imbibition has been characterized on earth (1g) to describe gravitydependent wetting processes and is of interest in reduced gravity for characterizing hydrodynamic properties of porous media. Short microgravity (µug) periods of about 20 seconds aboard NASA's parabolic flight aircraft provide limited experimental opportunities to observe imbibition in weightlessness. The objectives of this study were to i) obtain measurements of µg liquid imbibition during parabolic flight and ii) to apply capillary-dominated imbibition models to characterize and describe this process. Glass beads and baked ceramic aggregates ranging in size from 0.25 to 3.5 mm were used to visually record liquid imbibition during µg. The Lucas-Washburn (1918, 1921) and Philip (1957) equations were used to model imbibition in these media and to compare parameters obtained under earth's gravity using the same porous media. In µg, capillary forces dominate imbibition with wetting rates lying between horizontal and vertical (upward) 1g measurements. Pre-wet media exhibited repeatable enhanced imbibition rates compared to imbibition in dry media. Phenomena associated with wetting dry media include air entrapment caused by prefferential flow paths and instabilities at the wetting front.
Predicting heat and mass transfer in fractured porous media (Invited)
NASA Astrophysics Data System (ADS)
Geiger, S.; Cortis, A.; Emmanuel, S.
2010-12-01
Fractures are abundant in the subsurface and affect many relevant single- and multi-phase transport processes such as gas and oil extraction, contaminant transport, or geothermal reservoir engineering. However, making reliable predictions of heat and mass transfer in fractured porous media is an outstanding challenge due to its multi-scale nature and the orders-of-magnitude varations in transport rates. Direct high-resolution simulations provide fundamental insights into the local advective and diffusive transport processes in fractured porous media. However, this approach is intractable for inverse simulations because of its high computational requirements. Continuous Time Random Walks on the other hand are a viable alternative and general way to model heat and mass transfer in structurally complex and multi-scale geological media, particularly for inverse problems. But they do not offer the same insights into local transport processes as direct numerical simulations. Here we combine both approaches to simulate the detailed transport processes occurring during heat and mass transfer in fractured porous media and analyse how these affect the breakthrough curves used to calibrate the Continuous Time Random Walks. We show that heat transport in fractured porous media can be anomalous, i.e. characterised by early breakthrough and long tailing, like it is well known for solute transport. We also demonstrate that a careful analysis of the solute breakthrough curves can yield insights into the heterogeneity of the fracture pattern and the transport occurring between fracture and matrix as well as within the matrix and fractures.
A hierarchically porous anatase TiO2 coated-WO3 2D IO bilayer film and its photochromic properties.
Li, Hua; Wu, Huazhong; Xiao, Jiajia; Su, Yanli; Robichaud, Jacques; Brüning, Ralf; Djaoued, Yahia
2016-01-18
A hierarchically porous anatase TiO2 coated-WO3 2D inverse opal (IO) bilayer film was fabricated on ITO glass using a layer by layer route with a hierarchically porous TiO2 top layer and an ordered super-macroporous WO3 2D IO bottom layer. This novel TiO2 coated-WO3 2D IO bilayer film was evaluated for photochromic applications.
NASA Astrophysics Data System (ADS)
Rupert, Y. K.
2015-12-01
The remediation and monitoring of soils and groundwater contaminated with organic compounds is an important goal of many environmental restoration efforts. This laboratory research focuses on combining two innovative geophysical methods: nuclear magnetic resonance (NMR) and spectral induced polarization (SIP) to assess their suitability to characterize and quantify organic contaminants in porous media. Toluene, a light non-aqueous phase liquid (LNAPL), and ethoxy-nonafluorobutane, an engineered dense non-aqueous phase liquid (DNAPL), have been selected as representative organic contaminants. Low-field NMR relaxation time (T2) measurements and diffusion-relaxation (D-T2) correlation measurements, as well as low frequency SIP measurements (<10 kHz) are performed to quantify the amount of these two organic compounds in the presence of water in three types of porous media (sands, clay, and various sand-clay mixtures). The T2, D-T2, and SIP measurements are made on water, toluene, and the synthetic DNAPL in each porous media to understand the effect of different porous media on the NMR and SIP responses in each fluid. We then plan to make measurements on water-organic mixtures with varied concentrations of organic compounds in each porous medium to resolve the NMR and SIP response of the organic contaminants from that of water and to quantify the amount of organic contaminants. Building a relationship between SIP and NMR signatures from organic contaminants not only provides a fundamental yet important petrophysical relationship, but also builds a framework for continued investigation into how these two methods synergize. This will also provide spatially dense information about organic contaminated natural sediments at scales that will improve the quantitative characterization and remediation of contaminated sites.The remediation and monitoring of soils and groundwater contaminated with organic compounds is an important goal of many environmental restoration efforts
Simulation of the relationship between porosity and tortuosity in porous media with cubic particles
NASA Astrophysics Data System (ADS)
Tang, Xiao-Wu; Sun, Zu-Feng; Cheng, Guan-Chu
2012-10-01
Tortuosity is an important parameter used in areas such as vascular medicine, neurobiology, and the field of soil permeability and diffusion to express the mass transport in porous media. It is a function of the porosity and the shape and distribution of particles. In this paper, the tortuosity of cubic particles is calculated. With the assumption that the porous medium is homogeneous, the problem is converted to the micro-level over a unit cell, and geometry models of flow paths are proposed. In three-dimensional (3D) cells, the flow paths are too complicated to define. Hence, the 3D models are converted to two-dimensional (2D) models to simplify the calculation process. It is noticed that the path in the 2D model is shorter than that in the 3D model. As a result, triangular particles and the interaction are also taken into consideration to account for the longer distance respectively. We have proposed quadrate particle and interaction (QI) and quadrate and triangular particle (QT) models with cubic particles. Both models have shown good agreement with the experimental data. It is also found that they can predict the toruosities of some kinds of porous media, like freshwater sediment and Negev chalk.
Averaged model for momentum and dispersion in hierarchical porous media.
Chabanon, Morgan; David, Bertrand; Goyeau, Benoît
2015-08-01
Hierarchical porous media are multiscale systems, where different characteristic pore sizes and structures are encountered at each scale. Focusing the analysis to three pore scales, an upscaling procedure based on the volume-averaging method is applied twice, in order to obtain a macroscopic model for momentum and diffusion-dispersion. The effective transport properties at the macroscopic scale (permeability and dispersion tensors) are found to be explicitly dependent on the mesoscopic ones. Closure problems associated to these averaged properties are numerically solved at the different scales for two types of bidisperse porous media. Results show a strong influence of the lower-scale porous structures and flow intensity on the macroscopic effective transport properties.
Three-dimensional convection of binary mixtures in porous media.
Umla, R; Augustin, M; Huke, B; Lücke, M
2011-11-01
We investigate convection patterns of binary mixtures with a positive separation ratio in porous media. As setup, we choose the Rayleigh-Bénard system of a fluid layer heated from below. Results are obtained by a multimode Galerkin method. Using this method, we compute square and crossroll patterns, and we analyze their structural, bifurcation, and stability properties. Evidence is provided that, for a strong enough Soret effect, both structures exist as stable forms of convection. Some of their properties are found to be similar to square and crossroll convection in the system without porous medium. However, there are also qualitative differences. For example, squares can be destabilized by oscillatory perturbations with square symmetry in porous media, and their velocity isolines are deformed in the so-called Soret regime.
Fractal and Multifractal Models Applied to Porous Media - Editorial
Technology Transfer Automated Retrieval System (TEKTRAN)
Given the current high level of interest in the use of fractal geometry to characterize natural porous media, a special issue of the Vadose Zone Journal was organized in order to expose established fractal analysis techniques and cutting-edge new developments to a wider Earth science audience. The ...
Moisture Content and Migration Dynamics in Unsaturated Porous Media
NASA Technical Reports Server (NTRS)
Homsy, G. M.
1993-01-01
Fundamental studies of fluid mechanics and transport in partially saturated soils are presented. Solution of transient diffusion problems in support of the development of probes for the in-situ measurement of moisture content is given. Numerical and analytical methods are used to study the fundamental problem of meniscus and saturation front propagation in geometric models of porous media.
Modeling of coupled hydro-mechanical problem for porous media
NASA Astrophysics Data System (ADS)
Koudelka, T.; Krejci, T.; Broucek, M.
2013-10-01
The paper deals with numerical modelling of coupled hydro-mechanical problem for porous media. It is focused on coupled hydro-mechanical models for saturated - partially saturated soils. These models were implemented to the SIFEL software package and they were used for numerical simulation of a plate settlement experiment.
Acoustic Wave Monitoring of Biofilm Development in Porous Media
Biofilm development in porous media can result in significant changes to the hydrogeological properties of subsurface systems with implications for fluid flow and contaminant transport. As such, a number of numerical models and simulations have been developed in an attempt to qua...
Colloid adhesive parameters for chemical heterogeneous porous media
Technology Transfer Automated Retrieval System (TEKTRAN)
A simple modeling approach was developed to calculate colloid adhesive parameters for chemically heterogeneous porous media. The area of the zone of electrostatic influence between a colloid and solid-water interface (Az) was discretized into a number of equally sized grid cells to capture chemical...
Microscopic interfacial phenomena during flow in porous media
Miksis, M.J.; Ida, M.P.
1996-12-31
A fundamental process during any multiphase flow in porous media is the breaking apart of one of the phases into smaller components. Here the authors investigate this breaking process as applied to a thin liquid film. They study the breaking of both a two dimensional planar film and a cylindrical thread of liquid using both analytical and numerical methods.
NASA Astrophysics Data System (ADS)
Jiménez-Martínez, Joaquín.; Anna, Pietro de; Tabuteau, Hervé; Turuban, Régis; Borgne, Tanguy Le; Méheust, Yves
2015-07-01
Porous media in which different fluid phases coexist are common in nature (e.g., vadose zone and gas-oil reservoirs). In partially saturated porous media, the intricate spatial distributions of the wetting and nonwetting phases causes their flow to be focused onto preferential paths. Using a novel 2-D experimental setup allowing pore-scale measurement of concentration fields in a controlled unsaturated flow, we highlight mechanisms by which mixing of an invading fluid with the resident fluid is significantly enhanced when decreasing saturation. The mean scalar dissipation rate is observed to decrease slowly in time, while under saturated conditions it decays rapidly. This slow decrease is due to sustained longitudinal solute fingering, which causes concentration gradients to remain predominantly transverse to the average flow. Consequently, the effective reactivity is found to be much larger than under saturated conditions. These results provide new insights into the role that multiphase flows play on mixing/reaction in porous media.
Inertial capture in flow through porous media
NASA Astrophysics Data System (ADS)
Andrade, J. S., Jr.; Araújo, A. D.; Vasconcelos, T. F.; Herrmann, H. J.
2008-08-01
We investigate through numerical calculation of non-Brownian particles transported by a fluid in a porous medium, the influence of geometry and inertial effects on the capture efficiency of the solid matrix. In the case of a periodic array of cylinders and under the action of gravity, our results reveal that δ ˜ St, where δ is the particle capture efficiency, and St is the Stokes number. In the absence of gravity, we observe a typical second order transition between non-trapping and trapping of particles that can be expressed as δ ˜ ( St - St c ) α , with an exponent α ≈ 0.5, where St c is the critical Stokes number. We also perform simulations for flow through a random porous structure and confirm that its capture behavior is consistent with the simple periodic model.
Tritium transport in lithium ceramics porous media
NASA Astrophysics Data System (ADS)
Tam, S. W.; Ambrose, V.
1992-09-01
A random network model has been utilized to analyze the problem of tritium percolation through porous Li ceramic breeders. Local transport in each pore channel is described by a set of convection-diffusion reaction equations. Long range transport is described by a matrix technique. The heterogeneous structure of the porous medium is accounted for via Monte Carlo methods. The model was then applied to an analysis of the approach to steady state tritium release from solid breeders. Diffusion was found to be the dominant transport process. The time constant for the approach to steady state was found to obey a scaling law with respect to the size L of the network. This scaling law was found to closely approximate the scaling law obeyed by conventional diffusion process in a completely homogeneous medium.
Porous media for catalytic renewable energy conversion
NASA Astrophysics Data System (ADS)
Hotz, Nico
2012-05-01
A novel flow-based method is presented to place catalytic nanoparticles into a reactor by sol-gelation of a porous ceramic consisting of copper-based nanoparticles, silica sand, ceramic binder, and a gelation agent. This method allows for the placement of a liquid precursor containing the catalyst into the final reactor geometry without the need of impregnating or coating of a substrate with the catalytic material. The so generated foam-like porous ceramic shows properties highly appropriate for use as catalytic reactor material, e.g., reasonable pressure drop due to its porosity, high thermal and catalytic stability, and excellent catalytic behavior. The catalytic activity of micro-reactors containing this foam-like ceramic is tested in terms of their ability to convert alcoholic biofuel (e.g. methanol) to a hydrogen-rich gas mixture with low concentrations of carbon monoxide (up to 75% hydrogen content and less than 0.2% CO, for the case of methanol). This gas mixture is subsequently used in a low-temperature fuel cell, converting the hydrogen directly to electricity. A low concentration of CO is crucial to avoid poisoning of the fuel cell catalyst. Since conventional Polymer Electrolyte Membrane (PEM) fuel cells require CO concentrations far below 100 ppm and since most methods to reduce the mole fraction of CO (such as Preferential Oxidation or PROX) have CO conversions of up to 99%, the alcohol fuel reformer has to achieve initial CO mole fractions significantly below 1%. The catalyst and the porous ceramic reactor of the present study can successfully fulfill this requirement.
Diffusion of Bacterial Cells in Porous Media
Licata, Nicholas A.; Mohari, Bitan; Fuqua, Clay; Setayeshgar, Sima
2016-01-01
The chemotaxis signal transduction network regulates the biased random walk of many bacteria in favorable directions and away from harmful ones through modulating the frequency of directional reorientations. In mutants of diverse bacteria lacking the chemotaxis response, migration in classic motility agar, which constitutes a fluid-filled porous medium, is compromised; straight-swimming cells unable to tumble become trapped within the agar matrix. Spontaneous mutations that restore spreading have been previously observed in the enteric bacterium Escherichia coli, and recent work in other bacterial species has isolated and quantified different classes of nonchemotacting mutants exhibiting the same spreading phenotype. We present a theoretical description of bacterial diffusion in a porous medium—the natural habitat for many cell types—which elucidates how diverse modifications of the motility apparatus resulting in a nonzero tumbling frequency allows for unjamming of otherwise straight-swimming cells at internal boundaries and leads to net migration. A unique result of our analysis is increasing diffusive spread with increasing tumbling frequency in the small pore limit, consistent with earlier experimental observations but not captured by previous models. Our theoretical results, combined with a simple model of bacterial diffusion and growth in agar, are compared with our experimental measurements of swim ring expansion as a function of time, demonstrating good quantitative agreement. Our results suggest that the details of the cellular tumbling process may be adapted to enable bacteria to propagate efficiently through complex environments. For engineered, self-propelled microswimmers that navigate via alternating straight runs and changes in direction, these results suggest an optimal reorientation strategy for efficient migration in a porous environment with a given microarchitecture. PMID:26745427
Heat and mass transfer in unsaturated porous media. Final report
Childs, S.W.; Malstaff, G.
1982-02-01
A preliminary study of heat and water transport in unsaturated porous media is reported. The project provides background information regarding the feasibility of seasonal thermal energy storage in unconfined aquifers. A parametric analysis of the factors of importance, and an annotated bibliography of research findings pertinent to unconfined aquifer thermal energy storage (ATES) are presented. This analysis shows that heat and mass transfer of water vapor assume dominant importance in unsaturated porous media at elevated temperature. Although water vapor fluxes are seldom as large as saturated medium liquid water fluxes, they are important under unsaturated conditions. The major heat transport mechanism for unsaturated porous media at temperatures from 50 to 90/sup 0/C is latent heat flux. The mechanism is nonexistent under saturated conditions but may well control design of unconfined aquifer storage systems. The parametric analysis treats detailed physical phenomena which occur in the flow systems study and demonstrates the temperature and moisture dependence of the transport coefficients of importance. The question of design of an unconfined ATES site is also addressed by considering the effects of aquifer temperature, depth to water table, porous medium flow properties, and surface boundary conditions. Recommendations are made for continuation of this project in its second phase. Both scientific and engineering goals are considered and alternatives are presented.
Seismic wave propagation in cracked porous media
NASA Astrophysics Data System (ADS)
Pointer, Tim; Liu, Enru; Hudson, John A.
2000-07-01
The movement of interstitial fluids within a cracked solid can have a significant effect on the properties of seismic waves of long wavelength propagating through the solid. We consider three distinct mechanisms of wave-induced fluid flow: flow through connections between cracks in an otherwise non-porous material, fluid movement within partially saturated cracks, and diffusion from the cracks into a porous matrix material. In each case the cracks may be aligned or randomly oriented, leading, respectively, to anisotropic or isotropic wave speeds and attenuation factors. In general, seismic velocities exhibit behaviour that is intermediate between that of empty cracks and that of isolated liquid-filled cracks if fluid flow is significant. In the range of frequencies for which considerable fluid flow occurs there is high attenuation and dispersion of seismic waves. Fluid flow may be on either a wavelength scale or a local scale depending on the model and whether the cracks are aligned or randomly oriented, resulting in completely different effects on seismic wave propagation. A numerical analysis shows that all models can have an effect over the exploration seismic frequency range.
Statistical mechanics of unsaturated porous media
NASA Astrophysics Data System (ADS)
Xu, Jin; Louge, Michel Y.
2015-12-01
We explore a mean-field theory of fluid imbibition and drainage through permeable porous solids. In the limit of vanishing inertial and viscous forces, the theory predicts the hysteretic "retention curves" relating the capillary pressure applied across a connected domain to its degree of saturation in wetting fluid in terms of known surface energies and void space geometry. To avoid complicated calculations, we adopt the simplest statistical mechanics, in which a pore interacts with its neighbors through narrow openings called "necks," while being either full or empty of wetting fluid. We show how the main retention curves can be calculated from the statistical distribution of two dimensionless parameters λ and α measuring the specific areas of, respectively, neck cross section and wettable pore surface relative to pore volume. The theory attributes hysteresis of these curves to collective first-order phase transitions. We illustrate predictions with a porous domain consisting of a random packing of spheres, show that hysteresis strength grows with λ and weakens as the distribution of α broadens, and reproduce the behavior of Haines jumps observed in recent experiments on an ordered pore network.
NASA Astrophysics Data System (ADS)
Gao, Mingliang; Teng, Qizhi; He, Xiaohai; Zuo, Chen; Li, ZhengJi
2016-01-01
Three-dimensional (3D) structures are useful for studying the spatial structures and physical properties of porous media. A 3D structure can be reconstructed from a single two-dimensional (2D) training image (TI) by using mathematical modeling methods. Among many reconstruction algorithms, an optimal-based algorithm was developed and has strong stability. However, this type of algorithm generally uses an autocorrelation function (which is unable to accurately describe the morphological features of porous media) as its objective function. This has negatively affected further research on porous media. To accurately reconstruct 3D porous media, a pattern density function is proposed in this paper, which is based on a random variable employed to characterize image patterns. In addition, the paper proposes an original optimal-based algorithm called the pattern density function simulation; this algorithm uses a pattern density function as its objective function, and adopts a multiple-grid system. Meanwhile, to address the key point of algorithm reconstruction speed, we propose the use of neighborhood statistics, the adjacent grid and reversed phase method, and a simplified temperature-controlled mechanism. The pattern density function is a high-order statistical function; thus, when all grids in the reconstruction results converge in the objective functions, the morphological features and statistical properties of the reconstruction results will be consistent with those of the TI. The experiments include 2D reconstruction using one artificial structure, and 3D reconstruction using battery materials and cores. Hierarchical simulated annealing and single normal equation simulation are employed as the comparison algorithms. The autocorrelation function, linear path function, and pore network model are used as the quantitative measures. Comprehensive tests show that 3D porous media can be reconstructed accurately from a single 2D training image by using the method proposed
Gao, Mingliang; Teng, Qizhi; He, Xiaohai; Zuo, Chen; Li, ZhengJi
2016-01-01
Three-dimensional (3D) structures are useful for studying the spatial structures and physical properties of porous media. A 3D structure can be reconstructed from a single two-dimensional (2D) training image (TI) by using mathematical modeling methods. Among many reconstruction algorithms, an optimal-based algorithm was developed and has strong stability. However, this type of algorithm generally uses an autocorrelation function (which is unable to accurately describe the morphological features of porous media) as its objective function. This has negatively affected further research on porous media. To accurately reconstruct 3D porous media, a pattern density function is proposed in this paper, which is based on a random variable employed to characterize image patterns. In addition, the paper proposes an original optimal-based algorithm called the pattern density function simulation; this algorithm uses a pattern density function as its objective function, and adopts a multiple-grid system. Meanwhile, to address the key point of algorithm reconstruction speed, we propose the use of neighborhood statistics, the adjacent grid and reversed phase method, and a simplified temperature-controlled mechanism. The pattern density function is a high-order statistical function; thus, when all grids in the reconstruction results converge in the objective functions, the morphological features and statistical properties of the reconstruction results will be consistent with those of the TI. The experiments include 2D reconstruction using one artificial structure, and 3D reconstruction using battery materials and cores. Hierarchical simulated annealing and single normal equation simulation are employed as the comparison algorithms. The autocorrelation function, linear path function, and pore network model are used as the quantitative measures. Comprehensive tests show that 3D porous media can be reconstructed accurately from a single 2D training image by using the method proposed
Curating Media Learning: Towards a Porous Expertise
ERIC Educational Resources Information Center
McDougall, Julian; Potter, John
2015-01-01
This article combines research results from a range of projects with two consistent themes. Firstly, we explore the potential for curation to offer a productive metaphor for the convergence of digital media learning across and between home/lifeworld and formal educational/system-world spaces--or between the public and private spheres. Secondly, we…
Slip effects associated with Knudsen transport phenomena in porous media
NASA Technical Reports Server (NTRS)
Frederking, T. H. K.; Hepler, W. A.; Khandhar, P. K.
1988-01-01
Porous media used in phase separators and thermomechanical pumps have been the subject of characterization efforts based on the Darcy permeability of laminar continuum flow. The latter is not always observed at low speed, in particular at permeabilities below 10 to the -9th/squared cm. The present experimental and theoretical studies address questions of slip effects associated with long mean free paths of gas flow at room temperature. Data obtained are in good agreement, within data uncertainty, with a simplified asymptotic Knudsen equation proposed for porous plugs on the basis of Knudsen's classical flow equation for long mean free paths.
NASA Astrophysics Data System (ADS)
Jourabian, Mahmoud; Farhadi, Mousa; Rabienataj Darzi, Ahmad Ali
2016-12-01
In this study, the melting process of ice as a phase-change material (PCM) saturated with a nickel-steel porous matrix inside a horizontal elliptical tube is investigated. Due to the low thermal conductivity of the PCM, it is motivated to augment the heat transfer performance of the system simultaneously by finding an optimum value of the aspect ratio and impregnating a metallic porous matrix into the base PCM. The lattice Boltzmann method with a double distribution function formulated based on the enthalpy method, is applied at the representative elementary volume scale under the local thermal equilibrium assumption between the PCM and porous matrix in the composite. While reducing or increasing the aspect ratio of the circular tubes leads to the expedited melting, the 90° inclination of each elliptical tube in the case of the pure PCM melting does not affect the melting rate. With the reduction in the porosity, the effective thermal conductivity and melting rate in all tubes promoted. Although the natural convection is fully suppressed due to the significant flow blockage in the porous structure, the melting rates are generally increased in all cases.
An efficient numerical model for hydrodynamic parameterization in 2D fractured dual-porosity media
NASA Astrophysics Data System (ADS)
Fahs, Hassane; Hayek, Mohamed; Fahs, Marwan; Younes, Anis
2014-01-01
This paper presents a robust and efficient numerical model for the parameterization of the hydrodynamic in fractured porous media. The developed model is based upon the refinement indicators algorithm for adaptive multi-scale parameterization. For each level of refinement, the Levenberg-Marquardt method is used to minimize the difference between the measured and predicted data that are obtained by solving the direct problem with the mixed finite element method. Sensitivities of state variables with respect to the parameters are calculated by the sensitivity method. The adjoint-state method is used to calculate the local gradients of the objective function necessary for the computation of the refinement indicators. Validity and efficiency of the proposed model are demonstrated by means of several numerical experiments. The developed numerical model provides encouraging results, even for noisy data and/or with a reduced number of measured heads.
Lattice Boltzmann simulations of convection heat transfer in porous media
NASA Astrophysics Data System (ADS)
Liu, Qing; He, Ya-Ling
2017-01-01
A non-orthogonal multiple-relaxation-time (MRT) lattice Boltzmann (LB) method is developed to study convection heat transfer in porous media at the representative elementary volume scale based on the generalized non-Darcy model. In the method, two different LB models are constructed: one is constructed in the framework of the double-distribution-function approach, and the other is constructed in the framework of the hybrid approach. In particular, the transformation matrices used in the MRT-LB models are non-orthogonal matrices. The present method is applied to study mixed convection flow in a porous channel and natural convection flow in a porous cavity. It is found that the numerical results are in good agreement with the analytical solutions and/or other results reported in previous studies. Furthermore, the non-orthogonal MRT-LB method shows better numerical stability in comparison with the BGK-LB method.
Horizontal flow and capillarity-driven redistribution in porous media.
Doster, F; Hönig, O; Hilfer, R
2012-07-01
A recent macroscopic mixture theory for two-phase immiscible displacement in porous media has introduced percolating and nonpercolating phases. Quasi-analytic solutions are computed and compared to the traditional theory. The solutions illustrate physical insights and effects due to spatiotemporal changes of nonpercolating phases, and they highlight the differences from traditional theory. Two initial and boundary value problems are solved in one spatial dimension. In the first problem a fluid is displaced by another fluid in a horizontal homogeneous porous medium. The displacing fluid is injected with a flow rate that keeps the saturation constant at the injection point. In the second problem a horizontal homogeneous porous medium is considered which is divided into two subdomains with different but constant initial saturations. Capillary forces lead to a redistribution of the fluids. Errors in the literature are reported and corrected.
Effects of capillarity on microscopic flow in porous media
Miksis, M.J.
1993-01-01
Central theme of this proposal is to study effects of capillarity on motion of a fluid interface and to apply these results to flow in porous media. Here we report on several problems considered this year, the second year of the grant. In particular we have developed a numerical code to study the dynamics of a gas bubble in a pore in order to examine the fundamental mechanism for the generation of a foam in a porous material, we have started an investigation of the stability of a foam lamella in order to understand the stability of foam flow in a porous material and we have derived systematically a slip coefficient for flow over a rough surface, e.g., as in a pore. In addition we report on work on several other problems.
Deposition in two phase flow in porous media
NASA Astrophysics Data System (ADS)
Adler, P. M.
2007-12-01
The study of dispersion and deposition of an active tracer in multiphase flow through a porous medium is a difficult topic which has not received much attention in the past though it has a lot of practical and fundamental interest. For instance, asphaltene flocculation implies its deposition on the solid walls and this has two effects. The first one is to change the wettability of the walls; if they are initially water wet, they may become oil wet. The second one is to reduce the pore space. In both cases, the flow properties of the porous medium are expected to be influenced. Our purpose was to develop a new tool to analyse these two effects; this new tool had to be constructed by integrating existing codes. First, the basic ingredients which are necessary for the determination of dispersion and deposition at the local scale are presented. The pore space can be generated by means of the method of reconstructed media (1). The instantaneous phase distribution and the velocity fields are computed by an Immiscible Lattice Boltzmann model (2). The solute dispersion is obtained by the Random Walk technique (3); its deposition at the walls is supposed to follow a first order reaction (4). Finally, the rules for the solid and/or wettability changes will be precised. The main results of our calculations can be summarized as follows. The possibilities of the code are demonstrated on a three-dimensional medium; the evolution of the solid space, of the wettability properties and of the phase configurations are illustrated; dramatic results are shown for the evolution of the relative permeabilities and of the capillary pressures. Then, various parameters are studied in a systematic way, such as the porosity, the partition coefficient, the diffusion coefficient, the saturation and the kinetic coefficients. Some concluding remarks end up this study. Ref: (1) Adler P.M., Jacquin C.G., Quibier J.A., 1990, Flow in simulated porous media, Int. J. Multiphase flow, 16, 691- 712. (2
On growth and flow: bacterial biofilms in porous media
NASA Astrophysics Data System (ADS)
Durham, William; Leombruni, Alberto; Tranzer, Olivier; Stocker, Roman
2011-11-01
Bacterial biofilms often occur in porous media, where they play pivotal roles in medicine, industry and the environment. Though flow is ubiquitous in porous media, its effects on biofilm growth have been largely ignored. Using patterned microfluidic devices that simulate unconsolidated soil, we find that the structure of Escherichia coli biofilms undergoes a self-organization mediated by the interaction of growth and flow. Intriguingly, we find that biofilm productivity peaks at intermediate flow rates, when the biofilm is irrigated by a minimum number of preferential flow channels. At larger and smaller flow rates, fluid flows more uniformly through the matrix, but productivity drops due to removal by shear and reduced nutrient transport, respectively. These dynamics are correctly predicted by a simple network model. The observed tradeoff between growth and flow may have important consequences on biofilm-mediated processes such as biochemical cycling, antibiotic resistance and water filtration.
Dissipative particle dynamics model for colloid transport in porous media
Pan, W.; Tartakovsky, A. M.
2013-08-01
We present that the transport of colloidal particles in porous media can be effectively modeled with a new formulation of dissipative particle dynamics, which augments standard DPD with non-central dissipative shear forces between particles while preserving angular momentum. Our previous studies have demonstrated that the new formulation is able to capture accurately the drag forces as well as the drag torques on colloidal particles that result from the hydrodynamic retardation effect. In the present work, we use the new formulation to study the contact efficiency in colloid filtration in saturated porous media. Note that the present model include all transport mechanisms simultaneously, including gravitational sedimentation, interception and Brownian diffusion. Our results of contact efficiency show a good agreement with the predictions of the correlation equation proposed by Tufenkji and EliMelech, which also incorporate all transport mechanisms simultaneously without the additivity assumption.
Analytic studies of colloid transport in fractured porous media
Hwang, Y.; Chambre, P.L.; Lee, W.W.L.; Pigford, T.H.
1989-11-01
We analyze the interactive migration of radioactive colloids and solute in fractured rock. Two possible interactions between radionuclides as colloids and as solute are considered: solute sorption on nonradioactive colloids to form pseudocolloids, and dissolution of radioactive colloids. Previous studies have discussed the formation and transport of colloids in porous media, including removal of colloids by filtration and sedimentation. Colloids can migrate faster than solute because of weaker sorption on stationary solids and because of hydrochromatography of colloid particles in flow channels. However, the migration of colloids and pseudocolloids can be retarded by the interaction of colloids with solute, and the migration of solute in local equilibrium with colloids can be more rapid than if colloids were not present. Here we present a new quantative analysis to predict the interactive migration of colloids and solute in porous and fractured media. 4 figs.
Dynamic patterns of compaction in brittle porous media
NASA Astrophysics Data System (ADS)
Guillard, François; Golshan, Pouya; Shen, Luming; Valdes, Julio R.; Einav, Itai
2015-10-01
Brittle porous media exhibit a variety of irreversible patterns during densification, including stationary and moving compaction bands in rocks, foams, cereal packs and snow. We have recently found moving compaction bands in cereal packs; similar bands have been detected in snow. However, the question of generality remains: under what conditions can brittle porous media disclose other densification patterns? Here, using a new heuristic lattice spring model undergoing repeated crushing events, we first predict the possible emergence of new types of dynamic compaction; we then discover and confirm these new patterns experimentally in compressed cereal packs. In total, we distinguish three observed compaction patterns: short-lived erratic compaction bands, multiple oscillatory propagating compaction bands reminiscent of critical phenomena near phase transitions, and diffused irreversible densification. The manifestation of these three different patterns is mapped in a phase diagram using two dimensionless groups that represent fabric collapse and external dissipation.
Modeling Transverse Chemotaxis in Porous Media
NASA Astrophysics Data System (ADS)
Porter, M. L.; Valdés-Parada, F. J.; Wood, B. D.
2009-12-01
The movement of microorganisms toward a chemical attractant (chemotaxis) has been shown to aid in subsurface contaminant degradation and enhanced oil recovery. However, chemotaxis is inherently a pore scale process that must be upscaled to arrive at continuum scale models for field applications. In this work, the method of volume averaging is used to upscale the microscale chemotactic microbial transport equations in order to obtain the corresponding macroscale models for the mass balance of bacteria and the chemical attractant to which they respond. As a first approach, cellular growth/death and consumption of the attractant by chemical reaction are assumed to be negligible with respect to convective and diffusive transport mechanisms. Two effective medium coefficients are introduced in the model, namely a total motility tensor and a total velocity vector. Under certain conditions, it is shown that the coefficients can differ considerably from the values corresponding to non-chemotactic transport. The model is validated by comparing the predicted transverse motility coefficients and concentration profiles to those measured within an engineered porous medium. For the concentration profiles, we introduced a lag that accounts for the difference between the arrival time of the microorganisms and the their chemotactic response to the attractant.
Upscaling microbial chemotaxis in porous media
NASA Astrophysics Data System (ADS)
Valdés-Parada, Francisco J.; Porter, Mark L.; Narayanaswamy, Karthik; Ford, Roseanne M.; Wood, Brian D.
2009-09-01
Biodegradation is an important mechanism for contaminant reduction in groundwater environments; in fact, in situ bioremediation and bioaugmentation methods represent alternatives to traditional methods such as pump-and-treat. Microbial chemotaxis has been shown to significantly increase contaminant degradation in subsurface environments. In this work, the method of volume averaging is used to upscale the microscale chemotactic microbial transport equations in order to obtain the corresponding effective medium models for the mass balance of bacteria and the chemical attractant to which they respond. As a first approach, cellular growth/death and consumption of the attractant by chemical reaction are assumed to be negligible with respect to convective and diffusive transport mechanisms. For microorganisms, two effective coefficients are introduced, namely a total motility tensor and a total velocity vector. Our results show that, under certain conditions, these coefficients can differ considerably from the values corresponding to non-chemotactic transport. These transport coefficients show strong dependence of the microstructure of the porous medium, the fluid flow fields and the distribution of the attractant.
Electrokinetic coupling in unsaturated porous media
Revil, A.; Linde, N.; Cerepi, A.; Jougnot, D.; Matthai, S.; Finsterle, S.
2007-02-27
We consider a charged porous material that is saturated bytwo fluid phases that are immiscible and continuous on the scale of arepresentative elementary volume. The wetting phase for the grains iswater and the nonwetting phase is assumed to be an electricallyinsulating viscous fluid. We use a volume-averaging approach to derivethe linear constitutive equations for the electrical current density aswell as the seepage velocities of the wetting and nonwetting phases onthe scale of a representative elementary volume. These macroscopicconstitutive equations are obtained by volume-averaging Ampere's lawtogether with the Nernst Planck equation and the Stokes equations. Thematerial properties entering the macroscopic constitutive equations areexplicitly described as functions of the saturation of the water phase,the electrical formation factor, and parameters that describe thecapillary pressure function, the relative permeability function, and thevariation of electrical conductivity with saturation. New equations arederived for the streaming potential and electro-osmosis couplingcoefficients. A primary drainage and imbibition experiment is simulatednumerically to demonstrate that the relative streaming potential couplingcoefficient depends not only on the water saturation, but also on thematerial properties of the sample, as well as the saturation history. Wealso compare the predicted streaming potential coupling coefficients withexperimental data from four dolomite core samples. Measurements on thesesamples include electrical conductivity, capillary pressure, thestreaming potential coupling coefficient at various level of saturation,and the permeability at saturation of the rock samples. We found verygood agreement between these experimental data and the modelpredictions.
The Interfaces of One-Dimensional Flows in Porous Media.
1983-07-01
MRC-TSR-2538 DAAG2N-80-C-0041 UNCLASSIFIED FIG 12/1 N lm . 1.25 1.4 16 MICROCOY RESOLUTION TEST CHART sNarOAI.I U(’ OV $t MOAAI9 - -A A1 NRC Technical...Words: flows in porous media, interfaces, blow-up time, waiting time, asymptotic behaviour Work Unit Number 1 (Applied Analysis) D1 )iv. Matematicas
Point-to-point connectivity prediction in porous media using percolation theory
NASA Astrophysics Data System (ADS)
Tavagh-Mohammadi, Behnam; Masihi, Mohsen; Ganjeh-Ghazvini, Mostafa
2016-10-01
The connectivity between two points in porous media is important for evaluating hydrocarbon recovery in underground reservoirs or toxic migration in waste disposal. For example, the connectivity between a producer and an injector in a hydrocarbon reservoir impact the fluid dispersion throughout the system. The conventional approach, flow simulation, is computationally very expensive and time consuming. Alternative method employs percolation theory. Classical percolation approach investigates the connectivity between two lines (representing the wells) in 2D cross sectional models whereas we look for the connectivity between two points (representing the wells) in 2D aerial models. In this study, site percolation is used to determine the fraction of permeable regions connected between two cells at various occupancy probabilities and system sizes. The master curves of mean connectivity and its uncertainty are then generated by finite size scaling. The results help to predict well-to-well connectivity without need to any further simulation.
Dendrite Suppression by Shock Electrodeposition in Charged Porous Media
Han, Ji-Hyung; Wang, Miao; Bai, Peng; Brushett, Fikile R.; Bazant, Martin Z.
2016-01-01
It is shown that surface conduction can stabilize electrodeposition in random, charged porous media at high rates, above the diffusion-limited current. After linear sweep voltammetry and impedance spectroscopy, copper electrodeposits are visualized by scanning electron microscopy and energy dispersive spectroscopy in two different porous separators (cellulose nitrate, polyethylene), whose surfaces are modified by layer-by-layer deposition of positive or negative charged polyelectrolytes. Above the limiting current, surface conduction inhibits growth in the positive separators and produces irregular dendrites, while it enhances growth and suppresses dendrites behind a deionization shock in the negative separators, also leading to improved cycle life. The discovery of stable uniform growth in the random media differs from the non-uniform growth observed in parallel nanopores and cannot be explained by classic quasi-steady “leaky membrane” models, which always predict instability and dendritic growth. Instead, the experimental results suggest that transient electro-diffusion in random porous media imparts the stability of a deionization shock to the growing metal interface behind it. Shock electrodeposition could be exploited to enhance the cycle life and recharging rate of metal batteries or to accelerate the fabrication of metal matrix composite coatings. PMID:27307136
Mechanisms of anomalous dispersion in flow through heterogeneous porous media
NASA Astrophysics Data System (ADS)
Tyukhova, Alina; Dentz, Marco; Kinzelbach, Wolfgang; Willmann, Matthias
2016-11-01
We study the origins of anomalous dispersion in heterogeneous porous media in terms of the medium and flow properties. To identify and quantify the heterogeneity controls, we focus on porous media which are organized in assemblies of equally sized conductive inclusions embedded in a constant conductivity matrix. We study the behavior of particle arrival times for different conductivity distributions and link the statistical medium characteristics to large-scale transport using a continuous time random walk (CTRW) approach. The CTRW models particle motion as a sequence of transitions in space and time. We derive an explicit map of the conductivity onto the transition time distribution. The derived CTRW model predicts solute transport based on the conductivity distribution and the characteristic heterogeneity length. In this way, heavy tails in solute arrival times and anomalous particle dispersion as measured by the centered mean square displacement are directly related to the medium properties. These findings shed light on the mechanisms of anomalous dispersion in heterogeneous porous media, and provide a basis for the predictive modeling of large-scale transport.
Laboratory experiments with heterogeneous reactions in mixed porous media
Burris, D.R.; Hatfield, K.; Wolfe, N.L.
1996-08-01
The limited success and high cost of traditional active ground-water-contaminant plume management efforts (i.e., pump-and-treat systems) has stimulated a search for less expensive passive plume interception and in-situ treatment technologies. The funnel/gate system, which uses heterogeneous (surface-mediated) reactions on porous media to degrade dissolved contaminants, is one passive technology under consideration. Research on a heterogeneous reaction is presented in this paper, which can be extended to facilitate the design of engineered porous media systems (i.e., funnel/gates). Results are examined from batch and flow-through column experiments involving nitrobenzene degradation in a surface-mediated reaction with granular metallic iron. A nonequilibrium transport model that incorporates solute mass-transfer resistance near reactive iron surfaces is shown to simulate breakthrough curves (BTCs) from column systems, using model parameters estimated from batch systems. The investigation shows pseudo first-order degradation-rate coefficients increasing with higher solid:liquid ratios and with greater iron concentrations. In addition, nitrobenzene degradation is found to be faster in batch systems than in comparable column systems, indicating the presence of mass-transfer limitations in the flow-through systems. Finally, the present study provides insights on conditions pertinent to the design of engineered in-situ treatment zones, such as how mass-transfer, hydraulic, and reaction kinetic conditions affect ground-water-contaminant fate and transport through reactive porous media.
Dendrite Suppression by Shock Electrodeposition in Charged Porous Media
NASA Astrophysics Data System (ADS)
Han, Ji-Hyung; Wang, Miao; Bai, Peng; Brushett, Fikile R.; Bazant, Martin Z.
2016-06-01
It is shown that surface conduction can stabilize electrodeposition in random, charged porous media at high rates, above the diffusion-limited current. After linear sweep voltammetry and impedance spectroscopy, copper electrodeposits are visualized by scanning electron microscopy and energy dispersive spectroscopy in two different porous separators (cellulose nitrate, polyethylene), whose surfaces are modified by layer-by-layer deposition of positive or negative charged polyelectrolytes. Above the limiting current, surface conduction inhibits growth in the positive separators and produces irregular dendrites, while it enhances growth and suppresses dendrites behind a deionization shock in the negative separators, also leading to improved cycle life. The discovery of stable uniform growth in the random media differs from the non-uniform growth observed in parallel nanopores and cannot be explained by classic quasi-steady “leaky membrane” models, which always predict instability and dendritic growth. Instead, the experimental results suggest that transient electro-diffusion in random porous media imparts the stability of a deionization shock to the growing metal interface behind it. Shock electrodeposition could be exploited to enhance the cycle life and recharging rate of metal batteries or to accelerate the fabrication of metal matrix composite coatings.
Non-Fickian mass transport in fractured porous media
NASA Astrophysics Data System (ADS)
Fomin, Sergei A.; Chugunov, Vladimir A.; Hashida, Toshiyuki
2011-02-01
The paper provides an introduction to fundamental concepts of mathematical modeling of mass transport in fractured porous heterogeneous rocks. Keeping aside many important factors that can affect mass transport in subsurface, our main concern is the multi-scale character of the rock formation, which is constituted by porous domains dissected by the network of fractures. Taking into account the well-documented fact that porous rocks can be considered as a fractal medium and assuming that sizes of pores vary significantly (i.e. have different characteristic scales), the fractional-order differential equations that model the anomalous diffusive mass transport in such type of domains are derived and justified analytically. Analytical solutions of some particular problems of anomalous diffusion in the fractal media of various geometries are obtained. Extending this approach to more complex situation when diffusion is accompanied by advection, solute transport in a fractured porous medium is modeled by the advection-dispersion equation with fractional time derivative. In the case of confined fractured porous aquifer, accounting for anomalous non-Fickian diffusion in the surrounding rock mass, the adopted approach leads to introduction of an additional fractional time derivative in the equation for solute transport. The closed-form solutions for concentrations in the aquifer and surrounding rocks are obtained for the arbitrary time-dependent source of contamination located in the inlet of the aquifer. Based on these solutions, different regimes of contamination of the aquifers with different physical properties can be readily modeled and analyzed.
Modeling and Simulations of Particulate Flows through Functionalized Porous Media
NASA Astrophysics Data System (ADS)
Li, Chunhui; Dutta, Prashanta; Liu, Jin
2016-11-01
Transport of particulate fluid through a functionalized porous material is of significant interest in many industrial applications, such as earth sciences, battery designs and water/air purifications. The entire process is complex, which involves the convection of fluid, diffusion of reactants as well as reversible chemical reactions at the fluid-solid interface In this work we present a convection-diffusion-reaction model and simulate the transport of particulate fluid through a functionalized porous media. The porous structures are generated and manipulated through the quartet structure generation set method. The Navier-Stokes with convection-diffusion equations are solved using the lattice Boltzmann method. The chemical reactions at the interface are modeled by an absorption-desorption process and treated as the boundary conditions for above governing equations. Through our simulations we study the effects of porous structures, including porosity, pore orientation, and pore size as well as the kinetic rates of surface reactions on the overall performance of removal efficiency of the species from the solution. Our results show that whole process is highly affected by both the porous structures and absorption rate. The optimal parameters can be achieved by proper design. This work is supported by NSF Grants: CBET-1250107 and CBET -1604211.
Nonlinear Behavior Of Saturated Porous Media Under External Impact
NASA Astrophysics Data System (ADS)
Perepechko, Y.
2005-12-01
This paper deals with nonlinear behavior of liquid saturated porous media in gravity filed under external impact. The continuum is assumed to be a two-velocity medium; it consists of a deformable porous matrix (with Maxwell's reology) and a Newtonian liquid that saturates this matrix. The energy dissipation in this model takes place due the interface friction between the solid matrix and saturating liquid, and also through relaxation of inelastic shear stress in the porous matrix. The elaborated nonisothermal mathematical model for this kind of medium is a thermodynamically consistent and closed model. Godunov's explicit difference scheme was used for computer simulation; the method implies numerical simulation for discontinuity decay in flux calculations. As an illustrative example, we consider the formation of dissipation structures in a plain layer of that medium after pulse or periodic impact on the background of liquid filtration through the porous matrix. At the process beginning, one can observe elastic behavior of the porous matrix. Deformation spreading through the saturated porous matrix occurs almost without distortions and produces a channel-shaped zone of stretching with a high porosity. Later on, dissipation processes and reology properties of porous medium causes the diffusion of this channel. We also observe a correlation between the liquid distribution (porosity for the solid matrix) and dilatancy fields; this allows us to restore the dilatancy field from the measured fluid saturation of the medium. This work was supported by the RFBR (Grant No. 04-05-64107), the Presidium of SB RAS (Grant 106), the President's Grants (NSh-2118.2003.5, NSh-1573.2003.5).
Visual analysis of immiscible displacement processes in porous media under ultrasound effect
NASA Astrophysics Data System (ADS)
Naderi, Khosrow; Babadagli, Tayfun
2011-05-01
The effect of sonic waves, in particular, ultrasonic radiation, on immiscible displacement in porous media and enhanced oil recovery has been of interest for more than five decades. Attempts were made to investigate the effect through core scale experimental or theoretical models. Visual experiments are useful to scrutinize the reason for improved oil recovery under acoustic waves of different frequency but are not abundant in literature. In this paper, we report observations and analyses as to the effects of ultrasonic energy on immiscible displacement and interaction of the fluid matrix visually in porous media through two-dimensional (2D) sand pack experiments. 2D glass bead models with different wettabilities were saturated with different viscosity oils and water was injected into the models. The experiments were conducted with and without ultrasound. Dynamic water injection experiments were preferred as they had both viscous and capillary forces in effect. The displacement patterns were evaluated both in terms of their shape, size, and the interface characteristics quantitatively and qualitatively to account for the effects of ultrasonic waves on the displacement and the reason for increased oil production under this type of sonic wave. More compact clusters were observed when ultrasonic energy was present in water-wet systems. In the oil-wet cases, more oil was produced after breakthrough when ultrasound was applied and no compact clusters were formed in contrast to the water-wet cases.
Visual analysis of immiscible displacement processes in porous media under ultrasound effect.
Naderi, Khosrow; Babadagli, Tayfun
2011-05-01
The effect of sonic waves, in particular, ultrasonic radiation, on immiscible displacement in porous media and enhanced oil recovery has been of interest for more than five decades. Attempts were made to investigate the effect through core scale experimental or theoretical models. Visual experiments are useful to scrutinize the reason for improved oil recovery under acoustic waves of different frequency but are not abundant in literature. In this paper, we report observations and analyses as to the effects of ultrasonic energy on immiscible displacement and interaction of the fluid matrix visually in porous media through two-dimensional (2D) sand pack experiments. 2D glass bead models with different wettabilities were saturated with different viscosity oils and water was injected into the models. The experiments were conducted with and without ultrasound. Dynamic water injection experiments were preferred as they had both viscous and capillary forces in effect. The displacement patterns were evaluated both in terms of their shape, size, and the interface characteristics quantitatively and qualitatively to account for the effects of ultrasonic waves on the displacement and the reason for increased oil production under this type of sonic wave. More compact clusters were observed when ultrasonic energy was present in water-wet systems. In the oil-wet cases, more oil was produced after breakthrough when ultrasound was applied and no compact clusters were formed in contrast to the water-wet cases.
Hou, Yang; Wen, Zhenhai; Cui, Shumao; Guo, Xiaoru; Chen, Junhong
2013-11-20
A 2D porous graphitic C3 N4 nanosheets/nitrogen-doped graphene/layered MoS2 ternary nanojunction is synthesized using a simple pyrolysis process followed by a hydrothermal treatment. The 2D ternary nanojunction exhibits significantly enhanced photoelectrochemical and photocatalytic activities due to the large contact area, efficient light absorption, and rapid charge separation and transport.
Effects of surface active agents on DNAPL migration and distribution in saturated porous media.
Cheng, Zhou; Gao, Bin; Xu, Hongxia; Sun, Yuanyuan; Shi, Xiaoqing; Wu, Jichun
2016-11-15
Dissolved surface active agents such as surfactant and natural organic matter can affect the distribution and fate of dense nonaqueous liquids (DNAPLs) in soil and groundwater systems. This work investigated how two common groundwater surface active agents, humic acid (HA) and Tween 80, affected tetrachloroethylene (PCE) migration and source zone architecture in saturated porous media under environmentally relevant conditions. Batch experiments were first conducted to measure the contact angles and interfacial tensions (IFT) between PCE and quartz surface in water containing different amount of surface active agents. Results showed that the contact angle increased and IFT decreased with concentration of surface active agent increasing, and Tween 80 was much more effective than HA. Five 2-D flow cell experiments were then conducted. Correspondingly, Tween 80 showed strong effects on the migration and distribution of PCE in the porous media due to its ability to change the medium wettability from water-wet into intermediate/NAPL-wet. The downward migration velocities of the PCE in three Tween 80 cells were slower than those in the other two cells. In addition, the final saturation of the PCE in the cells containing surface active agents was higher than that in the water-only cell. Results from this work indicate that the presence of surface active agents in groundwater may strongly affect the fate and distribution of DNAPL through altering porous medium wettability.
Influence of biofilm accumulation on flow and reactive transport through porous media
NASA Astrophysics Data System (ADS)
Sharp, R.; Adgie, M.; Cunningham, A.
2003-04-01
A series of continuous flow, porous media reactor studies were performed to characterize the development of thick biofilms in porous media and the subsequent effects on flow and reactive transport. The bioluminescent organism Vibrio fischeri was used to produce various degrees of biofilm growth within the porous media system. V. fischeri biofilm growth, distribution, and activity in the porous media reactors was evaluated using bioluminescent imaging. Bulk fluid flow and flow channel dynamics in the porous media were monitored by imaging pulses of nigrosine bulk fluid dye. Hydrodynamics of the porous media/biofilm systems were analyzed using fluorescein break through curves and head loss across the system. Bioluminescent and bulk-fluid dye imaging, along with fluoroscein break through curve analysis, provided quantitative information on the transient distribution of biofilm within the reactor and the dynamic relationship between biofilm development and porous media hydraulics. Bioluminescent and bulk-fluid dye images showed continuous creation and closure of flow channels in the biofilm/porous media matrix. Flow channel size and distribution changed with increasing degrees of biofilm growth. Bioluminescence showed not only the density and distribution of biofilm growth in the porous media, but also the rate of oxygen uptake across the flow field. Results from the breakthrough curves suggest that thin biofilms transform the well-defined plug flow regime of clean porous media to a flow with severe axial and longitudinal dispersion. As the biofilm thickens, the flow regime is transformed to dispersed plug flow with an accelerated residence time. These studies provide a better quantitative understanding of the fundamental relationship between biofilm development and bulk fluid hydrodynamics in porous media. Results demonstrate the simultaneous visualization of biofilm growth and bulk fluid flow in porous media at the meso-scale. The studies also establish a novel
NASA Astrophysics Data System (ADS)
Turuban, R.; Jimenez-Martinez, J.; De Anna, P.; Tabuteau, H.; Meheust, Y.; Le Borgne, T.
2014-12-01
As dissolved chemical elements are transported in the subsurface, their mixing with other compounds and potential reactivity depends on the creation of local scale chemical gradients, which ultimately drive diffusive mass transfer and reaction. The distribution of concentration gradients is in turn shaped by the spatial gradients of flow velocity arising from the random distribution of solid grains. We present an experimental investigation of the relationship between the microscale flow stretching properties and the effective large scale mixing dynamics in porous media. We use a flow cell that models a horizontal quasi two-dimensional (2D) porous medium, the grains of which are cylinders randomly positioned between two glass plates [de Anna et al. 2013]. In this setup, we perform both non diffusive and diffusive transport tests, by injecting respectively microsphere solid tracers and a fluorescent dye. While the dye front propagates through the medium, it undergoes in time a kinematic stretching that is controlled by the flow heterogeneity, as it encounters stagnation zones and high velocity channels between the grains. The spatial distribution of the dye can then be described as a set of stretched lamellae whose rate of diffusive smoothing is locally enhanced by kinematic stretching [Le Borgne et al., 2013]. We show that this representation allows predicting the temporal evolution of the mixing rate and the probability distribution of concentration gradients for a range of Peclet numbers. This upscaling framework hence provides a quantification of the dynamics of effective mixing from the microscale Lagrangian velocity statistics. References:[1] P. de Anna, J. Jimenez-Martinez, H. Tabuteau, R. Turuban, T. Le Borgne, M. Derrien,and Yves Méheust, Mixing and reaction kinetics in porous media : an experimental pore scale quantification, Environ. Sci. Technol. 48, 508-516, 2014. [2] Le Borgne, T., M. Dentz, E. Villermaux, Stretching, coalescence and mixing in porous
Langevin model for reactive transport in porous media
NASA Astrophysics Data System (ADS)
Tartakovsky, Alexandre M.
2010-08-01
Existing continuum models for reactive transport in porous media tend to overestimate the extent of solute mixing and mixing-controlled reactions because the continuum models treat both the mechanical and diffusive mixings as an effective Fickian process. Recently, we have proposed a phenomenological Langevin model for flow and transport in porous media [A. M. Tartakovsky, D. M. Tartakovsky, and P. Meakin, Phys. Rev. Lett. 101, 044502 (2008)10.1103/PhysRevLett.101.044502]. In the Langevin model, the fluid flow in a porous continuum is governed by a combination of a Langevin equation and a continuity equation. Pore-scale velocity fluctuations, the source of mechanical dispersion, are represented by the white noise. The advective velocity (the solution of the Langevin flow equation) causes the mechanical dispersion of a solute. Molecular diffusion and sub-pore-scale Taylor-type dispersion are modeled by an effective stochastic advection-diffusion equation. Here, we propose a method for parameterization of the model for a synthetic porous medium, and we use the model to simulate multicomponent reactive transport in the porous medium. The detailed comparison of the results of the Langevin model with pore-scale and continuum (Darcy) simulations shows that: (1) for a wide range of Peclet numbers the Langevin model predicts the mass of reaction product more accurately than the Darcy model; (2) for small Peclet numbers predictions of both the Langevin and the Darcy models agree well with a prediction of the pore-scale model; and (3) the accuracy of the Langevin and Darcy model deteriorates with the increasing Peclet number but the accuracy of the Langevin model decreases more slowly than the accuracy of the Darcy model. These results show that the separate treatment of advective and diffusive mixing in the stochastic transport model is more accurate than the classical advection-dispersion theory, which uses a single effective diffusion coefficient (the dispersion
Time-resolved diffusion tomographic 2D and 3D imaging in highly scattering turbid media
NASA Technical Reports Server (NTRS)
Alfano, Robert R. (Inventor); Cai, Wei (Inventor); Liu, Feng (Inventor); Lax, Melvin (Inventor); Das, Bidyut B. (Inventor)
1999-01-01
A method for imaging objects in highly scattering turbid media. According to one embodiment of the invention, the method involves using a plurality of intersecting source/detectors sets and time-resolving equipment to generate a plurality of time-resolved intensity curves for the diffusive component of light emergent from the medium. For each of the curves, the intensities at a plurality of times are then inputted into the following inverse reconstruction algorithm to form an image of the medium: ##EQU1## wherein W is a matrix relating output at source and detector positions r.sub.s and r.sub.d, at time t, to position r, .LAMBDA. is a regularization matrix, chosen for convenience to be diagonal, but selected in a way related to the ratio of the noise,
Time-resolved diffusion tomographic 2D and 3D imaging in highly scattering turbid media
NASA Technical Reports Server (NTRS)
Alfano, Robert R. (Inventor); Cai, Wei (Inventor); Gayen, Swapan K. (Inventor)
2000-01-01
A method for imaging objects in highly scattering turbid media. According to one embodiment of the invention, the method involves using a plurality of intersecting source/detectors sets and time-resolving equipment to generate a plurality of time-resolved intensity curves for the diffusive component of light emergent from the medium. For each of the curves, the intensities at a plurality of times are then inputted into the following inverse reconstruction algorithm to form an image of the medium: wherein W is a matrix relating output at source and detector positions r.sub.s and r.sub.d, at time t, to position r, .LAMBDA. is a regularization matrix, chosen for convenience to be diagonal, but selected in a way related to the ratio of the noise,
Mathematical modeling of fines migration and clogging in porous media
NASA Astrophysics Data System (ADS)
Kampel, Guido
2007-05-01
A porous medium is a material that contains regions filled with fluid embedded in a solid matrix. These fluid filled regions are called pores or voids. Suspensions are fluids with small particles called fines. As a suspension flows through a porous material, some fines are trapped within the material while others that were trapped may be released. Filters are an example of porous media. We model filters as networks of channels. As a suspension flows across the filter, particles clog channels. We assume that there is no flow through clogged channels. In the first part of this thesis, we compute a sharp upper bound on the number of channels that can clog before fluid can no longer flow through the filter. Soil mass is another example of porous media. Fluid in porous media flows through tortuous paths. This tortuosity and inertial effects cause fines to collide with pore walls. After each collision, a particle looses momentum and needs to be accelerated again by hydrodynamic forces. As a result, the average velocity of fines is smaller than that of the fluid. This retardation of the fines with respect to the fluid may lead to an increase of the concentration of fines in certain regions which may eventually result in the plugging of the porous medium. This effect is of importance in flows near wells where the flow has circular symmetry and thus, it is not macroscopically homogeneous. In the second part of this thesis we develop and analyze a mathematical model to study the physical effect described above. In the third and last part of this thesis we study particle migration and clogging as suspension flows through filters by means of numerical simulations and elementary analysis. We model filters as networks of channels. Each channel is either open or clogged. There is no flow through clogged channels. Each particle and each channel is assigned a width. Particles flow with the fluid while inside a wider channel. When reaching an intersection of channels, a particle
Lattice Boltzmann simulation of chemical dissolution in porous media.
Kang, Qinjun; Zhang, Dongxiao; Chen, Shiyi; He, Xiaoyi
2002-03-01
In this paper, we develop a lattice Boltzmann model for simulating the transport and reaction of fluids in porous media. To simulate such a system, we account for the interaction of forced convection, molecular diffusion, and surface reaction. The problem is complicated by the evolution of the porous media geometry due to chemical reactions, which may significantly and continuously modify the hydrologic properties of the media. The particular application that motivates the present study is acid stimulation, a common technique used to increase production from petroleum reservoirs. This technique involves the injection of acid (e.g., hydrochloric acid, HCl, acetic acid, HAc) into the formation to dissolve minerals comprising the rock. As acid is injected, highly conductive channels or "wormholes" may be formed. The dissolution of carbonate rocks in 0.5M HCl and 0.5M HAc is simulated with the lattice Boltzmann model developed in this study. The dependence of dissolution process and the geometry of the final wormhole pattern on the acid type and the injection rate is studied. The results agree qualitatively with the experimental and theoretical analyses of others and substantiate the previous finding that there exists an optimal injection rate at which the wormhole is formed as well as the number of pore volumes of the injected fluid to break through is minimized. This study also confirms the experimentally observed phenomenon that the optimal injection rate decreases and the corresponding minimized number of pore volumes to break through increases as the acid is changed from HCl to HAc. Simulations suggest that the proposed lattice Boltzmann model may serve as an alternative reliable quantitative approach to study chemical dissolution in porous media.
Flow and Fracture in Deformable Porous Media: a Magmatic Perspective
NASA Astrophysics Data System (ADS)
Petford, N.
2012-12-01
This contribution reviews some recent advances in the flow and fracture of deformable porous media with implications for melt extraction in the lower crust and upper mantle. A long standing issue concerning extraction of partial melt from hot, high pressure regions (that is, most of the earth's solid interior) is the apparent contradiction that fracturing can occur in highly compliant material. I argue that much of the source of conflict surrounding the idea of 'fracture' in ductile/plastic rock is due to lack of clarity of terminology combined with conceptual notions equating fracture as defined in brittle rock through the theory of linear elasticity (a process well understood), with deformation and failure in weakly consolidated rock. So, while the former is based fundamentally on stress singularities and strain energy processes at a propagating fracture tip, continuum models of fracture in granular media struggle to define precisely the discontinuous nature of the physics involved. Thus, for fracture in porous media (and here an equivalence is made with igneous porous media, that is, a silicate melt phase plus skeletal, granular matrix), verbs like parting, dilation and seepage in response to fluid (melt) pressurised translation of a weakly bonded matrix become the equivalent of cracks/veins/fractures in traditional (Griffiths) fracture mechanics. At its simplest, the process of fracturing in both classes of material can be defined by the difference in lengthscale and geometry of dissipated energy around the opening fracture. Treated in this way, controversies about the ability of weak/ductile rock to 'fracture' become instead productive discussions on the relative roles of fluid pressure, flow rates and rheology in promoting localised deformation.
Effect of Bacterial Motility on Contaminant Mixing in Porous Media
NASA Astrophysics Data System (ADS)
Singh, R.; Olson, M. S.; Bioremediation At Drexel
2010-12-01
Groundwater flow is typically characterized by laminar flow and therefore contaminant mixing limited conditions prevail in subsurface environments. The presence of porous media introduces tortuosity to groundwater flow paths, thereby enhancing contaminant mixing. In addition, bacterial motility is reported to induce movement in their surrounding liquid, which may enhance contaminant mixing. Enhancement of chemical diffusion coefficients in bulk fluid due to bacterial random motility and chemotaxis has been already reported in literature. The aim of this study is to investigate the effect of bacterial motility on contaminant mixing in the presence of porous media. A microfluidic device was designed and fabricated using standard photolithography and soft-lithography techniques to simulate a contaminant plume in subsurface porous media due to leakage of an underground storage tank. A non-reactive conservative tracer, Dextran solution labeled with FITC (fluorescein isothiocyanate), was used as surrogate for the contaminant and the motile bacterial strain Escherichia coli HCB33 (wild type) was used for the experiments to enhance contaminant mixing. Images were obtained at various cross-sections along the device and fluorescence intensity profile distributions were analyzed to determine the transverse dispersion of the contaminant. Enhancement in contaminant mixing was assessed by comparing the contaminant transverse dispersion coefficients (Dyi) in porous media in presence of motile bacteria, immobilized bacteria, and with no bacteria. In order to quantify the contaminant dispersion coefficients under the various test conditions, experimental data obtained were fitted to concentration profiles predicted by the contaminant advection-dispersion equation for the given experimental conditions (Figure 1). The transverse dispersion coefficient values obtained in the presence of motile bacteria (Dymb)and with no bacteria (Dynb) were 2.49 x 10-4 cm2/s and 1.39 x 10-4 cm2/s
Stability analysis of dissolution-driven convection in porous media
NASA Astrophysics Data System (ADS)
Emami-Meybodi, Hamid
2017-01-01
We study the stability of dissolution-driven convection in the presence of a capillary transition zone and hydrodynamic dispersion in a saturated anisotropic porous medium, where the solute concentration is assumed to decay via a first-order chemical reaction. While the reaction enhances stability by consuming the solute, porous media anisotropy, hydrodynamic dispersion, and capillary transition zone destabilize the diffusive boundary layer that is unstably formed in a gravitational field. We perform linear stability analysis, based on the quasi-steady-state approximation, to assess critical times, critical wavenumbers, and neutral stability curves as a function of anisotropy ratio, dispersivity ratio, dispersion strength, material parameter, Bond number, Damköhler number, and Rayleigh number. The results show that the diffusive boundary layer becomes unstable in anisotropic porous media where both the capillary transition zone and dispersion are considered, even if the geochemical reaction is significantly large. Using direct numerical simulations, based on the finite difference method, we study the nonlinear dynamics of the system by examining dissolution flux, interaction of convective fingers, and flow topology. The results of nonlinear simulations confirm the predictions from the linear stability analysis and reveal that the fingering pattern is significantly influenced by combined effects of reaction, anisotropy, dispersion, and capillarity. Finally, we draw conclusions on implications of our results on carbon dioxide sequestration in deep saline aquifers.
Combustion Characteristics of Biofuels in Porous-Media Burners
NASA Astrophysics Data System (ADS)
Barajas, Pablo E.; Parthasarathy, R. N.; Gollahalli, S. R.
2010-05-01
Biofuels, such as canola methyl ester (CME) and soy methyl ester (SME) derived from vegetable oil are alternative sources of energy that have been developed to reduce the dependence on petroleum-based fuels. In the present study, CME, SME, commercial Jet-A fuel were tested in a porous-media burner. The measured combustion characteristics at an initial equivalence ratio of 0.8 included NOx and CO emission indices, radiative fractions of heat release, and axial temperatures. The effects of fuel on the injector and porous media durability were also documented. The NOx emission index was higher for the SME and CME flames than that of the Jet-A flame. Furthermore, the axial temperature profiles were similar for all the flames. The prolonged use of CME and SME resulted in the solid-particle deposition on the metal walls of the injector and within the structure of the porous medium, thereby increasing the restriction to the fuel/air flow.
Measurement of Interfacial Area Production and Permeability within Porous Media
Crandall, Dustin; Ahmadi, Goodarz; Smith, Duane H.
2010-01-01
An understanding of the pore-level interactions that affect multi-phase flow in porous media is important in many subsurface engineering applications, including enhanced oil recovery, remediation of dense non-aqueous liquid contaminated sites, and geologic CO2 sequestration. Standard models of two-phase flow in porous media have been shown to have several shortcomings, which might partially be overcome using a recently developed model based on thermodynamic principles that includes interfacial area as an additional parameter. A few static experimental studies have been previously performed, which allowed the determination of static parameters of the model, but no information exists concerning the interfacial area dynamic parameters. A new experimental porous flow cell that was constructed using stereolithography for two-phase gas-liquid flow studies was used in conjunction with an in-house analysis code to provide information on dynamic evolution of both fluid phases and gas-liquid interfaces. In this paper, we give a brief introduction to the new generalized model of two-phase flow model and describe how the stereolithography flow cell experimental setup was used to obtain the dynamic parameters for the interfacial area numerical model. In particular, the methods used to determine the interfacial area permeability and production terms are shown.
Diffusion with condensation and evaporation in porous media
Gu, L.; Plumb, O.A.; Ho, C.K.; Webb, S.W.
1998-03-01
Vapor phase transport in porous media is important in a number of environmental and industrial processes: soil moisture transport, vapor phase transport in the vadose zone, transport in the vicinity of buried nuclear waste, and industrial processes such as drying. The diffusion of water vapor in a packed bed containing residual liquid is examined experimentally. The objective is to quantify the effect of enhanced vapor diffusion resulting from evaporation/condensation in porous media subjected to a temperature gradient. Isothermal diffusion experiments in free-space were conducted to qualify the experimental apparatus and techniques. For these experiments measured diffusion coefficients are within 3.6% of those reported in the literature for the temperature range from 25 C to 40 C. Isothermal experiments in packed beds of glass beads were used to determine the tortuosity coefficient resulting in {tau} = 0.78 {+-} 0.028, which is also consistent with previously reported results. Nonisothermal experiments in packed beds in which condensation occurs were conducted to examine enhanced vapor diffusion. The interpretation of the results for these experiments is complicated by a gradual, but continuous, build-up of condensate in the packed beds during the course of the experiment. Results indicate diffusion coefficients which increase as a function of saturation resulting in enhancement of the vapor-phase transport by a factor of approximately four compared to a dry porous medium.
How reproducible is the acoustical characterization of porous media?
Pompoli, Francesco; Bonfiglio, Paolo; Horoshenkov, Kirill V; Khan, Amir; Jaouen, Luc; Bécot, François-Xavier; Sgard, Franck; Asdrubali, Francesco; D'Alessandro, Francesco; Hübelt, Jörn; Atalla, Noureddine; Amédin, Celse K; Lauriks, Walter; Boeckx, Laurens
2017-02-01
There is a considerable number of research publications on the characterization of porous media that is carried out in accordance with ISO 10534-2 (International Standards Organization, Geneva, Switzerland, 2001) and/or ISO 9053 (International Standards Organization, Geneva, Switzerland, 1991). According to the Web of Science(TM) (last accessed 22 September 2016) there were 339 publications in the Journal of the Acoustical Society of America alone which deal with the acoustics of porous media. However, the reproducibility of these characterization procedures is not well understood. This paper deals with the reproducibility of some standard characterization procedures for acoustic porous materials. The paper is an extension of the work published by Horoshenkov, Khan, Bécot, Jaouen, Sgard, Renault, Amirouche, Pompoli, Prodi, Bonfiglio, Pispola, Asdrubali, Hübelt, Atalla, Amédin, Lauriks, and Boeckx [J. Acoust. Soc. Am. 122(1), 345-353 (2007)]. In this paper, independent laboratory measurements were performed on the same material specimens so that the naturally occurring inhomogeneity in materials was controlled. It also presented the reproducibility data for the characteristic impedance, complex wavenumber, and for some related pore structure properties. This work can be helpful to better understand the tolerances of these material characterization procedures so improvements can be developed to reduce experimental errors and improve the reproducibility between laboratories.
NASA Astrophysics Data System (ADS)
Meheust, Y.; Turuban, R.; Jimenez-Martinez, J.; De Anna, P.; Tabuteau, H.; Le Borgne, T.
2014-12-01
Pore scale characterization of flow velocities and concentration spatial distributions is a key to understanding non-Fickian transport and mixing in porous media. We present a millifluidic setup aimed at investigating those processes in transparent porous media, at the pore scale. The porous media are quasi-2D, consisting of a Hele-Shaw cell containing cylindrical grains. They are made by soft lithography from a numerical model and provide full control on the geometry (medium porosity, permeability and heterogeneity). The setup allows for the study of primary drainage/imbibition, or the joint continuous injection of two fluids (e. g. water and air). A camera records the distributions of fluid phases, the position of solid tracers, and spatially-resolved images of light emissions inside the flow cell. The pore scale velocity field is thus measured from particle tracking, while pore scale concentration fields are measured accurately in passive transport experiments, using fluorescein; both continuous injection and finite volume solute injections can be achieved. Using two chemo-luminescent liquids, the reaction of which produces photons in addition to the reaction product, we are also able to study the local production rate of the reaction product as the reactive liquids flow through the system [1]. Pressure drops across the medium are also measured. This complete characterization (phase distributions, velocity and concentration fields, pressure drops) of the system allows to explain non-Fickian behaviors and test models that upscale transport and mixing properties from pore scale data. As examples, we shall discuss the upscaling of transport from the knowledge of Lagrangian velocities and the relationships between conservative and reactive transport under mixing-limited conditions (very large Damkhöler number). Other applications include the prediction of the mixing rate from the sole knowledge of the flow stretching [2], and the characterization of mixing by
P-adic model of transport in porous disordered media
NASA Astrophysics Data System (ADS)
Khrennikov, Adrei Yu.; Oleschko, Klaudia
2014-05-01
The soil porosity and permeability are the most important quantitative indicators of soil dynamics under the land-use change. The main problema in the modeling of this dynamic is still poor correlation between the real measuring data and the mathematical and computer simulation models. In order to overpassed this deep divorce we have designed a new technique, able to compare the data arised from the multiscale image analices and time series of the basic physical properties dynamics in porous media studied in time and space. We present a model of the diffusion reaction type describing transport in disordered porous media, e.g., water or oil flow in a complex network of pores. Our model is based on p-adic representation of such networks. This is a kind of fractal representation. We explore advantages of p- adic representation, namely, the possibility to endow p-adic trees with an algebraic structure and ultrametric topology and, hence, to apply analysis which have (at least some) similarities with ordinary real analysis on the straight line. We present the system of two diffusion reaction equations describing propagation of particles in networks of pores in disordered media. As an application, one can consider water transport through the soil pore Networks, or oil flow through capillaries nets. Under some restrictions on potentials and rate coefficients we found the stationary regime corresponding to water content or concentration of oil in a cluster of capillaries. Usage of p-adic analysis (in particular, p-adic wavelets) gives a possibility to find the stationary solution in the analytic form which makes possible to present a clear pedological or geological picture of the process. The mathematical model elaborated in this paper (Khrennikov, 2013) can be applied to variety of problems from water concentration in aquifers to the problem of formation of oil reservoirs in disordered media with porous structures. Another possible application may have real practical
Fixation of radioactive ions in porous media with ion exchange gels
Mercer, Jr., Basil W.; Godfrey, Wesley L.
1979-01-01
A method is provided for fixing radioactive ions in porous media by injecting into the porous media water-soluble organic monomers which are polymerizable to gel structures with ion exchange sites and polymerizing the monomers to form ion exchange gels. The ions and the particles of the porous media are thereby physically fixed in place by the gel structure and, in addition, the ions are chemically fixed by the ion exchange properties of the resulting gel.
Stochastic Langevin Model for Flow and Transport in Porous Media
Tartakovsky, Alexandre M.; Tartakovsky, Daniel M.; Meakin, Paul
2008-07-25
A new stochastic Lagrangian model for fluid flow and transport in porous media is described. The fluid is represented by particles whose flow and dispersion in a continuous porous medium is governed by a Langevin equation. Changes in the properties of the fluid particles (e.g. the solute concentration) due to molecular diffusion is governed by the advection-diffusion equation. The separate treatment of advective and diffusive mixing in the stochastic model has an advantage over the classical advection-dispersion theory, which uses a single effective diffusion coefficient (the dispersion coefficient) to describe both types of mixing leading to over-prediction of mixing induced effective reaction rates. The stochastic model predicts much lower reaction product concentrations in mixing induced reactions. In addition the dispersion theory predicts more stable fronts (with a higher effective fractal dimension) than the stochastic model during the growth of Rayleigh-Taylor instabilities.
Anomalous dynamics of capillary rise in porous media.
Shikhmurzaev, Yulii D; Sprittles, James E
2012-07-01
The anomalous dynamics of capillary rise in a porous medium discovered experimentally more than a decade ago [T. Delker et al., Phys. Rev. Lett. 76, 2902 (1996)] is described. The developed theory is based on considering the principal modes of motion of the menisci that collectively form the wetting front on the Darcy scale. These modes, which include (i) dynamic wetting mode, (ii) threshold mode, and (iii) interface depinning process, are incorporated into the boundary conditions for the bulk equations formulated in the regular framework of continuum mechanics of porous media, thus allowing one to consider a general case of three-dimensional flows. The developed theory makes it possible to describe all regimes observed in the experiment, with the time spanning more than four orders of magnitude, and highlights the dominant physical mechanisms at different stages of the process.
Model of oil ganglion movement in porous media
Egbogah, E.O.; Wright, R.J.; Dawe, R.A.
1981-01-01
This paper presents a simple theory of the movement of a discontinuous oil droplet (ganglion) through a model porous medium. A quantitative description of the ganglion flow in the system was obtained through a tractable solution to the balance of forces controlling ganglion stability during flow of two immiscible fluids within a well-defined geometry. Calculations were based on a constricted conical (divergent-convergent) pore model. Experimental data from a tetragonally packed sphere model were used interactively with a theoretical static analysis to synthesize the relevant features of the ganglion mechanics into a coherent theory of oil mobilization. The model analysis also permits the computation of relative ganglion velocity under various flow conditions. This is an essential parameter for enhanced oil recovery modelling which facilitates the prediction of oil bank movements in porous media. 34 refs.
Hydraulic properties of adsorbed water films in unsaturated porous media
Tokunaga, Tetsu K.
2009-03-01
Adsorbed water films strongly influence residual water saturations and hydraulic conductivities in porous media at low saturations. Hydraulic properties of adsorbed water films in unsaturated porous media were investigated through combining Langmuir's film model with scaling analysis, without use of any adjustable parameters. Diffuse double layer influences are predicted to be important through the strong dependence of adsorbed water film thickness (f) on matric potential ({Psi}) and ion charge (z). Film thickness, film velocity, and unsaturated hydraulic conductivity are predicted to vary with z{sup -1}, z{sup -2}, and z{sup -3}, respectively. In monodisperse granular media, the characteristic grain size ({lambda}) controls film hydraulics through {lambda}{sup -1} scaling of (1) the perimeter length per unit cross sectional area over which films occur, (2) the critical matric potential ({Psi}{sub c}) below which films control flow, and (3) the magnitude of the unsaturated hydraulic conductivity when {Psi} < {Psi}{sub c}. While it is recognized that finer textured sediments have higher unsaturated hydraulic conductivities than coarser sands at intermediate {Psi}, the {lambda}{sup -1} scaling of hydraulic conductivity predicted here extends this understanding to very low saturations where all pores are drained. Extremely low unsaturated hydraulic conductivities are predicted under adsorbed film-controlled conditions (generally < 0.1 mm y{sup -1}). On flat surfaces, the film hydraulic diffusivity is shown to be constant (invariant with respect to {Psi}).
Direct numerical simulation of inertial flows in porous media
NASA Astrophysics Data System (ADS)
Apte, S.; Finn, J.; Wood, B. D.
2010-12-01
At modest flow rates (10 ≤ Re ≤ 300) through porous media and packed beds, fluid inertia can result in complex steady and unsteady recirculation regions, dependent on the local pore geometry. Body fitted CFD is a broadly used design and analysis tool for flows in porous media and packed bed type reactors. Unfortunately, the inherent complexities of porous media make unstructured mesh generation a difficult and time consuming step in the simulation process. To accurately capture the inertial dynamics using high-fidelity direct simulations, body fitted meshes must be high quality and sufficiently refined. We present methods to parameterize and simplify mesh generation for packed beds, with an eye toward obtaining efficient mesh independence for Reynolds numbers in the inertial and unsteady regimes. The crux of mesh generation for packed beds is dealing with sphere-sphere or sphere-wall contact points, where a geometric singularity exists. To handle the sphere-sphere and sphere-wall contact points, we use a fillet bridge model, in which every pair of contacting entities are bridged by a fillet, eliminating a small fluid region near the contact point. This results in a continuous surface mesh which does not require resizing of the spheres and can accommodate prism cells for improved boundary layer resolution. A second order accurate, parallel, incompressible flow solver [Moin and Apte, AIAA J. 2006] is used to simulate flow through three different sphere packings: a periodic simple cubic packing, a wall bounded hexagonal close packing, and a randomly packed tube. Mesh independence is assessed using several measures including Ergun pressure drop coefficients, viscous and pressure components of drag force, kinetic energy, kinetic energy dissipation and interstitial velocity profiles. The results of these test cases are used to determine the feasibility of accurate and very large scale simulations of flow through a randomly packed bed of 103 pores. Preliminary results
1D and 2D simulations of seismic wave propagation in fractured media
NASA Astrophysics Data System (ADS)
Möller, Thomas; Friederich, Wolfgang
2016-04-01
Fractures and cracks have a significant influence on the propagation of seismic waves. Their presence causes reflections and scattering and makes the medium effectively anisotropic. We present a numerical approach to simulation of seismic waves in fractured media that does not require direct modelling of the fracture itself, but uses the concept of linear slip interfaces developed by Schoenberg (1980). This condition states that at an interface between two imperfectly bonded elastic media, stress is continuous across the interface while displacement is discontinuous. It is assumed that the jump of displacement is proportional to stress which implies a jump in particle velocity at the interface. We use this condition as a boundary condition to the elastic wave equation and solve this equation in the framework of a Nodal Discontinuous Galerkin scheme using a velocity-stress formulation. We use meshes with tetrahedral elements to discretise the medium. Each individual element face may be declared as a slip interface. Numerical fluxes have been derived by solving the 1D Riemann problem for slip interfaces with elastic and viscoelastic rheology. Viscoelasticity is realised either by a Kelvin-Voigt body or a Standard Linear Solid. These fluxes are not limited to 1D and can - with little modification - be used for simulations in higher dimensions as well. The Nodal Discontinuous Galerkin code "neXd" developed by Lambrecht (2013) is used as a basis for the numerical implementation of this concept. We present examples of simulations in 1D and 2D that illustrate the influence of fractures on the seismic wavefield. We demonstrate the accuracy of the simulation through comparison to an analytical solution in 1D.
A Porous Media Model for Blood Flow within Reticulated Foam
Ortega, J.M.
2013-01-01
A porous media model is developed for non-Newtonian blood flow through reticulated foam at Reynolds numbers ranging from 10−8 to 10. This empirical model effectively divides the pressure gradient versus flow speed curve into three regimes, in which either the non-Newtonian viscous forces, the Newtonian viscous forces, or the inertial fluid forces are most prevalent. When compared to simulation data of blood flow through two reticulated foam geometries, the model adequately captures the pressure gradient within all three regimes, especially that within the Newtonian regime where blood transitions from a power-law to a constant viscosity fluid. PMID:24031095
Combined Evaporation and Salt Precipitation in Porous Media
NASA Astrophysics Data System (ADS)
Weisbrod, N.; Dragila, M. I.; Nachshon, U.; Or, D.; Shaharani, E.; Grader, A.
2012-12-01
The vadose zone pore water contains dissolved salts and minerals; therefore, evaporation results in high rates of salt accumulation that may change the physical and chemical properties of the porous media. Here, a series of experiments, together with a mathematical model, are presented to shed new light on these processes. Experiments included: (1) long-term column evaporation experiments to quantify changes in evaporation rates due to salt precipitation; (2) CT scans of evaporated porous media samples saturated with salt solutions, to observe salt precipitation from micro to macro scales; and (3) Infrared thermography analysis to quantify evaporation rates from porous media surfaces for homogeneous and heterogeneous conditions and constant water table, in the presence of salt precipitation. As expected, the majority of salt crystallization occurs in the upper parts of the matrix, near the evaporation front. For heterogeneous porous matrices, salt precipitation will occur mainly in the fine pore regions as preferential evaporation takes place in these locations. In addition, it was found that the precipitated NaCl salt crust diffusion coefficient for water vapor is one to two orders of magnitude lower than the vapor diffusion coefficient in free air, depending on environmental conditions and salt crystallization rates. Three new stages of evaporation were defined for saline solutions: SS1, SS2 and SS3. SS1 exhibits a low and gradual decrease in the evaporation rate due to osmotic pressure. During SS2, the evaporation rate falls progressively due to salt precipitation; SS3 is characterized by a constant low evaporation rate and determined by the diffusion rate of water vapor through the precipitated salt layer. Even though phenomenologically similar to the classical evaporation stages of pure water, these stages correspond to different mechanisms and the transition between stages can occur regardless the hydraulic conditions. As well, it was shown that matrix
Title: Spatial velocity fluctuations in flow through porous media
NASA Astrophysics Data System (ADS)
Aramideh, Soroush; Guo, Tianqi; Vlachos, Pavlos P.; Ardekani, Arezoo M.
2016-11-01
Understanding the flow in porous media is of great importance and has direct impact on many processes in chemical and oil industries, fuel cell design, and filtration. In this work, we use direct numerical simulations (DNS) to examine the flow through variety of sphere packings with different levels of complexity and heterogeneity. DNS results are validated with velocity fields obtained via volumetric particle tracking velocimetry at high resolution. We show that flow in random close packing of spheres has unique statistical properties while the medium is random itself. Furthermore, we quantify the relationship between pore geometry and velocity fluctuations.
Bacteria transport through porous media. Annual report, December 31, 1984
Yen, T.F.
1986-09-01
The following five chapters in this report have been processed separately for inclusion in the Energy Data Base: (1) theoretical model of convective diffusion of motile and non-motile bacteria toward solid surfaces; (2) interfacial electrochemistry of oxide surfaces in oil-bearing sands and sandstones; (3) effects of sodium pyrophosphate additive on the ''huff and puff''/nutrient flooding MEOR process; (4) interaction of Escherichia coli B, B/4, and bacteriophage T4D with Berea sandstone rock in relation to enhanced oil recovery; and (5) transport of bacteria in porous media and its significance in microbial enhanced oil recovery.
Porous Media Approach for Modeling Closed Cell Foam
NASA Technical Reports Server (NTRS)
Ghosn, Louis J.; Sullivan, Roy M.
2006-01-01
In order to minimize boil off of the liquid oxygen and liquid hydrogen and to prevent the formation of ice on its exterior surface, the Space Shuttle External Tank (ET) is insulated using various low-density, closed-cell polymeric foams. Improved analysis methods for these foam materials are needed to predict the foam structural response and to help identify the foam fracture behavior in order to help minimize foam shedding occurrences. This presentation describes a continuum based approach to modeling the foam thermo-mechanical behavior that accounts for the cellular nature of the material and explicitly addresses the effect of the internal cell gas pressure. A porous media approach is implemented in a finite element frame work to model the mechanical behavior of the closed cell foam. The ABAQUS general purpose finite element program is used to simulate the continuum behavior of the foam. The soil mechanics element is implemented to account for the cell internal pressure and its effect on the stress and strain fields. The pressure variation inside the closed cells is calculated using the ideal gas laws. The soil mechanics element is compatible with an orthotropic materials model to capture the different behavior between the rise and in-plane directions of the foam. The porous media approach is applied to model the foam thermal strain and calculate the foam effective coefficient of thermal expansion. The calculated foam coefficients of thermal expansion were able to simulate the measured thermal strain during heat up from cryogenic temperature to room temperature in vacuum. The porous media approach was applied to an insulated substrate with one inch foam and compared to a simple elastic solution without pore pressure. The porous media approach is also applied to model the foam mechanical behavior during subscale laboratory experiments. In this test, a foam layer sprayed on a metal substrate is subjected to a temperature variation while the metal substrate is
Experimental study of seismic attenuation in partially saturated porous media
NASA Astrophysics Data System (ADS)
Barrière, Julien; Bordes, Clarisse; Sénéchal, Pascale
2010-05-01
Nowadays, it is well admitted that hydrogeological properties of the porous media (porosity, fluid saturation and permeability) can influence seismic properties. In geophysics, the major theory which links hydrogeological and seismic parameters is poroelasticity proposed by Biot (1956). The Biot relaxation process is due to the relative displacement of fluid in comparison to the solid which causes a significant attenuation of seismic waves, notably in unconsolidated medium. In partially saturated medium, pore fluids are considered as a perfect mixture and so called 'effective fluid'. However, in more consolidated rocks, the Biot theory is not sufficient to explain the attenuation level as measured from field seismic and sonic log data. In the last decade, some authors provide new theories to understand the attenuation caused by the interaction of the different fluids. Most experiments are done in the ultrasonic frequency range, where sources of attenuation (like scattering or local fluid flow) are different as in the low frequency range where the wavelength is greater than heterogeneities size. In this way, we propose a forward-looking experiment with the use of a vertical impulsionnal seismic source which have a strong amplitude spectrum ranging from 100Hz to 8kHz. We study three different unconsolidated porous media at atmospheric pressure: fine-grained sand, coarsed-grained sand and coarse gravel. Water content is measured with a calibrated capacitance probe and temperature effects are corrected. Seismic wave propagation is recorded by piezoelectric accelerometers designed for frequencies below 10kHz. The water injection is done by imbibition. We propose to analyse the attenuation in the [100Hz-1.5kHz] frequency range for the studied media with various water saturation levels. The attenuation varies according to the porous medium and the water content and appears more significant at dry condition and at high saturation level. The weak cohesion at dry condition
A study of vapor-liquid flow in porous media
Satik, Cengiz; Yortsos, Yanis C.
1994-01-20
We study the heat transfer-driven liquid-to-vapor phase change in single-component systems in porous media by using pore network models and flow visualization experiments. Experiments using glass micromodels were conducted. The flow visualization allowed us to define the rules for the numerical pore network model. A numerical pore network model is developed for vapor-liquid displacement where fluid flow, heat transfer and capillarity are included at the pore level. We examine the growth process at two different boundary conditions.
NASA Astrophysics Data System (ADS)
Kasperski, Adam; Rżysko, Wojciech; Szabelski, Paweł
2016-12-01
The ability of capturing guest molecules in a selective way is one of desirable properties of modern structured adsorbents. This refers to a wide class of guest molecules, especially to those which are chiral and whose enantiomers are to be efficiently separated. In this contribution, using Monte Carlo modeling, we show how simple molecular building blocks with cruciform shape can be used to create 2D porous matrices with tunable adsorptive properties. To that end we consider different self-assembled structures comprising cross-shaped molecules and probe their ability to retain model guest molecules differing in size and shape. In particular we focus on the adsorption of enantiomeric pairs on these substrates and quantify the associated selectivity. The obtained results show that a suitable choice of the building block, including size and aspect ratio allows for the creation of 2D functional matrices with programmed adsorption performance. The findings of our theoretical investigations can be helpful in designing molecular guest-host systems with potential applications in separations, sensing and heterogeneous catalysis.
NASA Astrophysics Data System (ADS)
Muniruzzaman, Muhammad; Haberer, Christina; Grathwohl, Peter; Rolle, Massimo
2014-05-01
We study the influence of Coulombic effects on transport of charged species in saturated porous media in advection-dominated flow regimes. We focus on transverse hydrodynamic dispersion and we performed quasi two-dimensional flow-through experiments in homogeneous and spatially variable flow fields to investigate transport of dilute electrolyte solutions. The experiments were conducted at flow velocities (1.0, 1.5 and 6 m/day) where advection is the dominant mass transfer process. High-resolution measurements at the outlet were performed to determine the concentration of different cations and anions. In order to interpret the laboratory experiments we develop a two-dimensional numerical model. The adopted modeling approach is based on a multicomponent formulation, charge conservation, and the accurate description of local transverse dispersion. The latter entails a non-linear dependence of the transverse dispersion coefficient on the flow velocity as well as a compound-specific dependence on the molecular diffusion of the transported solutes. The model was benchmarked by comparing the results of the 2D steady-state multicomponent simulations with 1D transient results of PHREEQC in homogeneous scenarios, and it was successively used to quantitatively evaluate the experimental results in both homogeneous and heterogeneous porous media. Our experimental and modeling results show that Coulombic cross-coupling of dispersive fluxes of charged species in porous media significantly affects the lateral displacement of charged ions in both homogeneous and heterogeneous flow-through systems. Such effects are remarkable not only in diffusion-dominated but also in advection-dominated flow regimes.
Maximum estimates for generalized Forchheimer flows in heterogeneous porous media
NASA Astrophysics Data System (ADS)
Celik, Emine; Hoang, Luan
2017-02-01
This article continues the study in [4] of generalized Forchheimer flows in heterogeneous porous media. Such flows are used to account for deviations from Darcy's law. In heterogeneous media, the derived nonlinear partial differential equation for the pressure can be singular and degenerate in the spatial variables, in addition to being degenerate for large pressure gradient. Here we obtain the estimates for the L∞-norms of the pressure and its time derivative in terms of the initial and the time-dependent boundary data. They are established by implementing De Giorgi-Moser's iteration in the context of weighted norms with the weights specifically defined by the Forchheimer equation's coefficient functions. With these weights, we prove suitable weighted parabolic Poincaré-Sobolev inequalities and use them to facilitate the iteration. Moreover, local in time L∞-bounds are combined with uniform Gronwall-type energy inequalities to obtain long-time L∞-estimates.
Robust solution of Richards' equation for nonuniform porous media
NASA Astrophysics Data System (ADS)
Miller, Cass T.; Williams, Glenn A.; Kelley, C. T.; Tocci, Michael D.
1998-10-01
Capillary pressure-saturation-relative permeability relations described using the van Genuchten [1980] and Mualem [1976] models for nonuniform porous media lead to numerical convergence difficulties when used with Richards' equation for certain auxiliary conditions. These difficulties arise because of discontinuities in the derivative of specific moisture capacity and relative permeability as a function of capillary pressure. Convergence difficulties are illustrated using standard numerical approaches to simulate such problems. We investigate constitutive relations, interblock permeability, nonlinear algebraic system approximation methods, and two time integration approaches. An integral permeability approach approximated by Hermite polynomials is recommended and shown to be robust and economical for a set of test problems, which correspond to sand, loam, and clay loam media.
Microscale simulation of particle deposition in porous media.
Boccardo, Gianluca; Marchisio, Daniele L; Sethi, Rajandrea
2014-03-01
In this work several geometries, each representing a different porous medium, are considered to perform detailed computational fluid dynamics simulation for fluid flow, particle transport and deposition. Only Brownian motions and steric interception are accounted for as deposition mechanisms. Firstly pressure drop in each porous medium is analyzed in order to determine an effective grain size, by fitting the results with the Ergun law. Then grid independence is assessed. Lastly, particle transport in the system is investigated via Eulerian steady-state simulations, where particle concentration is solved for, not following explicitly particles' trajectories, but solving the corresponding advection-diffusion equation. An assumption was made in considering favorable collector-particle interactions, resulting in a "perfect sink" boundary condition for the collectors. The gathered simulation data are used to calculate the deposition efficiency due to Brownian motions and steric interception. The original Levich law for one simple circular collector is verified; subsequently porous media constituted by a packing of collectors are scrutinized. Results show that the interactions between the different collectors result in behaviors which are not in line with the theory developed by Happel and co-workers, highlighting a different dependency of the deposition efficiency on the dimensionless groups involved in the relevant correlations.
Multicomponent, multiphase flow in porous media with temperature variation
Wingard, J.S.; Orr, F.M. Jr.
1990-10-01
Recovery of hydrocarbons from porous media is an ongoing concern. Advanced techniques augment conventional recovery methods by injecting fluids that favorably interact with the oil. These fluids interact with the oil by energy transfer, in the case of steam injection, or by mass transfer, as in a miscible gas flood. Often both thermal and compositional considerations are important. An understanding of these injection methods requires knowledge of how temperature variations, phase equilibrium and multiphase flow in porous media interact. The material balance for each component and energy balance are cast as a system of non-strictly hyperbolic partial differential equations. This system of equations is solved using the method of characteristics. The model takes into account the phase behavior by using the Peng-Robinson equation of state to partition the individual components into different phases. Temperature effects are accounted for by the energy balance. Flow effects are modelled by using fractional flow curves and a Stone's three phase relative permeability model. Three problems are discussed. The first problem eliminates the phase behavior aspect of the problem by studying the flow of a single component as it undergoes an isothermal phase change. The second couples the effects of temperature and flow behavior by including a second component that is immiscible with the original component. Phase behavior is added by using a set of three partially miscible components that partition into two or three separate phases. 66 refs., 54 figs., 14 tabs.
Miscible Quarter Five-Spot Flows in Porous Media
NASA Astrophysics Data System (ADS)
Chen, Ching-Yao; Meiburg, Eckart
1997-11-01
Miscible quarter five-spot flows in both homogeneous and heterogeneous porous media were investigated by means of direct numerical simulations based on compact finite differences. Comparisons of the algebraic growth rate and the preferred wave number of the viscous fingering instability with analytical linear stability results demonstrate excellent accuracy. A series of simulations illustrate the effects of the mobility ratio R, the dimensionless flow rate Pe, and the heterogeneity on the displacement process. For sufficiently large R and Pe, the homogeneous flow gives rise to a vigorous fingering instability, along with strong nonlinear interactions among the fingers. The spatial nonuniformity of the potential base flow leads to a clear separation in space and time of the large and small scales in the flow field. Small scales occur predominantly during the early stages near the injection well, and at late times near the production well. The central domain is dominated by larger scales. Both local and integral flow features are quantified by means of concentration, vorticity, stream function, and sweep efficiency data. For heterogeneous porous media, the influence of the parameters characterizing the permeability variation was investigated. Typically, the minimal sweep efficiency was observed at intermediate values of the correlation length. Partially supported by Chevron Petroleum Technology Co.
Fluid flow patterns in porous media with partially ordered microstructure
NASA Astrophysics Data System (ADS)
Mirsaeidi, A.; Thompson, K. E.
2014-12-01
Natural granular porous media found in geosciences applications are disordered at the pore scale, which contributes to the interesting behavior that they exhibit including hydrodynamic dispersion, capillary pressure and wetting behavior, and various types of fingering. Many standard equations and models that have been developed for transport in porous media are based on the assumption of uniform disorder, randomly distributed parameters, and isotropic behavior. However, factors that cause partial ordering (e.g., settling of oblong grains, alignment of elongated particles, or packing structures near a boundary) can lead to anomalous flow behavior relative to the base case, when in turn requires different ways to understand and describe transport. In this work we examine the packing structure and fluid flow patterns in packings of equilateral cylindrical particles that are packed in a tube. The detailed packing structures are obtained experimentally from microCT experiments, and the flow patterns are simulated by numerical solution of the Stokes equations using the finite element method. This research is of interest in chemical engineering because this type of packing is used in catalytic reactors. However, the structures are also interesting from both a fundamental perspective and as prototypes for partially ordered natural materials because the packings undergo a transition from fully disordered internally to highly structured at the wall, and therefore provide insight into differences caused by the ordering.
Multiscale modeling of chemotaxis in homogeneous porous media
NASA Astrophysics Data System (ADS)
Porter, Mark L.; ValdéS-Parada, Francisco J.; Wood, Brian D.
2011-06-01
We present a predictive, multiscale modeling framework for chemotaxis in porous media. This model results from volume averaging the governing equations for bacterial transport at the microscale and is expressed in terms of effective medium coefficients that are predicted from the solution of the associated closure problems. As a result, the averaged chemotactic velocity is an explicit function of the attractant concentration field and diffusivity, rather than an empirical effective chemotactic sensitivity coefficient. The model was validated by comparing the transverse bacterial concentration profiles with experimental measurements for Escherichia coli HCB1 in a T-sensor. The averaged chemotactic velocity predicted by the model was found to be within the range of values reported in the literature. Reasonable agreement (approximately 10% mean absolute error) between theory and experiments was found for several flow rates. In order to assess the potential for decreasing the computational demands of the model, the macroscale domain was divided into subdomains for the coupling of bacterial transport to that of the attractant. Sensitivity analysis was performed regarding the number of subdomains chosen, and the results indicate that bacterial transport (as measured by concentration profiles) was not highly affected by this choice. Overall, these results suggest that the predictive, multiscale modeling framework is reliable for modeling chemotaxis in porous media when chemotactic transport is significant compared to convective transport.
Studies on dispersive stabilization of porous media flows
NASA Astrophysics Data System (ADS)
Daripa, Prabir; Gin, Craig
2016-08-01
Motivated by a need to improve the performance of chemical enhanced oil recovery (EOR) processes, we investigate dispersive effects on the linear stability of three-layer porous media flow models of EOR for two different types of interfaces: permeable and impermeable interfaces. Results presented are relevant for the design of smarter interfaces in the available parameter space of capillary number, Peclet number, longitudinal and transverse dispersion, and the viscous profile of the middle layer. The stabilization capacity of each of these two interfaces is explored numerically and conditions for complete dispersive stabilization are identified for each of these two types of interfaces. Key results obtained are (i) three-layer porous media flows with permeable interfaces can be almost completely stabilized by diffusion if the optimal viscous profile is chosen, (ii) flows with impermeable interfaces can also be almost completely stabilized for short time, but become more unstable at later times because diffusion flattens out the basic viscous profile, (iii) diffusion stabilizes short waves more than long waves which leads to a "turning point" Peclet number at which short and long waves have the same growth rate, and (iv) mechanical dispersion further stabilizes flows with permeable interfaces but in some cases has a destabilizing effect for flows with impermeable interfaces, which is a surprising result. These results are then used to give a comparison of the two types of interfaces. It is found that for most values of the flow parameters, permeable interfaces suppress flow instability more than impermeable interfaces.
Analytical model for heterogeneous reactions in mixed porous media
Hatfield, K.; Burris, D.R.; Wolfe, N.L.
1996-08-01
The funnel/gate system is a developing technology for passive ground-water plume management and treatment. This technology uses sheet pilings as a funnel to force polluted ground water through a highly permeable zone of reactive porous media (the gate) where contaminants are degraded by biotic or abiotic heterogeneous reactions. This paper presents a new analytical nonequilibrium model for solute transport in saturated, nonhomogeneous or mixed porous media that could assist efforts to design funnel/gate systems and predict their performance. The model incorporates convective/dispersion transport, dissolved constituent decay, surface-mediated degradation, and time-dependent mass transfer between phases. Simulation studies of equilibrium and nonequilibrium transport conditions reveal manifestations of rate-limited degradation when mass-transfer times are longer than system hydraulic residence times, or when surface-mediated reaction rates are faster than solute mass-transfer processes (i.e., sorption, film diffusion, or intraparticle diffusion). For example, steady-state contaminant concentrations will be higher under a nonequilibrium transport scenario than would otherwise be expected when assuming equilibrium conditions. Thus, a funnel/gate system may fail to achieve desired ground-water treatment if the possibility of mass-transfer-limited degradation is not considered.
Evaluation of liquid aerosol transport through porous media
NASA Astrophysics Data System (ADS)
Hall, R.; Murdoch, L.; Falta, R.; Looney, B.; Riha, B.
2016-07-01
Application of remediation methods in contaminated vadose zones has been hindered by an inability to effectively distribute liquid- or solid-phase amendments. Injection as aerosols in a carrier gas could be a viable method for achieving useful distributions of amendments in unsaturated materials. The objectives of this work were to characterize radial transport of aerosols in unsaturated porous media, and to develop capabilities for predicting results of aerosol injection scenarios at the field-scale. Transport processes were investigated by conducting lab-scale injection experiments with radial flow geometry, and predictive capabilities were obtained by developing and validating a numerical model for simulating coupled aerosol transport, deposition, and multi-phase flow in porous media. Soybean oil was transported more than 2 m through sand by injecting it as micron-scale aerosol droplets. Oil saturation in the sand increased with time to a maximum of 0.25, and decreased with radial distance in the experiments. The numerical analysis predicted the distribution of oil saturation with only minor calibration. The results indicated that evolution of oil saturation was controlled by aerosol deposition and subsequent flow of the liquid oil, and simulation requires including these two coupled processes. The calibrated model was used to evaluate field applications. The results suggest that amendments can be delivered to the vadose zone as aerosols, and that gas injection rate and aerosol particle size will be important controls on the process.
Diffuse-Interface Modelling of Flow in Porous Media
NASA Astrophysics Data System (ADS)
Addy, Doug; Pradas, Marc; Schmuck, Marcus; Kalliadasis, Serafim
2016-11-01
Multiphase flows are ubiquitous in a wide spectrum of scientific and engineering applications, and their computational modelling often poses many challenges associated with the presence of free boundaries and interfaces. Interfacial flows in porous media encounter additional challenges and complexities due to their inherently multiscale behaviour. Here we investigate the dynamics of interfaces in porous media using an effective convective Cahn-Hilliard (CH) equation recently developed in from a Stokes-CH equation for microscopic heterogeneous domains by means of a homogenization methodology, where the microscopic details are taken into account as effective tensor coefficients which are given by a Poisson equation. The equations are decoupled under appropriate assumptions and solved in series using a classic finite-element formulation with the open-source software FEniCS. We investigate the effects of different microscopic geometries, including periodic and non-periodic, at the bulk fluid flow, and find that our model is able to describe the effective macroscopic behaviour without the need to resolve the microscopic details.
Thermal conductivity modeling in variably saturated porous media
NASA Astrophysics Data System (ADS)
Ghanbarian, B.; Daigle, H.
2015-12-01
Modeling effective thermal conductivity under variably saturated conditions is essential to study heat transfer in natural sediments, soils, and rocks. The effective thermal conductivity in completely dry and fully saturated porous media is an integrated quantity representing the complex behavior of two conducting phases, i.e., pore fluid (either air or water) and solid matrix. Under partially saturated conditions, however, the effective thermal conductivity becomes even more complicated since three phases (air, water, and solid matrix) conduct heat simultaneously. In this study, we invoke an upscaling treatment called percolation-based effective-medium approximation to model the effective thermal conductivity in fully and partially saturated porous media. Our theoretical porosity- and saturation-dependent models contain endmember properties, such as air, solid matrix, and saturating fluid thermal conductivities, a percolation exponent t, and a percolation threshold. Comparing our theory with 216 porosity-dependent thermal conductivity measurements and 25 saturation-dependent thermal conductivity datasets indicate excellent match between theory and experiments. Our results show that the effective thermal conductivity under fully and partially saturated conditions follows nonuniversal behavior. This means the value of t changes from medium to medium and depends not only on topological and geometrical properties of the medium but also characteristics of the saturating fluid.
Effective Gradients in Porous Media Due to Susceptibility Differences
Hürlimann
1998-04-01
In porous media, magnetic susceptibility differences between the solid phase and the fluid filling the pore space lead to field inhomogeneities inside the pore space. In many cases, diffusion of the spins in the fluid phase through these internal inhomogeneities controls the transverse decay rate of the NMR signal. In disordered porous media such as sedimentary rocks, a detailed evaluation of this process is in practice not possible because the field inhomogeneities depend not only on the susceptibility difference but also on the details of the pore geometry. In this report, the major features of diffusion in internal gradients are analyzed with the concept of effective gradients. Effective gradients are related to the field inhomogeneities over the dephasing length, the typical length over which the spins diffuse before they dephase. For the CPMG sequence, the dependence of relaxation rate on echo spacing can be described to first order by a distribution of effective gradients. It is argued that for a given susceptibility difference, there is a maximum value for these effective gradients, gmax, that depends on only the diffusion coefficient, the Larmor frequency, and the susceptibility difference. This analysis is applied to the case of water-saturated sedimentary rocks. From a set of NMR measurements and a compilation of a large number of susceptibility measurements, we conclude that the effective gradients in carbonates are typically smaller than gradients of current NMR well logging tools, whereas in many sandstones, internal gradients can be comparable to or larger than tool gradients. Copyright 1998 Academic Press.
Simulation of incompressible two-phase flow in porous media with large timesteps
NASA Astrophysics Data System (ADS)
Cogswell, Daniel; Szulczewski, Michael
2016-11-01
Simulations of flow in porous media suffer from severe timestep restrictions as the permeability and viscosity contrast become increasingly heterogeneous, even when solved with a fully implicit discretization. Previous efforts to alleviate these restrictions have focused on numerical methods, but the problem persists because it originates from the shape of the fractional flow function. Here we focus on regularizing the equations themselves with the addition of an energy constraint. The equations for the flow of two immiscible, incompressible fluid phases in porous media are recast as a gradient flow using the phase-field method, a macroscopic surface tension is introduced, and a convex energy splitting scheme is applied to enable unconditionally large timesteps. Using the phase-field formulation as a homotopy map, the unmodified flow equations can be solved with large timesteps, even with high degrees of heterogeneity in permeability and viscosity. For a 2D test problem, the homotopy method allows the timestep to be increased by more than four orders of magnitude relative to the unmodified equations.
Analysis of porous media heterogeneities using the diffusion of pressure waves
NASA Astrophysics Data System (ADS)
Rigord, P.; Caristan, Y.; Hulin, J. P.
1993-06-01
We present an experimental study and a model of the diffusion of sinusoidal pressure waves through porous media. We show that measurements of the hydraulic admittance A(omega) in the sine wave mode allow us to probe the structure of porous samples with an adjustable investigation depth depending on the frequency omega. The variations of A(omega) in heterogeneous media with a percolationlike geometry are modeled numerically on 2D percolation networks. One obtains a transition from normal diffusion at low frequencies to anomalous diffusion at higher frequencies. At the transition, the penetration depth of the wave is of the order of the percolation correlation length. The hydraulic admittance and transmittance of 20 percent porosity pressed calcite have been investigated experimentally with sine wave excitations at pulsations omega between 2 x 10 exp -4 and 0.42 rad/s. Both the modulus and the phase of the complex admittance A(omega) display normal diffusive variations as omega increases. Increasing the viscosity reduces the frequency above which the diffusive behavior is observed. The measured diffusion coefficient is 25 percent higher than that computed from permeability and compressibility values measured independently; this difference may be associated with nonconnected porosity.
Direct Numerical Simulation of Liquid Transport Through Fibrous Porous Media
NASA Astrophysics Data System (ADS)
Palakurthi, Nikhil Kumar
Fluid flow through fibrous media occurs in many industrial processes, including, but not limited, to fuel cell technology, drug delivery patches, sanitary products, textile reinforcement, filtration, heat exchangers, and performance fabrics. Understanding the physical processes involved in fluid flow through fibrous media is essential for their characterization as well as for the optimization and development of new products. Macroscopic porous-media equations require constitutive relations, which account for the physical processes occurring at the micro-scale, to predict liquid transport at the macro-scale. In this study, micro-scale simulations were conducted using conventional computational fluid dynamics (CFD) technique (finite-volume method) to determine the macroscopic constitutive relations. The first part of this thesis deals with the single-phase flow in fibrous media, following which multi-phase flow through fibrous media was studied. Darcy permeability is an important parameter that characterizes creeping flow through a fibrous porous medium. It has a complex dependence on the medium's properties such as fibers' in-plane and through-plane orientation, diameter, aspect ratio, curvature, and porosity. A suite of 3D virtual fibrous structures with a wide range of geometric properties were constructed, and the permeability values of the structures were calculated by solving the 3D incompressible Navier-Stokes equations. The through-plane permeability was found to be a function of only the fiber diameter, the fibers' through-plane orientation, and the porosity of the medium. The numerical results were used to extend a permeability-porosity relation, developed in literature for 3D isotropic fibrous media, to a wide range of fibers' through-plane orientations. In applications where rate of capillary penetration is important, characterization of porous media usually involves determination of either the effective pore radius from capillary penetration experiments
Experimentally Determined Interfacial Area Between Immiscible Fluids in Porous Media
Crandall, Dustin; Niessner, J; Hassanizadeh, S.M; Smith, Duane
2008-01-01
When multiple fluids flow through a porous medium, the interaction between the fluid interfaces can be of great importance. While this is widely recognized in practical applications, numerical models often disregard interactios between discrete fluid phases due to the computational complexity. And rightly so, for this level of detail is well beyond most extended Darcy Law relationships. A new model of two-phase flow including the interfacial area has been proposed by Hassarizadeh and Gray based upon thermodynamic principles. A version of this general equation set has been implemented by Nessner and Hassarizadeh. Many of the interfacial parameters required by this equation set have never been determined from experiments. The work presented here is a description of how the interfacial area, capillary pressure, interfacial velocity and interfacial permeability from two-phase flow experiments in porous media experiments can be used to determine the required parameters. This work, while on-going, has shown the possibility of digitizing images within translucent porous media and identifying the location and behavior of interfaces under dynamic conditions. Using the described methods experimentally derived interfacial functions to be used in larger scale simulations are currently being developed. In summary, the following conclusions can be drawn: (1) by mapping a pore-throat geometry onto an image of immiscible fluid flow, the saturation of fluids and the individual interfaces between the fluids can be identified; (2) the resulting saturation profiles of the low velocity drainage flows used in this study are well described by an invasion percolation fractal scaling; (3) the interfacial area between fluids has been observed to increase in a linear fashion during the initial invasion of the non-wetting fluid; and (4) the average capillary pressure within the entire cell and representative elemental volumes were observed to plateau after a small portion of the volume was
Review of key factors controlling engineered nanoparticle transport in porous media.
Wang, Mei; Gao, Bin; Tang, Deshan
2016-11-15
Nanotechnology, an emerging technology, has witnessed rapid development in production and application. Engineered nanomaterials revolutionize the industry due to their unique structure and superior performance. The release of engineered nanoparticles (ENPs) into the environment, however, may pose risks to the environment and public health. To advance current understanding of environmental behaviors of ENPs, this work provides an introductory overview of ENP fate and transport in porous media. It systematically reviews the key factors controlling their fate and transport in porous media. It first provides a brief overview of common ENPs in the environment and their sources. The key factors that govern ENP transport in porous media are then categorized into three groups: (1) nature of ENPs affecting their transport in porous media, (2) nature of porous media affecting ENP transport, and (3) nature of flow affecting ENP transport in porous media. In each group, findings in recent literature on the specific governing factors of ENP transport in porous media are discussed in details. Finally, this work concludes with remarks on the importance of ENP transport in porous media and directions for future research.
PREDICTION OF INTERFACIAL AREAS DURING IMBIBITION IN SIMPLE POROUS MEDIA. (R827116)
The interfacial area between wetting (W-) and non-wetting (NW-) phases is one of the crucial parameters in several flow and transport processes in porous media. This paper gives predictions of such areas during imbibition (displacement of NW-phase by W) in simple porous media....
NASA Astrophysics Data System (ADS)
Li, Yaofa; Kazemifar, Farzan; Blois, Gianluca; Christensen, Kenneth
2015-11-01
Geological sequestration of carbon dioxide (CO2) has been of great interest primarily for the reason of CO2 emission reduction and enhanced oil recovery. Yet, our fundamental understanding of the coupled flow dynamics of CO2 and water in geologic media still remains limited, especially at the pore scale. Therefore, in this work the pore-scale flow of water and liquid/supercritical CO2 are quantified in 2D homogeneous and heterogeneous porous micro-models under reservoir-relevant conditions. Fluorescent microscopy and the micro-PIV technique are employed to simultaneously visualize both phases and obtain the velocity field in the aqueous phase. The velocity measurements in the homogeneous micro-model illustrate active and passive flow pathways and circulation regions near the fluid-fluid interfaces induced by shear. Moreover, the results for heterogeneous micro-models are presented and compared with those for homogeneous micro-models, which give valuable insight into flow processes at the pore scale in natural rock.
Study on Two-Phase Flow in Heterogeneous Porous Media by Light Transmission Method
NASA Astrophysics Data System (ADS)
Qiao, W.
2015-12-01
The non-aqueous phase liquid (NAPL) released to the subsurface can form residual ganglia and globules occupying pores and also accumulate and form pools, in which multiphase system forms. Determining transient fluid saturations in a multiphase system is essential to understand the flow characteristics of systems and to perform effective remediation strategies. As a non-destructive and non-invasive laboratory technique utilized for the measurement of liquid saturation in porous media, light transmission is of the lowest cost and safe. Utilization of Coupled Charge Device camera in light transmission systems provides a nearly instantaneous high-density array of spatial measurements over a very large dynamic range. The migration of NAPL and air spariging technique applied to remove NAPL in aquifer systems are typically two-phase flow problem. Because of the natural aquifer normally being heterogeneous, two 2-D sandboxes (Length55cm×width1.3cm×hight45cm) are set up to study the migration of gas and DNAPL in heterogeneous porous media based on light transmission method and its application in two-phase flow. Model D for water/gas system developed by Niemet and Selker (2001) and Model NW-A for water/NAPL system developed by Zhang et al. (2014) are applied for the calculation of fluid saturation in the two experiments, respectively. The gas injection experiments show that the gas moves upward in the irregular channels, piling up beneath the low permeability lenses and starting lateral movement. Bypassing the lenses, the gas moves upward and forms continuous distribution in the top of the sandbox. The faster of gas injects, the wider of gas migration will be. The DNAPL infiltration experiment shows that TCE mainly moves downward as the influence of gravity, stopping vertical infiltration when reaching the low permeability lenses because of its failure to overcome the capillary pressure. Then, TCE accumulates on the surface and starts transverse movement. Bypassing the
Kalpakci, B.; Klaus, E.E.; Duda, J.L.; Nagarajan, R.
1981-12-01
This work presents a study on flow properties of surfactant solutions in porous media, using the Penn State porous media viscometer. The effects of permeability, shear rate, and surface characteristics of porous media on the flow of oil- and water-external microemulsions, as well as surfactant solutions with lamellar structures, are examined. Untreated Bradford and Berea sand-stones, oil- and water-wet treated sandstones, and filter papers are used as porous media. The study shows that the effective viscosity of the surfactant solution (as measured in porous media), on the basis of initial permeabilities, is greater than the bulk viscosity (as measured by conventional viscometers). This increase is small for Newtonian surfactant solutions but is quite substantial for non-Newtonian surfactant solutions. 31 refs.
Hypergravity to Explore the Role of Buoyancy in Boiling in Porous Media
NASA Astrophysics Data System (ADS)
Lioumbas, John S.; Krause, Jutta; Karapantsios, Thodoris D.
2013-02-01
Boiling in porous media is an active topic of research since it is associated with various applications, e.g. microelectronics cooling, wetted porous media as thermal barriers, food frying. Theoretical expressions customary scale boiling heat and mass transfer rates with the value of gravitational acceleration. Information obtained at low gravity conditions show a deviation from the above scaling law but refers exclusively to non-porous substrates. In addition, the role of buoyancy in boiling at varying gravitational levels (i.e. from microgravity—important to satellites and future Lunar and Martial missions, to high-g body forces—associated with fast aerial maneuvers) is still unknown since most experiments were conducted over a limited range of g-value. The present work aims at providing evidence regarding boiling in porous media over a broad range of hypergravity values. For this, a special device has been constructed for studying boiling inside porous media in the Large Diameter Centrifuge (LDC at ESA/ESTEC). LDC offers the unique opportunity to cancel the shear stresses and study only the effect of increased normal forces on boiling in porous media. The device permits measurement of the temperature field beneath the surface of the porous material and video recordings of bubble activity over the free surface of the porous material. The preliminary results presented from experiments conducted at terrestrial and hypergravity conditions, reveal for the first time the influence of increased levels of gravity on boiling in porous media.
Microbial growth and transport in saturated and unsaturated porous media
NASA Astrophysics Data System (ADS)
Hron, Pavel; Jost, Daniel; Bastian, Peter; Ippisch, Olaf
2014-05-01
There is a considerable ongoing effort aimed at understanding the behavior of microorganisms in porous media. Microbial activity is of significant interest in various environmental applications such as in situ bioremediation, protection of drinking water supplies and for subsurface geochemistry in general. The main limiting factors for bacterial growth are the availability of electron acceptors, nutrients and bio-available water. The capillary fringe, defined - in a wider sense than usual - as the region of the subsurface above the groundwater table, but still dominated by capillary rise, is a region where all these factors are abundantly available. It is thus a region where high microbial activity is to be expected. In a research unit 'Dynamic Capillary Fringes - A Multidisciplinary Approach (DyCap)' founded by the German Research Foundation (DFG), the growth of microorganisms in the capillary fringe was studied experimentally and with numerical simulations. Processes like component transport and diffusion, exchange between the liquid phase and the gas phase, microbial growth and cell attachment and detachment were incorporated into a numerical simulator. The growth of the facultative anaerobic Escherichia coli as a function of nutrient availability and oxygen concentration in the liquid phase is modeled with modified Monod-type models and modifications for the switch between aerobic and anaerobic growth. Laboratory batch experiments with aqueous solutions of bacteria have been carried out under various combinations of oxygen concentrations in the gas phase and added amounts of dissolved organic carbon to determine the growth model parameters by solution of a parameter estimation problem. For the transport of bacteria the adhesion to phase boundaries is also very important. As microorganisms are transported through porous media, they are removed from the pore fluid by physicochemical filtration (attachment to sediment grain surfaces) or are adhering to gas
Transport of molecular fluids through three-dimensional porous media
NASA Astrophysics Data System (ADS)
Adler, Pierre; Pazdniakou, Aliaksei
2014-05-01
The main purpose of this study is to extend the analysis which has been made for the double layer theory (summarized by [1]) to situations where the distance between the solid walls is of the order of several molecular diameters. This is of a large interest from a scientific viewpoint and for various engineering applications. The intermolecular forces and their influence on fluid structure and dynamics can be taken into account by using the mesoscopic scale models based on the Boltzmann equation [2]. The numerical methods derived from these models are less demanding in computational resources than conventional molecular dynamics methods and therefore long time evolution of large samples can be considered. Three types of fluid particles are considered, namely the anions, the cations and the solvent. They possess a finite diameter which should be at least a few lattice units. The collision frequency between particles is increased by the pair correlation function for hard spheres. The lattice Boltzmann model is built in three dimensions with 19 velocities; it involves two relaxation times. The particle distribution functions are discretized over a basis of Hermite polynomial tensors. Electric forces are included and a Poisson equation is simultaneously solved by a successive over-relaxation method. The numerical algorithm is detailed; it is devised in order to be able to address any three-dimensional porous media. It involves the determination of the densities of each particle species, of the overall density and of the equilibrium distribution function. Then, the electric forces are determined. Collision operators are applied as well as the boundary conditions. Finally, the propagation step is performed and the algorithm starts a new loop. The influence of parameters can be illustrated by systematic calculations in a plane Poiseuille configuration. The drastic influence of the ratio between the channel width and the particle sizes on the local densities and the
Adaptive multiresolution modeling of groundwater flow in heterogeneous porous media
NASA Astrophysics Data System (ADS)
Malenica, Luka; Gotovac, Hrvoje; Srzic, Veljko; Andric, Ivo
2016-04-01
Proposed methodology was originally developed by our scientific team in Split who designed multiresolution approach for analyzing flow and transport processes in highly heterogeneous porous media. The main properties of the adaptive Fup multi-resolution approach are: 1) computational capabilities of Fup basis functions with compact support capable to resolve all spatial and temporal scales, 2) multi-resolution presentation of heterogeneity as well as all other input and output variables, 3) accurate, adaptive and efficient strategy and 4) semi-analytical properties which increase our understanding of usually complex flow and transport processes in porous media. The main computational idea behind this approach is to separately find the minimum number of basis functions and resolution levels necessary to describe each flow and transport variable with the desired accuracy on a particular adaptive grid. Therefore, each variable is separately analyzed, and the adaptive and multi-scale nature of the methodology enables not only computational efficiency and accuracy, but it also describes subsurface processes closely related to their understood physical interpretation. The methodology inherently supports a mesh-free procedure, avoiding the classical numerical integration, and yields continuous velocity and flux fields, which is vitally important for flow and transport simulations. In this paper, we will show recent improvements within the proposed methodology. Since "state of the art" multiresolution approach usually uses method of lines and only spatial adaptive procedure, temporal approximation was rarely considered as a multiscale. Therefore, novel adaptive implicit Fup integration scheme is developed, resolving all time scales within each global time step. It means that algorithm uses smaller time steps only in lines where solution changes are intensive. Application of Fup basis functions enables continuous time approximation, simple interpolation calculations across
Mobility of engineered inorganic nanoparticles in porous media
NASA Astrophysics Data System (ADS)
Metreveli, George; Heidmann, Ilona; Schaumann, Gabriele Ellen
2013-04-01
Besides the excellent properties and great potential for various industrial, medical, pharmaceutical, cosmetic, and life science applications, engineered inorganic nanoparticles (EINP) can show also disadvantages concerning increasing risk potential with increasing application, if they are released in the environmental systems. EINP can influence microbial activity and can show toxic effects (Fabrega et al., 2009). Similar to the inorganic natural colloids, EINP can be transported in soil and groundwater systems (Metreveli et al., 2005). Furthermore, due to the large surface area and high sorption and complex formation capacity, EINP can facilitate transport of different contaminants. In this study the mobility behaviour of EINP and their effect on the transport of different metal(loid) species in water saturated porous media was investigated. For these experiments laboratory column system was used. The column was filled with quartz sand. The interactions between EINP and metal(loid)s were characterised by coupling of asymmetrical flow field flow fractionation (AF4) with inductively coupled plasma mass spectrometer (ICP-MS). As EINP laponite (synthetic three layer clay mineral), and as metal(loid)s Cu, Pb, Zn, Pt and As were used. In AF4 experiments sorption of metal(loid)s on the surface of EINP could be observed. The extent of interactions was influenced by pH value and was different for different metal(loid)s. Laboratory column experiments showed high mobility of EINP, which facilitated transport of most of metal(loid)s in water saturated porous media. Furthermore the migration of synthetic silver nanoparticles in natural soil columns was determined in leaching experiments. Acknowledgement Financial support by German Research Council (DFG) and Max-Buchner-Research Foundation (MBFSt) is gratefully acknowledged. We thank Karlsruhe Institute of Technology (KIT) for the opportunity to perform the column and AF4 experiments. References: Fabrega, J., Fawcett, S. R
Effect of pore structure on gas trapping in porous media
NASA Astrophysics Data System (ADS)
Mohammadian, Sadjad; Geistlinger, Helmut; Vogel, Hans-Jörg
2014-05-01
Capillary trapping of nonwetting phase in porous media plays an important role in many geological processes. For example, large portions of hydrocarbons cannot be extracted from reservoirs due to capillary forces, while in carbon sequestration processes; capillary trapping might improve the storage efficiency. An important case is when the wetting phase (mostly water) displaces a low-viscosity low-density fluid. In such cases, like water encroachment into gas reservoirs or rising of water table in soils, competition of gravity, viscous, and capillary forces determines the final configuration of the fluids in invaded zone. The trapped nonwetting phase and its distribution within the porous media will affect many other processes such as flow of the other fluids and mass transfer phenomena. Thus, investigating the parameters affecting phase trapping and distribution, especially their relation to pore structure, which controls the capillary action, is required. The aim is to predict gas trapping from structural properties of the material. We conducted a series of column experiments, in which water displaces air at a range of flow rates in different glass-bead packs. The final 3D configuration and morphology of fluids was observed using X-Ray Computed Tomography (CT). We extracted 3D structure of porous media as well as of the trapped gas phase, and quantified them in terms of volume ratios, interfacial area, and morphology. Then we investigated the relations of the trapped phase to capillary forces (pore structure) and viscous forces (front velocity). The results give us new insights to explore the flow and dissolution processes: We found no systematic dependency of the front velocity of the invading water phase in the velocity range from 0.1 to 0.6 cm/min what corresponds to capillary numbers from 2 to 12 ×10^-6. Our experimental results indicate that the capillary trapping mechanism is controlled by the local pore structure and local connectivity and not by
Heterogeneities of flow in stochastically generated porous media
NASA Astrophysics Data System (ADS)
Hyman, Jeffrey D.; Smolarkiewicz, Piotr K.; Winter, C. Larrabee
2012-11-01
Heterogeneous flows are observed to result from variations in the geometry and topology of pore structures within stochastically generated three dimensional porous media. A stochastic procedure generates media comprising complex networks of connected pores. Inside each pore space, the Navier-Stokes equations are numerically integrated until steady state velocity and pressure fields are attained. The intricate pore structures exert spatially variable resistance on the fluid, and resulting velocity fields have a wide range of magnitudes and directions. Spatially nonuniform fluid fluxes are observed, resulting in principal pathways of flow through the media. In some realizations, up to 25% of the flux occurs in 5% of the pore space depending on porosity. The degree of heterogeneity in the flow is quantified over a range of porosities by tracking particle trajectories and calculating their attributes including tortuosity, length, and first passage time. A representative elementary volume is first computed so the dependence of particle based attributes on the size of the domain through which they are followed is minimal. High correlations between the dimensionless quantities of porosity and tortuosity are calculated and a logarithmic relationship is proposed. As the porosity of a medium increases the flow field becomes more uniform.
Velocity measurement of flow over random soft porous media
NASA Astrophysics Data System (ADS)
Selkirk, Isreal; Mirbod, Parisa
2016-11-01
The aim of this work is to experimentally examine the flow over random soft porous media in a three-dimensional channel. Various combination of fibrous material and the morphology of the fibers were chosen to achieve void volume fraction (ɛ) ranging from 0.4 to 0.7. Care has been taken to keep the Reynolds number low so that the flow was laminar. The channel height was constant, however the thickness of the fibrous media was varied to achieve different filling fraction. Before starting the tests in the duct with fiber arrays, a series of tests in an empty duct (i.e., without fibers) conducted to validate the experimental measurements. We also discussed the error and uncertainty sources in the experiments and described the techniques to improve their impact. We studied detailed velocity measurements of the flow over fibrous material inside a rectangular duct using a planar particle image velocimetry (PIV) technique. Using these measurements, we determined the values of the slip velocity at the interface between the fibrous media and the flow. It was found that values of the slip velocity normalized by the maximum velocity in the flow depend on solid volume fraction, pore spaces, and fraction of channel filled by the fiber layers.
NASA Astrophysics Data System (ADS)
Darvini, G.; Salandin, P.
2009-12-01
To analyze the impact of the hydraulic conductivity K spatial variability in a real field case (as an example to delimitate a well catchment), numerical simulations can be reasonably developed in a two-dimensional vertical average context. Nevertheless the plume evolution is a consequence of a more complex three-dimensional heterogeneous structure whose vertical variability dominates the dispersion phenomena at local scale. In larger domains, the effect of the vertical heterogeneity combines itself with that one due to the horizontal variability of K, and only when the plume has travelled a large number of (horizontal) integral scales, its evolution can be analyzed in a regional context, under the hypothesis that the transmissivity spatial distribution prevails. Until this limit is reached, the vertical and horizontal variability of K are combined to give a fully 3-D dispersion process. In all these situations, to successfully accomplish the 3-D heterogeneous structure of the aquifer in 2-D simulations, more than the planimetric depth-averaged variability of K must be accounted for. To define the uncertainty related to the use of different planimetric schematizations of the real hydraulic conductivity spatial distribution, we present here the results of some numerical experiments that compare the 3-D plume evolution with 2-D simulations developed by tacking into account different hydraulic conductivity distribution schematization, by considering a hierarchical architecture of media also. This description of a sedimentary formation combined with the finite size of the plume requires theoretical and numerical tools able to take into account the flow field inhomogeneity and the ergodicity lack that characterize the transport phenomena. Following this way it will be possible to quantify / reduce the uncertainty related to a 2-D schematization in a large number of real cases where the domain spans between the local and the regional scale and whose dimension may lead to
NASA Astrophysics Data System (ADS)
Roth, E. J.; Tigera, R. G.; Crimaldi, J. P.; Mays, D. C.
2015-12-01
Research in porous media is often hampered by the difficulty in making pore-scale observations. By selecting porous media that is refractive index matched (RIM) to the pore fluid, the media becomes transparent. This allows optical imaging techniques such as static light scattering (SLS), dynamic light scattering (DLS), confocal microscopy, and planar laser-induced fluorescence (PLIF) to be employed. RIM is particularly useful for research concerning contaminant remediation in the subsurface, permitting visual observation of plume dynamics at the pore scale. The goal of this research is to explore and assess candidate combinations of porous media, fluid, and fluorescent dye. The strengths and weaknesses of each combination will then be evaluated in terms of safety, cost, and optical quality in order to select the best combination for use with PLIF. Within this framework, top-ranked RIM combinations include Pyrex glass beads, water beads, or granular Nafion saturated in vegetable glycerin, deionized water, and an aqueous solution of 48% isopropanol, respectively. This research lays the groundwork for future efforts to build a flow chamber in which the selected RIM porous media, solution, and dye will be used in evaluating subsurface pumping strategies designed to impose chaotic plume spreading in porous media. Though the RIM porous media explored in this research are selected based on the specifications of a particular experiment, the methods developed for working with and evaluating RIM porous media should be of utility to a wide variety of research interests.
NASA Astrophysics Data System (ADS)
Fan, Cui-Ying; Zhao, Ming-Hao; Zhou, You-He
2009-09-01
The polarization saturation (PS) model [Gao, H., Barnett, D.M., 1996. An invariance property of local energy release rates in a strip saturation model of piezoelectric fracture. Int. J. Fract. 79, R25-R29; Gao, H., Zhang, T.Y., Tong, P., 1997. Local and global energy release rates for an electrically yielded crack in a piezoelectric ceramic. J. Mech. Phys. Solids 45, 491-510], and the dielectric breakdown (DB) model [Zhang, T.Y., Zhao, M.H., Cao, C.F., 2005. The strip dielectric breakdown model. Int. J. Fract. 132, 311-327] explain very well some experimental observations of fracture of piezoelectric ceramics. In this paper, the nonlinear hybrid extended displacement discontinuity-fundamental solution method (NLHEDD-FSM) is presented for numerical analysis of both the PS and DB models of two-dimensional (2D) finite piezoelectric media under impermeable and semi-permeable electric boundary conditions. In this NLHEDD-FSM, the solution is expressed approximately by a linear combination of fundamental solutions of the governing equations, which includes the extended point force fundamental solutions with sources placed at chosen points outside the domain of the problem under consideration, and the extended Crouch fundamental solutions with extended displacement discontinuities placed on the crack and the electric yielding zone. The coefficients of the fundamental solutions are determined by letting the approximated solution satisfy certain conditions on the boundary of the domain, on the crack face and the electric yielding zone. The zero electric displacement intensity factor in the PS model or the zero electric field strength intensity factor in the DB model at the outer tips of the electric yielding zone is used as a supplementary condition to determine the size of the electric yielding zone. Iteration approaches are adopted in the NLHEDD-FSM. The electric yielding zone is determined, and the extended intensity factors and the local J-integral are calculated for
Centrifuge Techniques and Apparatus for Transport Experiments in Porous Media
Earl D. Mattson; Carl D. Paler; Robert W. Smith; Markus Flury
2010-06-01
This paper describes experimental approaches and apparatus that we have developed to study solute and colloid transport in porous media using Idaho National Laboratory's 2-m radius centrifuge. The ex-perimental techniques include water flux scaling with applied acceleration at the top of the column and sub-atmospheric pressure control at the column base, automation of data collection, and remote experimental con-trol over the internet. These apparatus include a constant displacement piston pump, a custom designed liquid fraction collector based on switching valve technology, and modified moisture monitoring equipment. Suc-cessful development of these experimental techniques and equipment is illustrated through application to transport of a conservative tracer through unsaturated sand column, with centrifugal acceleration up to 40 gs. Development of such experimental equipment that can withstand high accelerations enhances the centrifuge technique to conduct highly controlled unsaturated solute/colloid transport experiments and allows in-flight liquid sample collection of the effluent.
Generalized Newtonian fluid flow through fibrous porous media
NASA Astrophysics Data System (ADS)
Mierzwiczak, Magdalena; Kołodziej, Jan Adam; Grabski, Jakub Krzysztof
2016-06-01
The numerical calculations of the velocity field and the component of transverse permeability in the filtration equation for steady, incompressible flow of the generalized Newtonian fluid through the assemblages of cylindrical fibers are presented in this paper. The fibers are arranged regularly in arrays. Flow is transverse with respect to the fibers. The non-linear governing equation in the repeated element of the array is solved using iteration method. At each iteration step the method of fundamental solutions and the method of particular solutions are used. The bundle of fibers is treated as a porous media and on the base of velocity field the permeability coefficients are calculated as a function of porosity.
Solute transport across a contact interface in deformable porous media.
Ateshian, Gerard A; Maas, Steve; Weiss, Jeffrey A
2012-04-05
A finite element formulation of neutral solute transport across a contact interface between deformable porous media is implemented and validated against analytical solutions. By reducing the integral statements of external virtual work on the two contacting surfaces into a single contact integral, the algorithm automatically enforces continuity of solute molar flux across the contact interface, whereas continuity of the effective solute concentration (a measure of the solute mechano-chemical potential) is achieved using a penalty method. This novel formulation facilitates the analysis of problems in biomechanics where the transport of metabolites across contact interfaces of deformable tissues may be of interest. This contact algorithm is the first to address solute transport across deformable interfaces, and is made available in the public domain, open-source finite element code FEBio (http://www.febio.org).
Gravity Current in Horizontal Porous Media with A Permeability Gradient
NASA Astrophysics Data System (ADS)
Zheng, Zhong; Tsai, Peichun; Al-Housseiny, Talal; Stone, Howard; Complex Fluid Group Team
2011-11-01
We study the influence of a power-law porosity and permeability gradient on the front propagation of a gravity current in an unconfined porous media. We neglect mass transfer and surface tension on the interface. A similarity solution is found for the propagating front, which is different from the homogeneous case. Experiments have been performed using liquid pushing air in a Hele-Shaw cell with a constant gradient in gap thickness in the vertical direction. We measure the speed of the front and the shape of the interface. We observe a third layer of trapped air in the region where the permeability is low, while it appears that the propagating front still satisfies the similarity solution with a modified coefficient. This work is supported by a funding from Carbon Mitigation Initiative at Princeton University
Biopolymer system for permeability modification in porous media
Stepp, A.K.; Bryant, R.S.; Llave, F.M.
1995-12-31
New technologies are needed to reduce the current high rate of well abandonment. Improved sweep efficiency, reservoir conformance, and permeability modification can have a significant impact on oil recovery processes. Microorganisms can be used to selectively plug high-permeability zones to improve sweep efficiency and impart conformance control. Studies of a promising microbial system for polymer production were conducted to evaluate reservoir conditions in which this system would be effective. Factors which can affect microbial growth and polymer production include salinity, pH, temperature, divalent ions, presence of residual oil, and rock matrix. Flask tests and coreflooding experiments were conducted to optimize and evaluate the effectiveness of this system. Nuclear magnetic resonance imaging (NMRI) was used to visualize microbial polymer production in porous media. Changes in fluid distribution within the pore system of the core were detected.
Strength and stability of microbial plugs in porous media
Sarkar, A.K.
1995-12-31
Mobility reduction induced by the growth and metabolism of bacteria in high-permeability layers of heterogeneous reservoirs is an economically attractive technique to improve sweep efficiency. This paper describes an experimental study conducted in sandpacks using an injected bacterium to investigate the strength and stability of microbial plugs in porous media. Successful convective transport of bacteria is important for achieving sufficient initial bacteria distribution. The chemotactic and diffusive fluxes are probably not significant even under static conditions. Mobility reduction depends upon the initial cell concentrations and increase in cell mass. For single or multiple static or dynamic growth techniques, permeability reduction was approximately 70% of the original permeability. The stability of these microbial plugs to increases in pressure gradient and changes in cell physiology in a nutrient-depleted environment needs to be improved.
Effects of capillarity on microscopic flow in porous media
Not Available
1992-01-01
The central theme of this proposal is to study the effects of capillarity on the motion of a fluid interface and to apply these results to flow in porous media. Here we report on several problems considered this year. In particular we have investigated a new similarity solution of a moving boundary problem driven only by surface tension, we have started an investigation on the effect of roughness on the motion of a contact line and we have started both a numerical and analytical investigation of the motion of fluid interfaces in a pore. In addition we report on a new method to derive macroscopic effective equation of motion of two-phase flows at low volume fraction.
On the transport of emulsions in porous media
Cortis, Andrea; Ghezzehei, Teamrat A.
2007-06-27
Emulsions appear in many subsurface applications includingbioremediation, surfactant-enhanced remediation, and enhancedoil-recovery. Modeling emulsion transport in porous media is particularlychallenging because the rheological and physical properties of emulsionsare different from averages of the components. Current modelingapproaches are based on filtration theories, which are not suited toadequately address the pore-scale permeability fluctuations and reductionof absolute permeability that are often encountered during emulsiontransport. In this communication, we introduce a continuous time randomwalk based alternative approach that captures these unique features ofemulsion transport. Calculations based on the proposed approach resultedin excellent match with experimental observations of emulsionbreakthrough from the literature. Specifically, the new approach explainsthe slow late-time tailing behavior that could not be fitted using thestandard approach. The theory presented in this paper also provides animportant stepping stone toward a generalizedself-consistent modeling ofmultiphase flow.
Critical transport parameters for porous media subjected to counterflow
NASA Technical Reports Server (NTRS)
Frederking, T. H. K.; Afifi, F. A.; Ono, D. Y.
1989-01-01
Experimental and theoretical studies have been conducted to determine critical parameters at the onset of nonlinear counterflow in He II below the lambda point of He-4. Critical temperature differences have been measured in porous media for zero net mass flow and for Darcy permeabilities in the order of magnitude range from 10 to the -10th to 10 to the -8th sq cm. The normalized critical temperature gradients, which covered the liquid temperature range of 1.5 K to the lambda temperature, are found to vary with T proportional to the ratio of the superfluid density to the normal fluid density. This liquid temperature dependence appears to be consistent with duct data which are limited at low temperature by a Reynolds number criterion.
Advanced Laser Based Measurements in Porous Media Combustion
NASA Technical Reports Server (NTRS)
Tedder, Sarah A.
2009-01-01
We present measurements using dual-pump dual-broadband coherent anti-Stokes Raman scattering spectroscopy (DP-DBB-CARS) inside a porous media burner. This work continues our previous measurements in such combustion systems. The existing setup was significantly modified with the aim of providing improved data quality and data rate, reduction of interferences and additional species information. These changes are presented and discussed in detail. The CARS technique was expanded to a dual-pump dual-broadband CARS system which in principle enables acquisition of temperatures together with relative H2/N2- and O2/N2- species concentrations. Experimental complexity was reduced by the use of a modified spectrometer enabling the detection of both signals, vibrational and rotational CARS, with only one detection system.
Hybrid Models of Reactive Transport in Porous and Fractured Media
Battiato, Ilenia; Tartakovsky, Daniel M.; Tartakovsky, Alexandre M.; Scheibe, Timothy D.
2011-02-02
Darcy-scale models of flow and transport in porous media often fail to describe experimentally observed phenomena, while their pore-scale counterparts are accu- rate but can be computationally prohibitive. Most numerical multi-scale models, which seek to combine these two descriptions, require empirical closures and/or assumptions on the behavior of pore-scale quantities at the continuum (Darcy) scale. We present a general formulation of an iterative hybrid numerical method that links these two scales without resorting to such approximations. The algorithm treats the fluxes exchanged at the internal boundaries between the pore- and continuum-scale domains as unknown, and allows for iteratively determined boundary conditions to be applied at the pore-scale in order to guarantee their continuity. While the algorithm proposed is general, we use it to model Taylor dispersion in a fracture with chemically reactive walls. Results show significant improvement upon standard continuum-scale formulations.
Microbial transport through porous media: The importance of the microscale
NASA Astrophysics Data System (ADS)
de Anna, Pietro; Yawata, Yutaka; Stocker, Roman; Juanes, Ruben
2014-11-01
Bacteria play a key role in a plethora of subsurface processes, from geothermal energy, to enhanced oil recovery, to bioremediation. These large-scale consequences arise from microscale interactions within the highly heterogeneous subsurface environment. In particular, flow generates strong chemical gradients at the pore-scale and we hypothesized that, by actively responding to these microscale gradients, bacteria significantly change their transport properties at the macro-scale. We tested this hypothesis using video microscopy of Bacillus subtilis in microfluidic replica of porous media. We found that the bacteria's motility and chemotaxis resulted in a two-fold increase in their ability to spread in the pore volumes, as a result of active migration out of micro-pockets of stagnant fluid. These findings illustrate that microscale flow heterogeneity has strong implications for the transport of biota through the subsurface, and thus likely for the biogeochemical processes they mediate.
Modeling heating curve for gas hydrate dissociation in porous media.
Dicharry, Christophe; Gayet, Pascal; Marion, Gérard; Graciaa, Alain; Nesterov, Anatoliy N
2005-09-15
A method for modeling the heating curve for gas hydrate dissociation in porous media at isochoric conditions (constant cell volume) is presented. This method consists of using an equation of state of the gas, the cumulative volume distribution (CVD) of the porous medium, and a van der Waals-Platteeuw-type thermodynamic model that includes a capillary term. The proposed method was tested to predict the heating curves for methane hydrate dissociation in a mesoporous silica glass for saturated conditions (liquid volume = pore volume) and for a fractional conversion of water to hydrate of 1 (100% of the available water was converted to hydrate). The shape factor (F) of the hydrate-water interface was found equal to 1, supporting a cylindrical shape for the hydrate particles during hydrate dissociation. Using F = 1, it has been possible to predict the heating curve for different ranges of pressure and temperature. The excellent agreement between the calculated and experimental heating curves supports the validity of our approach.
Transport of bacteria in porous media; 1: An experimental investigation
Sarkar, A.K.; Georgiou, G.; Sharma, M.M. )
1994-08-05
The convective transport of concentrated suspensions of bacteria in porous media is of interest for several processes such as microbial enhanced oil recovery and in situ bioremediation. The parameters which affect the transport of the bacterium Bacillus licheniformis JF-2, a candidate microorganism for microbial enhanced oil recovery, were investigated experimentally in sandpacks. Bacteria retention and permeability reduction occurred primarily in the first few centimeters upon entering the porous medium. In downstream sections of the sandpack, the permeability reduction was low, even in cases in which high cell concentrations were detected in the effluent. The effects of (1) addition of a dispersant, (2) linear velocity of injection, (3) cell concentration, (4) salinity, (5) temperature, and (6) the presence of a residual oleic phase were determined experimentally. A lower reduction in permeability and a higher effluent bacterial concentration were obtained in the presence of dispersant, high injection velocities, low salinities, and at a higher temperature. Macroscopic measurements at different linear velocities and in the presence or absence of dispersants suggest that the formation of reversible microaggregates and multiparticle hydrodynamic exclusion may be the primary mechanisms for bacterial retention and permeability reduction.
Transient buoyant convection from a discrete source in porous media
NASA Astrophysics Data System (ADS)
Moradi, Ali; Flynn, Morris
2016-11-01
The study of porous media filling box flows informs (i) the dissolution of non-aqueous phase liquids or sequestered CO2 into potable groundwater, (ii) leakage of contaminants from waste piles, and (iii) enhanced oil recovery technologies. Here we examine the flow of a negatively buoyant, laminar plume in a box filled with a porous medium, which is connected to an infinite external ambient via upper and lower fissures. As t -> ∞ , the box contains two uniform layers of different densities. However, the approach towards steady state is characterized by a lower (contaminated) layer that is continuously stratified and is governed by the ratios of the virtual origin correction and lower fissure depth to the box height, and the ratio, μ, of the draining timescale to the filling timescale. Whereas the presence of a continuous stratification in the contaminated layer for finite time poses analytical challenges, we show that it is possible to derive bounds on the range of possible solutions. A separate component of our study considers time-variable forcing where the plume source strength is either abruptly altered or turned on and off with fixed half-period. Throughout, comparisons are drawn against filling boxes driven by turbulent free plumes. NSERC, Carbon Management Canada.
Modeling of Biomass Plug Development and Propagation in Porous Media
Stewart, Terri L.; Kim, Dong-Shik
2004-02-01
Biomass accumulation and evolution in porous media were simulated using a combination of biofilm evolution model and a biofilm removal model. Theses models describe biomass plug development, removal, and propagation in biological applications such as microbial enhanced oil recovery, in situ bioremediation, and bio-barrier techniques. The biofilm evolution model includes the cell growth rate and exopolymer production kinetics. The biofilm removal model was used for describing the biomass plug propagation and channel breakthrough using Bingham yield stress of biofilm, which represents the stability of biofilm against shear stress. Network model was used to describe a porous medium. The network model consists of pore body and pore bond of which the sizes were determined based on the pore size distribution of ceramic cores. The pressure drop across the network is assumed to be generated from pore bonds only, and the cell growth and biomass accumulation took place in pore bonds. The simulation results showed that the biofilm models based on Bingham yield stress predicted the biomass accumulation and channel breakthrough well. The pressure oscillation (or, permeability oscillation) was also demonstrated well indicating the process of biomass accumulation and breakthrough channel formation. In addition, the effects of cell and biofilm sucrose concentration were significant on the biomass plug development and permeability reduction rates. The modeling elucidated some deficiencies in our knowledge of the biomass yield stress that enables us to predict the stability of biomass plug against shear stress.
A Monte Carlo paradigm for capillarity in porous media
Lu, Ning; Zeidman, Benjamin D.; Lusk, Mark T.; Willson, Clinton S.; Wu, David T.
2011-08-09
Wet porous media are ubiquitous in nature as soils, rocks, plants, and bones, and in engineering settings such as oil production, ground stability, filtration and composites. Their physical and chemical behavior is governed by the distribution of liquid and interfaces between phases. Characterization of the interfacial distribution is mostly based on macroscopic experiments, aided by empirical formulae. We present an alternative computational paradigm utilizing a Monte Carlo algorithm to simulate interfaces in complex realistic pore geometries. The method agrees with analytical solutions available only for idealized pore geometries, and is in quantitative agreement with Micro X-ray Computed Tomography (microXCT), capillary pressure, and interfacial area measurements for natural soils. We demonstrate that this methodology predicts macroscopic properties such as the capillary pressure and air-liquid interface area versus liquid saturation based only on the pore size information from microXCT images and interfacial interaction energies. The generality of this method should allow simulation of capillarity in many porous materials.
A pore network model for adsorption in porous media
Satik, Cengiz; Yortsos, Yanis C.
1995-01-26
Using a pore network model to represent porous media we investigate adsorption-desorption processes over the entire range of the relative pressure, highlighting in particular capillary condensation. The model incorporates recent advances from density functional theory for adsorption-desorption in narrow pores (of order as low as 1 nm), which improve upon the traditional multi-layer adsorption and Kelvin's equation for phase change and provide for the dependence of the critical pore size on temperature. The limited accessibility of the pore network gives rise to hysteresis in the adsorption-desorption cycle. This is due to the blocking of larger pores, where adsorbed liquid is allowed to but cannot desorb, by smaller pores containing liquid that may not desorb. By allowing for the existence of supercritical liquid in pores in the nm range, it is found that the hysteresis area increases with an increase in temperature, in agreement with experiments of water adsorption-desorption in rock samples from The Geysers. It is also found that the hysteresis increases if the porous medium is represented as a fractured (dual porosity) system. The paper finds applications to general adsorption-desorption problems but it is illustrated here for geothermal applications in The Geysers.
Thermal Convection in Laboratory-Scale Porous Media
NASA Astrophysics Data System (ADS)
Breitmeyer, R. J.; Cooper, C. A.; Decker, D. L.
2006-12-01
Experiments in laboratory-scale porous media were conducted to observe the behavior of thermally driven convection. Experiments were conducted in two cells with dimensions of 24 x 20 x 2.54 cm and 100 x 75 x 2.54 cm. Each experiment consisted of constant temperature, thermally conductive, impermeable boundaries at the top and bottom with spherical glass beads comprising the medium. The porous medium was made up of two sizes of glass beads, 0.3 cm and 0.5 cm. A thermochromic liquid crystal (TLC) tracer was employed in conjunction with a CCD camera to develop a time-series of image data with a color-temperature relationship. Experiments were systematically designed to determine how convection develops in relation to permeability and its spatial variations, thermal gradient, and cell dimensions of the system. The physical behavior of convection was observed in terms of plume structure and velocity, and heat flux. Plume width appeared to be dependent on both permeability and the size of the initial instabilities at the onset of convection with wider plumes forming in lower permeability media and wider initial instabilities leading to wider plumes at later times. Heat flux behavior for each experiment was investigated through calculation of the Nusselt Number (Nu). Nu as a function of Rayleigh Number (Ra) appeared to scale as Nu~ Ra^{1/3} in the homogeneous medium, which is in agreement with previous work. Observations of the long-time behavior were made to determine whether or not the development of steady-state behavior occurred. In the small experimental cell with a 15° C temperature difference and containing only 0.5 cm beads, a steady state condition appeared to form shortly after the plumes reached the upper constant temperature boundary condition. Experiments were conducted in both cells in which higher permeability media underlay lower permeability media with a 10° C temperature difference. Similar behavior was seen in both cells with the plumes widening at
Freezing in porous media: Phase behavior, dynamics and transport phenomena
Wettlaufer, John S.
2012-12-21
This research was focused on developing the underlying framework for the mechanisms that control the nature of the solidification of a broad range of porous media. To encompass the scope of porous media under consideration we considered material ranging from a dilute colloidal suspension to a highly packed saturated host matrix with a known geometry. The basic physical processes that occur when the interstitial liquid phase solidifies revealed a host of surprises with a broad range of implications from geophysics to materials science and engineering. We now understand that ostensibly microscopic films of unfrozen liquid control both the equilibrium and transport properties of a highly packed saturated host matrix as well as a rather dilute colloidal suspension. However, our description of the effective medium behavior in these settings is rather different and this sets the stage for the future research based on our past results. Once the liquid phase of a saturated relatively densely packed material is frozen, there is a rich dynamical behavior of particles for example due to the directed motion driven by thermomolecular pressure gradients or the confined Brownian motion of the particles. In quite striking contrast, when one freezes a dilute suspension the behavior can be rather more like that of a binary alloy with the particles playing the role of a ``solute''. We probed such systems quantitatively by (i) using X ray photon correlation spectroscopy (XPCS) and Small Angle X-ray Scattering (SAXS) at the Advanced Photon Source at Argonne (ii) studying the Argonne cell in the laboratory using optical microscopy and imagery (because it is not directly visible while in the vacuum can). (3) analyzed the general transport phenomena within the framework of both irreversible thermodynamics and alloy solidification and (4) applied the results to the study of the redistribution of solid particles in a frozen interstitial material. This research has gone a long way towards
Fingering instability and mixing of a blob in porous media
NASA Astrophysics Data System (ADS)
Pramanik, Satyajit; Mishra, Manoranjan
2016-10-01
The curvature of the unstable part of the miscible interface between a circular blob and the ambient fluid in two-dimensional homogeneous porous media depends on the viscosity of the fluids. The influence of the interface curvature on the fingering instability and mixing of a miscible blob within a rectilinear displacement is investigated numerically. The fluid velocity in porous media is governed by Darcy's law, coupled with a convection-diffusion equation that determines the evolution of the solute concentration controlling the viscosity of the fluids. Numerical simulations are performed using a Fourier pseudospectral method to determine the dynamics of a miscible blob (circular or square). It is shown that for a less viscous circular blob, there exist three different instability regions without any finite R -window for viscous fingering, unlike the case of a more viscous circular blob. Critical blob radius for the onset of instability is smaller for a less viscous blob as compared to its more viscous counterpart. Fingering enhances spreading and mixing of miscible fluids. Hence a less viscous blob mixes with the ambient fluid quicker than the more viscous one. Furthermore, we show that mixing increases with the viscosity contrast for a less viscous blob, while for a more viscous one mixing depends nonmonotonically on the viscosity contrast. For a more viscous blob mixing depends nonmonotonically on the dispersion anisotropy, while it decreases monotonically with the anisotropic dispersion coefficient for a less viscous blob. We also show that the dynamics of a more viscous square blob is qualitatively similar to that of a circular one, except the existence of the lump-shaped instability region in the R -Pe plane. We have shown that the Rayleigh-Taylor instability in a circular blob (heavier or lighter than the ambient fluid) is independent of the interface curvature.
Mechanical Clogging Processes in Unconsolidated Porous Media Near Pumping Wells
NASA Astrophysics Data System (ADS)
de Zwart, B.; Schotting, R.; Hassanizadeh, M.
2003-12-01
In the Netherlands water supply companies produce over more than one billion cubic meters of drinking water every year. About 2500 water wells are used to pump up the groundwater from aquifers in the Dutch subsurface. More than 50% of these wells will encounter a number of technical problems during their lifetime. The main problem is the decrease in capacity due to well clogging. Clogging shows up after a number of operation years and results in extra, expensive cleaning operations and in early replacement of the pumping wells. This problem has been acknowledged by other industries, for example the metal, petroleum, beer industry and underground storage projects. Well clogging is the result of a number of interacting mechanisms creating a complex problem in the subsurface. In most clogging cases mechanical mechanisms are involved. A large number of studies have been performed to comprehend these processes. Investigations on mechanical processes are focused on transport of small particles through pores and deposition of particles due to physical or physical-chemical processes. After a period of deposition the particles plug the pores and decrease the permeability of the medium. Particle deposition in porous media is usually modelled using filtration theory. In order to get the dynamics of clogging this theory is not sufficient. The porous media is continuously altered due to deposition and mobilization. Therefore the capture characteristics will also continuously change and deposition rates will change in time. A new formula is derived to describe (re)mobilization of particles and allow changing deposition rates. This approach incorporates detachment and reattachment of deposited particles. This work also includes derivation of the filtration theory in radial coordinates. A comparison between the radial filtration theory and the new formula will be shown.
Multimodel framework for characterization of transport in porous media
NASA Astrophysics Data System (ADS)
Ciriello, Valentina; Edery, Yaniv; Guadagnini, Alberto; Berkowitz, Brian
2015-05-01
We consider modeling approaches to characterize solute transport in porous media, integrating them into a unique theoretical and experimental framework for model evaluation and data interpretation. To date, development of (conservative and reactive chemical) transport models and formulation of model calibration methods grounded on sensitivity-based collection of measurements have been pursued in parallel. Key questions that remain include: For a given set of measurements, which conceptual picture of the transport processes, as embodied in a mathematical model or models, is most appropriate? What are the most valuable space-time locations for solute concentration measurements, depending on the model selected? How is model parameter uncertainty propagated to model output, and how does this propagation affect model calibration? We address these questions by merging parallel streams of research—model formulation, reduction, calibration, sensitivity analysis, and discrimination—offering our view on an emerging framework that guides (i) selection of an appropriate number and location of time-dependent concentration measurements given a transport model and (ii) assessment (through discrimination criteria) of the relative benefit of applying any particular model from a set of several models. Our strategy is to employ metrics to quantify the relative contribution of each uncertain model parameter to the variability of the model output. We evaluate these metrics through construction of a surrogate (or "meta") transport model that has the additional benefit of enabling sensitivity analysis and model calibration at a highly reduced computational cost. We demonstrate the applicability of this framework, focusing on transport of reactive chemicals in laboratory-scale porous media.
Unstable infiltration fronts in porous media on laboratory scale
NASA Astrophysics Data System (ADS)
Schuetz, Cindi; Neuweiler, Insa
2014-05-01
Water flow and transport of substances in the unsaturated zone are important processes for the quality and quantity of water in the hydrologic cycle. The water movement through preferential paths is often much faster than standard models (e. g. Richards equation in homogeneous porous media) predict. One type/phenomenon of preferential flow can occur during water infiltration into coarse and/or dry porous media: the so-called gravity-driven fingering flow. To upscale the water content and to describe the averaged water fluxes in order to couple models of different spheres it is necessary to understand and to quantify the behavior of flow instabilities. We present different experiments of unstable infiltration in homogeneous and heterogeneous structures to analyze development and morphology of gravity-driven fingering flow on the laboratory scale. Experiments were carried out in two-dimensional and three-dimensional sand tanks as well as in larger two-dimensional sand tanks with homogeneous and heterogeneous filling of sand and glass beads. In the small systems, water content in the medium was measured at different times. We compare the experiments to prediction of theoretical approaches (e.g. Saffman and Taylor, 1958; Chuoke et al., 1959; Philip 1975a; White et al., 1976; Parlange and Hill, 1976a; Glass et al., 1989a; Glass et al., 1991; Wang et al., 1998c) that quantify properties of the gravity-driven fingers. We use hydraulic parameters needed for the theoretical predictions (the water-entry value (hwe), van Genuchten parameter (Wang et al., 1997, Wang et al., 2000) and saturated conductivity (Ks), van Genuchten parameter (Guarracino, 2007) to simplify the prediction of the finger properties and if necessary to identify a constant correction factor. We find in general that the finger properties correspond well to theoretical predictions. In heterogeneous settings, where fine inclusions are embedded into a coarse material, the finger properties do not change much
FLUID FLOW, SOLUTE MIXING AND PRECIPITATION IN POROUS MEDIA
Redden, George D; Y. Fang; T.D. Scheibe; A.M. Tartakovsky; Fox, Don T; Fujita, Yoshiko; White, Timothy A
2006-09-01
Reactions that lead to the formation of mineral precipitates, colloids or growth of biofilms in porous media often depend on the molecular-level diffusive mixing. For example, for the formation of mineral phases, exceeding the saturation index for a mineral is a minimum requirement for precipitation to proceed. Solute mixing frequently occurs at the interface between two solutions each containing one or more soluble reactants, particularly in engineered systems where contaminant degradation or modification or fluid flow are objectives. Although many of the fundamental component processes involved in the deposition or solubilization of solid phases are reasonably well understood, including precipitation equilibrium and kinetics, fluid flow and solute transport, the deposition of chemical precipitates, biofilms and colloidal particles are all coupled to flow, and the science of such coupled processes is not well developed. How such precipitates (and conversely, dissolution of solids) are distributed in the subsurface along flow paths with chemical gradients is a complex and challenging problem. This is especially true in systems that undergo rapid change where equilibrium conditions cannot be assumed, particularly in subsurface systems where reactants are introduced rapidly, compared to most natural flow conditions, and where mixing fronts are generated. Although the concept of dispersion in porous media is frequently used to approximate mixing at macroscopic scales, dispersion does not necessarily describe pore-level or molecular level mixing that must occur for chemical and biological reactions to be possible. An example of coupling between flow, mixing and mineral precipitation, with practical applications to controlling fluid flow or contaminant remediation in subsurface environments is shown in the mixing zone between parallel flowing solutions. Two- and three-dimensional experiments in packed-sand media were conducted where solutions containing calcium and
Direct, Dynamic Measurement of Interfacial Area within Porous Media
Crandall, Dustin; Ahmadi, Goodarz; Smith, Duane H.; Bromhal, Grant
2010-01-01
Standard models of two-phase flow in porous media have been shown to exhibit several shortcomings that might be partially overcome with a recently developed model based on thermodynamic principles (Hassanizadeh and Gray, 1990). This alternative two-phase flow model contains a set of new and non-standard parameters, including specific interfacial area. By incorporating interfacial area production, destruction, and propagation into functional relationships that describe the capillary pressure and saturation, a more physical model has been developed. Niessner and Hassanizadeh (2008) have examined this model numerically and have shown that the model captures saturation hysteresis with drainage/imbibition cycles. Several static experimental studies have been performed to examine the validity of this new thermodynamically based approach; these allow the determination of static parameters of the model. To date, no experimental studies have obtained information about the dynamic parameters required for the model. A new experimental porous flow cell has been constructed using stereolithography to study two-phase flow phenomena (Crandall et al. 2008). A novel image analysis tool was developed for an examination of the evolution of flow patterns during displacement experiments (Crandall et al. 2009). This analysis tool enables the direct quantification of interfacial area between fluids by matching known geometrical properties of the constructed flow cell with locations identified as interfaces from images of flowing fluids. Numerous images were obtained from two-phase experiments within the flow cell. The dynamic evolution of the fluid distribution and the fluid-fluid interface locations were determined by analyzing these images. In this paper, we give a brief introduction to the thermodynamically based two-phase flow model, review the properties of the stereolithography flow cell, and show how the image analysis procedure has been used to obtain dynamic parameters for the
Acoustical properties of dry and saturated porous media
NASA Astrophysics Data System (ADS)
Malinouskaya, I.; Mourzenko, V. V.; Bogdanov, B. B.; Thovert, J.; Adler, P. M.
2008-12-01
Our objective is to determine the macroscopic acoustical properties of porous media (either dry or saturated by an interstitial fluid) and to relate them to the mechanical and hydromechanical characteristics of the medium and its components. Wave propagation in a dry elastic material is governed by the elastodynamic equation. For a dry medium, the stress is zero on the pore surface. The medium is supposed to be spatially periodic and composed of identical cells. When the wave length λ is very large when compared to the scale l of the heterogeneities, the medium behaves in a first approximation as an equivalent homogeneous material. All the fields can expanded as series of the small parameter η= l/2πλ, in terms of two space variables x and y associated to the scales λ et l, respectively. This expansion is introduced into the elastodynamic equation with appropriate boundary conditions. A series of non homogeneous partial differential equations are found for the successive orders in η. The predominant order corresponds to the equivalent homogeneous material. The first order equation provides the polarization correction, the second one the celerity dispersion and the third one the attenuation. These equations are discretized by a finite volume formulation in a tetrahedral mesh which is either structured or not. The resulting linear system is solved by a conjugate gradient method. Each elementary volume may have specific properties. Wave propagation in a saturated medium is more complex since it is influenced by the solid and liquid phases. When a periodic oscillation is imposed, the solid displacements are governed by the elastodynamic and the Stokes equations coupled by boundary conditions at the interface. The solutions to these equations yield the macroscopic characteristics of the medium. The first equation yields two independent problems in the solid, one identical to dry media and one corresponding to a medium submitted to an interstitial macroscopic
Acoustical properties of dry and saturated porous media
NASA Astrophysics Data System (ADS)
Adler, P. M.; Malinouskaya, I.; Mourzenko, V. V.; Thovert, J. F.
2009-04-01
Our objective is to determine the macroscopic acoustical properties of porous media (either dry or saturated by an interstitial fluid) and to relate them to the mechanical and hydromechanical characteristics of the medium and its components. Wave propagation in a dry elastic material is governed by the elastodynamic equation. For a dry medium, the stress is zero on the pore surface. The medium is supposed to be spatially periodic and composed of identical cells. When the wave length lambda is very large when compared to the scale l of the heterogeneities, the medium behaves in a first approximation as an equivalent homogeneous material. All the fields can expanded as series of the small parameter eta= l/2 pi lambda, in terms of two space variables associated to the scales lambda et l, respectively. This expansion is introduced into the elastodynamic equation with appropriate boundary conditions. A series of non homogeneous partial differential equations are found for the successive orders in eta. The predominant order corresponds to the equivalent homogeneous material. The first order equation provides the polarization correction, the second one the celerity dispersion and the third one the attenuation. These equations are discretized by a finite volume formulation in a tetrahedral mesh which is either structured or not. The resulting linear system is solved by a conjugate gradient method. Each elementary volume may have specific properties. Wave propagation in a saturated medium is more complex since it is influenced by the solid and liquid phases. When a periodic oscillation is imposed, the solid displacements are governed by the elastodynamic and the Stokes equations coupled by boundary conditions at the interface. The solutions to these equations yield the macroscopic characteristics of the medium. The first equation yields two independent problems in the solid, one identical to dry media and one corresponding to a medium submitted to an interstitial
Physics-based preconditioners for flow in fractured porous media
NASA Astrophysics Data System (ADS)
Sandve, T. H.; Keilegavlen, E.; Nordbotten, J. M.
2014-02-01
Discrete fracture models are an attractive alternative to upscaled models for flow in fractured media, as they provide a more accurate representation of the flow characteristics. A major challenge in discrete fracture simulation is to overcome the large computational cost associated with resolving the individual fractures in large-scale simulations. In this work, two characteristics of the fractured porous media are utilized to construct efficient preconditioners for the discretized flow equations. First, the preconditioners are tailored to the fracture geometry and presumed flow properties so that the dominant features are well represented there. This assures good scalability of the preconditioners in terms of problem size and permeability contrast. For fracture dominated problems, numerical examples show that such geometric preconditioners are comparable or preferable when compared to state-of-the-art algebraic multigrid preconditioners. The robustness of the physics-based preconditioner for less favorable fracture conditions is further demonstrated by a systematic degradation of the fracture hierarchy. Second, the preconditioners are physics preserving in the sense that conservative fluxes can be computed even for an inexact pressure solutions. This facilitates a scheme where accuracy in the linear solver can be traded for efficiency by terminating the iterative solvers based on error estimates, and without sacrificing basic physical modeling principles. With the combination of these two properties a novel preconditioner is obtained which bridges the gap between multiscale approximations and iterative linear solvers.
The formation of microbial barriers in saturated porous media
Hendry, M.J.; Lawrence, J.R. )
1993-10-01
Control of contaminant migration in the subsurface to prevent off-site migration and facilitate treatment is an essential component of any remediation scheme. In situ plugging of pore spaces by introduced bacteria has been suggested as a mechanism to seal permeable zones and to enhance bioremediation. This procedure involves the injection of bacteria which adsorb to the geologic media, are stimulated with a nutrient solution and grow producing an exopolysaccharide plug. The objective of the current research was to evaluate the feasibility of in situ placement of biological barriers for containment of contaminants in subsurface environments. Transport of bacteria through sands at a groundwater velocity of 0.3 m/day and the impact of growth and exopolymer production during nutrient stimulation were studied over time using confocal laser microscopy and viable fluorescence exclusion techniques. The inoculum rapidly colonized the sand matrix and dominated surface sites while forming extensive biofilms. After three to four days the native ground-water flora invaded the established biofilm, creating a mixed species biofilm which reduced the effective porosity of the geologic medium. The resulting biobarrier reduced the hydraulic conductivity of the porous media by two orders of magnitude, and exhibited self-sealing properties in response to changes in hydraulic head.
FEA for damping of structures having elastic bodies, viscoelastic bodies, porous media and gas
NASA Astrophysics Data System (ADS)
Yamaguchi, Takao; Kurosawa, Yoshio; Matsumura, Shuuji
2007-01-01
A numerical method is proposed to calculate damping properties for soundproof structures involving solid bodies, porous media and air in two-dimensional regions. Both effective density and bulk modulus have complex quantity to represent damped sound fields in the porous media. Particle displacements in the media are discretized using finite element method. For damped solid bodies, displacements are formulated using conventional finite elements including complex modulus of elasticity. Displacement vectors as common unknown variables are solved under coupled condition between solid bodies, porous media and gas. Further, by applying asymptotic method to complex eigenvalue problem, explicit expressions of modal loss factor for the mixed structures are derived. The proposed methods yield appropriate results for some typical problems and this method diminish computational time for large-scaled finite element models concerning the mixed structure. Moreover, it is found that damping can be coupled in the mixed structures between solid bodies, porous media and air.
Wei, Xiaorong; Shao, Mingan; Du, Lina; Horton, Robert
2014-12-01
Understanding the transport of humic acids (HAs) in porous media can provide important and practical evidence needed for accurate prediction of organic/inorganic contaminant transport in different environmental media and interfaces. A series of column transport experiments was conducted to evaluate the transport of HA in different porous media at different flow velocities and influent HA concentrations. Low flow velocity and influent concentration were found to favor the adsorption and deposition of HA onto sand grains packed into columns and to give higher equilibrium distribution coefficients and deposition rate coefficients, which resulted in an increased fraction of HA being retained in columns. Consequently, retardation factors were increased and the transport of HA through the columns was delayed. These results suggest that the transport of HA in porous media is primarily controlled by the attachment of HA to the solid matrix. Accordingly, this attachment should be considered in studies of HA behavior in porous media.
Colwell, Frederick; Wildenschild, Dorthe; Wood, Brian; Gerlach, Robin; Mitchell, Andrew; Redden, George
2014-08-29
The goal for this research was to understand how best to add compounds to receptive microbial communities in porous media in order to achieve optimal calcite precipitation in a volumetrically significant space and to understand the physiological health of the cells that are responsible for the calcite precipitation. The specific objectives were to: (1) develop better tools for visually examining biofilms in porous media and calcium carbonate precipitation being mediated by microbes in porous media, and (2) demonstrate the effectiveness of using that tool within a flow cell model system.
An Introduction to Flow and Transport in Fractal Models of Porous Media: Part I
NASA Astrophysics Data System (ADS)
Cai, Jianchao; San José Martínez, Fernando; Martín, Miguel Angel; Perfect, Edmund
2014-09-01
This special issue gathers together a number of recent papers on fractal geometry and its applications to the modeling of flow and transport in porous media. The aim is to provide a systematic approach for analyzing the statics and dynamics of fluids in fractal porous media by means of theory, modeling and experimentation. The topics covered include lacunarity analyses of multifractal and natural grayscale patterns, random packing's of self-similar pore/particle size distributions, Darcian and non-Darcian hydraulic flows, diffusion within fractals, models for the permeability and thermal conductivity of fractal porous media and hydrophobicity and surface erosion properties of fractal structures.
An Introduction to Flow and Transport in Fractal Models of Porous Media: Part II
NASA Astrophysics Data System (ADS)
Cai, Jianchao; San José Martínez, Fernando; Martín, Miguel Angel; Hu, Xiangyun
2015-03-01
This is the second part of the special issue on fractal geometry and its applications to the modeling of flow and transport in porous media, in which 10 original research articles and one review article are included. Combining to the first part of 11 original research articles, these two issues summarized current research on fractal models applied to porous media that will help to further advance this multidisciplinary development. This whole special issue is published also to celebrate the 70th birthday of Professor Boming Yu for his distinguished researches on fractal geometry and its application to transport physics of porous media.
Stable-phase method for hierarchical annealing in the reconstruction of porous media images.
Chen, Dongdong; Teng, Qizhi; He, Xiaohai; Xu, Zhi; Li, Zhengji
2014-01-01
In this paper, we introduce a stable-phase approach for hierarchical annealing which addresses the very large computational costs associated with simulated annealing for the reconstruction of large-scale binary porous media images. Our presented method, which uses the two-point correlation function as the morphological descriptor, involves the reconstruction of three-phase and two-phase structures. We consider reconstructing the three-phase structures based on standard annealing and the two-phase structures based on standard and hierarchical annealings. From the result of the two-dimensional (2D) reconstruction, we find that the 2D generation does not fully capture the morphological information of the original image, even though the two-point correlation function of the reconstruction is in excellent agreement with that of the reference image. For the reconstructed three-dimensional (3D) microstructure, we calculate its permeability and compare it to that of the reference 3D microstructure. The result indicates that the reconstructed structure has a lower degree of connectedness than that of the actual sandstone. We also compare the computation time of our presented method to that of the standard annealing, which shows that our presented method of orders of magnitude improves the convergence rate. That is because only a small part of the pixels in the overall hierarchy need to be considered for sampling by the annealer.
Droplet Mobility Manipulation on Porous Media Using Backpressure.
Vourdas, N; Pashos, G; Kokkoris, G; Boudouvis, A G; Stathopoulos, V N
2016-05-31
Wetting phenomena on hydrophobic surfaces are strongly related to the volume and pressure of gas pockets residing at the solid-liquid interface. In this study, we explore the underlying mechanisms of droplet actuation and mobility manipulation when backpressure is applied through a porous medium under a sessile pinned droplet. Reversible transitions between the initially sticky state and the slippery states are thus incited by modulating the backpressure. The sliding angles of deionized (DI) water and ethanol in DI water droplets of various volumes are presented to quantify the effect of the backpressure on the droplet mobility. For a 50 μL water droplet, the sliding angle decreases from 45 to 0° when the backpressure increases to ca. 0.60 bar. Significantly smaller backpressure levels are required for lower surface energy liquids. We shed light on the droplet actuation and movement mechanisms by means of simulations encompassing the momentum conservation and the continuity equations along with the Cahn-Hilliard phase-field equations in a 2D computational domain. The droplet actuation mechanism entails depinning of the receding contact line and movement by means of forward wave propagation reaching the front of the droplet. Eventually, the droplet skips forward. The contact line depinning is also corroborated by analytical calculations based on the governing vertical force balance, properly modified to incorporate the effect of the backpressure.
Imaging spectral electrical properties of variably saturated porous media
NASA Astrophysics Data System (ADS)
Kelter, Matthias; Huisman, Johann A.; Kemna, Andreas; Zimmermann, Egon; Vereecken, Harry
2013-04-01
The spatial distribution of unsaturated hydraulic conductivity in the subsurface is of importance for hydrological modeling. Conventional methods to determine unsaturated hydraulic properties in the field are invasive and typically have a poor spatial resolution. In order to overcome these drawbacks, geophysical methods have received much attention in the last decades. Recent results of electrical impedance spectroscopy (EIS) on a range of saturated and unsaturated porous media revealed promising relationships between spectral electrical and hydraulic properties. Therefore, spectral electrical impedance tomography (EIT) is a promising method to image hydraulic properties in the subsurface. While this approach is emerging for aquifer characterization, unsaturated hydraulic properties have not yet been determined by EIT. In order to do so, a laboratory setup has been developed to perform controlled infiltration, drainage and stationary flow experiments on soil columns. A lysimeter with a height of 50 cm and a diameter of 22 cm is equipped with 40 electrodes and 4 tensiometers. An irrigation device at the top controlled by a peristaltic pump is used for a constant and homogeneous infiltration. Outflow is controlled by a suction plate at the bottom where an adjustable vacuum of up to 500 hPa can be applied. In a first measurement series, spectral EIT measurements were performed on a homogeneous sand column during stepwise drainage of the saturated porous medium using predefined pressure at the bottom. First results show that with decreasing water content the low frequency phase shift of complex electrical conductivity increases. This is consistent with previously reported EIS results. Calibrated relationships between electrical and hydraulic properties were used to convert the resulting electrical into hydraulic conductivity images.
Scaling behavior of microbubbles rising in water-saturated porous media
NASA Astrophysics Data System (ADS)
Kong, X.; Ma, Y.; Scheuermann, A.; Bringemeier, D.; Galindo-Torres, S. A.; Saar, M. O.; Li, L.
2015-12-01
Gas transport in the form of discrete microbubbles in saturated porous media is of importance in a number of processes relevant to many geo-environmental and engineering systems such as bubbling of greenhouse gases in river and sea beds, hydrocarbon gas migration in coal cleats and rock fractures, and air sparging for remediation of soil contaminated with volatile organic compounds. Under the assumption of no or minor volume expansion during gravity-driven migration, the transport of a single microbubble can be well described using various drag force models. However, not enough attention has been paid to the collective behavior of microbubbles during their ascend as a plume through the saturated porous medium, involving dynamic interactions between individual bubbles, bubbles and the ambient fluid, as well as bubbles and the solid matrix. With our quasi-2D, lab-scale microbubble migration experiments, where bubbles are continuously released from a diffuser at the bottom of a porous bed of hydrated gel beads, we establish a scaling relationship between the gas (bubble) release rate and various characteristic parameters of the bubble plume, such as plume tip velocity, plume width, and breakthrough time of the plume front. We find that the characteristic width of the bubble plume varies as a power of both the gas release rate and the bed thickness, with exponents of 0.2 and 0.4, respectively. Moreover, the characteristic breakthrough time also scales with both the gas release rate and the bed thickness with power-law exponents of -0.4 and 1.2, respectively. The mean pore-water velocity of the circulating ambient water also follows a power-law relationship with the gas release rate being an exponent of 0.6 of the gas release rate. This can be quantitatively proven using a simplified momentum exchange model together with the above power-law exponents for the bubble plume. These analyses on the experimental results are carried out on the basis of non
Targeted delivery by smart capsules for controlling two-phase flow in porous media
NASA Astrophysics Data System (ADS)
Fan, Jing; Abbaspourrad, Alireza; Weitz, David; Harvard Weitzgroup Team
2015-11-01
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. Advanced Energy Consortium BEG08-027.
NASA Astrophysics Data System (ADS)
Pepona, Marianna; Favier, Julien
2016-09-01
In this work, we propose a numerical framework to simulate fluid flows in interaction with moving porous media of complex geometry. It is based on the Lattice Boltzmann method including porous effects via a Brinkman-Forchheimer-Darcy force model coupled to the Immersed Boundary method to handle complex geometries and moving structures. The coupling algorithm is described in detail and it is validated on well-established literature test cases for both stationary and moving porous configurations. The proposed method is easy to implement and efficient in terms of CPU cost and memory management compared to alternative methods which can be used to deal with moving immersed porous media, e.g. re-meshing at each time step or use of a moving/chimera mesh. An overall good agreement was obtained with reference results, opening the way to the numerical simulation of moving porous media for flow control applications.
3-D Distribution of Retained Colloids in Unsaturated Porous Media
NASA Astrophysics Data System (ADS)
Morales, V. L.; Perez-Reche, F. J.; Holzner, M.; Kinzelbach, W. K.; Otten, W.
2013-12-01
It is well accepted that colloid transport processes in porous media differ substantially between water saturated and unsaturated conditions. Differences are frequently ascribed to colloid immobilization by association with interfaces with the gas, as well as to restrictions of the liquid medium through which colloids are transported. Such factors depend on interfacial conditions provided by the water saturation of the porous medium. Yet, the current understanding of the importance of colloid retention at gas interfaces is based on observations of single pores or two-dimensional pore network representations, leaving open the question of their statistical significance when all pores in the medium are considered. In order to address this question, column experiments were performed using a model porous medium of glass beads through which colloidal silver particles were transported for conditions of varying water content. X-ray microtomography was subsequently employed as a non-destructive imaging technique to obtain pore-scale information of the entire column regarding: i) the presence and distribution of the four main locations where colloids can become retained (interfaces with the liquid-solid, gas-liquid and gas-solid, and the bulk liquid), ii) deposition profiles of colloids along the column classified by the available retention location, iii) morphological characteristics of the deposited colloidal aggregates, and iv) channel widths of 3-dimensional pore-water network representations. The results presented provide, for the first time, a direct statistical evaluation on the significance of colloid retention by attachment to the liquid-solid, gas-liquid, gas-solid interfaces, and by straining in the bulk liquid. Additionally, an effective-pore structure characteristic is proposed to improve predictions of mass removal by straining under various water saturations. A) Unsaturated conditions. B) Saturated conditions. Left: Tomograph slice illustrating with false
Uncertainty Quantification Bayesian Framework for Porous Media Flows
NASA Astrophysics Data System (ADS)
Demyanov, V.; Christie, M.; Erbas, D.
2005-12-01
Uncertainty quantification is an increasingly important aspect of many areas of applied science, where the challenge is to make reliable predictions about the performance of complex physical systems in the absence of complete or reliable data. Predicting flows of fluids through undersurface reservoirs is an example of a complex system where accuracy in prediction is needed (e.g. in oil industry it is essential for financial reasons). Simulation of fluid flow in oil reservoirs is usually carried out using large commercially written finite difference simulators solving conservation equations describing the multi-phase flow through the porous reservoir rocks, which is a highly computationally expensive task. This work examines a Bayesian Framework for uncertainty quantification in porous media flows that uses a stochastic sampling algorithm to generate models that match observed time series data. The framework is flexible for a wide range of general physical/statistical parametric models, which are used to describe the underlying hydro-geological process in its temporal dynamics. The approach is based on exploration of the parameter space and update of the prior beliefs about what the most likely model definitions are. Optimization problem for a highly parametric physical model usually have multiple solutions, which impact the uncertainty of the made predictions. Stochastic search algorithm (e.g. genetic algorithm) allows to identify multiple "good enough" models in the parameter space. Furthermore, inference of the generated model ensemble via MCMC based algorithm evaluates the posterior probability of the generated models and quantifies uncertainty of the predictions. Machine learning algorithm - Artificial Neural Networks - are used to speed up the identification of regions in parameter space where good matches to observed data can be found. Adaptive nature of ANN allows to develop different ways of integrating them into the Bayesian framework: as direct time
Static light scattering resolves colloid structure in index-matched porous media.
Mays, David C; Cannon, Orion T; Kanold, Adam W; Harris, Kevin J; Lei, Tim C; Gilbert, Benjamin
2011-11-01
Colloidal phenomena play an important role in natural porous media, where they influence soil structuring, contaminant migration, filtration, and clogging. Several methods are available to measure pore space geometry within porous media, but these methods have limited applicability when the relevant physical, chemical, or biological processes are dominated by dynamic colloidal phenomena. Here we report a new technique to quantify colloid aggregate structure as a fractal dimension using static light scattering within index-matched porous media (granular Nafion). We validate the method by obtaining consistent results for scattering in suspensions and in porous media, and verify that multiple scattering at environmentally relevant colloid concentrations does not affect the determination of fractal dimension. We also observe restructuring of aggregates during homogenization in the porous media, indicated by an apparent increase in fractal dimension, which can be explained by an analysis of the fluid shear stress caused by repeated inversions of test tubes either containing or not containing granular media. This technique will permit progress in obtaining fundamental descriptions of colloidal phenomena in porous media.
Lu, Chenbao; Tranca, Diana; Zhang, Jian; Rodrı Guez Hernández, Fermı N; Su, Yuezeng; Zhuang, Xiaodong; Zhang, Fan; Seifert, Gotthard; Feng, Xinliang
2017-03-20
Molybdenum carbide (Mo2C) based catalysts were found to be one of the most promising electrocatalysts for hydrogen evolution reaction (HER) in acid media in comparison with Pt-based catalysts but were seldom investigated in alkaline media, probably due to the limited active sites, poor conductivity, and high energy barrier for water dissociation. In this work, Mo2C-embedded nitrogen-doped porous carbon nanosheets (Mo2C@2D-NPCs) were successfully achieved with the help of a convenient interfacial strategy. As a HER electrocatalyst in alkaline solution, Mo2C@2D-NPC exhibited an extremely low onset potential of ∼0 mV and a current density of 10 mA cm(-2) at an overpotential of ∼45 mV, which is much lower than the values of most reported HER electrocatalysts and comparable to the noble metal catalyst Pt. In addition, the Tafel slope and the exchange current density of Mo2C@2D-NPC were 46 mV decade(-1) and 1.14 × 10(-3) A cm(-2), respectively, outperforming the state-of-the-art metal-carbide-based electrocatalysts in alkaline media. Such excellent HER activity was attributed to the rich Mo2C/NPC heterostructures and synergistic contribution of nitrogen doping, outstanding conductivity of graphene, and abundant active sites at the heterostructures.
Macroscopic laws for immiscible two-phase flow in porous media: Results From numerical experiments
NASA Astrophysics Data System (ADS)
Rothman, Daniel H.
1990-06-01
be approximately equal, which is the behavior predicted by Onsager's reciprocity theorem. However, persistent transient effects can render the reciprocity unobservable. The numerical study is performed with a discrete numerical model of the molecular dynamics of immiscible mixtures called the immiscible lattice gas. The immiscible lattice gas models both the Navier-Stokes equations and surface tension. Numerical tests presented here additionally provide quantitative validation of the method's ability to simulate wetting phenomena and the effects of capillary pressure. Whereas the numerical study of the linear phenomenological laws utilizes a highly simplified porous medium with one pore and two throats, numerical examples of wetting and nonwetting invasion experiments in a geometrically complex 2-D porous medium are also provided.
Numerical studies of gravity destabilized percolation in 2D porous media
NASA Astrophysics Data System (ADS)
Bo, Z.; Loggia, D.; Xiaorong, L.; Vasseur, G.; Ping, H.
2006-04-01
Two dimensional simulations of percolation are realized on square networks of pore throats with a random capillary pressure distribution. We analyse the influence of a destabilizing gravity field (g) and of the standard deviation of the distribution of the capillary pressure thresholds (Wt). The fragmentation process is not taken into account in this study. For an increase of g or/and when Wt decreases, two transitions are analyzed with three different regimes displacement patterns: Invasion percolation, invasion percolation in a gradient, and invasion in a pure gradient. The transitions are controlled both by the ratio g/Wt and by the sample size (L). A scaling law between the saturation at the percolation threshold and g/Wt allows delineating the three regimes in agreement with theoretical argument of the percolation in a gradient.
Lab-on-chip methodologies for the study of transport in porous media: energy applications.
Berejnov, Viatcheslav; Djilali, Ned; Sinton, David
2008-05-01
We present a lab-on-chip approach to the study of multiphase transport in porous media. The applicability of microfluidics to biological and chemical analysis has motivated much development in lab-on-chip methodologies. Several of these methodologies are also well suited to the study of transport in porous media. We demonstrate the application of rapid prototyping of microfluidic networks with approximately 5000 channels, controllable wettability, and fluorescence-based analysis to the study of multiphase transport phenomena in porous media. The method is applied to measure the influence of wettability relative to network regularity, and to differentiate initial percolation patterns from active flow paths. Transport phenomena in porous media are of critical importance to many fields and particularly in many energy-related applications including liquid water transport in fuel cells, oil recovery, and CO(2) sequestration.
Technology Transfer Automated Retrieval System (TEKTRAN)
Saturated packed column and micromodel transport studies wereconducted to gain insightonmechanismsof colloid retention and release under unfavorable attachment conditions. The initial deposition of colloids in porous media was found to be a strongly coupled process that depended on solution chemistr...
NASA Astrophysics Data System (ADS)
Xia, Lu; Zheng, Xilai; Shao, Haibing; Xin, Jia; Peng, Tao
2014-11-01
Bioclogging of natural porous media occurs frequently under a wide range of conditions. It may influence the performance of permeable reactive barrier and constructed wetland. It is also one of the factors that determine the effect of artificial groundwater recharge and in situ bioremediation process. In this study, a series of percolation column experiments were conducted to simulate bioclogging process in porous media. The predominant bacteria in porous media which induced clogging were identified to be Methylobacterium, Janthinobacterium, Yersinia, Staphylococcus and Acidovorax, most of which had been shown to effectively produce viscous extracellular polymeric substances (EPS). The column in which EPS production was maximized also coincided with the largest reduction in saturated hydraulic conductivity of porous media. In addition, carbon concentration was the most significant factor to affect polysaccharide, protein and EPS secretion, followed by phosphorus concentration and temperature. The coupled effect of carbon and phosphorus concentration was also very important to stimulate polysaccharide and EPS production.
SURFACE CHEMICAL EFFECTS ON COLLOID STABILITY AND TRANSPORT THROUGH NATURAL POROUS MEDIA
Surface chemical effects on colloidal stability and transport through porous media were investigated using laboratory column techniques. Approximately 100 nm diameter, spherical, iron oxide particles were synthesized as the mobile colloidal phase. The column packing material was ...
Prediction of Effective Permeability in Porous Media Based on Spontaneous Imbibition Effect
NASA Astrophysics Data System (ADS)
Cai, Jianchao; You, Lijun; Hu, Xiangyun; Wang, Jing; Peng, Ronghua
2012-07-01
Permeability is an important parameter for characterizing the transport properties (e.g. heat and mass transfer) of porous media. It is one of the crucial issues that the permeability of porous media is exactly and quickly decided in many fields such as reservoir engineering, groundwater engineering and composite material modeling. Spontaneous imbibition is a fundamental and ubiquitous natural phenomenon extensively existing in a variety of processes. In this paper, the relationships between the height and weight of imbibition versus the time are derived based on Darcy's law, and a simple method for predicting effective permeability of porous media using spontaneous imbibition effect is proposed, including expressions for permeabilities of artificial and natural porous media. The validity of the proposed models is analysed and tested by experimental data.
FITTING OF THE DATA FOR DIFFUSION COEFFICIENTS IN UNSATURATED POROUS MEDIA
B. Bullard
1999-05-01
The purpose of this calculation is to evaluate diffusion coefficients in unsaturated porous media for use in the TSPA-VA analyses. Using experimental data, regression techniques were used to curve fit the diffusion coefficient in unsaturated porous media as a function of volumetric water content. This calculation substantiates the model fit used in Total System Performance Assessment-1995 An Evaluation of the Potential Yucca Mountain Repository (TSPA-1995), Section 6.5.4.
Feasibility and induced effects of subsurface porous media hydrogen storage
NASA Astrophysics Data System (ADS)
Tilmann Pfeiffer, Wolf; Li, Dedong; Wang, Bo; Bauer, Sebastian
2015-04-01
Fluctuations in energy production from renewable sources like wind or solar power can lead to shortages in energy supply which can be mitigated using energy storage concepts. Underground storage of hydrogen in porous sandstone formations could be a storage option for large amounts of energy over long storage cycles. However, this use of the subsurface requires an analysis of possible interactions with other uses of the subsurface such as geothermal energy storage or groundwater abstraction. This study aims at quantifying the feasibility of porous media hydrogen storage to provide stored energy on a timescale of several days to weeks as well as possible impacts on the subsurface. The hypothetical storage site is based on an anticlinal structure located in Schleswig-Holstein, northern Germany. The storage is injected and extracted using five wells completed in a partially eroded, heterogeneous sandstone layer in the top of the structure at a depth of about 500 m. The storage formation was parameterized based on a local facies model with intrinsic permeabilities of 250-2500 mD and porosities of 35-40%. Storage initialization and subsequent storage cycles, each consisting of a hydrogen injection and extraction, were numerically simulated. The simulation results indicate the general feasibility of this hydrogen storage concept. The simulated sandstone formation is able to provide an average of around 1480 t of hydrogen per week (1830 TJ) which is about 5% of the total weekly energy production or about 10% of the weekly energy consumption of Schleswig-Holstein with the hydrogen production rate being the limiting factor of the overall performance. Induced hydraulic effects are a result of the induced overpressure within the storage formation. Propagation of the pressure signal does not strongly depend on the formation heterogeneity and thus shows approximately radial characteristics with one bar pressure change in distances of about 5 km from the injection wells. Thermal
Modeling NAPL dissolution from pendular rings in idealized porous media
NASA Astrophysics Data System (ADS)
Huang, Junqi; Christ, John A.; Goltz, Mark N.; Demond, Avery H.
2015-10-01
The dissolution rate of nonaqueous phase liquid (NAPL) often governs the remediation time frame at subsurface hazardous waste sites. Most formulations for estimating this rate are empirical and assume that the NAPL is the nonwetting fluid. However, field evidence suggests that some waste sites might be organic wet. Thus, formulations that assume the NAPL is nonwetting may be inappropriate for estimating the rates of NAPL dissolution. An exact solution to the Young-Laplace equation, assuming NAPL resides as pendular rings around the contact points of porous media idealized as spherical particles in a hexagonal close packing arrangement, is presented in this work to provide a theoretical prediction for NAPL-water interfacial area. This analytic expression for interfacial area is then coupled with an exact solution to the advection-diffusion equation in a capillary tube assuming Hagen-Poiseuille flow to provide a theoretical means of calculating the mass transfer rate coefficient for dissolution at the NAPL-water interface in an organic-wet system. A comparison of the predictions from this theoretical model with predictions from empirically derived formulations from the literature for water-wet systems showed a consistent range of values for the mass transfer rate coefficient, despite the significant differences in model foundations (water wetting versus NAPL wetting, theoretical versus empirical). This finding implies that, under these system conditions, the important parameter is interfacial area, with a lesser role played by NAPL configuration.
Multiscale modelling of hydraulic conductivity in vuggy porous media.
Daly, K R; Roose, T
2014-02-08
Flow in both saturated and non-saturated vuggy porous media, i.e. soil, is inherently multiscale. The complex microporous structure of the soil aggregates and the wider vugs provides a multitude of flow pathways and has received significant attention from the X-ray computed tomography (CT) community with a constant drive to image at higher resolution. Using multiscale homogenization, we derive averaged equations to study the effects of the microscale structure on the macroscopic flow. The averaged model captures the underlying geometry through a series of cell problems and is verified through direct comparison to numerical simulations of the full structure. These methods offer significant reductions in computation time and allow us to perform three-dimensional calculations with complex geometries on a desktop PC. The results show that the surface roughness of the aggregate has a significantly greater effect on the flow than the microstructure within the aggregate. Hence, this is the region in which the resolution of X-ray CT for image-based modelling has the greatest impact.
Modeling multidimensional and multispecies biofilms in porous media.
Tang, Youneng; Liu, Haihu
2017-03-21
Modeling multidimensional and multispecies biofilm in porous media at the pore scale is challenging due to the need to simultaneously track the microbial community in the biofilms and the interfaces between the biofilms and the fluid. Therefore, researchers usually assume that the model has only one dimension in space or has only one microbial species. This work uses bioremediation of U(VI)-contaminated groundwater as the context to develop a two-dimensional and multispecies biofilm model. The model simulates the transverse mixing zone in which U(VI) is mixed with propionate, a nutrient externally supplied to stimulate the growth of microorganisms. The model considers multiple interactions among fluid flow, transport and reaction of chemical species, and growth of biofilm. The biofilm consists of two types of active biomass (syntrophs and dissimilatory metal reducing bacteria) and inert biomass. The two types of active biomass collaboratively remove U(VI). The model outputs biomass distribution, chemical species concentrations, and fluid flow at the pore scale to fundamentally study the multiple interactions. The model also outputs the contaminant removal rate that can be potentially used for up-scaling studies. The simulated results are generally consistent with experimental observations from other studies in trend. The trend can be explained by the multiple interactions based on thermodynamics and microbial kinetics. This article is protected by copyright. All rights reserved.
Stochastic effects on single phase fluid flow in porous media.
Mansfield, P; Bencsik, M
2001-01-01
The flow encoded PEPI technique has been used to measure the fluid velocity distribution and fluid flow of water passing through a phantom comprising randomly distributed 10 mm glass beads. The object of these experiments is to determine the degree of causality between one steady-state flow condition and another. That is to say, knowing the mean fluid velocity and velocity distribution, can one predict what happens at a higher mean fluid velocity? In a second related experiment flow is established at a given mean fluid velocity. The velocity distribution is measured. The flow is then turned off and later re-established. In both kinds of experiment we conclude that the errors in predicting the flow velocity distribution and the errors in re-establishing a given velocity distribution lie well outside the intrinsic thermal noise associated with velocity measurement. It follows, therefore, that the causal approach to prediction of flow velocity distributions in porous media using the Navier-Stokes approach is invalid.
Pore network model of electrokinetic transport through charged porous media
NASA Astrophysics Data System (ADS)
Obliger, Amaël; Jardat, Marie; Coelho, Daniel; Bekri, Samir; Rotenberg, Benjamin
2014-04-01
We introduce a method for the numerical determination of the steady-state response of complex charged porous media to pressure, salt concentration, and electric potential gradients. The macroscopic fluxes of solvent, salt, and charge are computed within the framework of the Pore Network Model (PNM), which describes the pore structure of the samples as networks of pores connected to each other by channels. The PNM approach is used to capture the couplings between solvent and ionic flows which arise from the charge of the solid surfaces. For the microscopic transport coefficients on the channel scale, we take a simple analytical form obtained previously by solving the Poisson-Nernst-Planck and Stokes equations in a cylindrical channel. These transport coefficients are upscaled for a given network by imposing conservation laws for each pores, in the presence of macroscopic gradients across the sample. The complex pore structure of the material is captured by the distribution of channel diameters. We investigate the combined effects of this complex geometry, the surface charge, and the salt concentration on the macroscopic transport coefficients. The upscaled numerical model preserves the Onsager relations between the latter, as expected. The calculated macroscopic coefficients behave qualitatively as their microscopic counterparts, except for the permeability and the electro-osmotic coupling coefficient when the electrokinetic effects are strong. Quantitatively, the electrokinetic couplings increase the difference between the macroscopic coefficients and the corresponding ones for a single channel of average diameter.
Effect of Foam on Liquid Phase Mobility in Porous Media
Eftekhari, A. A.; Farajzadeh, R.
2017-01-01
We investigate the validity of the assumption that foam in porous media reduces the mobility of gas phase only and does not impact the liquid-phase mobility. The foam is generated by simultaneous injection of nitrogen gas and a surfactant solution into sandstone cores and its strength is varied by changing surfactant type and concentration. We find, indeed, that the effect of foam on liquid-phase mobility is not pronounced and can be ignored. Our new experimental results and analyses resolve apparent discrepancies in the literature. Previously, some researchers erroneously applied relative permeability relationships measured at small to moderate capillary numbers to foam floods at large capillary number. Our results indicate that the water relative permeability in the absence of surfactant should be measured with the capillary pressure ranging up to values reached during the foam floods. This requires conducting a steady-state gas/water core flood with capillary numbers similar to that of foam floods or measuring the water relative-permeability curve using a centrifuge. PMID:28262795
Effect of Foam on Liquid Phase Mobility in Porous Media
NASA Astrophysics Data System (ADS)
Eftekhari, A. A.; Farajzadeh, R.
2017-03-01
We investigate the validity of the assumption that foam in porous media reduces the mobility of gas phase only and does not impact the liquid-phase mobility. The foam is generated by simultaneous injection of nitrogen gas and a surfactant solution into sandstone cores and its strength is varied by changing surfactant type and concentration. We find, indeed, that the effect of foam on liquid-phase mobility is not pronounced and can be ignored. Our new experimental results and analyses resolve apparent discrepancies in the literature. Previously, some researchers erroneously applied relative permeability relationships measured at small to moderate capillary numbers to foam floods at large capillary number. Our results indicate that the water relative permeability in the absence of surfactant should be measured with the capillary pressure ranging up to values reached during the foam floods. This requires conducting a steady-state gas/water core flood with capillary numbers similar to that of foam floods or measuring the water relative-permeability curve using a centrifuge.
Quantifying colloid retention in partially saturated porous media
NASA Astrophysics Data System (ADS)
Zevi, Yuniati; Dathe, Annette; Gao, Bin; Richards, Brian K.; Steenhuis, Tammo S.
2006-12-01
The transport of colloid-contaminant complexes and colloid-sized pathogens through soil to groundwater is of concern. Visualization and quantification of pore-scale colloid behavior will enable better description and simulation of retention mechanisms at individual surfaces, in contrast to breakthrough curves which only provide an integrated signal. We tested two procedures for quantifying colloid movement and retention as observed in pore-scale image sequences. After initial testing with static images, three series of images of synthetic microbead suspensions passing through unsaturated sand were examined. The region procedure (implemented in ImageJ) and the Boolean procedure (implemented in KS400) yielded nearly identical results for initial test images and for total colloid-covered areas in three image series. Because of electronic noise resulting in pixel-level brightness fluctuations the Boolean procedure tended to underestimate attached colloid counts and conversely overestimate mobile colloid counts. The region procedure had a smaller overestimation error of attached colloids. Reliable quantification of colloid retention at pore scale can be used to improve current understanding on the transport mechanisms of colloids in unsaturated porous media. For example, attachment counts at individual air/water meniscus/solid interface were well described by Langmuir isotherms.
Percolation Theory and Models of Unsaturated Porous Media
NASA Astrophysics Data System (ADS)
Golden, J. M.
1980-02-01
Concepts from percolation theory (Broadbent and Hammersley, 1957) are applied to a model of unsaturated flow through porous media. This approach in principle allows one to build into the model aspects of the topological structure of pore space. At a very general level the input of results from percolation theory gives a relationship between minimum and maximum saturation values for a medium which should be experimentally checkable, though probably not without sophisticated techniques. Also, it gives some qualitative insight into known properties of unsaturated flow. Furthermore, there emerges a way of looking at the phenomenon of hysteresis that is quite different from the standard approach. This aspect is explored in some detail, and two possible new models are presented. A subsidiary result obtained from the detailed model used is that in a simple pore model the inclusion of a pore length parameter, statistically correlated with pore radius, is equivalent, at least in a restricted sense, to incorporating into the model the concept of tortuosity.
Volumetric microscale particle tracking velocimetry (PTV) in porous media
NASA Astrophysics Data System (ADS)
Guo, Tianqi; Aramideh, Soroush; Ardekani, Arezoo M.; Vlachos, Pavlos P.
2016-11-01
The steady-state flow through refractive-index-matched glass bead microchannels is measured using microscopic particle tracking velocimetry (μPTV). A novel technique is developed to volumetrically reconstruct particles from oversampled two-dimensional microscopic images of fluorescent particles. Fast oversampling of the quasi-steady-state flow field in the lateral direction is realized by a nano-positioning piezo stage synchronized with a fast CMOS camera. Experiments at different Reynolds numbers are carried out for flows through a series of both monodispersed and bidispersed glass bead microchannels with various porosities. The obtained velocity fields at pore-scale (on the order of 10 μm) are compared with direct numerical simulations (DNS) conducted in the exact same geometries reconstructed from micro-CT scans of the glass bead microchannels. The developed experimental method would serve as a new approach for exploring the flow physics at pore-scale in porous media, and also provide benchmark measurements for validation of numerical simulations.
Effects of starvation on bacterial transport through porous media
NASA Astrophysics Data System (ADS)
Cunningham, Alfred B.; Sharp, Robert R.; Caccavo, Frank; Gerlach, Robin
2007-06-01
A major problem preventing widespread implementation of microbial injection strategies for bioremediation and/or microbially enhanced oil recovery is the tendency of bacteria to strongly adhere to surfaces in the immediate vicinity of the injection point. Long term (weeks to months) nutrient starvation of bacteria prior to injection can decrease attachment and enhance transport through porous media. This paper summarizes results of starvation-enhanced transport experiments in sand columns of 30 cm, 3 m, and 16 m in length. The 16 m column experiments compared transport, breakthrough and distribution of adhered cells for starved and vegetative cultures of Klebsiella oxytoca, a copious biofilm producer. Results from these experiments were subsequently used to design and construct a field-scale biofilm barrier using starved Pseudomonas fluorescens. The 30 cm and 3 m sand columns experiments investigated starvation-enhanced transport of Shewanella algae BrY, a dissimilatory metal-reducing bacterium. In both cases the vegetative cells adsorbed onto the sand in higher numbers than the starved cells, especially near the entrance of the column. These results, taken together with studies cited in the literature, indicate that starved cells penetrate farther (i.e. higher breakthrough concentration) and adsorb more uniformly along the flow path than vegetative cells.
Colloid suspension stability and transport through unsaturated porous media
McGraw, M.A.; Kaplan, D.I.
1997-04-01
Contaminant transport is traditionally modeled in a two-phase system: a mobile aqueous phase and an immobile solid phase. Over the last 15 years, there has been an increasing awareness of a third, mobile solid phase. This mobile solid phase, or mobile colloids, are organic or inorganic submicron-sized particles that move with groundwater flow. When colloids are present, the net effect on radionuclide transport is that radionuclides can move faster through the system. It is not known whether mobile colloids exist in the subsurface environment of the Hanford Site. Furthermore, it is not known if mobile colloids would likely exist in a plume emanating from a Low Level Waste (LLW) disposal site. No attempt was made in this study to ascertain whether colloids would form. Instead, experiments and calculations were conducted to evaluate the likelihood that colloids, if formed, would remain in suspension and move through saturated and unsaturated sediments. The objectives of this study were to evaluate three aspects of colloid-facilitated transport of radionuclides as they specifically relate to the LLW Performance Assessment. These objectives were: (1) determine if the chemical conditions likely to exist in the near and far field of the proposed disposal site are prone to induce flocculation (settling of colloids from suspension) or dispersion of naturally occurring Hanford colloids, (2) identify the important mechanisms likely involved in the removal of colloids from a Hanford sediment, and (3) determine if colloids can move through unsaturated porous media.
Oil drainage in model porous media by viscoelastic fluids
NASA Astrophysics Data System (ADS)
Beaumont, Julien; Bodiguel, Hugues; Colin, Annie
2012-11-01
Crude oil recovery efficiency has been shown to depend directly on the capillary number (Ca). If the capillary phenomenon is well described for Newtonian fluids, the consequences of non linear rheology and viscoelasticity require more experimental work at the pore scale. In this work we take advantage of microfluidic to revisit this field. We carried out oil drainage experiments through a micromodel made up with photoresist resin. The wetting phase trapped is a model oil. The invading phases used are aqueous solutions of high molecular weight hydrolyzed polyacrylamide (HPAM) and surfactant. Qualitatively, we observed a transition between a capillary fingering at low flow rates and a stable front at high flow rates for the drainage experiments with HPAM and surfactant solutions as it happened for drainage with Newtonian fluids. From movies of the filling of the device, we determine the local velocity of all menisci in the porous media. Thus, we quantify the capillary fingering. Surprisingly, local velocities are not significantly different from those measured using water, whereas the HPAM solutions are much more viscous. With betaine solutions, we observed an emulsification of the oil clusters trapped during the invasion leading to a very high oil recovery after percolation.
Transport of large particles in flow through porous media
NASA Astrophysics Data System (ADS)
Imdakm, A. O.; Sahimi, Muhammad
1987-12-01
There is considerable evidence indicating that significant reduction in the efficiency of many processes in porous media, such as enhancing oil recovery, heterogeneous chemical reactions, deep-bed filtration, gel permeation, and liquid chromatography, is due to the reduction in the permeability of the pore space. This reduction is due to the transport of particles, whose sizes are comparable with those of the pores, and the subsequent blocking of the pores by various mechanisms. In this paper we develop a novel Monte Carlo method for theoretical modeling of this phenomenon. Particles of various sizes are injected into the medium, and their migration in the flow field is modeled by a random walk whose transition porbability is proportional to the local pore fluxes. Pores are blocked and their flow capacity is reduced (or vanished) when large particles pass through them (and reduce their flow) or totally block them. The permeability of the medium can ultimately vanish and, therefore, this phenomenon is a percolation process. Various quantities of interest such as the variations of the permeability with process time and the distribution of pore-plugging times are computed. The critical exponent characterizing the vanishing of the permeability near the percolation threshold appears to be different from that of percolation conductivity. The agreement between our results and the available experimental data is excellent.
Coupled Flow and Mechanics in Porous and Fractured Media*
NASA Astrophysics Data System (ADS)
Martinez, M. J.; Newell, P.; Bishop, J.
2012-12-01
Numerical models describing subsurface flow through deformable porous materials are important for understanding and enabling energy security and climate security. Some applications of current interest come from such diverse areas as geologic sequestration of anthropogenic CO2, hydro-fracturing for stimulation of hydrocarbon reservoirs, and modeling electrochemistry-induced swelling of fluid-filled porous electrodes. Induced stress fields in any of these applications can lead to structural failure and fracture. The ultimate goal of this research is to model evolving faults and fracture networks and flow within the networks while coupling to flow and mechanics within the intact porous structure. We report here on a new computational capability for coupling of multiphase porous flow with geomechanics including assessment of over-pressure-induced structural damage. The geomechanics is coupled to the flow via the variation in the fluid pore pressures, whereas the flow problem is coupled to mechanics by the concomitant material strains which alter the pore volume (porosity field) and hence the permeability field. For linear elastic solid mechanics a monolithic coupling strategy is utilized. For nonlinear elastic/plastic and fractured media, a segregated coupling is presented. To facilitate coupling with disparate flow and mechanics time scales, the coupling strategy allows for different time steps in the flow solve compared to the mechanics solve. If time steps are synchronized, the controller allows user-specified intra-time-step iterations. The iterative coupling is dynamically controlled based on a norm measuring the degree of variation in the deformed porosity. The model is applied for evaluation of the integrity of jointed caprock systems during CO2 sequestration operations. Creation or reactivation of joints can lead to enhanced pathways for leakage. Similarly, over-pressures can induce flow along faults. Fluid flow rates in fractures are strongly dependent on the
NASA Astrophysics Data System (ADS)
Wildenschild, D.; Iltis, G.
2013-12-01
Microbial biofilms are observed in both natural and engineered subsurface environments and can dramatically alter the physical properties of porous media. Current understanding of biofilm formation and the associated impacts to structural and hydrodynamic properties of porous media are limited by our ability to observe changes to pore morphology non-destructively. Imaging biofilm within opaque porous media has historically presented a significant challenge. X-ray computed microtomography has traditionally been used for non-destructive imaging of a variety of processes and phenomena in porous media, yet, the conventional contrast agents used in tomography research tend to diffuse quite readily into both the aqueous phase as well as the porous media-associated biofilm, thereby preventing delineation of the two phases. A couple of new methods for imaging biofilm within opaque porous media using x-ray microtomography have been developed in recent years, and this presentation will discuss advantages and limitations to using polychromatic vs. monochromatic (synchrotron) radiation, as well as different types, and various concentrations of, contrast agents.
Theoretical studies of non-Newtonian and Newtonian fluid flow through porous media
Wu, Yu-Shu.
1990-02-01
A comprehensive theoretical study has been carried out on the flow behavior of both single and multiple phase non-Newtonian fluids in porous media. This work is divided into three parts: development of numerical and analytical solutions; theoretical studies of transient flow of non-Newtonian fluids in porous media; and applications of well test analysis and displacement efficiency evaluation to field problems. A fully implicit, integral finite difference model has been developed for simulation of non-Newtonian and Newtonian fluid flow through porous media. Several commonly-used rheological models of power-law and Bingham plastic non-Newtonian fluids have been incorporated in the simulator. A Buckley-Leverett type analytical solution for one-dimensional, immiscible displacement involving non-Newtonian fluids in porous media has been developed. An integral method is also presented for the study of transient flow of Bingham fluids in porous media. In addition, two well test analysis methods have been developed for analyzing pressure transient tests of power-law and Bingham fluids, respectively. Applications are included to demonstrate this new technology. The physical mechanisms involved in immiscible displacement with non-Newtonian fluids in porous media have been studied using the Buckley-Leverett type analytical solution. In another study, an idealized fracture model has been used to obtain some insights into the flow of a power-law fluid in a double-porosity medium. Transient flow of a general pseudoplastic fluid has been studied numerically. 125 refs., 91 figs., 12 tabs.
Effect of sequential release of NAPLs on NAPL migration in porous media
NASA Astrophysics Data System (ADS)
Bang, Woohui; Yeo, In Wook
2016-04-01
NAPLs (Non-aqueous phase liquids) are common groundwater contaminants and are classified as LNAPLs (Light non-aqueous phase liquids) and DNAPLs (Dense non-aqueous phase liquids) according to relative density for water. Due to their low solubility in water, NAPLs remain for a long time in groundwater, and they pose a serious environmental problem. Therefore, understanding NAPLs migration in porous media is essential for effective NAPLs remediation. DNAPLs tend to move downward through the water table by gravity force because its density is higher than water. However, if DNAPLs do not have sufficient energy which breaks capillary force of porous media, they will just accumulate above capillary zone or water table. Mobile phase of LNAPLs rises and falls depending on fluctuation of water table, and it could change the wettability of porous media from hydrophilic to hydrophobic. This could impacts on the migration characteristics of subsequently-released DNAPLs. LNAPLs and DNAPLs are sometime disposed at the same place (for example, the Hill air force base, USA). Therefore, this study focuses on the effect of sequential release of NAPLs on NAPLs (in particular, DNAPL) migration in porous media. We have conducted laboratory experiments. Gasoline, which is known to change wettability of porous media from hydrophilic to intermediate, and TCE (Trichloroethylene) were used as LNAPL and DNAPL, respectively. Glass beads with the grain size of 1 mm and 2 mm were prepared for two sets of porous media. Gasoline and TCE was dyed for visualization. First, respective LNAPL and DNAPL of 10 ml were separately released into prepared porous media. For the grain size of 2 mm glass beads, LNAPL became buoyant above the water table, and DNAPL just moved downward through porous media. However, for the experiment with the grain size of 1 mm glass beads, NAPLs behaved very differently. DNAPL did not migrate downward below and just remained above the water table due to capillary pressure of
Flow and dispersion in anisotropic porous media: A lattice-Boltzmann study
NASA Astrophysics Data System (ADS)
Maggiolo, D.; Picano, F.; Guarnieri, M.
2016-10-01
Given their capability of spreading active chemical species and collecting electricity, porous media made of carbon fibers are extensively used as diffusion layers in energy storage systems, such as redox flow batteries. In spite of this, the dispersion dynamics of species inside porous media is still not well understood and often lends itself to different interpretations. Actually, the microscopic design of efficient porous media, which can potentially and effectively improve the performances of flow batteries, is still an open challenge. The present study aims to investigate the effect of fibrous media micro-structure on dispersion, in particular the effect of fiber orientation on drag and dispersion dynamics. Several lattice-Boltzmann simulations of flows through differently oriented fibrous media coupled with Lagrangian simulations of particle tracers have been performed. Results show that orienting fibers preferentially along the streamwise direction minimizes the drag and maximizes the dispersion, which is the most desirable condition for diffusion layers in flow batteries' applications.
NASA Technical Reports Server (NTRS)
Chau, Jessica Furrer; Or, Dani; Sukop, Michael C.; Steinberg, S. L. (Principal Investigator)
2005-01-01
Liquid distributions in unsaturated porous media under different gravitational accelerations and corresponding macroscopic gaseous diffusion coefficients were investigated to enhance understanding of plant growth conditions in microgravity. We used a single-component, multiphase lattice Boltzmann code to simulate liquid configurations in two-dimensional porous media at varying water contents for different gravity conditions and measured gas diffusion through the media using a multicomponent lattice Boltzmann code. The relative diffusion coefficients (D rel) for simulations with and without gravity as functions of air-filled porosity were in good agreement with measured data and established models. We found significant differences in liquid configuration in porous media, leading to reductions in D rel of up to 25% under zero gravity. The study highlights potential applications of the lattice Boltzmann method for rapid and cost-effective evaluation of alternative plant growth media designs under variable gravity.
NASA Astrophysics Data System (ADS)
Chau, Jessica Furrer; Or, Dani; Sukop, Michael C.
2005-08-01
Liquid distributions in unsaturated porous media under different gravitational accelerations and corresponding macroscopic gaseous diffusion coefficients were investigated to enhance understanding of plant growth conditions in microgravity. We used a single-component, multiphase lattice Boltzmann code to simulate liquid configurations in two-dimensional porous media at varying water contents for different gravity conditions and measured gas diffusion through the media using a multicomponent lattice Boltzmann code. The relative diffusion coefficients (Drel) for simulations with and without gravity as functions of air-filled porosity were in good agreement with measured data and established models. We found significant differences in liquid configuration in porous media, leading to reductions in Drel of up to 25% under zero gravity. The study highlights potential applications of the lattice Boltzmann method for rapid and cost-effective evaluation of alternative plant growth media designs under variable gravity.
Rolling, Sliding and Mixing of a 2D Granular Media in a Thin Vertical Drum
NASA Astrophysics Data System (ADS)
Kolsky, Daniel; Galbreath, Ashford; Olafsen, Jeffrey S.
2000-11-01
Even for a relatively small number of particles, interactions of collision and friction complicate the understanding of the dynamics in granular flows. A rich assortment of interesting dynamics is exhibited in a 2D experiment of stainless steel disks contained in a rotating, thin, vertical drum. Analysis of high-speed and high-resolution photography reveals various distributions of translational and rotational kinetic energy within the granular flow as the number of particles in the drum is increased. A detailed examination of the collective behavior in this experiment is important for understanding mixing in granular flows.
Determination of the Darcy permeability of porous media including sintered metal plugs
NASA Technical Reports Server (NTRS)
Frederking, T. H. K.; Hepler, W. A.; Yuan, S. W. K.; Feng, W. F.
1986-01-01
Sintered-metal porous plugs with a normal size of the order of 1-10 microns are used to evaluate the Darcy permeability of laminar flow at very small velocities in laminar fluids. Porous media experiment results and data adduced from the literature are noted to support the Darcy law analog for normal fluid convection in the laminar regime. Low temperature results suggest the importance of collecting room temperature data prior to runs at liquid He(4) temperatures. The characteristic length diagram gives a useful picture of the tolerance range encountered with a particular class of porous media.
Mineral carbonation in water-unsaturated porous media
NASA Astrophysics Data System (ADS)
Harrison, A. L.; Dipple, G. M.; Mayer, K. U.; Power, I. M.
2014-12-01
Ultramafic mine tailings have an untapped capacity to sequester CO2 directly from air or CO2-rich gas streams via carbonation of tailings minerals [1]. The CO2 sequestration capacity of these sites could be exploited simply by increasing the supply of CO2 into tailings, such as through circulation of air or flue gas from mine site power plants [1,2]. Mine tailings storage facilities typically have heterogeneously distributed pore water [1], affecting both the reactive capacity of the porous medium and the exposure of reactive phases to CO2 [3]. We examine the physical reaction processes that govern carbonation efficiency in variably saturated porous media using meter-scale column experiments containing the tailings mineral, brucite [Mg(OH)2], that were supplied with 10% CO2 gas streams. The experiments were instrumented with water content and gas phase CO2 sensors to track changes in water saturation and CO2concentration with time. The precipitation of hydrated Mg-carbonates as rinds encasing brucite particles resulted in passivation of brucite surfaces and an abrupt shut down of the reaction prior to completion. Moreover, the extent of reaction was further limited at low water saturation due to the lack of water available to form hydrated Mg-carbonates, which incorporate water into their crystal structures. Reactive transport modeling using MIN3P-DUSTY [4] revealed that the instantaneous reaction rate was not strongly affected by water saturation, but the reactive capacity was reduced significantly. Surface passivation and water-limited reaction resulted in a highly non-geometric evolution of reactive surface area. The extent of reaction was also limited at high water content because viscous fingering of the gas streams injected at the base of the columns resulted in narrow zones of highly carbonated material, but left a large proportion of brucite unreacted. The implication is that carbonation efficiency in mine tailings could be maximized by targeting an
Fundamental Studies of Fluid Mechanics: Stability in Porous Media
George M. Homsy
2005-04-28
This work has been concerned with theoretical, computational and experimental studies of a variety of flow and transport problems that are of generic interest and applicability in energy-related and energy-intensive processes. These include the following. (1) Problems associated with oil recovery: the global economy continues to be dependent on the stable and predictable supply of oil and fossil fuels. This will remain the case for the near term, as current estimates are that world production of oil will peak between 2025 and 2100, depending on assumptions regarding growth. Most of these resources reside in porous rocks and other naturally occurring media. Studies of flow-induced instabilities are relevant to the areas of secondary and enhanced oil recovery. (2) Small scale and Stokes flows: flows in microgeometries and involving interfaces and surfactants are of interest in a myriad of energy-related contexts. These include: pore-level modeling of the fundamental processes by which oil held in porous materials is mobilized and produced; heating and cooling energy cycles involving significant expenditure of energy in conditioning of human environments, heat pipes, and compact heat exchangers; and energy efficiency in large scale separation processes such as distillation and absorption-processes that underlie the chemical process industries. (3) Coating flows: these are of interest in information technologies, including the manufacture of integrated circuits and data storage and retrieval devices. It is estimated that 50-70% of the starting raw materials and intermediate devices in information technology processes must be discarded as a result of imperfections and failure to meet specifications. These in turn are often the result of the inability to control fluid-mechanical processes and flow instabilities. Our work over the grant period is primarily fundamental in nature. We are interested in establishing general principles and behaviors that relate to a variety of
Spectral induced polarization signatures of hydroxyl adsorption in porous media
NASA Astrophysics Data System (ADS)
Zhang, C.; Johnson, T. C.; Slater, L. D.; Redden, G. D.
2010-12-01
There is a growing interest in applying geophysical methods to monitor microbial enhanced mineral precipitation through urea hydrolysis. Sensing changes in mineral surface properties as well as changes in fluid chemistry could be used to track geochemical reactions fronts in subsurface environments. Frequency-dependent complex conductivity measured with the spectral induced polarization (SIP) technique is sensitive to both fluid chemistry and mineral surface properties. We had previously observed phase shifts (φ) between current and voltage waveforms associated with hydroxyl concentration changes in a silica gel column during a urea hydrolysis experiment. In a study using less complex conditions we applied both SIP and geochemical measurements on a saturated column composed of sequential zones with Ottawa sand and silica gel in order to: 1) understand whether adsorption of hydroxyl contributes to the changes in complex conductivity, and 2) to determine whether changes in solution chemistry follow changes in surface chemistry in porous media (or vice versa). Silica gel is a highly porous form of silica (surface area is ~500 m2/g vs. <0.1 m2/g for Ottawa sand) and has a high sorption capacity for hydroxide ions. A column (48 cm) was packed with Ottawa sand at both the bottom and top sections, and with silica gel beads in the middle part of the column. The experiment started with a pH 7 sodium chloride solution (50 mM) flowing through the column at 10 ml/min, then sodium chloride solutions at higher pH (pH 8 and pH 10) replaced this solution and continued flow at the same rate for 49 hours. SIP measurements were made along the column as a function of time, and effluent samples along the column were taken for pH and conductivity measurements. The results show phase angle shifts (~4.5 mrad) in the silica gel, while no significant phase changes occurred in the Ottawa sands. Although changes in complex conductivity were only observed on synthetic high surface area
NASA Astrophysics Data System (ADS)
Johnson, David Linton; Plona, Thomas J.; Kojima, Haruo
1994-07-01
The ultrasonic properties (reflection/transmission and bulk attenuation/speed) of porous and permeable media saturated with a Newtonian fluid, namely water, are considered. The frequency dependence of the transmission amplitudes of pulses is measured through a slab of thickness d1, repeated for another slab of thickness d2 for a given material. With these two measurements on two different thicknesses, it is possible in principle to separate bulk losses from reflection/transmission losses for compressional waves in these materials. The bulk properties are calculated from the Biot theory for which all of the input parameters have been measured separately; the attenuations are particularly sensitive to the values of Λ, determined from second-sound attenuation measurements reported in the companion article. There is excellent quantitative agreement between the theoretical and experimental values in the cases considered; there are no adjustable parameters involved. The reflection and transmission coefficients are reported for some of the multiply reflected pulses and their amplitudes are compared with those calculated from the Deresiewicz-Skalak and Rosenbaum boundary conditions appropriate to either the open-pore or sealed-pore surfaces, as the case may be. Again, there is excellent quantitative agreement between theory and experiment. Compared with the open-pore boundary conditions, it is noted that there is a large reduction, both theoretically and experimentally, in the efficiency with which the slow compressional wave is generated when the sealed-pore boundary conditions apply, but this efficiency is not reduced to zero.
NASA Astrophysics Data System (ADS)
Di Federico, V.; Longo, S.; Ciriello, V.; Chiapponi, L.
2015-12-01
A theoretical and experimental analysis of non-Newtonian gravity-driven flow in porous media with spatially variable properties is presented. The motivation for our study is the rheological complexity exhibited by several environmental contaminants (wastewater sludge, oil pollutants, waste produced by the minerals and coal industries) and remediation agents (suspensions employed to enhance the efficiency of in-situ remediation). Natural porous media are inherently heterogeneous, and this heterogeneity influences the extent and shape of the porous domain invaded by the contaminant or remediation agent. To grasp the combined effect of rheology and spatial heterogeneity, we consider: a) the release of a thin current of non-Newtonian power-law fluid into a 2-D, semi-infinite and saturated porous medium above a horizontal bed; b) perfectly stratified media, with permeability and porosity varying along the direction transverse (vertical) or parallel (horizontal) to the flow direction. This continuous variation of spatial properties is described by two additional parameters. In order to represent several possible spreading scenarios, we consider: i) instantaneous injection with constant mass; ii) continuous injection with time-variable mass; iii) instantaneous release of a mound of fluid, which can drain freely out of the formation at the origin (dipole flow). Under these assumptions, scalings for current length and thickness are derived in self similar form. An analysis of the conditions on model parameters required to avoid an unphysical or asymptotically invalid result is presented. Theoretical results are validated against multiple sets of experiments, conducted for different combinations of spreading scenarios and types of stratification. Two basic setups are employed for the experiments: I) direct flow simulation in an artificial porous medium constructed superimposing layers of glass beads of different diameter; II) a Hele-Shaw (HS) analogue made of two parallel
Investigation of the rheology and transport of polymers in porous media using network models
Sorbie, K.S.; Clifford, P.J.
1988-05-01
Polymers have been used in improved oil recovery operations as mobility control agents in surfactant and polymer flooding and in gel treatments. In order to predict the outcome of such processes, it is necessary to have a good understanding of the rheology and transport of polymer solutions in porous media. The rheological behavior refers essentially to the pressure drop/flow rate relationship observed for the polymer solution in the porous medium. It is relatively straightforward to measure rheological properties of bulk polymer solutions such as the viscosity/shear rate behavior or, for elastic fluids, the normal stress differences. However, the pressure drop/flow rate behavior of the polymers in flow through porous media may be either qualitatively quite similar or very different from bulk flow behavior as measured, for example, in a capillary viscometer. In both the rheology and dispersion behavior of polymers in porous media, they see that the phenomenon being observed macroscopically is a result of the interaction between a fluid or molecular property and the stochastic nature of the porous medium at the microscopic level. If one views the porous medium as a network of joined capillaries, then the rheological behavior in each capillary will be quite well defined, e.g. through a single constitutive relationship. In the investigation of hydrodynamic dispersion of polymer and tracer in porous media, the role of the stochastic nature of the medium is clearly evident.
Targeted Delivery by Smart Capsules for Controlling Two-phase Flow in Porous Media
NASA Astrophysics Data System (ADS)
Fan, J.; Weitz, D.
2015-12-01
Understanding and controlling two-phase flow in porous media are of particular importance to the relevant industry applications, such as enhanced oil recovery, CO2 sequestration, and groundwater remediation. 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 (a) delivering surfactant to the vicinity of oil-water interface and (b) delivering microgels to the high permeability region and therefore blocking the pore space there, respectively. We also show that flooding these two capsules into porous media effectively reduces the trapped oil and improves the homogeneity of the medium, respectively. Besides of its industrial applications, this technique also opens a new window to study the mechanism of two-phase flow in porous media.
Dynamics of water evaporation from saline porous media with mixed wettability
NASA Astrophysics Data System (ADS)
Bergstad, Mina; Shokri, Nima
2016-04-01
Understanding of the dynamics of salt transport and precipitation in porous media during evaporation is of crucial concern in various environmental and hydrological applications such as soil salinization, rock weathering, terrestrial ecosystem functioning, microbiological activities and biodiversity in vadose zone. Vegetation, plant growth and soil organisms can be severely limited in salt-affected land. This process is influenced by the complex interaction among atmospheric conditions, transport properties of porous media and properties of the evaporating solution (1-5). We investigated effects of mixed wettability conditions on salt precipitation during evaporation from saline porous media. To do so, we conducted a series of evaporation experiments with sand mixtures containing different fractions of hydrophobic grains saturated with NaCl solutions. The dynamics of salt precipitation at the surface of sand columns (mounted on digital balances to record the evaporation curves) as well as the displacement of the receding drying front (the interface between wet and partially wet zone) were recorded using an automatic imaging system at well-defined time intervals. The experiments were conducted with sand packs containing 0, 25, 40, 50, 65, and 80% fraction of hydrophobic grains. All experiments were conducted in an environmental chamber in which the relative humidity and ambient temperature were kept constant at 30% and 30 C, respectively. Our results show that partial wettability conditions had minor impacts on the evaporative mass losses from saline sand packs due to the presence of salt. This is significantly different than what is normally observed during evaporation from mixed wettability porous media saturated with pure water (6). In our experiments, increasing the fraction of hydrophobic grains did not result in any notable reduction of the evaporative mass losses from saline porous media. Our results show that the presence of hydrophobic grains on the surface
Porous liquids: A promising class of media for gas separation
Zhang, Jinshui; Chai, Song -Hai; Qiao, Zhen -An; Mahurin, Shannon M.; Chen, Jihua; Fang, Youxing; Wan, Shun; Nelson, Kimberly; Zhang, Pengfei; Dai, Sheng
2014-11-17
In porous liquids with empty cavities we successfully has been successfully fabricated by surface engineering of hollow structures with suitable corona and canopy species. By taking advantage of the liquid-like polymeric matrices as a separation medium and the empty cavities as gas transport pathway, this unique porous liquid can function as a promising candidate for gas separation. A facile synthetic strategy can be further extended to other types of nanostructure-based porous liquid fabrication, opening up new opportunities for preparation of porous liquids with attractive properties for specific tasks.
Multi-phase Thermohaline Convection in Porous Media
NASA Astrophysics Data System (ADS)
Geiger, S.; Driesner, T.; Matthai, S. K.; Heinrich, C. A.
2003-12-01
The simultaneous motion of heat and dissolved solutes by aqueous or magmatic fluids through porous or fractured media within the earth's crust is a key factor that drives many important geological processes, such as the formation of large ore deposits, cooling of new-formed oceanic crust along mid-ocean ridges, metamorphism, or the evolution of geothermal systems. The motion of such crustal fluids is usually dominated by convection due to density differences within the fluids that arise from pressure, temperature and compositional variations present in the fluids. Oxygen isotope data and fluid inclusion data indicate that fluids may percolate down to 15 km depth and experience temperatures exceeding 700 {o}C. Although crustal fluids commonly contain various dissolved chemical components and gases, the most abundant solute is salt, i.e. NaCl. Hence, changes in the concentration of NaCl influence the density variations of crustal fluids the most. The presence of NaCl in H2O has decisive effects on the thermodynamics and hydrodynamics of crustal fluids. NaCl-H2O fluids can boil and separate into a high-density brine and low-salinity vapor at much higher temperatures and pressures than the critical temperature and pressure for pure H2O. NaCl-H2O fluids may also become saturated with respect to NaCl such that a solid NaCl phase coexists with a liquid or vapor fluid phase. Because salt advects faster than heat but diffuses slower than heat, the resulting double-diffusive and double-convective motion of salt and heat may lead to non-linear flow instabilities such as periodic or chaotic behavior. While many studies have addressed the theory of convection driven by temperature and/or salinity gradients, they were limited to a Boussinesq approximation and neglected phase separation. In this study we have numerically examined the behavior of multi-phase thermohaline convection in a porous media heated and salted from below using a novel finite element - finite volume
SURVEY AND EVALUATION OF POROUS POLYETHYLENE MEDIA FINE BUBBLE TUBE AND DISK AERATORS
Historically, while alternative media materials have been employed over the years with varying degrees of success, the principal fine pore diffuser medium has been porous ceramic. In the early-to-mid-1970s, diffusers with plastic porus media were installed in secondary treatment...
Transport of carbon-based nanoparticles in saturated porous media
NASA Astrophysics Data System (ADS)
Fagerlund, Fritjof; Hedayati, Maryeh; Sharma, Prabhakar; Katyal, Deeksha
2015-04-01
Carbon-based nanoparticles (NPs) are commonly occurring, both with origin from natural sources such as fires, and in the form of man-made, engineered nanoparticles, manufactured and widely used in many applications due to their unique properties. Toxicity of carbonbased NPs has been observed, and their release and distribution into the environment is therefore a matter of concern. In this research, transport and retention of three types of carbon-based NPs in saturated porous media were investigated. This included two types of engineered NPs; multi-walled carbon nanotubes (MWCNTs) and C60 with cylindrical and spherical shapes, respectively, and natural carbon NPs in the extinguishing water collected at a site of a building fire. Several laboratory experiments were conducted to study the transport and mobility of NPs in a sand-packed column. The effect of ionic strength on transport of the NPs with different shapes was investigated. Results were interpreted using Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. It was observed that the mobility of the two types of engineered NPs was reduced with an increase in ionic strength from 1.3 mM to 60 mM. However, at ionic strength up to 10.9 mM, C60 was relatively more mobile than MWCNTs but the mobility of MWCNTs became significantly higher than C60 at 60 mM. In comparison with natural particles originating from a fire, both engineered NPs were much less mobile at the selected experimental condition. Inverse modelling was also used to calculate parameters such as attachment efficiency, the longitudinal dispersivity, and capacity of the solid phase for the removal of particles. The simulated results were in good agreement with the observed data.
Cotransport of bismerthiazol and montmorillonite colloids in saturated porous media
NASA Astrophysics Data System (ADS)
Shen, Chongyang; Wang, Hong; Lazouskaya, Volha; Du, Yichun; Lu, Weilan; Wu, Junxue; Zhang, Hongyan; Huang, Yuanfang
2015-06-01
While bismerthiazol [N,N‧-methylene-bis-(2-amino-5-mercapto-1,3,4-thiadiazole)] is one of the most widely used bactericides, the transport of bismerthiazol in subsurface environments is unclear to date. Moreover, natural colloids are ubiquitous in the subsurface environments. The cotransport of bismerthiazol and natural colloids has not been investigated. This study conducted laboratory column experiments to examine the transport of bismerthiazol in saturated sand porous media both in the absence and presence of montmorillonite colloids. Results show that a fraction of bismerthiazol was retained in sand and the retention was higher at pH 7 than at pH 4 and 10. The retention did not change with ionic strength. The retention was attributed to the complex of bismerthiazol with metals/metal oxides on sand surfaces through ligand exchange. The transport of bismerthiazol was enhanced with montmorillonite colloids copresent in the solutions and, concurrently, the transport of montmorillonite colloids was facilitated by the bismerthiazol. The transport of montmorillonite colloids was enhanced likely because the bismerthiazol and the colloids competed for the attachment/adsorption sites on collector surfaces and the presence of bismerthiazol changed the Derjaguin-Landau-Verwey-Overbeek (DLVO) interaction energies between colloids and collectors. The transport of bismerthiazol was inhibited if montmorillonite colloids were pre-deposited in sand because bismerthiazol could adsorb onto the colloid surfaces. The adsorbed bismerthiazol could be co-remobilized with the colloids from primary minima by decreasing ionic strength. Whereas colloid-facilitated transport of pesticides has been emphasized, our study implies that transport of colloids could also be facilitated by the presence of pesticides.
Migration and entrapment of mercury in porous media.
Devasena, M; Nambi, Indumathi M
2010-09-20
Elemental mercury is an immiscible liquid with high density and high interfacial tension with water. Its movement in the saturated subsurface region is therefore considered as a case of two phase flow involving mercury and water and is expected to be governed by gravity, viscous, hydrodynamic and capillary forces. This paper investigates the migration and capillary entrapment of mercury in the subsurface based on controlled laboratory capillary pressure-saturation experiments. In the first place, entrapment of mercury was observed in homogeneous porous media. Residual mercury saturation and van Genuchten's parameters for mercury entrapment were generated. These data will provide vital inputs for mercury migration and entrapment models. Secondly, the dependency of residual saturation on fluid properties was brought out in this work by comparing the experimental results of mercury-water system and DNAPL-water systems. Capillary forces were large enough in mercury-water systems to counteract the high gravity forces and caused the entrapment of mercury. Large density differences between mercury and water lead to a high Bond number and thus a low residual mercury saturation was obtained which corroborates with existing DNAPL theories. However, the inverse relationship between residual saturation and capillary number established for NAPL-water systems cannot be compared with mercury-water systems. Moreover, the critical capillary numbers and Bond numbers to mobilize DNAPLs may not be applicable to mercury since mercury has a low capillary number and high Bond number. This work has enabled the understanding of the process of migration and entrapment of mercury and provided useful inputs for two phase flow models specific to mercury-water systems. It has also highlighted the influence of fluid properties on entrapment and mobilization particularly for highly dense, viscous fluid which also possesses high interfacial tension with water.
Migration and entrapment of mercury in porous media
NASA Astrophysics Data System (ADS)
Devasena, M.; Nambi, Indumathi M.
2010-09-01
Elemental mercury is an immiscible liquid with high density and high interfacial tension with water. Its movement in the saturated subsurface region is therefore considered as a case of two phase flow involving mercury and water and is expected to be governed by gravity, viscous, hydrodynamic and capillary forces. This paper investigates the migration and capillary entrapment of mercury in the subsurface based on controlled laboratory capillary pressure-saturation experiments. In the first place, entrapment of mercury was observed in homogeneous porous media. Residual mercury saturation and van Genuchten's parameters for mercury entrapment were generated. These data will provide vital inputs for mercury migration and entrapment models. Secondly, the dependency of residual saturation on fluid properties was brought out in this work by comparing the experimental results of mercury-water system and DNAPL-water systems. Capillary forces were large enough in mercury-water systems to counteract the high gravity forces and caused the entrapment of mercury. Large density differences between mercury and water lead to a high Bond number and thus a low residual mercury saturation was obtained which corroborates with existing DNAPL theories. However, the inverse relationship between residual saturation and capillary number established for NAPL-water systems cannot be compared with mercury-water systems. Moreover, the critical capillary numbers and Bond numbers to mobilize DNAPLs may not be applicable to mercury since mercury has a low capillary number and high Bond number. This work has enabled the understanding of the process of migration and entrapment of mercury and provided useful inputs for two phase flow models specific to mercury-water systems. It has also highlighted the influence of fluid properties on entrapment and mobilization particularly for highly dense, viscous fluid which also possesses high interfacial tension with water.
Complex resistivity signatures of ethanol biodegradation in porous media.
Personna, Yves Robert; Slater, Lee; Ntarlagiannis, Dimitrios; Werkema, Dale; Szabo, Zoltan
2013-10-01
Numerous adverse effects are associated with the accidental release of ethanol (EtOH) and its persistence in the subsurface. Geophysical techniques may permit non-invasive, real time monitoring of microbial degradation of hydrocarbon. We performed complex resistivity (CR) measurements in conjunction with geochemical data analysis on three microbial-stimulated and two control columns to investigate changes in electrical properties during EtOH biodegradation processes in porous media. A Debye Decomposition approach was applied to determine the chargeability (m), normalized chargeability (m(n)) and time constant (τ) of the polarization magnitude and relaxation length scale as a function of time. The CR responses showed a clear distinction between the bioaugmented and control columns in terms of real (σ') and imaginary (σ″) conductivity, phase (ϕ) and apparent formation factor (F(app)). Unlike the control columns, a substantial decrease in σ' and increase in F(app) occurred at an early time (within 4 days) of the experiment for all three bioaugmented columns. The observed decrease in σ' is opposite to previous studies on hydrocarbon biodegradation. These columns also exhibited increases in ϕ (up to ~9 mrad) and σ″ (up to two order of magnitude higher) 5 weeks after microbial inoculation. Variations in m and m(n) were consistent with temporal changes in ϕ and σ″ responses, respectively. Temporal geochemical changes and high resolution scanning electron microscopy imaging corroborated the CR findings, thus indicating the sensitivity of CR measurements to EtOH biodegradation processes. Our results offer insight into the potential application of CR measurements for long-term monitoring of biogeochemical and mineralogical changes during intrinsic and induced EtOH biodegradation in the subsurface.
Exact Averaging of Stochastic Equations for Flow in Porous Media
Karasaki, Kenzi; Shvidler, Mark; Karasaki, Kenzi
2008-03-15
It is well known that at present, exact averaging of the equations for flow and transport in random porous media have been proposed for limited special fields. Moreover, approximate averaging methods--for example, the convergence behavior and the accuracy of truncated perturbation series--are not well studied, and in addition, calculation of high-order perturbations is very complicated. These problems have for a long time stimulated attempts to find the answer to the question: Are there in existence some, exact, and sufficiently general forms of averaged equations? Here, we present an approach for finding the general exactly averaged system of basic equations for steady flow with sources in unbounded stochastically homogeneous fields. We do this by using (1) the existence and some general properties of Green's functions for the appropriate stochastic problem, and (2) some information about the random field of conductivity. This approach enables us to find the form of the averaged equations without directly solving the stochastic equations or using the usual assumption regarding any small parameters. In the common case of a stochastically homogeneous conductivity field we present the exactly averaged new basic nonlocal equation with a unique kernel-vector. We show that in the case of some type of global symmetry (isotropy, transversal isotropy, or orthotropy), we can for three-dimensional and two-dimensional flow in the same way derive the exact averaged nonlocal equations with a unique kernel-tensor. When global symmetry does not exist, the nonlocal equation with a kernel-tensor involves complications and leads to an ill-posed problem.
Complex resistivity signatures of ethanol biodegradation in porous media
Personna, Yves Robert; Slater, Lee; Ntarlagiannis, Dimitrios; Werkema, Dale; Szabo, Zoltan
2013-01-01
Numerous adverse effects are associated with the accidental release of ethanol (EtOH) and its persistence in the subsurface. Geophysical techniques may permit non-invasive, real time monitoring of microbial degradation of hydrocarbon. We performed complex resistivity (CR) measurements in conjunction with geochemical data analysis on three microbial-stimulated and two control columns to investigate changes in electrical properties during EtOH biodegradation processes in porous media. A Debye Decomposition approach was applied to determine the chargeability (m), normalized chargeability (mn) and time constant (τ) of the polarization magnitude and relaxation length scale as a function of time. The CR responses showed a clear distinction between the bioaugmented and control columns in terms of real (σ′) and imaginary (σ″) conductivity, phase (ϕ) and apparent formation factor (Fapp). Unlike the control columns, a substantial decrease in σ′ and increase in Fapp occurred at an early time (within 4 days) of the experiment for all three bioaugmented columns. The observed decrease in σ′ is opposite to previous studies on hydrocarbon biodegradation. These columns also exhibited increases in ϕ (up to ~ 9 mrad) and σ″ (up to two order of magnitude higher) 5 weeks after microbial inoculation. Variations in m and mn were consistent with temporal changes in ϕ and σ″ responses, respectively. Temporal geochemical changes and high resolution scanning electron microscopy imaging corroborated the CR findings, thus indicating the sensitivity of CR measurements to EtOH biodegradation processes. Our results offer insight into the potential application of CR measurements for long-term monitoring of biogeochemical and mineralogical changes during intrinsic and induced EtOH biodegradation in the subsurface.
Cotransport of bismerthiazol and montmorillonite colloids in saturated porous media.
Shen, Chongyang; Wang, Hong; Lazouskaya, Volha; Du, Yichun; Lu, Weilan; Wu, Junxue; Zhang, Hongyan; Huang, Yuanfang
2015-01-01
While bismerthiazol [N,N'-methylene-bis-(2-amino-5-mercapto-1,3,4-thiadiazole)] is one of the most widely used bactericides, the transport of bismerthiazol in subsurface environments is unclear to date. Moreover, natural colloids are ubiquitous in the subsurface environments. The cotransport of bismerthiazol and natural colloids has not been investigated. This study conducted laboratory column experiments to examine the transport of bismerthiazol in saturated sand porous media both in the absence and presence of montmorillonite colloids. Results show that a fraction of bismerthiazol was retained in sand and the retention was higher at pH7 than at pH 4 and 10. The retention did not change with ionic strength. The retention was attributed to the complex of bismerthiazol with metals/metal oxides on sand surfaces through ligand exchange. The transport of bismerthiazol was enhanced with montmorillonite colloids copresent in the solutions and, concurrently, the transport of montmorillonite colloids was facilitated by the bismerthiazol. The transport of montmorillonite colloids was enhanced likely because the bismerthiazol and the colloids competed for the attachment/adsorption sites on collector surfaces and the presence of bismerthiazol changed the Derjaguin-Landau-Verwey-Overbeek (DLVO) interaction energies between colloids and collectors. The transport of bismerthiazol was inhibited if montmorillonite colloids were pre-deposited in sand because bismerthiazol could adsorb onto the colloid surfaces. The adsorbed bismerthiazol could be co-remobilized with the colloids from primary minima by decreasing ionic strength. Whereas colloid-facilitated transport of pesticides has been emphasized, our study implies that transport of colloids could also be facilitated by the presence of pesticides.
Transport in porous and fractured media of the Creede Formation
Conca, J.L.
1995-12-31
Direct measurement was made of the hydraulic conductivity of Creede Formation rocks using a new experimental method. The UFA{trademark} method employs open-flow centrifugation. Centrifugation, like gravity, has the effect on a material of a whole-body force exerting equal force at all points within the sample. The equivalent gravitational force exerted throughout the sample can be chosen to be from one to four orders of magnitude higher than earth gravity (from 10 to 10,000 g). The result is an increase in rate of fluid flow equally at all points throughout the sample so that hydraulic steady state is obtained in most geologic materials in hours, even under highly unsaturated conditions. This extraordinarily short time allows direct measurement of transport parameters, such as hydraulic conductivity, diffusion coefficient, and retardation factors, in any porous media over the complete range of field moisture contents. Hydraulic conductivities in the Creede Formation rocks ranged from 10{sup {minus}12} cm/s to 10{sup {minus}7} cm/s (10{sup {minus}9} Darcy to 10{sup {minus}4} Darcy) and showed no correlation with any other physical or mineralogical properties including porosity. The high degree of alteration to clay minerals appears to obscure any porosity/permeability relationship of the kind that occurs in many reservoir rocks. However, down-hole neutron porosities correlated well with laboratory-determined porosities. The objective of this investigation is to determine the hydrologic transport parameters of Creede Formation rocks for use in transport model development and for image analysis of transport pathways to produce a porosity/permeability evolution curve in support of geochemical and isotopic water/rock interaction models.
Complex resistivity signatures of ethanol biodegradation in porous media
NASA Astrophysics Data System (ADS)
Personna, Yves Robert; Slater, Lee; Ntarlagiannis, Dimitrios; Werkema, Dale; Szabo, Zoltan
2013-10-01
Numerous adverse effects are associated with the accidental release of ethanol (EtOH) and its persistence in the subsurface. Geophysical techniques may permit non-invasive, real time monitoring of microbial degradation of hydrocarbon. We performed complex resistivity (CR) measurements in conjunction with geochemical data analysis on three microbial-stimulated and two control columns to investigate changes in electrical properties during EtOH biodegradation processes in porous media. A Debye Decomposition approach was applied to determine the chargeability (m), normalized chargeability (mn) and time constant (τ) of the polarization magnitude and relaxation length scale as a function of time. The CR responses showed a clear distinction between the bioaugmented and control columns in terms of real (σ‧) and imaginary (σ″) conductivity, phase (ϕ) and apparent formation factor (Fapp). Unlike the control columns, a substantial decrease in σ‧ and increase in Fapp occurred at an early time (within 4 days) of the experiment for all three bioaugmented columns. The observed decrease in σ‧ is opposite to previous studies on hydrocarbon biodegradation. These columns also exhibited increases in ϕ (up to ~ 9 mrad) and σ″ (up to two order of magnitude higher) 5 weeks after microbial inoculation. Variations in m and mn were consistent with temporal changes in ϕ and σ″ responses, respectively. Temporal geochemical changes and high resolution scanning electron microscopy imaging corroborated the CR findings, thus indicating the sensitivity of CR measurements to EtOH biodegradation processes. Our results offer insight into the potential application of CR measurements for long-term monitoring of biogeochemical and mineralogical changes during intrinsic and induced EtOH biodegradation in the subsurface.
NASA Astrophysics Data System (ADS)
Patel, Amar; Bilbao, Alejandro; Rahman, Mizanur; Vanapalli, Siva; Blawzdziewicz, Jerzy
Caenorhabditis elegans is a powerful genetic model, essential for studies in diverse areas ranging from behavior to neuroscience to aging, and locomotion and chemotaxis are the two key observables used. We combine our recently developed theory of nematode locomotion and turning maneuvers [Phys. Fluids 25, 081902 (2013)] with simple models of chemosensation to analyze nematode chemotaxis strategies in 2D and 3D environments. We show that the sharp-turn (pirouette) chemotaxis mechanism is efficient in diverse media; in particular, the nematode does not need to adjust the sensing or motion-control parameters to efficiently chemotax in 2D crawling, 3D burrowing, and 2D or 3D swimming. In contrast, the graduate-turn mechanism becomes inefficient in swimming, unless a phase-shift is introduced between the sensing signal and modulation of body wave to generate the gradual turn. We hypothesize that there exists a new ``controlled fluctuations'' chemotaxis mechanism, in which the nematode changes the intensity of undulation fluctuations to adjust the persistence length of the trajectory in response to a variation in chemoattractant concentration. Supported by NSF Grant No. CBET 1059745.
Modal method for the 2D wave propagation in heterogeneous anisotropic media.
Maurel, Agnès; Mercier, Jean-François; Félix, Simon
2015-05-01
A multimodal method based on a generalization of the admittance matrix is used to analyze wave propagation in heterogeneous two-dimensional anisotropic media. The heterogeneity of the medium can be due to the presence of anisotropic inclusions with arbitrary shapes, to a succession of anisotropic media with complex interfaces between them, or both. Using a modal expansion of the wave field, the problem is reduced to a system of two sets of first-order differential equations for the modal components of the field, similar to the system obtained in the rigorous coupled wave analysis. The system is solved numerically, using the admittance matrix, which leads to a stable numerical method, the basic properties of which are discussed. The convergence of the method is discussed, considering arrays of anisotropic inclusions with complex shapes, which tend to show that Li's rules are not concerned within our approach. The method is validated by comparison with a subwavelength layered structure presenting an effective anisotropy at the wave scale.
Natural Convection in Enclosed Porous or Fluid Media
ERIC Educational Resources Information Center
Saatdjian, Esteban; Lesage, François; Mota, José Paulo B.
2014-01-01
In Saatdjian, E., Lesage, F., and Mota, J.P.B, "Transport Phenomena Projects: A Method to Learn and to Innovate, Natural Convection Between Porous, Horizontal Cylinders," "Chemical Engineering Education," 47(1), 59-64, (2013), the numerical solution of natural convection between two porous, concentric, impermeable cylinders was…
Micro/macroscopic fluid flow in open cell fibrous structures and porous media
NASA Astrophysics Data System (ADS)
Tamayol, Ali
Fibrous porous materials are involved in a wide range of applications including composite fabrication, filtration, compact heat exchangers, fuel cell technology, and tissue engineering to name a few. Fibrous structures, such as metalfoams, have unique characteristics such as low weight, high porosity, high mechanical strength, and high surface to volume ratio. More importantly, in many applications the fibrous microstructures can be tailored to meet a range of requirements. Therefore, fibrous materials have the potential to be used in emerging sustainable energy conversion applications. The first step for analyzing transport phenomena in porous materials is to determine the micro/macroscopic flow-field inside the medium. In applications where the porous media is confined in a channel, the system performance is tightly related to the flow properties of the porous medium and its interaction with the channel walls, i.e., macroscopic velocity distribution. Therefore, the focus of the study has been on: developing new mechanistic model(s) for determining permeability and inertial coefficient of fibrous porous materials; investigating the effects of microstructural and mechanical parameters such as porosity, fiber orientation, mechanical compression, and fiber distribution on the flow properties and pressure drop of fibrous structures; determining the macroscopic flow-field in confined porous media where the porous structure fills the channel cross-section totally or partially. A systematic approach has been followed to study different aspects of the flow through fibrous materials. The complex microstructure of real materials has been modelled using unit cells that have been assumed to be repeated throughout the media. Implementing various exact and approximate analytical techniques such as integral technique, point matching, blending rules, and scale analysis the flow properties of such media have been modelled; the targeted properties include permeability and inertial
Effects of Heterogeneity on Transport of Graphene Oxide in Saturated and Unsaturated Porous Media
NASA Astrophysics Data System (ADS)
Dong, S.; Sun, Y.; Shi, X.; Wu, J.; Gao, B.
2015-12-01
Graphene oxide (GO) has received increasing attention in many fields with its wide applications and rapid growth in production. Therefore, it is expected that GO nanoparticles will inevitably be released into the subsurface and cause the environmental risk subsequently. In view of this, knowledge of the fate for GO in the vadose zone and groundwater systems is indispensable. So far most research has focused on the deposition and transport of GO nanoparticles in one-dimensional homogenous porous media; nonetheless, the complex heterogeneous system is extensively distributed in natural subsurface environment and may not be well represented by the homogeneous packed columns. However, little investigations have been directed toward understanding the transport of GO in heterogeneous porous media. The overarching objective of this study is to advance current understanding of GO transport in structured heterogeneous porous media. The saturated and unsaturated columns packed with different sand combinations and solution ionic strength, were used to examine the breakthrough behavior of GO in heterogeneous porous media. A two-domain model considering GO exchange between zones was developed to describe GO transport in structured, heterogeneous porous media. The experimental data indicate that volumetric moisture content and water flow are the critical factors that control GO transport in heterogeneous porous media. And higher ionic strength decrease the mobility of GO particles in both saturated and unsaturated heterogeneous pore media. Simulations of this two-domain nanoparticle transport model matched experimental breakthrough data well for all the experimental conditions. Experimental and model results show that under saturated conditions, both fast-flow and slow-flow domains affect colloid transport in heterogeneous media. Under unsaturated conditions, however, our results indicate that flows in the fast flow domain dominate the colloid transport and retention processes.
NASA Astrophysics Data System (ADS)
Yang, Jianwen
2012-04-01
A general analytical solution is derived by using the Laplace transformation to describe transient reactive silica transport in a conceptualized 2-D system involving a set of parallel fractures embedded in an impermeable host rock matrix, taking into account of hydrodynamic dispersion and advection of silica transport along the fractures, molecular diffusion from each fracture to the intervening rock matrix, and dissolution of quartz. A special analytical solution is also developed by ignoring the longitudinal hydrodynamic dispersion term but remaining other conditions the same. The general and special solutions are in the form of a double infinite integral and a single infinite integral, respectively, and can be evaluated using Gauss-Legendre quadrature technique. A simple criterion is developed to determine under what conditions the general analytical solution can be approximated by the special analytical solution. It is proved analytically that the general solution always lags behind the special solution, unless a dimensionless parameter is less than a critical value. Several illustrative calculations are undertaken to demonstrate the effect of fracture spacing, fracture aperture and fluid flow rate on silica transport. The analytical solutions developed here can serve as a benchmark to validate numerical models that simulate reactive mass transport in fractured porous media.
Three dimensional simulation of fluid flow in X-ray CT images of porous media
NASA Astrophysics Data System (ADS)
Al-Omari, A.; Masad, E.
2004-11-01
A numerical scheme is developed in order to simulate fluid flow in three dimensional (3-D) microstructures. The governing equations for steady incompressible flow are solved using the semi-implicit method for pressure-linked equations (SIMPLE) finite difference scheme within a non-staggered grid system that represents the 3-D microstructure. This system allows solving the governing equations using only one computational cell. The numerical scheme is verified through simulating fluid flow in idealized 3-D microstructures with known closed form solutions for permeability. The numerical factors affecting the solution in terms of convergence and accuracy are also discussed. These factors include the resolution of the analysed microstructure and the truncation criterion. Fluid flow in 2-D X-ray computed tomography (CT) images of real porous media microstructure is also simulated using this numerical model. These real microstructures include field cores of asphalt mixes, laboratory linear kneading compactor (LKC) specimens, and laboratory Superpave gyratory compactor (SGC) specimens. The numerical results for the permeability of the real microstructures are compared with the results from closed form solutions. Copyright
A Semi-implicit Treatment of Porous Media in Steady-State CFD.
Domaingo, Andreas; Langmayr, Daniel; Somogyi, Bence; Almbauer, Raimund
There are many situations in computational fluid dynamics which require the definition of source terms in the Navier-Stokes equations. These source terms not only allow to model the physics of interest but also have a strong impact on the reliability, stability, and convergence of the numerics involved. Therefore, sophisticated numerical approaches exist for the description of such source terms. In this paper, we focus on the source terms present in the Navier-Stokes or Euler equations due to porous media-in particular the Darcy-Forchheimer equation. We introduce a method for the numerical treatment of the source term which is independent of the spatial discretization and based on linearization. In this description, the source term is treated in a fully implicit way whereas the other flow variables can be computed in an implicit or explicit manner. This leads to a more robust description in comparison with a fully explicit approach. The method is well suited to be combined with coarse-grid-CFD on Cartesian grids, which makes it especially favorable for accelerated solution of coupled 1D-3D problems. To demonstrate the applicability and robustness of the proposed method, a proof-of-concept example in 1D, as well as more complex examples in 2D and 3D, is presented.
2D spectral element modeling of GPR wave propagation in inhomogeneous media
NASA Astrophysics Data System (ADS)
Zarei, Sajad; Oskooi, Behrooz; Amini, Navid; Dalkhani, Amin Rahimi
2016-10-01
We present a spectral element method, for simulation of ground-penetrating radar (GPR) in two dimensions. The technique is based upon a weak formulation of the equations of Maxwell and combines the flexibility of the elemental-based methods with the accuracy of the spectral based methods. The wave field on the elements is discretized using high-degree Lagrange interpolation and integration over an element is accomplished based upon the Gauss-Lobatto-Legendre integration rule. As a result, the mass matrix and the damping matrix are always diagonal, which drastically reduces the computational cost. We first develop the formulation of 2D spectral element method (SEM) in the time-domain based on Maxwell's equations. The presented formulation is with matrix notation that simplifies the implementation of the relations in computer programs, especially in MATLAB application. We discuss the differences between spectral element method and finite-element method in the time-domain. Also, we show that the SEM numerical dispersion is much lower than FEM. To absorb waves at the edges of the modeling domain, we implement first order Clayton and Engquist absorbing boundary conditions (CE-ABC) introduced in numerical finite-difference modeling of seismic wave propagation. We used the SEM to simulate a complex model to show its abilities and limitations. As well as, one distinct advantage of SEM is that we can easily define our model features in nodal points, because the integration points and the interpolation points are similar that makes it very flexible in simulation of complex models.
The flow around circular cylinders partially coated with porous media
NASA Astrophysics Data System (ADS)
Ruck, Bodo; Klausmann, Katharina; Wacker, Tobias
2012-05-01
There are indications that the flow resistance of bodies can be reduced by a porous coating or porous sheath. A few numerical investigations exists in this field, however, experimental evidence is lacking. In order to investigate this phenomenon, the drag resistance of cylinders with porous coating has been investigated qualitatively and quantitatively in wind tunnel experiments. The Reynolds number was systematically varied in the range from 104 to 1.3*105. The results show that the boundary layer over the porous surface is turbulent right from the beginning and thickens faster because of the possible vertical momentum exchange at the interface. The region of flow detachment is widened resulting in a broader area with almost vanishing low flow velocities. All in all, the measurements show that a full porous coating of the cylinders increase the flow resistance. However, the measurements show that a partial coating only on the leeward side can decrease the flow resistance of the body. This effect seems due to the fact that the recirculating velocity and the underpressure in the wake is reduced significantly through a leeward porous coating. Thus, combining a smooth non-permeable windward side with a porous-coated leeward side can lead to a reduction of the body's flow resistance. These findings can be applied advantageously in many technical areas, such as energy saving of moving bodies (cars/trains/planes) or in reducing fluid loads on submersed bodies.
Relaxation-relaxation exchange experiments in porous media with portable Halbach-Magnets.
NASA Astrophysics Data System (ADS)
Haber, A.; Haber-Pohlmeier, S.; Casanova, F.; Blümich, B.
2009-04-01
Mobile NMR became a powerful tool following the development of portable NMR sensors for well logging. By now there are numerous applications of mobile NMR in materials analysis and chemical engineering where, for example, unique information about the structure, morphology and dynamics of polymers is obtained, and new opportunities are provided for geo-physical investigations [1]. In particular, dynamic information can be retrieved by two-dimensional Laplace exchange NMR, where the initial NMR relaxation environment is correlated with the final relaxation environment of molecules migrating from one environment to the other within a so-called NMR mixing time tm [2]. Relaxation-relaxation exchange experiments of water in inorganic porous media were performed at low and moderately inhomogeneous magnetic field with a simple, portable Halbach-Magnet. By conducting NMR transverse relaxation exchange experiments for several mixing times and converting the results to 2D T2 distributions (joint probability densities of transverse relaxation times T2) with the help of the inverse 2D Laplace Transformation (ILT), we obtained characteristic exchange times for different pore sizes. The results of first experiments on soil samples are reported, which reveal information about the complex pore structure of soil and the moisture content. References: 1. B. Blümich, J. Mauler, A. Haber, J. Perlo, E. Danieli, F. Casanova, Mobile NMR for Geo-Physical Analysis and Material Testing, Petroleum Science, xx (2009) xxx - xxx. 2. K. E. Washburn, P.T. Callaghan, Tracking pore to pore exchange using relaxation exchange spectroscopy, Phys. Rev. Lett. 97 (2006) 175502.
Evaporation of NaCl solution from porous media with mixed wettability
NASA Astrophysics Data System (ADS)
Bergstad, Mina; Shokri, Nima
2016-05-01
Evaporation of saline water from porous media is ubiquitous in many processes including soil salinization, crop production, and CO2 sequestration in deep saline acquirer. It is controlled by the transport properties of porous media, atmospheric conditions, and properties of the evaporating saline solution. In the present study, the effects of mixed wettability conditions on the general dynamics of water evaporation from porous media saturated with NaCl solution were investigated. To do so, we conducted a comprehensive series of evaporation experiments using sand mixtures containing different fractions of hydrophobic grains saturated with NaCl solutions. Our results showed that increasing fraction of hydrophobic grains in the mixed wettability sand pack had minor impact on the evaporative mass losses due to the presence of salt whose precipitation patterns were significantly influenced by the mixed wettability condition. Through macroscale and microscale investigations, we found formation of patchy efflorescence in the case of mixed wettability sand pack as opposed to crusty efflorescence in the case of completely hydrophilic porous media. Furthermore, the presence of salty water and hydrophobic grains in the sand pack significantly influenced the general dynamics and morphology of the receding drying front. Our results extend the understanding of the saline water evaporation from porous media with direct applications to various hydrological and engineering processes.
Cushman, J.H.; Madilyn Fletcher
2000-06-01
Dynamic microbial attachment/detachment occurs in subsurface systems in response to changing environmental conditions caused by contaminant movement and degradation. Understanding the environmental conditions and mechanisms by which anaerobic bacteria partition between aqueous and solid phases is a critical requirement for designing and evaluating in situ bioremediation efforts. This interdisciplinary research project, of which we report only the Purdue contribution, provides fundamental information on the attachment/detachment dynamics of bacteria in heterogeneous porous media. Fundamental results from the Purdue collaboration are: (a) development of a matched-index method for obtaining 3-D Lagrangian trajectories of microbial sized particles transporting within porous media or microflow cells, (b) application of advanced numerical methods to optimally design a microflow cell for studying anaerobic bacterial attachment/detachment phenomena, (c) development of two types of models for simulating bacterial movement and attachment/detachment in microflow cells and natural porous media, (d) application of stochastic analysis to upscale pore scale microbial attachment/detachment models to natural heterogeneous porous media, and (e) evaluation of the role nonlocality plays in microbial dynamics in heterogeneous porous media
Cushman, J.H.
2000-06-01
Dynamic microbial attachment/detachment occurs in subsurface systems in response to changing environmental conditions caused by contaminant movement and degradation. Understanding the environmental conditions and mechanisms by which anaerobic bacteria partition between aqueous and solid phases is a critical requirement for designing and evaluating in situ bioremediation efforts. This interdisciplinary research project, of which we report only the Purdue contribution, provides fundamental information on the attachment/detachment dynamics of bacteria in heterogeneous porous media. Fundamental results from the Purdue collaboration are: (a) development of a matched-index method for obtaining 3-D Lagrangian trajectories of microbial sized particles transporting within porous media or microflow cells, (b) application of advanced numerical methods to optimally design a microflow cell for studying anaerobic bacterial attachment/detachment phenomena, (c) development of two types of models for simulating bacterial movement and attachment/detachment in microflow cells and natural porous media, (d) application of stochastic analysis to upscale pore scale microbial attachment/detachment models to natural heterogeneous porous media, and (e) evaluation of the role nonlocality plays in microbial dynamics in heterogeneous porous media.
Experimental investigation of magnetically driven flow of ferrofluids in porous media
Borglin, S.E.; Moridis, G.J.; Oldenburg, C.M.
1998-08-01
This report presents experimental results of the flow of ferrofluids in porous media to investigate the potential for precisely controlling fluid emplacement in porous media using magnetic fields. Ferrofluids are colloidal suspensions of magnetic particles stabilized in various carrier liquids. In the presence of an external magnetic field, the ferrofluid becomes magnetized as the particles align with the magnetic field. Potential applications of ferrofluids to subsurface contamination problems include magnetic guidance of reactants to contaminated target zones in the subsurface for in situ treatment or emplacement of containment barriers. Laboratory experiments of magnetically induced ferrofluid flow in porous media in this report demonstrate the potential for mobilizing ferrofluid and controlling fluid emplacement through control of the external magnetic field. The pressures measured in ferrofluid due to the attraction of ferrofluid to a permanent magnet agree well with calculated values. The results show that a predictable pressure gradient is produced in the fluid which is strong near the magnet and drops off quickly with distance. This pressure gradient drives the fluid through sand without significant loss of ferrofluid strength due to filtration or dilution. Flow visualization experiments of ferrofluid in water-filled horizontal Hele-Shaw cells demonstrate that ferrofluid obtains a consistent final arc-shaped configuration around the magnet regardless of initial configuration or flow path toward the magnet. Analogous experiments in actual porous media showed similar features and confirm the ability of ferrofluid to move through porous media by magnetic forces.
Fluid flow in porous media with rough pore-solid interface
NASA Astrophysics Data System (ADS)
Ghanbarian, Behzad; Hunt, Allen G.; Daigle, Hugh
2016-03-01
Quantifying fluid flow through porous media hinges on the description of permeability, a property of considerable importance in many fields ranging from oil and gas exploration to hydrology. A common building block for modeling porous media permeability is consideration of fluid flow through tubes with circular cross section described by Poiseuille's law in which flow discharge is proportional to the fourth power of the tube's radius. In most natural porous media, pores are neither cylindrical nor smooth; they often have an irregular cross section and rough surfaces. This study presents a theoretical scaling of Poiseuille's approximation for flow in pores with irregular rough cross section quantified by a surface fractal dimension Ds2. The flow rate is a function of the average pore radius to the power 2(3-Ds2) instead of 4 in the original Poiseuille's law. Values of Ds2 range from 1 to 2, hence, the power in the modified Poiseuille's approximation varies between 4 and 2, indicating that flow rate decreases as pore surface roughness (and surface fractal dimension Ds2) increases. We also proposed pore length-radius relations for isotropic and anisotropic fractal porous media. The new theoretical derivations are compared with standard approximations and with experimental values of relative permeability. The new approach results in substantially improved prediction of relative permeability of natural porous media relative to the original Poiseuille equation.
NASA Astrophysics Data System (ADS)
Dupont, S.; Gazalet, J.; Kastelik, J. C.
2014-03-01
Phononic crystal is a structured media with periodic modulation of its physical properties that influences the propagation of elastic waves and leads to a peculiar behaviour, for instance the phononic band gap effect by which elastic waves cannot propagate in certain frequency ranges. The formulation of the problem leads to a second order partial differential equation with periodic coefficients; different methods exist to determine the structure of the eigenmodes propagating in the material, both in the real or Fourier domain. Brillouin explains the periodicity of the band structure as a direct result of the discretization of the crystal in the real domain. Extending the Brillouin vision, we introduce digital signal processing tools developed in the frame of distribution functions theory. These tools associate physical meaning to mathematical expressions and reveal the correspondence between real and Fourier domains whatever is the physical domain under consideration. We present an illustrative practical example concerning two dimensions phononic crystals and highlight the appreciable shortcuts brought by the method and the benefits for physical interpretation.
Laboratory Models of Thermal Convection in Porous Media
NASA Astrophysics Data System (ADS)
Cooper, C. A.; Breitmeyer, R.; Schumer, R.; Voepel, H.; Decker, D.
2011-12-01
Experiments have been conducted to measure the length and times scales of thermal plumes in laboratory porous media. A polycarbonate cell 1 m high x 75 cm wide x 2.54 cm deep filled with 3 mm glass beads is heated uniformly from the bottom using electrical heat tape. The heat tape is in direct contact with an aluminum alloy heat exchanger sandwiched between the two vertical plates, and a digital controller is used to maintain constant temperature. The upper boundary is kept at constant temperature by circulating cold water from a constant-temperature refrigerating bath through copper tubes in contact with the upper part of the cell. Flow is visualized by mixing a neutrally buoyant thermochromic liquid tracer in the working fluid (water and glycerin). TLCs are liquid crystals manufactured to change color as a function of temperature. Color change is repeatable and reversible with a response time to temperature change is less than 0.01 s. Image acquisition is done using a CCD camera, and three images are captured nearly simultaneously, each with a red, blue, or green filter over the camera lens. The three images are then combined to make a true color image. At each pixel in the image, hue is extracted and a calibration curve is developed to relate hue to temperature. In one experiment with a 10 degree C temperature difference between the upper and lower boundaries, the onset of convection began within 26 minutes, which is about half the time predicted by a scale analysis. The initial velocity of all plumes is on the order of 15 cm/hr, although some plumes stop moving before reaching the upper boundary of the cell. There are several reasons for plume deceleration: (1) As plumes travel vertically, they alter the initial temperature profile of the fluid such that the temperature field makes constant adjustments, which affects the dimensions, velocities, and interactions of the plumes; (2) adjacent plumes merge, resulting in a single larger plume; and (3) interactions
Variance of Dispersion Coefficients in Heterogeneous Porous Media
NASA Astrophysics Data System (ADS)
Dentz, Marco; De Barros, Felipe P. J.
2013-04-01
We study the dispersion of a passive solute in heterogeneous porous media using a stochastic modeling approach. Heterogeneity on one hand leads to an increase of solute spreading, which is described by the well-known macrodispersion phenomenon. On the other hand, it induces uncertainty about the dispersion behavior, which is quantified by ensemble averages over suitably defined dispersion coefficients in single medium realizations. We focus here on the sample to sample fluctuations of dispersion coefficients about their ensemble mean values for solutes evolving from point-like and extended source distributions in d = 2 and d = 3 spatial dimensions. The definition of dispersion coefficients in single medium realizations for finite source sizes is not unique, unlike for point-like sources. Thus, we first discuss a series of dispersion measures, which describe the extension of the solute plume, as well as dispersion measures that quantify the solute dispersion relative to the injection point. The sample to sample fluctuations of these observables are quantified in terms of the variance with respect to their ensemble averages. We find that the ensemble averages of these dispersion measures may be identical, their fluctuation behavior, however, may be very different. This is quantified using perturbation expansions in the fluctuations of the random flow field. We derive explicit expressions for the time evolution of the variance of the dispersion coefficients. The characteristic time scale for the variance evolution is given by the typical dispersion time over the characteristic heterogeneity scale and the dimensions of the source. We find that the dispersion variances asymptotically decrease to zero in d = 3 dimensions, which means, the dispersion coefficients are self-averaging observables, at least for moderate heterogeneity. In d = 2 dimensions, the variance converges towards a finite asymptotic value that is independent of the source distribution. Dispersion is not
Predicting colloid transport through saturated porous media: A critical review
NASA Astrophysics Data System (ADS)
Molnar, Ian L.; Johnson, William P.; Gerhard, Jason I.; Willson, Clinton S.; O'Carroll, Denis M.
2015-09-01
Understanding and predicting colloid transport and retention in water-saturated porous media is important for the protection of human and ecological health. Early applications of colloid transport research before the 1990s included the removal of pathogens in granular drinking water filters. Since then, interest has expanded significantly to include such areas as source zone protection of drinking water systems and injection of nanometals for contaminated site remediation. This review summarizes predictive tools for colloid transport from the pore to field scales. First, we review experimental breakthrough and retention of colloids under favorable and unfavorable colloid/collector interactions (i.e., no significant and significant colloid-surface repulsion, respectively). Second, we review the continuum-scale modeling strategies used to describe observed transport behavior. Third, we review the following two components of colloid filtration theory: (i) mechanistic force/torque balance models of pore-scale colloid trajectories and (ii) approximating correlation equations used to predict colloid retention. The successes and limitations of these approaches for favorable conditions are summarized, as are recent developments to predict colloid retention under the unfavorable conditions particularly relevant to environmental applications. Fourth, we summarize the influences of physical and chemical heterogeneities on colloid transport and avenues for their prediction. Fifth, we review the upscaling of mechanistic model results to rate constants for use in continuum models of colloid behavior at the column and field scales. Overall, this paper clarifies the foundation for existing knowledge of colloid transport and retention, features recent advances in the field, critically assesses where existing approaches are successful and the limits of their application, and highlights outstanding challenges and future research opportunities. These challenges and opportunities
{Quantification of Colloidal Blocking by Humic Acids in Porous Media
NASA Astrophysics Data System (ADS)
Yang, X.; Flynn, R.; von der Kammer, F.; Hofmann, T.
2009-04-01
Humic acids (humics), resulting from the partial decomposition of organic matter, occur widely in nature and form a major constituent of environmental natural organic matter (NOM). Although their ability to promote the dissolution of many substances has been widely recognized, quantification of the influence of humics on the fate and transport of particulate matter has proven less conclusive. One dimensional dynamic column tests involving the injection of suspensions of fluorescence stained 200nm latex microspheres (microspheres) and Suwannee River Humic Acid (SRHA) through columns filled with partly iron-coated quartz sand permitted the influence of humics on colloid deposition in water saturated porous media under controlled conditions to be studied. Tests consisted of two series of experiments. The first involved the injection of an initial pulse of 13 pore volumes (PV) of 10.4ppm microspheres that resulted in a gradual rise in the colloid's concentration in the column effluent to 8.4% of that injected. Injection of further two identical pulses of 13 PV of colloid, separated by pulses of about 10 PV of colloid-free flushing water resulted in a sustained rise in effluent concentration in the breakthrough of successive pulses. Colloid response, modeled using a random sequential adsorption (RSA) model, suggested that the system required the deposition 1.35x1010 colloids on the sand surface for each 1% rise in relative concentration observed in column effluent. The second series of experiments involved the injection of an initial pulse of 13 pore volumes of colloid suspension followed by the injection of four pore volumes of 5 mg/l SRHA. A mass balance of column effluent suggested that the column retained 98.8% of SRHA injected. Subsequent injection of a second pulse of 13 PV of microspheres saw colloidal concentration breakthrough in column effluent jump to 16% after which it continued to rise at a rate comparable to that in SRHA-free experiments. RSA modeling of
Capillary pinning of immiscible gravity currents in porous media
NASA Astrophysics Data System (ADS)
Zhao, B.; MacMinn, C. W.; Huppert, H. E.; Juanes, R.
2013-12-01
Gravity currents in porous media have attracted interest recently in the context of geological carbon dioxide (CO2) storage, where supercritical CO2 is captured from the flue gas of power plants and injected underground into deep saline aquifers. Capillarity can be important in the spreading and migration of the buoyant CO2 after injection because the typical pore size is very small (~10-100 microns), but the impact of capillarity on these flows is not well understood. Here, we study the impact of capillarity on the buoyant spreading of a finite gravity current of non-wetting fluid into a dense, wetting fluid in a vertically confined, horizontal aquifer. We show via simple, table-top experiments using glass bead packs that capillary pressure hysteresis pins a portion of the fluid-fluid interface. The horizontal extent of the pinned portion of the interface grows over time and this is responsible for ultimately stopping the spreading of the buoyant current after a finite distance. In addition, capillarity blunts the leading edge of the buoyant current. We demonstrate through micromodel experiments that the characteristic height of the nose of the current is controlled by the pore throat size distribution and the balance between capillarity and gravity. We develop a theoretical model that captures the evolution of immiscible gravity currents and predicts the maximum migration distance. Our work suggests that capillary pinning and capillary blunting exert an important control on finite-release gravity currents in the context of CO2 sequestration in deep saline aquifers. Gravity driven flow of a buoyant, nonwetting fluid (air) over a dense, wetting fluid (propylene glycol). Starting with a vertical interface between the fluids, the flow first undergoes a lock-exchange process. The process models a finite release problem after the dense fluid hits the left boundary. In contrast to finite release of a miscible current that spreads indefinitely, spreading of an immiscible
Determination of the heat transfer coefficients in porous media
Kim, L.V.
1994-06-01
The process of transpiration cooling is considered. Methods are suggested for estimating the volumetric coefficient of heat transfer with the use of a two-temperature model and the surface heat transfer coefficient at entry into a porous wall. The development of new technology under conditions of increasing heat loads puts the search for effective methods of heat transfer enhancement in the forefront of theoretical investigations. One of the promising trends in the solution of this problem is the use of porous materials (PM) in the elements of power units. For thermal protection against convective or radiative heat fluxes, the method of transpiration cooling is successfully used. The mechanism operative in the thermal protection involves the injection of a coolant through a porous medium to produce a screen over the contour of a body in a flow for removing heat energy from the skeleton of the porous material.
Influence of gas law on ultrasonic behaviour of porous media under pressure.
Griffiths, S; Ayrault, C
2010-06-01
This paper deals with the influence of gas law on ultrasonic behaviour of porous media when the saturating fluid is high pressured. Previous works have demonstrated that ultrasonic transmission through a porous sample with variations of the static pressure (up to 18 bars) of the saturating fluid allows the characterization of high damping materials. In these studies, the perfect gas law was used to link static pressure and density, which is disputable for high pressures. This paper compares the effects of real and perfect gas laws on modeled transmission coefficient for porous foams at these pressures. Direct simulations and a mechanical parameters estimation from minimization show that results are very similar in both cases. The real gas law is thus not necessary to describe the acoustic behaviour of porous media at low ultrasonic frequencies (100 kHz) up to 20 bars.
Volume Averaging Study of the Capacitive Deionization Process in Homogeneous Porous Media
Gabitto, Jorge; Tsouris, Costas
2015-05-05
Ion storage in porous electrodes is important in applications such as energy storage by supercapacitors, water purification by capacitive deionization, extraction of energy from a salinity difference and heavy ion purification. In this paper, a model is presented to simulate the charge process in homogeneous porous media comprising big pores. It is based on a theory for capacitive charging by ideally polarizable porous electrodes without faradaic reactions or specific adsorption of ions. A volume averaging technique is used to derive the averaged transport equations in the limit of thin electrical double layers. Transport between the electrolyte solution and the chargedmore » wall is described using the Gouy–Chapman–Stern model. The effective transport parameters for isotropic porous media are calculated solving the corresponding closure problems. Finally, the source terms that appear in the average equations are calculated using numerical computations. An alternative way to deal with the source terms is proposed.« less
Volume Averaging Study of the Capacitive Deionization Process in Homogeneous Porous Media
Gabitto, Jorge; Tsouris, Costas
2015-05-05
Ion storage in porous electrodes is important in applications such as energy storage by supercapacitors, water purification by capacitive deionization, extraction of energy from a salinity difference and heavy ion purification. In this paper, a model is presented to simulate the charge process in homogeneous porous media comprising big pores. It is based on a theory for capacitive charging by ideally polarizable porous electrodes without faradaic reactions or specific adsorption of ions. A volume averaging technique is used to derive the averaged transport equations in the limit of thin electrical double layers. Transport between the electrolyte solution and the charged wall is described using the Gouy–Chapman–Stern model. The effective transport parameters for isotropic porous media are calculated solving the corresponding closure problems. Finally, the source terms that appear in the average equations are calculated using numerical computations. An alternative way to deal with the source terms is proposed.
Dynamics and stability of two-potential flows in the porous media
NASA Astrophysics Data System (ADS)
Markicevic, B.; Bijeljic, B.; Navaz, H. K.
2011-11-01
The experimental and numerical results of the capillary-force-driven climb of wetting liquid in porous media, which is opposed by the gravity force, are analyzed with respect to the emergence of a multiphase flow front and flow stability of the climbing liquid. Two dynamic characteristics are used: (i) the multiphase flow front thickness as a function of time, and (ii) the capillary number as a function of Bond number, where both numbers are calculated from the harmonic average of pores radii. Throughout the climb, the influence of capillary, gravity, and viscous force variations on the flow behavior is investigated for different porous media. For a specific porous medium, a unique flow front power law function of time is observed for the capillary flow climbs with or without gravity force. Distinct dynamic flow front power law functions are found for different porous media. However, for capillary climb in different porous media, one is able to predict a unique behavior for the wetting height (the interface between wetted and dry regions of porous medium) using the capillary and Bond number. It is found that these two numbers correlate as a unique exponential function, even for porous media whose permeabilities vary for two orders of magnitude. For climbs without the gravity force (capillary spreads), the initial climb dynamics follows this exponential law, but for later flow times and when a significant flow front is developed, one observes a constant value of the capillary number. Using this approach to describe the capillary climb, only the capillary versus Bond number correlation is needed, which is completely measureable from the experiments.
Dynamics and stability of two-potential flows in the porous media.
Markicevic, B; Bijeljic, B; Navaz, H K
2011-11-01
The experimental and numerical results of the capillary-force-driven climb of wetting liquid in porous media, which is opposed by the gravity force, are analyzed with respect to the emergence of a multiphase flow front and flow stability of the climbing liquid. Two dynamic characteristics are used: (i) the multiphase flow front thickness as a function of time, and (ii) the capillary number as a function of Bond number, where both numbers are calculated from the harmonic average of pores radii. Throughout the climb, the influence of capillary, gravity, and viscous force variations on the flow behavior is investigated for different porous media. For a specific porous medium, a unique flow front power law function of time is observed for the capillary flow climbs with or without gravity force. Distinct dynamic flow front power law functions are found for different porous media. However, for capillary climb in different porous media, one is able to predict a unique behavior for the wetting height (the interface between wetted and dry regions of porous medium) using the capillary and Bond number. It is found that these two numbers correlate as a unique exponential function, even for porous media whose permeabilities vary for two orders of magnitude. For climbs without the gravity force (capillary spreads), the initial climb dynamics follows this exponential law, but for later flow times and when a significant flow front is developed, one observes a constant value of the capillary number. Using this approach to describe the capillary climb, only the capillary versus Bond number correlation is needed, which is completely measureable from the experiments.
Impact of pore size variability and network coupling on electrokinetic transport in porous media
NASA Astrophysics Data System (ADS)
Alizadeh, Shima; Bazant, Martin Z.; Mani, Ali
2016-11-01
We have developed and validated an efficient and robust computational model to study the coupled fluid and ion transport through electrokinetic porous media, which are exposed to external gradients of pressure, electric potential, and concentration. In our approach a porous media is modeled as a network of many pores through which the transport is described by the coupled Poisson-Nernst-Planck-Stokes equations. When the pore sizes are random, the interactions between various modes of transport may provoke complexities such as concentration polarization shocks and internal flow circulations. These phenomena impact mixing and transport in various systems including deionization and filtration systems, supercapacitors, and lab-on-a-chip devices. In this work, we present simulations of massive networks of pores and we demonstrate the impact of pore size variation, and pore-pore coupling on the overall electrokinetic transport in porous media.
Foam-oil interaction in porous media: implications for foam assisted enhanced oil recovery.
Farajzadeh, R; Andrianov, A; Krastev, R; Hirasaki, G J; Rossen, W R
2012-11-15
The efficiency of a foam displacement process in enhanced oil recovery (EOR) depends largely on the stability of foam films in the presence of oil. Experimental studies have demonstrated the detrimental impact of oil on foam stability. This paper reviews the mechanisms and theories (disjoining pressure, coalescence and drainage, entering and spreading of oil, oil emulsification, pinch-off, etc.) suggested in the literature to explain the impact of oil on foam stability in the bulk and porous media. Moreover, we describe the existing approaches to foam modeling in porous media and the ways these models describe the oil effect on foam propagation in porous media. Further, we present various ideas on an improvement of foam stability and longevity in the presence of oil. The outstanding questions regarding foam-oil interactions and modeling of these interactions are pointed out.
The Importance of Moving Air-Water Interfaces for Colloid Transport in Porous Media
NASA Astrophysics Data System (ADS)
Flury, M.
2015-12-01
In the vadose zone, or in unsaturated porous media in general, transport of colloids is usually less pronounced than in groundwater. An important retention mechanism for colloids in unsaturated porous media is attachment to air-water interfaces. However, air-water interfaces can also lead to colloid mobilization and enhanced transport if air-water interfaces are moving, such as during infiltration, imbibition, and drainage. Colloid attachment to air-water interfaces is caused by surface tension forces, and these forces usually exceed other interactions forces; therefore, surface tension forces play a dominant role for colloid transport in unsaturated porous media. In this presentation, experimental and theoretical evidence of surface tension forces acting on colloids will be presented, and the role of moving air-water interfaces will be discussed.
Generalized lattice Boltzmann model for flow through tight porous media with Klinkenberg's effect
NASA Astrophysics Data System (ADS)
Chen, Li; Fang, Wenzhen; Kang, Qinjun; De'Haven Hyman, Jeffrey; Viswanathan, Hari S.; Tao, Wen-Quan
2015-03-01
Gas slippage occurs when the mean free path of the gas molecules is in the order of the characteristic pore size of a porous medium. This phenomenon leads to Klinkenberg's effect where the measured permeability of a gas (apparent permeability) is higher than that of the liquid (intrinsic permeability). A generalized lattice Boltzmann model is proposed for flow through porous media that includes Klinkenberg's effect, which is based on the model of Guo et al. [Phys. Rev. E 65, 046308 (2002), 10.1103/PhysRevE.65.046308]. The second-order Beskok and Karniadakis-Civan's correlation [A. Beskok and G. Karniadakis, Microscale Thermophys. Eng. 3, 43 (1999), 10.1080/108939599199864 and F. Civan, Transp. Porous Med. 82, 375 (2010), 10.1007/s11242-009-9432-z] is adopted to calculate the apparent permeability based on intrinsic permeability and the Knudsen number. Fluid flow between two parallel plates filled with porous media is simulated to validate the model. Simulations performed in a heterogeneous porous medium with components of different porosity and permeability indicate that Klinkenberg's effect plays a significant role on fluid flow in low-permeability porous media, and it is more pronounced as the Knudsen number increases. Fluid flow in a shale matrix with and without fractures is also studied, and it is found that the fractures greatly enhance the fluid flow and Klinkenberg's effect leads to higher global permeability of the shale matrix.
Conformal mapping technique for two-dimensional porous media and jet impingement heat transfer
NASA Technical Reports Server (NTRS)
Siegel, R.
1973-01-01
Transpiration cooling and liquid metals both provide highly effective heat transfer. Using Darcy's law in porous media, and the inviscid approximation for liquid metals, the local fluid velocity in these flows equals the gradient of a potential, The energy equation and flow region are simplified when transformed into potential plane coordinates. In these coordinates the present problems are reduced to heat conduction solutions which are mapped into the physical geometry. Results are obtained for a porous region with simultaneously prescribed surface temperature and heat flux, heat transfer in a two-dimensional porous bed, and heat transfer for two liquid metal slot jets impinging on a heated plate.
Conformal mapping technique for two-dimensional porous media and jet impingement heat transfer
NASA Technical Reports Server (NTRS)
Siegel, R.
1974-01-01
Transpiration cooling and liquid metals both provide highly effective heat transfer. Using Darcy's law in porous media and the inviscid approximation for liquid metals, the local fluid velocity in these flows equals the gradient of a potential. The energy equation and flow region are simplified when transformed into potential plane coordinates. In these coordinates, the present problems are reduced to heat conduction solutions which are mapped into the physical geometry. Results are obtained for a porous region with simultaneously prescribed surface temperature and heat flux, heat transfer in a two-dimensional porous bed, and heat transfer for two liquid metal slot jets impinging on a heated plate.
Effects of texture on salt precipitation dynamics and deposition patterns in drying porous media
NASA Astrophysics Data System (ADS)
Norouzi Rad, Mansoureh; Shokri, Nima
2015-04-01
Understanding the physics of water evaporation from saline porous media is important in many natural and engineering applications such as durability of building materials and preservation of monuments, CO2 sequestration and water quality. Also excess of salt accumulation in soil may result in soil salinization which is a global problem adversely affecting vegetation, plant growth and crop production. Thus it is important to understand the parameters affecting salt transport and precipitation in porous media. We applied X-ray micro-tomography to investigate the dynamics of salt precipitation during evaporation from porous media as influenced by the particle and pore sizes. The packed beds were saturated with NaCl solution of 3 Molal and the time-lapse X-ray imaging was continued for one day. The results show that the presence of preferential evaporation sites (associated with fine pores) on the surface of the sand columns influences significantly the patterns and dynamics of NaCl precipitation (Norouzi Rad et al., 2013; Norouzi Rad and Shokri, 2014). They confirm the formation of an increasingly thick and discrete salt crust with increasing grain size in the sand column due to the presence of fewer fine pores (preferential precipitation sites) at the surface compared to the sand packs with finer grains. Fewer fine pores on the surface also results in shorter stage-1 precipitation for the columns with larger grain sizes. A simple model for the evolution of salt crust thickness based on this principle shows a good agreement with our experiments. Our results provide new insights regarding the physics of salt precipitation and its complex dynamics in porous media during evaporation. References Norouzi Rad, M., Shokri, N., Sahimi, M. (2013), Pore-Scale Dynamics of Salt Precipitation in Drying Porous Media, Phys. Rev. E, 88, 032404. Norouzi Rad, M., Shokri, N. (2014), Effects of grain angularity on NaCl precipitation in porous media during evaporation, Water Resour. Res
On the Study of Lifting Mechanism of a Soft Porous Media under Fast Compression
NASA Astrophysics Data System (ADS)
Wu, Qianhong; Santhanam, S.; Nathan, R.; Vucbmss Team
2015-11-01
Fluid flow in a soft porous media under fast compressions is widely observed in biological systems and industrial applications. Despite of much progress, it remains unclear for the lifting mechanisms of the porous media due to the lack of complete experimental verifications of theoretical models. We report herein a unique approach to treat the limitation. The permeability of a synthetic fibrous porous media as a function of its compression was first measured. The material was then employed in a dynamic compression experiment using a porous-walled cylinder piston apparatus. The obtained transient compression of the porous media and the aforementioned permeability data were applied in different theoretical models for the pore pressure generation, which conclusively proved the validity of the consolidation theory developed by Wu et al. (JFM, 542, 281, 2005). Furthermore, the solid phase lifting force was separated from the total reaction force and was characterized by a new viscoelastic model, containing a nonlinear spring in conjunction with a linear viscoelastic Generalized Maxwell mechanical module. Excellent agreement was obtained between the experiment and the theory. Thus, the lifting forces from both the fluid and the solid were determined. This project is supported by NSF Grant 1511096.
Unifying diffusion and seepage for nonlinear gas transport in multiscale porous media
NASA Astrophysics Data System (ADS)
Song, Hongqing; Wang, Yuhe; Wang, Jiulong; Li, Zhengyi
2016-09-01
We unify the diffusion and seepage process for nonlinear gas transport in multiscale porous media via a proposed new general transport equation. A coherent theoretical derivation indicates the wall-molecule and molecule-molecule collisions drive the Knudsen and collective diffusive fluxes, and constitute the system pressure across the porous media. A new terminology, nominal diffusion coefficient can summarize Knudsen and collective diffusion coefficients. Physical and numerical experiments show the support of the new formulation and provide approaches to obtain the diffusion coefficient and permeability simultaneously. This work has important implication for natural gas extraction and greenhouse gases sequestration in geological formations.
Mesoscopic modeling of multi-physicochemical transport phenomena in porous media
Kang, Qinjin; Wang, Moran; Mukherjee, Partha P; Lichtner, Peter C
2009-01-01
We present our recent progress on mesoscopic modeling of multi-physicochemical transport phenomena in porous media based on the lattice Boltzmann method. Simulation examples include injection of CO{sub 2} saturated brine into a limestone rock, two-phase behavior and flooding phenomena in polymer electrolyte fuel cells, and electroosmosis in homogeneously charged porous media. It is shown that the lattice Boltzmann method can account for multiple, coupled physicochemical processes in these systems and can shed some light on the underlying physics occuning at the fundamental scale. Therefore, it can be a potential powerful numerical tool to analyze multi-physicochemical processes in various energy, earth, and environmental systems.
Flow of polymer solutions in porous media: inadequacy of the capillary model
Duda, J.L.; Klaus, E.E.; Hong, S.A.
1983-08-01
Experimental measurements show that conventional capillary models are inadequate for the description of the flow of nonlinear purely viscous solutions in porous media. A theoretical analysis indicates that any model for the flow of purely viscous polymer solutions in porous media must meet 2 criteria. First, the model must include expansion and contraction regions where excess pressure drops occur. Secondly, the rheologic model for the fluid must include the characteristic transition from Newtonian behavior at low shear rates to shear-thinning behavior at high shear rates. 17 references.
Diffusion of colloidal fluids in random porous media.
Chávez-Rojo, M A; Juárez-Maldonado, R; Medina-Noyola, M
2008-04-01
The diffusive relaxation of a colloidal fluid adsorbed in a porous medium depends on many factors, including the concentration and composition of the adsorbed colloidal fluid, the average structure of the porous matrix, and the nature of the colloid-colloid and colloid-substrate interactions. A simple manner to describe these effects is to model the porous medium as a set of spherical particles fixed in space at random positions with prescribed statistical structural properties. Within this model one may describe the relaxation of concentration fluctuations of the adsorbed fluid by simply setting to zero the short-time mobility of one species (the porous matrix) in a theory of the dynamics of equilibrium colloidal mixtures, or by extending such dynamic theory to explicitly consider the porous matrix as a random external field, as recently done in the framework of mode coupling theory [V. Krakoviack, Phys. Rev. Lett. 94, 065703 (2005)]. Here we consider the first approach and employ the self-consistent generalized Langevin equation (SCGLE) theory of the dynamics of equilibrium colloidal mixtures, to describe the dynamics of the mobile component. We focus on the short- and intermediate-time regimes, which we compare with Brownian dynamics simulations involving a binary mixture with screened Coulomb interactions for two models of the average static structure of the matrix: a porous matrix constructed by quenching configurations of an equilibrium mixture in which both species were first equilibrated together, and a preexisting matrix with prescribed average structure, in which we later add the mobile species. We conclude that in both cases, if the correct static structure factors are provided as input, the SCGLE theory correctly predicts the main features of the dynamics of the permeating fluid.
Mechano-chemical effects in weakly charged porous media.
Zholkovskij, Emiliy K; Yaroshchuk, Andriy E; Koval'chuk, Volodymyr I; Bondarenko, Mykola P
2015-08-01
The paper is concerned with mechano-chemical effects, namely, osmosis and pressure-driven separation of ions that can be observed when a charged porous medium is placed between two electrolyte solutions. The study is focused on porous systems with low equilibrium interfacial potentials (about 30 mV or lower). At such low potentials, osmosis and pressure-driven separation of ions noticeably manifest themselves provided that the ions in the electrolyte solutions have different diffusion coefficients. The analysis is conducted by combining the irreversible thermodynamic approach and the linearized (in terms of the normalized equilibrium interfacial potential) version of the Standard Electrokinetic Model. Osmosis and the pressure-driven separation of ions are considered for an arbitrary mixed electrolyte solution and various porous space geometries. It is shown that the effects under consideration are proportional to a geometrical factor which, for all the considered geometries of porous space, can be expressed as a function of porosity and the Λ- parameter of porous medium normalized by the Debye length. For all the studied geometries, this function turns out to be weakly dependent on both the porosity and the geometry type. The latter allows for a rough evaluation of the geometrical factor from experimental data on electric conductivity and hydraulic permeability without previous knowledge of the porous space geometry. The obtained results are used to illustrate how the composition of electrolyte solution affects the mechano-chemical effects. For various examples of electrolyte solution compositions, the obtained results are capable of describing positive, negative and anomalous osmosis, positive and negative rejection of binary electrolytes, and pressure-driven separation of binary electrolyte mixtures.
Technology Transfer Automated Retrieval System (TEKTRAN)
Fractal and prefractal geometric models have substantial potential of contributing to the analysis of flow and transport in porous media such as soils and reservoir rocks. In this study, geometric and hydrodynamic parameters of saturated 3D mass and pore-solid prefractal porous media were characteri...
Paéz-García, Catherine Teresa; Valdés-Parada, Francisco J; Lasseux, Didier
2017-02-01
Modeling flow in porous media is usually focused on the governing equations for mass and momentum transport, which yield the velocity and pressure at the pore or Darcy scales. However, in many applications, it is important to determine the work (or power) needed to induce flow in porous media, and this can be achieved when the mechanical energy equation is taken into account. At the macroscopic scale, this equation may be postulated to be the result of the inner product of Darcy's law and the seepage velocity. However, near the porous medium boundaries, this postulate seems questionable due to the spatial variations of the effective properties (velocity, permeability, porosity, etc.). In this work we derive the macroscopic mechanical energy equation using the method of volume averaging for the simple case of incompressible single-phase flow in porous media. Our analysis shows that the result of averaging the pore-scale version of the mechanical energy equation at the Darcy scale is not, in general, the expected product of Darcy's law and the seepage velocity. As a matter of fact, this result is only applicable in the bulk region of the porous medium and, in the derivation of this result, the properties of the permeability tensor are determinant. Furthermore, near the porous medium boundaries, a more novel version of the mechanical energy equation is obtained, which incorporates additional terms that take into account the rapid variations of structural properties taking place in this particular portion of the system. This analysis can be applied to multiphase and compressible flows in porous media and in many other multiscale systems.
NASA Astrophysics Data System (ADS)
Paéz-García, Catherine Teresa; Valdés-Parada, Francisco J.; Lasseux, Didier
2017-02-01
Modeling flow in porous media is usually focused on the governing equations for mass and momentum transport, which yield the velocity and pressure at the pore or Darcy scales. However, in many applications, it is important to determine the work (or power) needed to induce flow in porous media, and this can be achieved when the mechanical energy equation is taken into account. At the macroscopic scale, this equation may be postulated to be the result of the inner product of Darcy's law and the seepage velocity. However, near the porous medium boundaries, this postulate seems questionable due to the spatial variations of the effective properties (velocity, permeability, porosity, etc.). In this work we derive the macroscopic mechanical energy equation using the method of volume averaging for the simple case of incompressible single-phase flow in porous media. Our analysis shows that the result of averaging the pore-scale version of the mechanical energy equation at the Darcy scale is not, in general, the expected product of Darcy's law and the seepage velocity. As a matter of fact, this result is only applicable in the bulk region of the porous medium and, in the derivation of this result, the properties of the permeability tensor are determinant. Furthermore, near the porous medium boundaries, a more novel version of the mechanical energy equation is obtained, which incorporates additional terms that take into account the rapid variations of structural properties taking place in this particular portion of the system. This analysis can be applied to multiphase and compressible flows in porous media and in many other multiscale systems.
Characteristic evaluation of cooling technique using liquid nitrogen and metal porous media
Tanno, Yusuke; Ito, Satoshi; Hashizume, Hidetoshi
2014-01-29
A remountable high-temperature superconducting magnet, whose segments can be mounted and demounted repeatedly, has been proposed for construction and maintenance of superconducting magnet and inner reactor components of a fusion reactor. One of the issues in this design is that the performance of the magnet deteriorates by a local temperature rise due to Joule heating in jointing regions. In order to prevent local temperature rise, a cooling system using a cryogenic coolant and metal porous media was proposed and experimental studies have been carried out using liquid nitrogen. In this study, flow and heat transfer characteristics of cooling system using subcooled liquid nitrogen and bronze particle sintered porous media are evaluated through experiments in which the inlet degree of subcooling and flow rate of the liquid nitrogen. The flow characteristics without heat input were coincided with Ergun’s equation expressing single-phase flow in porous materials. The obtained boiling curve was categorized into three conditions; convection region, nucleate boiling region and mixed region with nucleate and film boiling. Wall superheat did not increase drastically with porous media after departure from nucleate boiling point, which is different from a situation of usual boiling curve in a smooth tube. The fact is important characteristic to cooling superconducting magnet to avoid its quench. Heat transfer coefficient with bronze particle sintered porous media was at least twice larger than that without the porous media. It was also indicated qualitatively that departure from nucleate boiling point and heat transfer coefficient depends on degree of subcooling and mass flow rate. The quantitative evaluation of them and further discussion for the cooling system will be performed as future tasks.
Nuclear magnetic resonance as a method of fluid mobility detection in porous media
NASA Astrophysics Data System (ADS)
Zhakov, Sergey; Loskutov, Valentin
2016-04-01
The nuclear magnetic resonance (NMR) method is widely used for studying the structure of porous media and processes taking place in such media. This method permits to determine porosity and pore-size distributions, which have direct practical application in various areas. The problem of porous media permeability determination is connected directly with extraction of hydrocarbons from pays and water from aquiferous layers. But it is impossible to measure directly amount of fluid past through the fixes cross section for determination of bed permeability. So various indirect approaches are used to find correlation of permeability value with porosity and pore size distribution which can be determined directly using NMR relaxometry. In contrast to porosity, permeability is dynamic characteristic of porous media so it may be measured correctly only in conditions of moving fluid. Natural porous medium has branched pore structure, so a chaotic component of fluid velocity will occur even for constant mean filtration fluid velocity. In the presence of magnetic field gradient this chaotic fluid velocity will produce additional spin dephasing and decrease of relaxation time [1]. Direct detecting of fluid movement in porous core samples through the Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence has been demonstrated and theoretical model and analysis was given. Experiments were made on a set of sandstone samples (Berea, Bentheimer, Castle Gate, Leopard) and with synthetic high-perm samples made of abrasive material. The experiments show that the NMR spin echo measurements permit to fix mean fluid velocity mm/sec. The experiments and the theoretical model show that for low fluid velocities the mean relaxation rate is proportional to fluid velocity . The results may serve as the basis for determination of mobility of liquids in porous media and permeability. 1. P.T.Callaghan. Principles of Nuclear Magnetic Resonance Microscopy. 1991, Oxford University Press.
Modeling evaporation from porous media influenced by atmospheric processes
NASA Astrophysics Data System (ADS)
Mosthaf, K.; Baber, K.; Flemisch, B.; Helmig, R.
2012-04-01
Modeling evaporation processes from partially saturated soils into the ambient air is a challenging task. It involves usually a variety of interacting processes and depends on the multitude of properties of the fluids and of the porous medium. Often, the ambient free-flow and the porous-medium compartments are modeled separately with a specification of the evaporation rate as boundary condition. We have developed a coupling concept, which allows the combined modeling of a free-flow and a porous-medium system under non-isothermal conditions with the evaporative fluxes across the soil-atmosphere interface as model output. It is based on flux continuity and local thermodynamic equilibrium at the interface. Darcy's law for multiple phases is used in the porous medium, whereas the ambient air flow is modeled as a compositional single-phase Stokes system. The concept has been implemented in the numerical simulator DuMux. A comparison of simulated and measured data from wind tunnel experiments performed in the group of D. Or (ETH Zürich) will be shown. Furthermore, the impact of several parameters, such as a varying wind velocity, temperature or different soil properties on the evaporation process has been analyzed in a numerical parameter study. The results will be presented and discussed.
Flow of foams in two-dimensional disordered porous media
NASA Astrophysics Data System (ADS)
Dollet, Benjamin; Geraud, Baudouin; Jones, Sian A.; Meheust, Yves; Cantat, Isabelle; Institut de Physique de Rennes Team; Geosciences Rennes Team
2015-11-01
Liquid foams are a yield stress fluid with elastic properties. When a foam flow is confined by solid walls, viscous dissipation arises from the contact zones between soap films and walls, giving very peculiar friction laws. In particular, foams potentially invade narrow pores much more efficiently than Newtonian fluids, which is of great importance for enhanced oil recovery. To quantify this effect, we study experimentally flows of foam in a model two-dimensional porous medium, consisting of an assembly of circular obstacles placed randomly in a Hele-Shaw cell, and use image analysis to quantify foam flow at the local scale. We show that bubbles split as they flow through the porous medium, by a mechanism of film pinching during contact with an obstacle, yielding two daughter bubbles per split bubble. We quantify the evolution of the bubble size distribution as a function of the distance along the porous medium, the splitting probability as a function of bubble size, and the probability distribution function of the daughter bubbles. We propose an evolution equation to model this splitting phenomenon and compare it successfully to the experiments, showing how at long distance, the porous medium itself dictates the size distribution of the foam.
Magnetic Resonance Microscopy of Scale Dependent Transport Phenomena and Bioactivity in Porous Media
NASA Astrophysics Data System (ADS)
Seymour, J. D.; Codd, S. L.; Romanenko, K. V.; Hornemann, J. A.; Brosten, T. R.
2008-05-01
Magnetic resonance microscopy (MRM) provides the ability to obtain data on the pore scale via imaging and the sample scale by bulk measurement, allowing for connection between microscale dynamics and macroscale transport phenomena. This has led to MRM techniques becoming a preeminent method for characterization of dynamics in porous media. A significant question in modeling transport in porous media is definition of the porous media structure as homogeneous (ordered) or heterogeneous (disordered)[1]. One means of defining the 'complexity' of a porous media is based on the dynamics of the system[2]. The ability of MRM to measure the time dependent statistics of the dynamics [3,4,5] provides quantification of the pre-asymptotic dynamics. The transition from preasymptotic to Gaussian transport consistent with models of homogeneous porous media is clearly visualized. Biological activity in porous media, such as microbial growth, typically manifests itself as biofilms or colonies of microbes that adhere to surfaces and are surrounded by a hydrogel of extracellular polymeric substance (EPS). The biofilm growth introduces complexity into the system structure in generation of physical pore blocking, trapping within the EPS gel, elastic interfaces due to the EPS and generation of channels in which faster flow occur. The hierarchy of length and time scales and multiple physical processes which are introduced by the biofilm growth impacts the porous media transport as reflected in the change in dynamics [6]. The transition can be modeled using statistical mechanical approaches based on continuous time random walk (CTRW) processes that generate fractional differential equations[7]. The bioactivity alters the structure of the porous media from homogeneous to heterogeneous resulting in the transition from a Gaussian to a non Gaussian subdiffusive dispersion process. References 1. M. Quintard and S. Whitaker, Transport in ordered and disordered porous media: Volume averaged
Experimental Analysis of Entrance Effects in Low Reynolds Flow in Porous Media
NASA Astrophysics Data System (ADS)
Munro, Ben; Becker, Sid
2014-11-01
The topic of this research concerns the experimentally observed influences of the developmental effects in a rigid porous media. A test rig has been constructed that accurately measures the pressure drop across the media and the corresponding average bulk flow velocity. The porous media has been developed using a 3D printer so that the pore geometries are uniform throughout the media. The fluid is a mixture of glycerol and water for which the viscosity is varied. Measurements of the global pressure drop versus bulk flow rate have been made over a range of Re in which the overall length of the porous media (in the direction of flow) has been varied. Because all tests have been conducted at low Re (and thus within the Darcy regime) comparisons of experimentally determined permeability between the overall media lengths provide insight into the non linear component of pressure drop that occur within the developing region. Supported by the Marsden Fund Council from Government funding, Administered by the Royal Society of New Zealand.
Modelling the growth of porous alumina matrix for creating hyperbolic media
NASA Astrophysics Data System (ADS)
Aryslanova, E. M.; Alfimov, A. V.; Chivilikhin, S. A.
2016-08-01
Porous aluminum oxide is a regular self-assembled structure. During anodization it is possible to control nano-parameters of the structure using macroscopic parameters of anodization. Porous alumina films can be used as a template for the creation of hyperbolic media. In this work we consider the anodization process, our model takes into account the influence of layers of aluminum and electrolyte on the rate of growth of aluminum oxide, as well as the effect of surface diffusion. As a result of our model we obtain the minimum distance between centers of alumina pores in the beginning of anodizing process. We also present the results obtained by numerical modelling of hyperbolic media based on porous alumina film.
Lattice Boltzmann Method for Diffusion-Reaction-Transport Processes in Heterogeneous Porous Media
NASA Astrophysics Data System (ADS)
Xu, You-Sheng; Zhong, Yi-Jun; Huang, Guo-Xiang
2004-07-01
Based on the lattice Boltzmann method and general theory of fluids flowing in porous media, a numerical model is presented for the diffusion-reaction-transport (DRT) processes in porous media. As a test, we simulate a DRT process in a two-dimensional horizontal heterogeneous porous medium. The influence of gravitation in this case can be neglected, and the DRT process can be described by a strongly heterogeneous diagnostic test strip or a thin confined piece of soil with stochastically distributing property in horizontal directions. The results obtained for the relations between reduced fluid saturation S, concentration c1, and concentration c2 are shown by using the visualization computing technique. The computational efficiency and stability of the model are satisfactory.
Optimization of Fluid Front Dynamics in Porous Media Using Rate Control: I. Equal Mobility Fluids
Sundaryanto, Bagus; Yortsos, Yanis C.
1999-10-18
In applications involving this injection of a fluid in a porous medium to displace another fluid, a main objective is the maximization of the displacement efficiency. For a fixed arrangement of injection and production points (sources and sinks), such optimization is possible by controlling the injection rate policy. Despite its practical relevance, however, this aspect has received scant attention in the literature. In this paper, a fundamental approach based on optimal control theory, for the case when the fluids are miscible, of equal viscosity and in the absence of dispersion and gravity effects. Both homogeneous and heterogeneous porous media are considered. From a fluid dynamics viewpoint, this is a problem in the deformation of material lines in porous media, as a function of time-varying injection rates.
Transport and Retention of Colloids in Porous Media: Does Shape Really Matter?
The effect of particle shape on its transport and retention in porous media was evaluated by stretching carboxylate-modified fluorescent polystyrene spheres into rod shapes with aspect ratios of 2:1 and 4:1. Quartz crystal microbalance with dissipation experiments (QCM-D) were c...
Experiments and network model of flow of oil-water emulsion in porous media
NASA Astrophysics Data System (ADS)
Romero, Mao Illich; Carvalho, Marcio S.; Alvarado, Vladimir
2011-10-01
Transport of emulsions in porous media is relevant to several subsurface applications. Many enhanced oil recovery (EOR) processes lead to emulsion formation and as a result conformance originating in the flow of a dispersed phase may arise. In some EOR processes, emulsion is injected directly as a mobility control agent. Modeling the flow of emulsion in porous media is extremely challenging due to the complex nature of the associated flows and numerous interfaces. The descriptions based on effective viscosity are not valid when the drop size is of the same order of magnitude as the pore-throat characteristic length scale. An accurate model of emulsion flow through porous media should describe this local change in mobility. The available filtration models do not take into account the variation of the straining and capturing rates with the local capillary number. In this work, we present experiments of emulsion flow through sandstone cores of different permeability and a first step on a capillary network model that uses experimentally determined pore-level constitutive relationships between flow rate and pressure drop in constricted capillaries to obtain representative macroscopic flow behavior emerging from microscopic emulsion flow at the pore level. A parametric analysis is conducted to study the effect of the permeability and dispersed phase droplet size on the flow response to emulsion flooding in porous media. The network model predictions qualitatively describe the oil-water emulsion flow behavior observed in the experiments.
ENHANCING THE STABILITY OF POROUS CATALYSTS WITH SUPERCRITICAL REACTION MEDIA. (R826034)
Adsorption/desorption and pore-transport are key parameters influencing the activity and product selectivity in porous catalysts. With conventional reaction media (gas or liquid phase), one of these parameters is generally favorable while the other is not. For instance, while ...
Technology Transfer Automated Retrieval System (TEKTRAN)
A mathematical model is presented for colloid transport and retention in saturated porous media under unfavorable attachment conditions. The model accounts for colloid transport in the bulk aqueous phase and adjacent to the solid surface, and rates of colloid collision, interaction, release and imm...
Pipe network model for scaling of dynamic interfaces in porous media
Lam; Horvath
2000-08-07
We present a numerical study on the dynamics of imbibition fronts in porous media using a pipe network model. This model quantitatively reproduces the anomalous scaling behavior found in imbibition experiments [Phys. Rev. E 52, 5166 (1995)]. Using simple scaling arguments, we derive a new identity among the scaling exponents in agreement with the experimental results.
Organic Dye Effects on DNAPL Entry Pressure in Water Saturated Porous Media
Iversen, G.M.
2001-10-02
One of three diazo dyes with the same fundamental structure have been used in most studies of DNAPL behavior in porous media to stain the NAPL: Sudan III, Sudan IV, or Oil-Red-O. The dyes are generally implicitly assumed to not influence DNAPL behavior. That assumption was tested using simple entry pressure experiments.
MODELING MULTICOMPONENT ORGANIC CHEMICAL TRANSPORT IN THREE FLUID PHASE POROUS MEDIA
A two-dimensional finite-element model was developed to predict coupled transient flow and multicomponent transport of organic chemicals which can partition between nonaqueous phase liquid, water, gas and solid phases in porous media under the assumption of local chemical equilib...
Phase Behavior and Percolation Properties of the Patchy Colloidal Fluids in the Random Porous Media.
Kalyuzhnyi, Y V; Holovko, M; Patsahan, T; Cummings, P T
2014-12-18
The lack of a simple analytical description of the hard-sphere fluid in a matrix with hard-core obstacles is limiting progress in the development of thermodynamic perturbation theories for the fluid in random porous media. We propose a simple and highly accurate analytical scheme, which allows us to calculate thermodynamic and percolation properties of a network-forming fluid confined in the random porous media, represented by the hard-sphere fluid and overlapping hard-sphere matrices, respectively. Our scheme is based on the combination of scaled-particle theory, Wertheim's thermodynamic perturbation theory for associating fluids and extension of the Flory-Stockmayer theory for percolation. The liquid-gas phase diagram and percolation threshold line for several versions of the patchy colloidal fluid model confined in a random porous media are calculated and discussed. The method presented enables calculation of the thermodynamic and percolation properties of a large variety of polymerizing and network-forming fluids confined in random porous media.
General slip regime permeability model for gas flow through porous media
NASA Astrophysics Data System (ADS)
Zhou, Bo; Jiang, Peixue; Xu, Ruina; Ouyang, Xiaolong
2016-07-01
A theoretical effective gas permeability model was developed for rarefied gas flow in porous media, which holds over the entire slip regime with the permeability derived as a function of the Knudsen number. This general slip regime model (GSR model) is derived from the pore-scale Navier-Stokes equations subject to the first-order wall slip boundary condition using the volume-averaging method. The local closure problem for the volume-averaged equations is studied analytically and numerically using a periodic sphere array geometry. The GSR model includes a rational fraction function of the Knudsen number which leads to a limit effective permeability as the Knudsen number increases. The mechanism for this behavior is the viscous fluid inner friction caused by converging-diverging flow channels in porous media. A linearization of the GSR model leads to the Klinkenberg equation for slightly rarefied gas flows. Finite element simulations show that the Klinkenberg model overestimates the effective permeability by as much as 33% when a flow approaches the transition regime. The GSR model reduces to the unified permeability model [F. Civan, "Effective correlation of apparent gas permeability in tight porous media," Transp. Porous Media 82, 375 (2010)] for the flow in the slip regime and clarifies the physical significance of the empirical parameter b in the unified model.
Resolving the coupled effects of hydrodynamics and DLVO forces on colloid attachment in porous media
Technology Transfer Automated Retrieval System (TEKTRAN)
Transport of colloidal particles in porous media is governed by the rate at which the colloids strike and stick to collector surfaces. Classic filtration theory has considered the influence of system hydrodynamics on determining the rate that colloids strike collector surfaces, but has neglected the...
Application of X-ray CT investigation of CO2-brine flow in porous media
NASA Astrophysics Data System (ADS)
Jiang, Lanlan; Liu, Yu; Song, Yongchen; Yang, Mingjun; Xue, Ziqiu; Zhao, Yuechao; Zhao, Jiafei; Zhang, Yi; Suekane, Tetsuya; Shen, Zijian
2015-05-01
A clear understanding of two-phase flows in porous media is important for investigating CO2 geological storage. In this study, we conducted an experiment of CO2/brine flow process in porous media under sequestration conditions using X-ray CT technique. The flow properties of relative permeability, porosity heterogeneity, and CO2 saturation were observed in this experiment. The porous media was packed with glass beads having a diameter of 0.2 mm. The porosity distribution along the flow direction is heterogeneous owing to the diameter and shape of glass beads along the flow direction. There is a relationship between CO2 saturation and porosity distribution, which changes with different flow rates and fractional flows. The heterogeneity of the porous media influences the distribution of CO2; moreover, gravity, fractional flows, and flow rates influence CO2 distribution and saturation. The relative permeability curve was constructed using the steady-state method. The results agreed well with the relative permeability curve simulated using pore-network model.
Influence of the dynamic contact angle on the characterization of porous media.
Martic, G; De Coninck, J; Blake, T D
2003-07-01
It has been shown recently that the classical Lucas-Washburn equation, often used to model the dynamics of liquid penetration into porous media, should be modified to take account of the dynamic contact angle between the liquid and the pore. Here we show how neglect of this effect can lead to significant errors in estimation of the effective pore radius.
Moments on a Coning Projectile by a Spinning Liquid in Porous Media
2005-09-01
Axial Porous Media Configuration For this problem the moment arm 0R0 = in Eqs. (3 & 5) and the position vector becomes ( )θsinrθ,cosrx,=R since...Sedney, R., “moment on a Liquid-Filled Spinning and Nutating Projectile: Solid Body Rotation,” ARBRL-TR-02470, US Army Ballistic Research
Du, Liming; Xie, Maozhao
2011-06-01
A numerical study of Reciprocating Superadiabatic Combustion of Premixed gases in porous media (hereafter, referred to as RSCP) is performed. In this system the transient combustion of methane-air mixture is stabilized in a porous media combustor by periodically switching flow directions. The mass, momentum, energy and species conservation equations are solved using a two-dimensional control volume method. Local thermal non-equilibrium between the gas and the solid phases is considered by solving separate energy equations for the two phases and coupling them through a convective heat transfer coefficient. The porous media is assumed to emit, absorb and isotropically scatter radiation. The influences of the dominating operating parameters, such as filtration velocity, equivalence ratio and half cycle on the temperature profile, heat release rate, radiant flux, radiant efficiency and combustion efficiency are discussed. The results show that coupling calculating of flow field, combustion reaction and volume radiation of the optically thick media is successively achieved and heat radiation plays an important role in the overall performance of the burner. The temperature profile inside the RSCP combustor has a typical trapezoidal shape and the profile of radiation flux is similar to sinusoidal shape. Compared with the conventional premixed combustion in porous medium, combustion behavior in RSCP combustor is superior, such as better thermal structure and higher radiation efficiency and combustion efficiency.
Critical role of surface roughness on colloid retention and release in porous media
Technology Transfer Automated Retrieval System (TEKTRAN)
A thorough understanding of colloid transport in porous media is of great importance in many environmental and industrial applications. Extended-DLVO theory was employed to investigate the influence of nanoscale surface roughness (NSR) on the magnitudes of the secondary (F2min) and primary energy (F...
Existence and Uniqueness of Solutions to the Stochastic Porous Media Equations of Saturated Flows
Ciotir, Ioana
2010-02-15
This paper proves the existence and uniqueness of nonnegative solutions for the stochastic porous media equations with multiplicative noise, infinite jump and discontinuous diffusivity function relevant in description of saturation processes in underground water infiltration in a bounded domain of R{sup 3}.
Effects of heat sink compounds on contact resistance of porous media
Technology Transfer Automated Retrieval System (TEKTRAN)
High and low-conductivity heat sink compounds were applied in succession on a thermal probe, which was then used to determine the thermal conductivity and thermal diffusivity of some porous media at room temperature. The experiment was conducted separately under different packing densities and water...
A KINETIC MODEL FOR CELL DENSITY DEPENDENT BACTERIAL TRANSPORT IN POROUS MEDIA
A kinetic transport model with the ability to account for variations in cell density of the aqueous and solid phases was developed for bacteria in porous media. Sorption kinetics in the advective-dispersive-sorptive equation was described by assuming that adsorption was proportio...
Aspects of non-Newtonian flow and displacement in porous media
Shah, C.; Yortsos, Y.C.
1993-02-01
The rheology of many heavy oils has been shown to be non-Newtonian, Bingham plastics being one manifestation of heavy oil flow. In EOR applications, non-Newtonian fluids such as low concentration polymer solutions, emulsions, gels etc. are simultaneously injected to increase the viscosity of driving agents that displace oil. Such rheologically complex fluids are used to improve sweep efficiencies, divert displacing fluids and block swept zones. The present study has been undertaken to understand the flow of non-Newtonian fluids through porous media. The work considered involves the numerical (pore network) modeling of both single and multiphase flow of power-law and Bingham plastic fluids in network-like porous media. We consider aspects of both single- and multi-phase flow and displacement. Section 2 describes elementary aspects of non-Newtonian flow and some simple models for porous media. Viscoelastic effects in the flow of non-Newtonian fluids are also discussed. The section includes a brief literature review on non-Newtonian flow in porous media. Section 3 describes single-phase flow.
Surface properties and flow behavior of foams in relation to fluid displacement in porous media
Ling, T.F.T.
1987-01-01
Surface properties such as surface tension, surface viscosity, foaminess, foam quality, apparent foam viscosity, rate of drainage, bubble size distribution, etc., were investigated and correlated with fluid displacement in porous media. The effect of chain length compatability, i.e., similarity, on surface properties of foaming solutions and fluid displacement in porous media were also studied. Two mathematical models for foam flow through porous media were developed which can be used to predict foam viscosity and foam behavior in porous media. To better understand the foam stability, a numerical solution of the Poisson-Boltzmann equation in two dimensional bispherical coordinates was obtained and used to calculate the potential energy of interaction between two spherical bubbles. Predicted potential energies were consistent with results from other models. The effect of polymer on foam properties was also studied. The improvement of surface activity of the surfactants was due mainly to the effect of the excluded polymer volume and electrical double layers. The change of the surface properties of the polymer containing foam was dependent on the counterbalance of the rheology of the liquid films and the water content in the liquid films. These studies have been successfully applied to enhanced oil recovery and to characterization of biological polymers. A concept of surfactant-polymer-foam flooding is proposed, including the use of nonionic surfactants to form alcohol-free microemulsions and the injection of foam for the mobility control in heavy oil recovery.
VIRUS TRANSPORT IN PHYSICALLY AND GEOCHEMICALLY HETEROGENEOUS SUBSURFACE POROUS MEDIA. (R826179)
A two-dimensional model for virus transport in physically and geochemically heterogeneous subsurface porous media is presented. The model involves solution of the advection–dispersion equation, which additionally considers virus inactivation in the solution, as well as ...
Pore-Scale Study of Miscible Displacements in Porous Media Using Lattice Boltzmann Method
NASA Astrophysics Data System (ADS)
Zhang, Ting; Shi, Baochang; Huang, Changsheng; Liang, Hong
2015-12-01
In the past few years, the miscible displacements in porous media were usually simulated by some semiempirical models based on the volume averaging at the representative elementary volume scale. To better understand the microscopic mechanism of the viscous fingering phenomenon in porous media for miscible fluids, in this paper the miscible displacements processes in porous media are studied using the lattice Boltzmann method (LBM) at the pore scale. First, the code of LBM is tested by simulating the displacement process of two miscible fluids with the same viscosity between two parallel plates which is the well-known Taylor-Aris dispersion problem, and comparing the results with the theoretical predictions. Then, the effects of the Péclet number Pe, the viscosity ratio M and the structure of the porous media on the displacement phenomenon are investigated, and the location and velocity of the finger tip, the displacement efficiency are also studied. In this paper, the displacement efficiency is calculated by 1-m, here the quantity m is defined as m=V_M/V_T, where V_M is the volume of more viscous fluids (the displaced fluid) left behind the finger tip, V_T is the total pore volume behind the finger tip. It can be found that the "interface" of two fluids will become clearer with the increasing of the Péclet number. As Pe and M are large enough, the viscous fingering phenomenon will occur, and in the front of the finger, "mushroom-like" pattern can be observed. Besides, with the increasing of Pe or M the quantity m will be increased too, i.e., the displacement efficiency will be decreased. While Pe (or M) is greater than a certain value, the growth rate of the quantity m will slow down. The same trend was observed for the miscible displacement in capillary tubes or Hele-Shaw cells. Besides, changing the structure of the porous media makes the finger pattern different. The present simulation results provide a good understanding of the microscopic mechanism of the
Transport properties of porous media from the microstructure
Torquato, S.
1995-12-31
The determination of the effective transport properties of a random porous medium remains a challenging area of research because the properties depend on the microstructure in a highly complex fashion. This paper reviews recent theoretical and experimental progress that we have made on various aspects of this problem. A unified approach is taken to characterize the microstructure and the seemingly disparate properties of the medium.
Thermal inertia and reversing buoyancy in flow in porous media
NASA Astrophysics Data System (ADS)
Menand, Thierry; Raw, Alan; Woods, Andrew W.
2003-03-01
The displacement of fluids through porous rocks is fundamental for the recharge of geothermal and hydrocarbon reservoirs [Grant et al., 1982; Lake, 1989], for contaminant dispersal through the groundwater [Bear, 1972] and in controlling mineral reactions in permeable rocks [Phillips, 1991]. In many cases, the buoyancy force associated with density differences between the formation fluid and the displacing fluid controls the rate and pattern of flow through the permeable rock [Phillips, 1991; Barenblatt, 1996; Turcotte and Schubert, 2002]. Here, using new laboratory experiments, we establish that a striking range of different flow patterns may develop depending on whether this density contrast is associated with differences in temperature and/or composition between the two fluids. Owing to the effects of thermal inertia in a porous rock, thermal fronts lag behind compositional fronts [Woods and Fitzgerald, 1993; Turcotte and Schubert, 2002], so that two zones of different density develop in the region flooded with injected fluid. This can lead to increasing, decreasing or even reversing buoyancy in the injected liquid; in the latter case it may then form a double-flood front, spreading along both the upper and lower boundary of the rock. Recognition of these different flow regimes is key for predicting sweep efficiency and dispersal patterns in natural and engineered flows, and offers new opportunities for the enhanced recovery of natural resources in porous rocks.
Freeze fracturing of elastic porous media: a mathematical model
Vlahou, I.; Worster, M. G.
2015-01-01
We present a mathematical model of the fracturing of water-saturated rocks and other porous materials in cold climates. Ice growing inside porous rocks causes large pressures to develop that can significantly damage the rock. We study the growth of ice inside a penny-shaped cavity in a water-saturated porous rock and the consequent fracturing of the medium. Premelting of the ice against the rock, which results in thin films of unfrozen water forming between the ice and the rock, is one of the dominant processes of rock fracturing. We find that the fracture toughness of the rock, the size of pre-existing faults and the undercooling of the environment are the main parameters determining the susceptibility of a medium to fracturing. We 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. We 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. PMID:25792954
Interface effects on multiphase flows in porous media
Zhang, Duan Z
2008-01-01
Most models for multiphase flows in a porous medium are based on the straightforward extension of Darcy's law, in which each fluid phase is driven by its own pressure gradient. The pressure difference between the phases is thought to be an effect of surface tension and is called capillary pressure. Independent of Darcy's law, for liquid imbibition processes in a porous material, diffusion models are sometime used. In this paper, an ensemble phase averaging technique for continuous multi phase flows is applied to derive averaged equations and to examine the validity of the commonly used models. The closure for the averaged equations is quite complicated for general multiphase flows in a porous material. For flows with a small ratio of the characteristic length of the phase interfaces to the macroscopic length, the closure relations can be simplified significantly by an approximation with a second order error in the length ratio. The approximation reveals the information of the length scale separation obscured during the ensemble averaging process, and leads to an equation system similar to Darcy's law, but with additional terms. Based on interactions on phase interfaces, relations among closure quantities are studied.
Three-Dimensional Imaging and Quantification of Biomass and Biofilms in Porous Media
Dorthe Wildenschild
2012-10-10
A new method to resolve biofilms in three dimensions in porous media using high-resolution synchrotron-based x-ray computed microtomography (CMT) has been developed. Imaging biofilms in porous media without disturbing the natural spatial arrangement of the porous media and associated biofilm has been a challenging task, primarily because porous media generally precludes conventional imaging via optical microscopy; x-ray tomography offers a potential alternative. One challenge for using this method is that most conventional x-ray contrast agents are water-soluble and easily diffuse into biofilms. To overcome this problem, silver-coated microspheres were added to the fluid phase to create an x-ray contrast that does not diffuse into the biofilm mass. Using this approach, biofilm imaging in porous media was accomplished with sufficient contrast to differentiate between the biomass- and fluid-filled pore spaces. The method was validated by using a two-dimensional micro-model flow cell where both light microscopy and CMT imaging were used to im age the biofilm. The results of this work has been published in Water Resources Research (Iltis et al., 2010). Additional work needs to be done to optimize this imaging approach, specifically, we find that the quality of the images are highly dependent on the coverage of the biofilm with Ag particles, - which means that we may have issues in dead-end pore space and for very low density (fluffy) biofilms. What we can image for certain with this technique is the biofilm surface that is well-connected to flow paths and thus well-supplied with nutrients etc.
Effect of Porous Media Particle Size on Bacterial Motility and Chemotaxis
NASA Astrophysics Data System (ADS)
Olson, M. S.; Smith, J. A.; Ford, R. M.; Fernandez, E. J.
2003-12-01
Many soil-inhabiting bacteria that degrade chemical contaminants are both motile and chemotactic. Chemotaxis refers to the ability of bacteria to sense pollutant concentration gradients in water and preferentially swim toward regions of high pollutant concentration, and is thought to be important in guiding subsurface microbial populations toward chemical contaminants. Bacterial motion consists of a series of smooth-swimming runs interrupted by changes in direction. In the presence of a chemical gradient, bacteria bias their frequency of changing direction and demonstrate longer run lengths in the direction of increasing attractant concentration. One concern when studying bacterial chemotaxis in porous media is that in small pores, the porous media may interrupt the extended run lengths of bacteria swimming in the direction of a positive chemical gradient. The purpose of this study is to examine how a decrease in particle size affects the motility and chemotactic response of bacteria traveling through porous media. We employ an innovative technique for noninvasive visualization of changes in bacterial density distributions in a packed column as a function of time. Paramagnetic magnetite particles are attached to the surface of Pseudomonas putida F1 cells using an antibody. Bacterial distributions within a column of glass-coated polystyrene beads are imaged using magnetic resonance imaging (MRI), with a spatial resolution of 300 μ m. Experiments are conducted with both 250-300 μ m beads and 90-150 μ m beads. Bacteria labeled with magnetite are introduced into a specially designed chromatography column packed with glass-coated polystyrene beads. Bacterial migration is monitored over time using MRI, with and without the presence of a chemical gradient of trichloroethylene (TCE). Comparisons of the motility and chemotactic transport coefficients for Pseudomonas putida F1 cells traveling through different-sized samples of porous media in the presence of TCE will be
Evaporation and capillary coupling across vertical textural contrasts in porous media.
Lehmann, Peter; Or, Dani
2009-10-01
High and nearly constant evaporation rates from initially saturated porous media are sustained by capillary-driven flow from receding drying front below the evaporating surface. The spatial extent of continuous liquid pathways in homogeneous porous medium is defined by its hydraulically connected pore size distribution. We consider here evaporative losses from porous media consisting of two hydraulically coupled dissimilar domains each with own pore and particle size distributions separated by sharp vertical textural contrast. Evaporation experiments from texturally dissimilar media were monitored using neutron transmission and dye pattern imaging to quantify water distribution and drying front dynamics. Drying front invades exclusively coarse-textured domain while fine-textured domain remains saturated and its surface continuously coupled with the atmosphere. Results show that evaporation from fine-textured surface was supplied by liquid flow from adjacent coarse domain driven by capillary pressure differences between the porous media. A first characteristic length defining limiting drying front depth during which fine sand region remains saturated is deduced from difference in air-entry pressures of the two porous media. A second characteristic length defining the end of high evaporation rate includes the extent of continuous liquid films pinned in the crevices of the pore space and between particle contacts in the fine medium. We established numerically the lateral extent of evaporation-induced hydraulic coupling that is limited by viscous losses and gravity. For certain combinations of soil types the lateral extent of hydraulic coupling may exceed distances of 10 m. Results suggest that evaporative water losses from heterogeneous and coupled system are larger compared with uncoupled or homogenized equivalent systems.
NASA Astrophysics Data System (ADS)
Sato, Haruo; Fehler, Michael C.
2016-10-01
The envelope broadening and the peak delay of the S-wavelet of a small earthquake with increasing travel distance are results of scattering by random velocity inhomogeneities in the earth medium. As a simple mathematical model, Sato proposed a new stochastic synthesis of the scalar wavelet envelope in 3-D von Kármán type random media when the centre wavenumber of the wavelet is in the power-law spectral range of the random velocity fluctuation. The essential idea is to split the random medium spectrum into two components using the centre wavenumber as a reference: the long-scale (low-wavenumber spectral) component produces the peak delay and the envelope broadening by multiple scattering around the forward direction; the short-scale (high-wavenumber spectral) component attenuates wave amplitude by wide angle scattering. The former is calculated by the Markov approximation based on the parabolic approximation and the latter is calculated by the Born approximation. Here, we extend the theory for the envelope synthesis of a wavelet in 2-D random media, which makes it easy to compare with finite difference (FD) simulation results. The synthetic wavelet envelope is analytically written by using the random medium parameters in the angular frequency domain. For the case that the power spectral density function of the random velocity fluctuation has a steep roll-off at large wavenumbers, the envelope broadening is small and frequency independent, and scattering attenuation is weak. For the case of a small roll-off, however, the envelope broadening is large and increases with frequency, and the scattering attenuation is strong and increases with frequency. As a preliminary study, we compare synthetic wavelet envelopes with the average of FD simulation wavelet envelopes in 50 synthesized random media, which are characterized by the RMS fractional velocity fluctuation ε = 0.05, correlation scale a = 5 km and the background wave velocity V0 = 4 km s-1. We use the radiation
An Initial Non-Equilibrium Porous-Media Model for CFD Simulation of Stirling Regenerators
NASA Technical Reports Server (NTRS)
Tew, Roy; Simon, Terry; Gedeon, David; Ibrahim, Mounir; Rong, Wei
2006-01-01
The objective of this paper is to define empirical parameters (or closwre models) for an initial thermai non-equilibrium porous-media model for use in Computational Fluid Dynamics (CFD) codes for simulation of Stirling regenerators. The two CFD codes currently being used at Glenn Research Center (GRC) for Stirling engine modeling are Fluent and CFD-ACE. The porous-media models available in each of these codes are equilibrium models, which assmne that the solid matrix and the fluid are in thermal equilibrium at each spatial location within the porous medium. This is believed to be a poor assumption for the oscillating-flow environment within Stirling regenerators; Stirling 1-D regenerator models, used in Stirling design, we non-equilibrium regenerator models and suggest regenerator matrix and gas average temperatures can differ by several degrees at a given axial location end time during the cycle. A NASA regenerator research grant has been providing experimental and computational results to support definition of various empirical coefficients needed in defining a noa-equilibrium, macroscopic, porous-media model (i.e., to define "closure" relations). The grant effort is being led by Cleveland State University, with subcontractor assistance from the University of Minnesota, Gedeon Associates, and Sunpower, Inc. Friction-factor and heat-transfer correlations based on data taken with the NASAlSunpower oscillating-flow test rig also provide experimentally based correlations that are useful in defining parameters for the porous-media model; these correlations are documented in Gedeon Associates' Sage Stirling-Code Manuals. These sources of experimentally based information were used to define the following terms and parameters needed in the non-equilibrium porous-media model: hydrodynamic dispersion, permeability, inertial coefficient, fluid effective thermal conductivity (including themal dispersion and estimate of tortuosity effects}, and fluid-solid heat transfer
NASA Astrophysics Data System (ADS)
Jin, G.
2012-12-01
Multiphase flow modeling is an important numerical tool for a better understanding of transport processes in the fields including, but not limited to, petroleum reservoir engineering, remedy of ground water contamination, and risk evaluation of greenhouse gases such as CO2 injected into deep saline reservoirs. However, accurate numerical modeling for multiphase flow remains many challenges that arise from the inherent tight coupling and strong non-linear nature of the governing equations and the highly heterogeneous media. The existence of counter current flow which is caused by the effect of adverse relative mobility contrast and gravitational and capillary forces will introduce additional numerical instability. Recently multipoint flux approximation (MPFA) has become a subject of extensive research and has been demonstrated with great success in reducing considerable grid orientation effects compared to the conventional single point upstream (SPU) weighting scheme, especially in higher dimensions. However, the present available MPFA schemes are mathematically targeted to certain types of grids in two dimensions, a more general form of MPFA scheme is needed for both 2-D and 3-D problems. In this work a new upstream weighting scheme based on multipoint directional incoming fluxes is proposed which incorporates full permeability tensor to account for the heterogeneity of the porous media. First, the multiphase governing equations are decoupled into an elliptic pressure equation and a hyperbolic or parabolic saturation depends on whether the gravitational and capillary pressures are presented or not. Next, a dual secondary grid (called finite volume grid) is formulated from a primary grid (called finite element grid) to create interaction regions for each grid cell over the entire simulation domain. Such a discretization must ensure the conservation of mass and maintain the continuity of the Darcy velocity across the boundaries between neighboring interaction regions
NASA Astrophysics Data System (ADS)
Liao, M. W.; Chung, C. K.
2014-08-01
The porous anodic aluminum oxide (AAO) with high-aspect-ratio pore channels is widely used as a template for fabricating nanowires or other one-dimensional (1D) nanostructures. The high specific surface area of AAO can also be applied to the super capacitor and the supporting substrate for catalysis. The rough surface could be helpful to enhance specific surface area but it generally results in electrical field concentration even to ruin AAO. In this article, the aluminum (Al) films with the varied 2D-3D morphology on Si substrates were prepared using magnetron sputtering at a power of 50 W-185 W for 1 h at a working pressure of 2.5 × 10-1 Pa. Then, AAO was fabricated from the different Al films by means of one-step hybrid pulse anodizing (HPA) between the positive 40 V and the negative -2 V (1 s:1 s) for 3 min in 0.3 M oxalic acid at a room temperature. The microstructure and morphology of Al films were characterized by X-ray diffraction, scanning electron microscope and atomic force microscope, respectively. Some hillocks formed at the high target power could be attributed to the grain texture growth in the normal orientation of Al(1 1 1). The 3D porous AAO structure which is different from the conventional 2D planar one has been successfully demonstrated using HPA on the film with greatly rough hillock-surface formed at the highest power of 185 W. It offers a potential application of the new 3D AAO to high specific surface area devices.
Entropy-induced separation of star polymers in porous media
Blavats'ka, V.; Ferber, C. von; Holovatch, Yu.
2006-09-15
We present a quantitative picture of the separation of star polymers in a solution where part of the volume is influenced by a porous medium. To this end, we study the impact of long-range-correlated quenched disorder on the entropy and scaling properties of f-arm star polymers in a good solvent. We assume that the disorder is correlated on the polymer length scale with a power-law decay of the pair correlation function g(r){approx}r{sup -a}. Applying the field-theoretical renormalization group approach we show in a double expansion in {epsilon}=4-d and {delta}=4-a that there is a range of correlation strengths {delta} for which the disorder changes the scaling behavior of star polymers. In a second approach we calculate for fixed space dimension d=3 and different values of the correlation parameter a the corresponding scaling exponents {gamma}{sub f} that govern entropic effects. We find that {gamma}{sub f}-1, the deviation of {gamma}{sub f} from its mean field value is amplified by the disorder once we increase {delta} beyond a threshold. The consequences for a solution of diluted chain and star polymers of equal molecular weight inside a porous medium are that star polymers exert a higher osmotic pressure than chain polymers and in general higher branched star polymers are expelled more strongly from the correlated porous medium. Surprisingly, polymer chains will prefer a stronger correlated medium to a less or uncorrelated medium of the same density while the opposite is the case for star polymers.
Numerical simulation of magnetic nanofluid natural convection in porous media
NASA Astrophysics Data System (ADS)
Sheikholeslami, Mohsen
2017-02-01
Free convection of magnetic nanofluid in a porous curved cavity is investigated. Influence of external magnetic source is taken into account. Innovative numerical approach, namely CVFEM, is applied. Impacts of Darcy number (Da), Rayleigh (Ra), Hartmann (Ha) numbers and volume fraction of Fe3O4 (ϕ) on hydrothermal characteristics are examined. Results indicate that heat transfer augmentation augments with rise of Ha and reduces with rise of Da , Ra . Lorentz forces make the nanofluid motion to decrease and enhance the thermal boundary layer thickness. Temperature gradient enhances with increase of Da , Ra , ϕ, but it reduces with rise of Ha.
A new technology for determining transport parameters in porous media
Conca, J.L.; Wright, J.
1995-12-31
The UFA Method can directly and rapidly measure transport parameters for any porous medium over a wide range of water contents and conditions. UFA results for subsurface sediments at a mixed-waste disposal site at the Hanford Site in Washington State provided the data necessary for detailed hydrostratigraphic mapping, subsurface flux and recharge distributions, and subsurface chemical mapping. Seven hundred unsaturated conductivity measurements along with pristine pore water extractions were obtained in only six months using the UFA. These data are used to provide realistic information to conceptual models, predictive models and restoration strategies.
Brusseau, M.L.; Narter, M.; Schnaar, G.; Marble, J.
2009-06-01
The objective of this study was to quantitatively characterize the impact of porous-medium texture on interfacial area between immiscible organic liquid and water residing within natural porous media. Synchrotron X-ray microtomography was used to obtain high-resolution, three-dimensional images of solid and liquid phases in packed columns. The image data were processed to generate quantitative measurements of organic-liquid/water interfacial area and of organic-liquid blob sizes. Ten porous media, comprising a range of median grain sizes, grain-size distributions, and geochemical properties, were used to evaluate the impact of porous-medium texture on interfacial area. The results show that fluid-normalized specific interfacial area (A{sub f}) and maximum specific interfacial area (A{sub m}) correlate very well to inverse median grain diameter. These functionalities were shown to result from a linear relationship between effective organic-liquid blob diameter and median grain diameter. These results provide the basis for a simple method for estimating specific organic-liquid/water interfacial area as a function of fluid saturation for a given porous medium. The availability of a method for which the only parameter needed is the simple-to-measure median grain diameter should be of great utility for a variety of applications.
Simultaneous sorption and mechanical entrapment during polymer flow through porous media
NASA Astrophysics Data System (ADS)
Farajzadeh, R.; Bedrikovetsky, P.; Lotfollahi, M.; Lake, L. W.
2016-03-01
Physical adsorption and mechanical entrapment are two major causes of polymer retention in porous media. Physical adsorption is considered an equilibrium process and is often modeled by assuming a Langmuir isotherm. The outcome is a steady state pressure response because the permeability reduction is also accounted for by adsorption. However, some experimental data show gradual increase of pressure with time, implying that polymer retention is a time-dependent process. We discuss simultaneous effect of sorption and mechanical entrapment on the polymer retention in porous media. An exact solution for 1-D flow problem for the case of constant filtration coefficient and Langmuir-sorption isotherm, including explicit formulae for breakthrough concentration and pressure drop across the core is derived. The general model with a varying filtration coefficient was successfully matched with experimental data confirming the occurrence of simultaneous sorption with deep-bed filtration during polymer flow in porous media. In the absence of mechanical entrapment, the physical adsorption causes delay in the polymer front and does not affect the polymer concentration behind the front. Addition of mechanical entrapment results in slow recovery of the injected concentration at the outlet (for a varying filtration coefficient) or reaching to a steady state concentration, which is only a fraction of the injected concentration (for a constant filtration coefficient). Accurate assessment and quantification of the polymer retention requires both pressure and effluent concentration data at the outlet of the porous medium.
Neutron imaging of hydrogen-rich fluids in geomaterials and engineered porous media: A review
NASA Astrophysics Data System (ADS)
Perfect, E.; Cheng, C.-L.; Kang, M.; Bilheux, H. Z.; Lamanna, J. M.; Gragg, M. J.; Wright, D. M.
2014-02-01
Recent advances in visualization technologies are providing new discoveries as well as answering old questions with respect to the phase structure and flow of hydrogen-rich fluids, such as water and oil, within porous media. Magnetic resonance and x-ray imaging are sometimes employed in this context, but are subject to significant limitations. In contrast, neutrons are ideally suited for imaging hydrogen-rich fluids in abiotic non-hydrogenous porous media because they are strongly attenuated by hydrogen and can "see" through the solid matrix in a non-destructive fashion. This review paper provides an overview of the general principles behind the use of neutrons to image hydrogen-rich fluids in both 2-dimensions (radiography) and 3-dimensions (tomography). Engineering standards for the neutron imaging method are examined. The main body of the paper consists of a comprehensive review of the diverse scientific literature on neutron imaging of static and dynamic experiments involving variably-saturated geomaterials (rocks and soils) and engineered porous media (bricks and ceramics, concrete, fuel cells, heat pipes, and porous glass). Finally some emerging areas that offer promising opportunities for future research are discussed.
Numerical schemes for anomalous diffusion of single-phase fluids in porous media
NASA Astrophysics Data System (ADS)
Awotunde, Abeeb A.; Ghanam, Ryad A.; Al-Homidan, Suliman S.; Tatar, Nasser-eddine
2016-10-01
Simulation of fluid flow in porous media is an indispensable part of oil and gas reservoir management. Accurate prediction of reservoir performance and profitability of investment rely on our ability to model the flow behavior of reservoir fluids. Over the years, numerical reservoir simulation models have been based mainly on solutions to the normal diffusion of fluids in the porous reservoir. Recently, however, it has been documented that fluid flow in porous media does not always follow strictly the normal diffusion process. Small deviations from normal diffusion, called anomalous diffusion, have been reported in some experimental studies. Such deviations can be caused by different factors such as the viscous state of the fluid, the fractal nature of the porous media and the pressure pulse in the system. In this work, we present explicit and implicit numerical solutions to the anomalous diffusion of single-phase fluids in heterogeneous reservoirs. An analytical solution is used to validate the numerical solution to the simple homogeneous case. The conventional wellbore flow model is modified to account for anomalous behavior. Example applications are used to show the behavior of wellbore and wellblock pressures during the single-phase anomalous flow of fluids in the reservoirs considered.
NASA Astrophysics Data System (ADS)
Chau, J. F.; Or, D.; Jones, S.; Sukop, M.
2004-05-01
Liquid distribution in unsaturated porous media under different gravitational forces and resulting gaseous diffusion coefficients were investigated to enhance understanding of plant growth conditions in microgravity. Different fluid behavior in plant growth media under microgravity conditions as compared to earth presents a challenge to plant growth in long duration space exploration missions. Our primary objective was to provide qualitative description and quantitative measures of the role of reduced gravity on hydraulic and gaseous transport properties in simulated porous media. We implemented a multi-phase lattice Boltzmann code for equilibrium distribution of liquid in an idealized two-dimensional porous medium under microgravity and "normal" gravity conditions. The information was then used to provide boundary conditions for simulation of gaseous diffusion through the equilibrium domains (considering diffusion through liquid phase negligibly small). The models were tested by comparison with several analytical solutions to the diffusion equation, with excellent results. The relative diffusion coefficient for both series of simulations (with and without gravity) as functions of air-filled porosity was in good agreement with established models of Millington-Quirk. Liquid distribution under earth's gravity featured increased water content at the lower part of the medium relative to the distribution in reduced gravity, which resulted in decreased gas diffusion through a vertically oriented column of a porous medium. Simulation results for larger domains under various orientations will be presented.
NASA Astrophysics Data System (ADS)
Atis, S.; Saha, S.; Auradou, H.; Martin, J.; Rakotomalala, N.; Talon, L.; Salin, D.
2012-09-01
Autocatalytic reaction fronts between two reacting species in the absence of fluid flow, propagate as solitary waves. The coupling between autocatalytic reaction front and forced simple hydrodynamic flows leads to stationary fronts whose velocity and shape depend on the underlying flow field. We address the issue of the chemico-hydrodynamic coupling between forced advection in porous media and self-sustained chemical waves. Towards that purpose, we perform experiments over a wide range of flow velocities with the well characterized iodate arsenious acid and chlorite-tetrathionate autocatalytic reactions in transparent packed beads porous media. The characteristics of these porous media such as their porosity, tortuosity, and hydrodynamics dispersion are determined. In a pack of beads, the characteristic pore size and the velocity field correlation length are of the order of the bead size. In order to address these two length scales separately, we perform lattice Boltzmann numerical simulations in a stochastic porous medium, which takes into account the log-normal permeability distribution and the spatial correlation of the permeability field. In both experiments and numerical simulations, we observe stationary fronts propagating at a constant velocity with an almost constant front width. Experiments without flow in packed bead porous media with different bead sizes show that the front propagation depends on the tortuous nature of diffusion in the pore space. We observe microscopic effects when the pores are of the size of the chemical front width. We address both supportive co-current and adverse flows with respect to the direction of propagation of the chemical reaction. For supportive flows, experiments and simulations allow observation of two flow regimes. For adverse flow, we observe upstream and downstream front motion as well as static front behaviors over a wide range of flow rates. In order to understand better these observed static state fronts, flow
A new tracer-density criterion for heterogeneous porous media
Barth, G.R.; Illangasekare, T.H.; Hill, M.C.; Rajaram, H.
2001-01-01
Tracerexperiments provide information about aquifer material properties vital for accurate site characterization. Unfortunately, density-induced sinking can distort tracer movement, leading to an inaccurate assessment of material properties. Yet existing criteria for selecting appropriate tracer concentrations are based on analysis of homogeneous media instead of media with heterogeneities typical of field sites. This work introduces a hydraulic-gradient correction for heterogeneous media and applies it to a criterion previously used to indicate density-induced instabilities in homogeneous media. The modified criterion was tested using a series of two-dimensional heterogeneous intermediate-scale tracer experiments and data from several detailed field tracer tests. The intermediate-scale experimental facility (10.0 ?? 1.2 ?? 0.06 m) included both homogeneous and heterogeneous (??2/In ?? = 1.22) zones. The field tracer tests were less heterogeneous (0.24 < ??2/ln ?? < 0.37), but measurements were sufficient to detect density-induced sinking. Evaluation of the modified criterion using the experiments and field tests demonstrates that the new criterion appears to account for the change in density-induced sinking due to heterogeneity. The criterion demonstrates the importance of accounting for heterogeneity to predict density-induced sinking and differences in the onset of density induced sinking in two-and three-dimensional systems.
Application of a portable nuclear magnetic resonance surface probe to porous media.
Marko, Andriy; Wolter, Bernd; Arnold, Walter
2007-03-01
A portable nuclear magnetic resonance (NMR) surface probe was used to determine the time-dependent self-diffusion coefficient D(t) of water molecules in two fluid-filled porous media. The measuring equipment and the inhomogeneous magnetic fields in the sensitive volume of the probe are described. It is discussed how to evaluate D(t) using a surface probe from the primary and stimulated echoes generated in three-pulse experiments. Furthermore, the evaluation of D(t) allows one to determine the geometrical structure of porous materials.
Analytical approximations for flow in compressible, saturated, one-dimensional porous media
NASA Astrophysics Data System (ADS)
Barry, D. A.; Lockington, D. A.; Jeng, D.-S.; Parlange, J.-Y.; Li, L.; Stagnitti, F.
2007-04-01
A nonlinear model for single-phase fluid flow in slightly compressible porous media is presented and solved approximately. The model assumes state equations for density, porosity, viscosity and permeability that are exponential functions of the fluid (either gas or liquid) pressure. The governing equation is transformed into a nonlinear diffusion equation. It is solved for a semi-infinite domain for either constant pressure or constant flux boundary conditions at the surface. The solutions obtained, although approximate, are extremely accurate as demonstrated by comparisons with numerical results. Predictions for the surface pressure resulting from a constant flux into a porous medium are compared with published experimental data.
NASA Astrophysics Data System (ADS)
Ghanbarian, Behzad; Daigle, Hugh; Hunt, Allen G.; Ewing, Robert P.; Sahimi, Muhammad
2015-01-01
Understanding and accurate prediction of gas or liquid phase (solute) diffusion are essential to accurate prediction of contaminant transport in partially saturated porous media. In this study, we propose analytical equations, using concepts from percolation theory and the Effective Medium Approximation (EMA) to model the saturation dependence of both gas and solute diffusion in porous media. The predictions of our theoretical approach agree well with the results of nine lattice Boltzmann simulations. We find that the universal quadratic scaling predicted by percolation theory, combined with the universal linear scaling predicted by the EMA, describes diffusion in porous media with both relatively broad and extremely narrow pore size distributions.
Influence of porous media structure in colloid retention in the absence of an energy barrier
NASA Astrophysics Data System (ADS)
Pazmino, E. F.; Johnson, W. P.; Ma, H.
2010-12-01
Many colloid transport experiments have been conducted in a porous media with narrow size distribution, which allows a single collector size to be used in filtration theory to predict deposition rates. In this work, deposition of colloids (ranging from 0.21 μm to 9.1 μm) in packed columns is examined in the absence of an energy barrier with three different glass bead porous media: uniform mono-dispersed, mono-modal poly-dispersed and bimodal poly-dispersed. The corresponding porosities to these media are 0.378, 0.339 and 0.282. The effect of gravitational settling on deposition is studied by injecting the particles co-current and counter-current with gravity, especially for larger size colloids. Also, direct observations are conducted in a flow cell for selected colloid sizes for a better understanding of the mechanisms of attachment. Experimental results are compared with theoretical predictions to determine characteristic collector sizes that represent poly-dispersed porous media in filtration theory.
Jones, S B; Or, D
1999-04-01
Plants grown in porous media are part of a bioregenerative life support system designed for long-duration space missions. Reduced gravity conditions of orbiting spacecraft (microgravity) alter several aspects of liquid flow and distribution within partially saturated porous media. The objectives of this study were to evaluate the suitability of conventional capillary flow theory in simulating water distribution in porous media measured in a microgravity environment. Data from experiments aboard the Russian space station Mir and a U.S. space shuttle were simulated by elimination of the gravitational term from the Richards equation. Qualitative comparisons with media hydraulic parameters measured on Earth suggest narrower pore size distributions and inactive or nonparticipating large pores in microgravity. Evidence of accentuated hysteresis, altered soil-water characteristic, and reduced unsaturated hydraulic conductivity from microgravity simulations may be attributable to a number of proposed secondary mechanisms. These are likely spawned by enhanced and modified paths of interfacial flows and an altered force ratio of capillary to body forces in microgravity.
Simplified Model for the Remobilization of Colloids and Nanoparticles in Porous Media
NASA Astrophysics Data System (ADS)
Gao, B.
2015-12-01
When entering the hydrological pathways, natural colloids and engineered nanoparticles may present potential risks to the environment, particularly the soil and groundwater systems. While soils can serve as filter media to immobilize the particles, flow perturbations, such as changes in solution chemistry and flow rate, may remobilize them. Most of the current models on the release of particles in porous media require solving coupled partial different equations that simulate both flow conditions and particle behaviors. This work will present a simple method to model the remobilization of colloids or nanoparticles in porous media. The simplified model assumes that the release of the immobilized particles in the porous media is only controlled by the wet front. It thus can be described by the advection-dispersion equation couple with simple kinetic expressions of particle release. Simulations from the simplified model were tested against experimental data of the remobilization of clay particles in sand column under transient flow conditions. The model results matched the experimental data very well.
An improved gray lattice Boltzmann model for simulating fluid flow in multi-scale porous media
NASA Astrophysics Data System (ADS)
Zhu, Jiujiang; Ma, Jingsheng
2013-06-01
A lattice Boltzmann (LB) model is proposed for simulating fluid flow in porous media by allowing the aggregates of finer-scale pores and solids to be treated as 'equivalent media'. This model employs a partially bouncing-back scheme to mimic the resistance of each aggregate, represented as a gray node in the model, to the fluid flow. Like several other lattice Boltzmann models that take the same approach, which are collectively referred to as gray lattice Boltzmann (GLB) models in this paper, it introduces an extra model parameter, ns, which represents a volume fraction of fluid particles to be bounced back by the solid phase rather than the volume fraction of the solid phase at each gray node. The proposed model is shown to conserve the mass even for heterogeneous media, while this model and that model of Walsh et al. (2009) [1], referred to the WBS model thereafter, are shown analytically to recover Darcy-Brinkman's equations for homogenous and isotropic porous media where the effective viscosity and the permeability are related to ns and the relaxation parameter of LB model. The key differences between these two models along with others are analyzed while their implications are highlighted. An attempt is made to rectify the misconception about the model parameter ns being the volume fraction of the solid phase. Both models are then numerically verified against the analytical solutions for a set of homogenous porous models and compared each other for another two sets of heterogeneous porous models of practical importance. It is shown that the proposed model allows true no-slip boundary conditions to be incorporated with a significant effect on reducing errors that would otherwise heavily skew flow fields near solid walls. The proposed model is shown to be numerically more stable than the WBS model at solid walls and interfaces between two porous media. The causes to the instability in the latter case are examined. The link between these two GLB models and a
A novel approach to model hydraulic and electrical conductivity in fractal porous media
NASA Astrophysics Data System (ADS)
Ghanbarian, B.; Daigle, H.; Sahimi, M.
2014-12-01
Accurate prediction of conductivity in partially-saturated porous media has broad applications in various phenomena in porous media, and has been studied intensively since the 1940s by petroleum, chemical and civil engineers, and hydrologists. Many of the models developed in the past are based on the bundle of capillary tubes. In addition, pore network models have also been developed for simulating multiphase fluid flow in porous media and computing the conductivity in unsaturated porous media. In this study, we propose a novel approach using concepts from the effective-medium approximation (EMA) and percolation theory to model hydraulic and electrical conductivity in fractal porous media whose pore-size distributions exhibit power-law scaling. In our approach, the EMA, originally developed for predicting electrical conductivity of composite materials, is used to predict the effective conductivity, from complete saturation to some intermediate water content that represents a crossover point. Below the crossover water content, but still above a critical saturation (percolation threshold), a universal scaling predicted by percolation theory, a power law that expresses the dependence of the conductivity on the water content (less a critical water saturation) with an exponent of 2, is invoked to describe the effective conductivity. In order to evaluate the accuracy of the approach, experimental data were used from the literature. The predicted hydraulic conductivities for most cases are in excellent agreement with the data. In a few cases the theory underestimates the hydraulic conductivities, which correspond to porous media with very broad pore-size distribution in which the largest pore radius is more than 7 orders of magnitude greater than the smallest one. The approach is also used to predict the saturation dependence of the electrical conductivity for experiments in which capillary pressure data are available. The results indicate that the universal scaling of
Theoretical Studies of Non-Newtonian and Newtonian Fluid Flowthrough Porous Media
Wu, Y.S.
1990-02-01
A comprehensive theoretical study has been carried out on the flow behavior of both single and multiple phase non-Newtonian fluids in porous media. This work is divided into three parts: (1) development of numerical and analytical solutions; (2) theoretical studies of transient flow of non-Newtonian fluids in porous media; and (3) applications of well test analysis and displacement efficiency evaluation to field problems. A fully implicit, integral finite difference model has been developed for simulation of non-Newtonian and Newtonian fluid flow through porous media. Several commonly-used rheological models of power-law and Bingham plastic non-Newtonian fluids have been incorporated in the simulator. A Buckley-Leverett type analytical solution for one-dimensional, immiscible displacement involving non-Newtonian fluids in porous media has been developed. Based on this solution, a graphic approach for evaluating non-Newtonian displacement efficiency has been developed. The Buckley-Leverett-Welge theory is extended to flow problems with non-Newtonian fluids. An integral method is also presented for the study of transient flow of Bingham fluids in porous media. In addition, two well test analysis methods have been developed for analyzing pressure transient tests of power-law and Bingham fluids, respectively. Applications are included to demonstrate this new technology. The physical mechanisms involved in immiscible displacement with non-Newtonian fluids in porous media have been studied using the Buckley-Leverett type analytical solution. The results show that this kind of displacement is a complicated process and is determined by the rheological properties of the non-Newtonian fluids and the flow conditions, in addition to relative permeability data. In another study, an idealized fracture model has been used to obtain some insights into the flow of a power-law fluid in a double-porosity medium. For flow at a constant rate, non-Newtonian flow behavior in a fractured
Growth kinetics and microstructure of methane hydrates formed in porous media
NASA Astrophysics Data System (ADS)
Falenty, A.; Klapproth, A.; Techmer, K.; Murshed, M. M.; Kuhs, W. F.
2007-12-01
The occurrence of natural gas hydrates within sediments is known from a large number of locations. They commonly occupy pore spaces cementing sedimentary deposits. Yet, detailed information about the influence of mineral composition on the formation process in porous media is still very limited. Laboratory investigations of the microstructure of gas hydrate in porous media, as a function of p-T conditions, mineral composition and water/gas supersaturation are therefore of considerable interest. Such studies may allow a better understanding of the formation process and even the prediction of accumulation /decomposition rates of some natural gas hydrates in a given geological setting. As a model study, we carried out various reactions with methane gas and water in three types of media: 1) quartz, 2) quartz + kaolinite, 3) quartz + montmorillonite. The progress of the reactions was recorded by gas consumption (pressure drop) at 3°C. Samples recovered at various stages of the formation or decomposition reactions were investigated using field-emission scanning electron microscopes (FE-SEM) equipped with a cryo-stage [1]. In the SEM investigations, methane hydrates appeared between the quartz grains acting as cement. Kaolinite particles were observed as a filigree network on the surface of hydrate cement, while montmorillonite form flakes or crust like features. Each of the minerals may play individual/coupled interaction with water and gas hydrate, and thereby display a characteristic configuration in the SEM images. Dissimilar kinetic features, using different porous media at the investigated conditions, confirm that mineral composition directly influences the progress of gas hydrate formation. Medium 3 shows the fastest hydrate saturation. With increasing water content of the porous media the formation tends to proceed in a multi-stage process with a slower diffusion-limited later stage. Reference: [1] A. Klapproth, K. Techmer, S.A. Klapp, M.M. Murshed and W.F. Kuhs
Pressure drop of He II flow through a porous media
NASA Technical Reports Server (NTRS)
Maddocks, J. R.; Van Sciver, S. W.
1990-01-01
The paper reports on measurements of He II pressure drop across two porous SiO2 ceramic filter materials. These materials vary only in porosity, having values of 0.94 and 0.96. The average fiber diameter in both cases is approximately 5 microns. The experiment consists of a glass tube containing a piece of this sponge in one end. The tube is rapidly displaced downward in a bath of helium and the liquid levels are allowed to equilibrate over time producing variable velocities up to 10 cm/sec. The results are compared with those previously obtained using fine mesh screens. Good qualitative agreement is observed for turbulent flow; however, the behavior in the laminar flow regime is not fully understood.
Ion transport in porous media studied by NMR.
Pel, L; Huinink, H P; Kopinga, K; Rijniers, L A; Kaasschieter, E F
2001-01-01
Moisture and salt transport in masonry can give rise to damages. Therefore a detailed knowledge of the moisture and salt transport is essential for understanding the durability of masonry. A special NMR apparatus has been made allowing quasi-simultaneous measurements of both moisture and Na profiles in porous building materials. Using this apparatus both the absorption of a 4 M NaCl solution in a calcium silicate brick and the drying of a 3 M NaCl capillary saturated fired-clay brick have been studied. It was found that during the absorption process the Na ions clearly stay behind, which this is caused by adsorption of these ions to the pore surface. For the drying it was found that at the beginning of the drying process the ions accumulate near the surface. As the drying rate decreases, diffusion becomes dominant and the ion profile levels off again.
Instationary compaction wave propagation in highly porous cohesive granular media
NASA Astrophysics Data System (ADS)
Gunkelmann, Nina; Ringl, Christian; Urbassek, Herbert M.
2016-07-01
We study the collision of a highly porous granular aggregate of adhesive \\upmu m-sized silica grains with a hard wall using a granular discrete element method. A compaction wave runs through the granular sample building up an inhomogeneous density profile. The compaction is independent of the length of the aggregate, within the regime of lengths studied here. Also short pulses, as they might be exerted by a piston pushing the granular material, excite a compaction wave that runs through the entire material. The speed of the compaction wave is larger than the impact velocity but considerably smaller than the sound speed. The wave speed is related to the compaction rate at the colliding surface and the average slope of the linear density profile.
Characterization of porous media by means of the depolarization metrics
NASA Astrophysics Data System (ADS)
Savenkov, S.; Priezzhev, A.; Oberemok, Ye.; Silfsten, P.; Ervasti, T.; Ketolainen, J.; Peiponen, K.-E.
2012-12-01
In this paper Mueller polarimetry is applied to study the samples with different porosity compacted from microcrystalline cellulose. We measure the whole Mueller matrices of the samples as a function of the incident angle at a wavelength of 632.8 nm. To quantify separability of the different porous samples based on differences in their Mueller matrix behavior we apply depolarization and anisotropy analysis to measured Mueller matrices by calculating parameters characterizing depolarization (depolarization index, Q(M)-metric, first and second Lorenz indices, Cloude and Lorenz entropy) and anisotropy (values and azimuths of phase and amplitude anisotropy) properties of a sample. The results show that anisotropy parameters are almost completely insensitive to the range of porosity at least at 632.8 nm. Whereas, all depolarization metrics considered are sensitive to the range of porosity. Most sensitive (not worst than 5%) among depolarization metrics are the Lorenz entropy and Q(M)-metric.
Macrodispersion by diverging radial flows in randomly heterogeneous porous media.
Severino, Gerardo; Santini, Alessandro; Sommella, Angelo
2011-04-01
Radial flow takes place in a heterogeneous porous formation where the transmissivity T is modelled as a stationary random space function (RSF). The steady flow is driven by a given rate, and the mean velocity is radial. A pulse-like of a tracer is injected in the porous formation, and the thin plume spreads due to the fluctuations of the velocity which results a RSF as well. Transport is characterized by the mean front, and by the second spatial moment of the plume. We are primarily interested in tracer macrodispersion modelling. With the neglect of pore-scale dispersion, macrodispersion coefficients are computed at the second order of approximation, without neglecting the head-gradient fluctuations. Although transport is non-ergodic at the source, it is shown that ergodicity is achieved at small distances from the source. This is due to the fact that close to the source local velocities are quite large, and therefore solute particles become uncorrelated very soon. Under ergodic conditions, we compare macrodispersion mechanism in radial flows with that occurring in mean uniform flows. At short distances the spreading effect is highly enhanced by the large variability of the flow field, whereas at large distances transport exhibits a lesser dispersion due to the reduction of velocities. This supports the explanation provided by Indelman and Dagan (1999) to justify why the macrodispersivity is found smaller than that pertaining to mean uniform flows. The model is tested against a tracer transport experiment (Fernàndez-Garcia et al., 2004) by comparing the theoretical and experimental breakthrough curves. The accordance with real data, that is achieved without any fitting to concentration values, strengthens the capability of the proposed model to grasp the main features of such an experiment, the approximations as well as experimental uncertainties notwithstanding.
Adapted MR velocimetry of slow liquid flow in porous media
NASA Astrophysics Data System (ADS)
Huang, Li; Mikolajczyk, Gerd; Küstermann, Ekkehard; Wilhelm, Michaela; Odenbach, Stefan; Dreher, Wolfgang
2017-03-01
MR velocimetry of liquid flow in opaque porous filters may play an important role in better understanding the mechanisms of deep bed filtration. With this knowledge, the efficiency of separating the suspended solid particles from the vertically flowing liquid can be improved, and thus a wide range of industrial applications such as wastewater treatment and desalination can be optimized. However, MR velocimetry is challenging for such studies due to the low velocities, the severe B0 inhomogeneity in porous structures, and the demand for high spatial resolution and an appropriate total measurement time during which the particle deposition will change velocities only marginally. In this work, a modified RARE-based MR velocimetry method is proposed to address these issues for velocity mapping on a deep bed filtration cell. A dedicated RF coil with a high filling factor is constructed considering the limited space available for the vertical cell in a horizontal MR magnet. Several means are applied to optimize the phase contrast RARE MRI pulse sequence for accurately measuring the phase contrast in a long echo train, even in the case of a low B1 homogeneity. Two means are of particular importance. One uses data acquired with zero flow to correct the phase contrast offsets from gradient imperfections, and the other combines the phase contrast from signals of both odd and even echoes. Results obtained on a 7T preclinical MR scanner indicate that the low velocities in the heterogeneous system can be correctly quantified with high spatial resolution and an adequate total measurement time, enabling future studies on flow during the filtration process.
Hydrodynamic controls on particle transport through heterogeneous porous media
Silliman, S.E.
1992-09-30
The initial stages of this project have been focused on equipment development and preliminary experimental efforts. Among the accomplishments to date are the development of a successful flow cell design, proof of the utility of the UV resin, adjustment of the Laser Particle Counter to produce reliable readings, installation of a low particle content water supply, installation of a microscope for viewing discharge samples, development of a fiber/rod optic system for freezing the UV resin in situ and performance of initial experiments on layered and complex heterogeneities. The work is currently following very closely the original schedule for research efforts. Continuing efforts in year one will include continued efforts in simple and complex heterogeneity in two-dimensions, extension into three-dimensions, consideration of the most appropriate methods for creating geologically realistic structures in the laboratory, interaction with other SSP research programs and organization of the spring meeting on intermediate-scale experimentation to be held at Notre Dame. Efforts in year two will be focused on three-dimensional experiments in saturated media, extension of results into unsaturated media, development of techniques for unsaturated media characterization, and development of research ties with outside research interests.
NASA Astrophysics Data System (ADS)
Mondal, P.; Krol, M.; Sleep, B. E.
2015-12-01
A wide variety of groundwater contaminants can be treated with nano-scale zero valent iron (nZVI). However, delivery of nZVI in the subsurface to the treatment zones is challenging as the bare nZVI particles have a higher tendency to agglomerate. The subsurface mobility of nZVI can be enhanced by stabilizing nZVI with polymer, such as carboxymethyl cellulose (CMC). In this study, numerical simulations were conducted to evaluate CMC stabilized nZVI transport behavior in porous media. The numerical simulations were based on a set of laboratory-scale transport experiments that were conducted in a two-dimensional water-saturated glass-walled sandbox (length - 55 cm; height - 45 cm; width - 1.4 cm), uniformly packed with silica sand. In the transport experiments: CMC stabilized nZVI and a non-reactive dye tracer Lissamine Green B (LGB) were used; water specific discharge and CMC concentration were varied; movements of LGB, and CMC-nZVI in the sandbox were tracked using a camera, a light source and a dark box. The concentrations of LGB, CMC, and CMC-nZVI at the sandbox outlet were analyzed. A 2D multiphase flow and transport model was applied to simulate experimental results. The images from LGB dye transport experiments were used to determine the pore water velocities and media permeabilities in various layers in the sand box. These permeability values were used in the subsequent simulations of CMC-nZVI transport. The 2D compositional simulator, modified to include colloid filtration theory (CFT), treated CMC as a solute and nZVI as a colloid. The simulator included composition dependent viscosity to account for CMC injection and mixing, and attachment efficiency as a fitting parameter for nZVI transport modeling. In the experiments, LGB and CMC recoveries were greater than 95%; however, CMC residence time was significantly higher than the LGB residence time and the higher CMC concentration caused higher pressure drops in the sandbox. The nZVI recovery was lower than 40
Structural optimization of porous media for fast and controlled capillary flows
NASA Astrophysics Data System (ADS)
Shou, Dahua; Fan, Jintu
2015-05-01
A general quantitative model of capillary flow in homogeneous porous media with varying cross-sectional sizes is presented. We optimize the porous structure for the minimization of the penetration time under global constraints. Programmable capillary flows with constant volumetric flow rate and linear evolution of flow distance to time are also obtained. The controlled innovative flow behaviors are derived based on a dynamic competition between capillary force and viscous resistance. A comparison of dynamic transport on the basis of the present design with Washburn's equation is presented. The regulation and maximization of flow velocity in porous materials is significant for a variety of applications including biomedical diagnostics, oil recovery, microfluidic transport, and water management of fabrics.
Horoshenkov, Kirill V; Khan, Amir; Bécot, François-Xavier; Jaouen, Luc; Sgard, Franck; Renault, Amélie; Amirouche, Nesrine; Pompoli, Francesco; Prodi, Nicola; Bonfiglio, Paolo; Pispola, Giulio; Asdrubali, Francesco; Hübelt, Jörn; Atalla, Noureddine; Amédin, Celse K; Lauriks, Walter; Boeckx, Laurens
2007-07-01
This paper reports the results of reproducibility experiments on the interlaboratory characterization of the acoustical properties of three types of consolidated porous media: granulated porous rubber, reticulated foam, and fiberglass. The measurements are conducted in several independent laboratories in Europe and North America. The studied acoustical characteristics are the surface complex acoustic impedance at normal incidence and plane wave absorption coefficient which are determined using the standard impedance tube method. The paper provides detailed procedures related to sample preparation and installation and it discusses the dispersion in the acoustical material property observed between individual material samples and laboratories. The importance of the boundary conditions, homogeneity of the porous material structure, and stability of the adopted signal processing method are highlighted.
NASA Astrophysics Data System (ADS)
Wang, J. X.; Jia, P. Y.; Wang, Y. S.; Jiang, L.
2010-03-01
In this article, using Gibson-Ashby constitutive model, we suggest a new method for numerical investigation of forced convection heat transfer in porous foam metal, and try to consolidate the study for mechanical property and that for thermal characteristic. By available experimental data, we simulated to two cases, namely as the transfer in porous media for diameter is 0.6 mm and porosity is 0.402, and for diameter is 1.6 mm and porosity is 0.462. The result, from our constitutive model for single forced convection heat transfer, corresponds well with the experimental data. As for pressure drop prediction in porous is in good agreement with experiment, and the error is only 5% to 10%, but for transfer is less accurate, the error is about 20%, which is acceptable in practice. So it is done that constitutive model is used to simulate the transfer property.
Martinez, M.J.; Hopkins, P.L.; Shadid, J.N.
1997-07-01
This document reports on the accomplishments of a laboratory-directed research and development (LDRD) project whose objective was to initiate a research program for developing a fundamental understanding of multiphase multicomponent subsurface transport in heterogeneous porous media and to develop parallel processing computational tools for numerical simulation of such problems. The main achievement of this project was the successful development of a general-purpose, unstructured grid, multiphase thermal simulator for subsurface transport in heterogeneous porous media implemented for use on massively parallel (MP) computers via message-passing and domain decomposition techniques. The numerical platform provides an excellent base for new and continuing project development in areas of current interest to SNL and the DOE complex including, subsurface nuclear waste disposal and cleanup, groundwater availability and contamination studies, fuel-spill transport for accident analysis, and DNAPL transport and remediation.
A model system to study the precipitation and migration of colloidal particles in porous media
Rosario, F. do; Louvisse, A.M.T.; Saraiva, S.M.; Gonzalez, G.; Oliveira, J.F. de
1996-07-15
Studies on the formation and migration of colloidal iron sulfide in porous media were carried out using consolidated artificial alumina-kaolin cores sintered at 1,500 C. The artificial alumina-kaolin cores were imbibed with a solution containing thioacetamide and ferrous ions and heated at 80 C to obtain the formation of FeS particles. Scanning electron micrographs showed particles less than 1 {micro}m in diameter and aggregates of different sizes covering the surface of the porous media. Core flooding experiments showed that the migration of the fine FeS particles reduced the permeability of core and the injection of surfactant solutions at constant salinity restored the original permeability after the production of the redispersed iron sulfide particles, in some cases. The problem is particularly relevant to filtration, pollution of underground water, soil erosion, and petroleum exploitation.
NASA Astrophysics Data System (ADS)
Paradelo, Marcos; Soto-Gómez, Diego; Pérez-Rodríguez, Paula; Pose-Juan, Eva; López-Periago, J. Eugenio
2014-03-01
The release and transport of active ingredients (AIs) from controlled-release formulations (CRFs) have potential to reduce groundwater pesticide pollution. These formulations have a major effect on the release rate and subsequent transport to groundwater. Therefore the influence of CRFs should be included in modeling non-point source pollution by pesticides. We propose a simplified approach that uses a phase transition equation coupled to the diffusion equation that describes the release rate of AIs from commercial CRFs in porous media; the parameters are as follows: a release coefficient, the solubility of the AI, and diffusion transport with decay. The model gives acceptable predictions of the pesticides release from commercial CRFs in diffusion cells filled with quartz sand. This approach can be used to study the dynamics of the CRF-porous media interaction. It also could be implemented in fate of agricultural chemical models to include the effect of CRFs.
Chen, C I; Reinsel, M A; Mueller, R F
1994-07-01
Microbial souring (H2S production) in porous media was investigated in an anaerobic upflow porous media reactor at 60 degrees C using microbial consortia obtained from oil reservoirs. Multiple carbon sources (formate, acetate, propionate, iso- and n-butyrates) found in reservoir waters as well as sulfate as the electron acceptor was used. Kinetics and rates of souring in the reactor system were analyzed. Higher volumetric substrate consumption rates (organic acids and sulfate) and a higher volumetric H(2)S production rate were found at the from part of the reactor column after H(2)S production had stabilized. Concentration gradients for the substrates (organic acids and sulfate) and H(2)S were generated along the column. Biomass accumulation throughout the entire column was observed. The average specific sulfate reduction rate (H(2)S production rate) in the present reactor after H(2)S production had stabilized was calculated to be 11062 +/-2.22 mg sulfate-S/day g biomass.
A Mixed Finite Volume Element Method for Flow Calculations in Porous Media
NASA Technical Reports Server (NTRS)
Jones, Jim E.
1996-01-01
A key ingredient in the simulation of flow in porous media is the accurate determination of the velocities that drive the flow. The large scale irregularities of the geology, such as faults, fractures, and layers suggest the use of irregular grids in the simulation. Work has been done in applying the finite volume element (FVE) methodology as developed by McCormick in conjunction with mixed methods which were developed by Raviart and Thomas. The resulting mixed finite volume element discretization scheme has the potential to generate more accurate solutions than standard approaches. The focus of this paper is on a multilevel algorithm for solving the discrete mixed FVE equations. The algorithm uses a standard cell centered finite difference scheme as the 'coarse' level and the more accurate mixed FVE scheme as the 'fine' level. The algorithm appears to have potential as a fast solver for large size simulations of flow in porous media.
FEMWASTE: a Finite-Element Model of Waste transport through porous saturated-unsaturated media
Yeh, G.T.; Ward, D.S.
1981-04-01
A two-dimensional transient model for the transport of dissolved constituents through porous media originally developed at Oak Ridge National Laboratory (ORNL) has been expanded and modified. Transport mechanisms include: convection, hydrodynamic dispersion, chemical sorption, and first-order decay. Implementation of quadrilateral iso-parametric finite elements, bilinear spatial interpolation, asymmetric weighting functions, several time-marching techniques, and Gaussian elimination are employed in the numerical formulation. A comparative example is included to demonstrate the difference between the new and original models. Results from 12 alternative numerical schemes of the new model are compared. The waste transport model is compatible with the water flow model developed at ORNL for predicting convective Darcy velocities in porous media which may be partially saturated.
Acoustic technique to monitor the kinetics of porous development phenomena in viscoelastic media
NASA Astrophysics Data System (ADS)
Nassar, G.; Skaf, A.; Saad, N.
2012-01-01
In this paper, the potential of a low frequency acoustic technique for the study and characterisation of viscoelastic porous media is investigated. This work was based on the limits of ultrasonic applications in highly absorbent porous media. In this context, fermenting dough was used as a model propagation medium. This type of product has a very complex matrix in terms of texture, openings and moisture. The basic theory of sound in such matter is recalled, especially the effects of the scattering of sound energy in matrices like that of the product under investigation. Depending on the properties of the openings, acoustic velocity and intensity of sound were chosen to represent the state of evolution of the matter. A tap-test acoustic technique was employed and allowed a quality indicator to be obtained. The results of the validation step using various technological parameters indicate that a high degree of sensitivity can be reached with non-destructive acoustic techniques.
Steady dissolution rate due to convective mixing in anisotropic porous media
NASA Astrophysics Data System (ADS)
Green, Christopher P.; Ennis-King, Jonathan
2014-11-01
Enhanced dissolution of CO2 into a saline aquifer due to convective mixing is an important physical process for the secure long-term storage of significant quantities of CO2. Numerical simulations have previously shown that the dissolution rate of CO2 into reservoir brine will stabilise after a certain time period, with only small oscillations about a long-term average. A theoretical estimate for this average long-term mass flux in an isotropic homogeneous reservoir has previously appeared in the literature. In this paper, an estimate for the steady dissolution rate in anisotropic homogenous porous media is developed using a simple theoretical argument. Detailed numerical simulations confirm that the steady dissolution rate scales as (kvkh) 1 / 2 in an anisotropic homogeneous porous media, where kv and kh are the vertical and horizontal permeabilities, respectively. The scaling is also shown to be appropriate for heterogeneous models where vertical heterogeneity is introduced by including a random distribution of impermeable barriers.
Advection Scheme for Phase-changing Porous Media Flow of Fluids with Large Density Ratio
NASA Astrophysics Data System (ADS)
Zhang, Duan; Padrino, Juan
2015-11-01
Many flows in a porous media involve phase changes between fluids with a large density ratio. For instance, in the water-steam phase change the density ratio is about 1000. These phase changes can be results of physical changes, or chemical reactions, such as fuel combustion in a porous media. Based on the mass conservation, the velocity ratio between the fluids is of the same order of the density ratio. As the result the controlling Courant number for the time step in a numerical simulation is determined by the high velocity and low density phase, leading to small time steps. In this work we introduce a numerical approximation to increase the time step by taking advantage of the large density ratio. We provide analytical error estimation for this approximate numerical scheme. Numerical examples show that using this approximation about 40-fold speedup can be achieved at the cost of a few percent error. Work partially supported by LDRD project of LANL.
Analysis of Porous Media as Inlet Concept for Rotating Detonation Engines
NASA Astrophysics Data System (ADS)
Grogan, Kevin; Ihme, Matthias; Department of Mechanical Engineering Team
2016-11-01
Rotating detonation engines combust reactive gas mixtures with a high-speed, annularly-propagating detonation wave, which provides many advantages including a stagnation pressure gain and a compact, lightweight design. However, the optimal design of the inlet to the combustion chamber inlet is a moot topic since improper design can significantly reduce detonability and increase pressure losses. The highly diffusive properties of porous media could make it an ideal material to prevent the flashback of the detonation wave and therefore, allow the inlet gas to be premixed. Motivated by this potential, this work employs simulation to evaluate the application of porous media to the inlet of a rotating detonation engine as a novel means to stabilize a detonation wave while reducing the pressure losses incurred by non-ideal mixing strategies. Department of the Air Force.
Lattice Boltzmann model for incompressible axisymmetric thermal flows through porous media
NASA Astrophysics Data System (ADS)
Grissa, Kods; Chaabane, Raoudha; Lataoui, Zied; Benselama, Adel; Bertin, Yves; Jemni, Abdelmajid
2016-10-01
The present work proposes a simple lattice Boltzmann model for incompressible axisymmetric thermal flows through porous media. By incorporating forces and source terms into the lattice Boltzmann equation, the incompressible Navier-Stokes equations are recovered through the Chapman-Enskog expansion. It is found that the added terms are just the extra terms in the governing equations for the axisymmetric thermal flows through porous media compared with the Navier-Stokes equations. Four numerical simulations are performed to validate this model. Good agreement is obtained between the present work and the analytic solutions and/or the results of previous studies. This proves its efficacy and simplicity regarding other methods. Also, this approach provides guidance for problems with more physical phenomena and complicated force forms.
Microbial Growth, Water Flow, and Solute Transport in Unsaturated Porous Media
NASA Astrophysics Data System (ADS)
Yarwood, R. R.; Rockhold, M. L.; Niemet, M. R.; Bottomley, P. J.; Selker, J. S.
2004-05-01
We present an investigation that studied interactions between microbial growth, water flow, and solute transport in variably saturated porous media. The experimental system provided for continuous, noninvasive observation of microbial activity, while simultaneously monitoring water content and solute flow paths in a two-dimensional porous matrix. The spatial and temporal development of microbial colonization by a Pseudomonas fluorescens bacterium was monitored by induction of a bioluminescent phenotype. A model was developed that allowed quantification of population density from bioluminescence measurements. Liquid saturation was quantified from the transmission of light through the system, and solute flow paths were determined with a dye tracer. Dramatic changes in microbial colonization were observed, including upward migration against flow. This migration was particularly interesting because it cannot be explained by passive transport. Bacterial growth and accumulation significantly impacted the hydrologic properties of the media, including apparent desaturation within the colonized region, diversion of flow around the colonized region, and lowering of the capillary fringe height.
Enhanced retention of bacteria by TiO2 nanoparticles in saturated porous media
NASA Astrophysics Data System (ADS)
Gentile, Guillermina J.; Fidalgo de Cortalezzi, María M.
2016-08-01
The simultaneous transport of TiO2 nanoparticles and bacteria Pseudomonas aeruginosa in saturated porous media was investigated. Nanoparticle and bacterium size and surface charge were measured as a function of electrolyte concentration. Sand column breakthrough curves were obtained for single and combined suspensions, at four different ionic strengths. DLVO and classical filtration theories were employed to model the interactions between particles and between particles and sand grains. Attachment of TiO2 to the sand was explained by electrostatic forces and these nanoparticles acted as bonds between the bacteria and the sand, leading to retention. Presence of TiO2 significantly increased the retention of bacteria in the sand bed, but microorganisms were released when nanomaterial influx ceased. The inclusion of nanomaterials in saturated porous media may have implications for the design and operation of sand filters in water treatment.
Hornung, R.D.
1996-12-31
An adaptive local mesh refinement (AMR) algorithm originally developed for unsteady gas dynamics is extended to multi-phase flow in porous media. Within the AMR framework, we combine specialized numerical methods to treat the different aspects of the partial differential equations. Multi-level iteration and domain decomposition techniques are incorporated to accommodate elliptic/parabolic behavior. High-resolution shock capturing schemes are used in the time integration of the hyperbolic mass conservation equations. When combined with AMR, these numerical schemes provide high resolution locally in a more efficient manner than if they were applied on a uniformly fine computational mesh. We will discuss the interplay of physical, mathematical, and numerical concerns in the application of adaptive mesh refinement to flow in porous media problems of practical interest.
An advective volume-balance model for flow in porous media
NASA Astrophysics Data System (ADS)
Malaga, Carlos; Mandujano, Francisco; Becerra, Julian
2016-11-01
Volume-balance models are used by petroleum engineers to simulate multiphase and multicomponent flow phenomena in porous media and the extraction process in oil reservoirs. In these models, mass conservation equations and Darcy's law are supplemented by a balance condition for the pore and fluid volumes. This provides a pressure equation suitable for simulating a compressible flow within a compressible solid matrix. Here we present an alternative interpretation of the volume-balance condition that includes the advective transport within a consolidated porous media. We obtain a modified equation for the time evolution of the pressure field. Preliminary numerical tests of phase separation due to gravity suggest the model reproduces qualitatively the physical phenomena. Fondo Sectorial CONACYT-SENER Grant Number 42536 (DGAJ-SPI-34-170412-217).
Cross-property relations for momentum and diffusional transport in porous media
NASA Astrophysics Data System (ADS)
Torquato, S.; Kim, In Chan
1992-10-01
Cross-property relations linking the fluid permeability k associated with viscous flow through a porous medium to effective diffusion properties of the medium have recently been derived. Torquato [Phys. Rev. Lett. 64, 2644 (1990)] found that k≤Dφ1τ, where τ is the ``mean survival time'' associated with steady-state diffusion of ``reactants'' in the fluid region of diffusion coefficient D and porosity φ1 of a porous medium containing absorbing walls (i.e., trap boundaries). Subsequently, Avellaneda and Torquato [Phys. Fluids A 3, 2529 (1991)] related k to the electrical formation factor F (inverse of the dimensionless effective electrical conductivity) and the principal (largest) diffusion relaxation time T1 associated with the time-dependent trapping problem, namely, k≤DT1/F. In this study, we compute the aforementioned bounds, using an efficient first-passage-time algorithm, for grain-consolidation models of porous media and compare them to exact results for these models. We also conjecture a new relation connecting k to τ and F for a wide class of porous media, namely, k≤Dτ/F, and show that it gives the sharpest permeability estimate among the existing bounds. The importance of this relation lies not only in its usefulness as an estimator of the permeability but that it involves the diffusional parameters τ and F which can be measured in situ.
Impact of biofilm on bacterial transport and deposition in porous media
NASA Astrophysics Data System (ADS)
Bozorg, Ali; Gates, Ian D.; Sen, Arindom
2015-12-01
Laboratory scale experiments were conducted to obtain insights into factors that influence bacterial transport and deposition in porous media. According to colloidal filtration theory, the removal efficiency of a filter medium is characterized by two main factors: collision efficiency and sticking efficiency. In the case of bacterial transport in porous media, bacteria attached to a solid surface can establish a thin layer of biofilm by excreting extracellular polymeric substances which can significantly influence both of these factors in a porous medium, and thus, affect the overall removal efficiency of the filter medium. However, such polymeric interactions in bacterial adhesion are not well understood and a method to calculate polymeric interactions is not yet available. Here, to determine how the migration of bacteria flowing within a porous medium is affected by the presence of surface-associated extracellular polymeric substances previously produced and deposited by the same bacterial species, a commonly used colloidal filtration model was applied to study transport and deposition of Pseudomonas fluorescens in small-scale columns packed with clean and biofilm coated glass beads. Bacterial recoveries were monitored in column effluents and used to quantify biofilm interactions and sticking efficiencies of the biofilm coated packed-beds. The results indicated that, under identical hydraulic conditions, the sticking efficiencies in packed-beds were improved consistently by 36% when covered by biofilm.
Influence of the Gas-Water Interface on Transport of Microorganisms through Unsaturated Porous Media
Wan, Jiamin; Wilson, John L.; Kieft, Thomas L.
1994-01-01
In this article, a new mechanism influencing the transport of microorganisms through unsaturated porous media is examined, and a new method for directly visualizing bacterial behavior within a porous medium under controlled chemical and flow conditions is introduced. Resting cells of hydrophilic and relatively hydrophobic bacterial strains isolated from groundwater were used as model microorganisms. The degree of hydrophobicity was determined by contact-angle measurements. Glass micromodels allowed the direct observation of bacterial behavior on a pore scale, and three types of sand columns with different gas saturations provided quantitative measurements of the observed phenomena on a porous medium scale. The reproducibility of each break-through curve was established in three to five repeated experiments. The data collected from the column experiments can be explained by phenomena directly observed in the micromodel experiments. The retention rate of bacteria is proportional to the gas saturation in porous media because of the preferential sorption of bacteria onto the gas-water interface over the solid-water interface. The degree of sorption is controlled mainly by cell surface hydrophobicity under the simulated groundwater conditions because of hydrophobic forces between the organisms and the interfaces. The sorption onto the gas-water interface is essentially irreversible because of capillary forces. This preferential and irreversible sorption at the gas-water interface strongly influences the movement and spatial distribution of microorganisms. Images PMID:16349180
NASA Astrophysics Data System (ADS)
Madeo, A.; Djeran-Maigre, I.; Rosi, G.; Silvani, C.
2013-03-01
In geomechanics, a relevant role is played by coupling phenomena between compressible fluid seepage flow and deformation of the solid matrix. The behavior of complex porous materials can be greatly influenced by such coupling phenomena. A satisfactorily theoretical framework for their description is not yet completely attained. In this paper, we discuss how the model developed in dell'Isola et al. (Int J Solids Struct 46:3150-3164, 2009) can describe how underground flows or, more generally, confined streams of fluid in deformable porous matrices affect compression wave propagation and their reflection and transmission at a solid-material discontinuity surface. Further work will investigate the effect of stream flow in porous media on shear waves, generalizing what done in Djeran Maigre and Kuznetsov (Comptes Rendus Mécanique 336(1-2):102-107, 2008) for shear waves in one-constituent orthotropic two-layered plates. The presented treatment shows that the presence of fluid streams considerably affect reflection and transmission phenomena in porous media.
NASA Astrophysics Data System (ADS)
Bakhshian, Sahar; Sahimi, Muhammad
2016-10-01
We report on the results of extensive computer simulation of the effect of deformation on the morphology of a porous medium and its fluid flow properties. The porous medium is represented by packings of spherical particles. Both random and regular as well as dense and nondense packings are used. A quasistatic model based on Hertz's contact theory is used to model the mechanical deformation of the packings, while the evolution of the permeability with the deformation is computed by the lattice-Boltzmann approach. The evolution of the pore-size and pore-length distributions, the porosity, the particles' contacts, the permeability, and the distribution of the stresses that the fluid exerts in the pore space are all studied in detail. The distribution of the pores' lengths, the porosity, and the particles' connectivity change strongly with the application of an external strain to the porous media, whereas the pore-size distribution is not affected as strongly. The permeability of the porous media strongly reduces even when the applied strain is small. When the permeabilities and porosities of the random packings are normalized with respect to their predeformation values, they all collapse onto a single curve, independent of the particle-size distribution. The porosity reduces as a power law with the external strain. The fluid stresses in the pore space follow roughly a log-normal distribution, both before and after deformation.
Network simulation of steady-state two-phase flow in consolidated porous media
Constantinides, G.N.; Payatakes, A.C.
1996-02-01
Multiphase flow in porous media is a complex process encountered in many fields of practical engineering interest, such as oil recovery from reservoir rocks, aquifer pollution by liquid wastes and soil reconstitution, and agricultural irrigation. A computer-aided simulator of steady-state two-phase flow in consolidated porous media is developed. The porous medium is modeled as a 3-D pore network of suitably shaped and randomly sized unit cells of the constricted-tube type. The problem of two-phase flow is solved using the network approach. The wetting phase saturation, the viscosity ratio, the capillary number, and the probability of coalescence between two colliding ganglia are changed systematically, where as the geometrical and topological characteristics of the porous medium and wettability (dynamic contact angles) are kept constant. In the range of the parameter values investigated, the flow behavior observed is ganglion population dynamics (intrinsically unsteady, but giving a time-averaged steady state). The mean ganglion size and fraction of the nonwetting phase in the form of stranded ganglia are studied as functions of the main dimensionless parameters. Fractional flows and relative permeabilities are determined and correlated with flow phenomena at pore level. Effects of the wetting phase saturation, the viscosity ratio, the capillary number, and the coalescence factor on relative permeabilities are examined.
Analytical and numerical investigations of spontaneous imbibition in porous media
NASA Astrophysics Data System (ADS)
Nooruddin, Hasan A.; Blunt, Martin J.
2016-09-01
We present semianalytical solutions for cocurrent displacements with some degree of countercurrent flow. The solution assumes a one-dimensional horizontal displacement of two immiscible incompressible fluids with arbitrary viscosities and saturation-dependent relative permeability and capillary pressures. We address the impact of the system length on the degree of countercurrent flow when there is no pressure drop in the nonwetting phase across the system, assuming negligible capillary back pressure at the inlet boundary of the system. It is shown that in such displacements, the fractional flow can be used to determine a critical water saturation, from which regions of both cocurrent and countercurrent flow are identified. This critical saturation changes with time as the saturation front moves into the porous medium. Furthermore, the saturation profile in the approach presented here is not necessarily a function of distance divided by the square root of time. We also present approximate solutions using a perturbative approach, which is valid for a wide range of flow conditions. This approach requires less computational power and is much easier to implement than the implicit integral solutions used in previous work. Finally, a comprehensive comparison between analytical and numerical solutions is presented. Numerical computations are performed using traditional finite-difference formulations and convergence analysis shows a generally slow convergence rate for water imbibition rates and saturation profiles. This suggests that most coarsely gridded simulations give a poor estimate of imbibition rates, while demonstrating the value of these analytical solutions as benchmarks for numerical studies, complementing Buckley-Leverett analysis.
Tartakovsky, Alexandre M.; Trask, Nathaniel; Pan, K.; Jones, Bruce D.; Pan, Wenxiao; Williams, John R.
2016-03-11
Smoothed Particle Hydrodynamics (SPH) is a Lagrangian method based on a meshless discretization of partial differential equations. In this review, we present SPH discretization of the Navier-Stokes and Advection-Diffusion-Reaction equations, implementation of various boundary conditions, and time integration of the SPH equations, and we discuss applications of the SPH method for modeling pore-scale multiphase flows and reactive transport in porous and fractured media.
NASA Astrophysics Data System (ADS)
Norouzi Rad, M.; Shokri, N.
2011-12-01
Understanding the physics of salt distribution in drying porous media is of relevance to various environmental and hydrological applications such as the soil salinization, terrestrial ecosystem functioning, microbiological activities in the vadose zone and structural damage to buildings, and historical monuments. Early stage of the evaporation process from saturated porous media is supplied by the capillary-induced liquid flow hydraulically connecting a receding drying front to surface (the so-called stage 1 evaporation). During stage 1, dissolved salt is transported by the capillary flow toward the evaporating surface where it accumulates, whereas diffusion (Brownian motion) tends to spread the salt and homogenize the concentrations in space. Relative humidity and ambient temperature limit the stage-1 evaporation and consequently influence the dynamics of salt distribution in porous media. The resulting interplay between convective and diffusive transport during evaporation is commonly quantified by the dimensionless Peclet number which is proportional to the evaporation rate. We have applied the convection-diffusion equation to describe the dynamics of salt distribution in drying porous media under different Peclet numbers. The predicted salt profiles were evaluated by a complete series of laboratory evaporation experiments using an environmental chamber where the relative humidity and temperature were accurately controlled. We have used sand with average particle size of 0.48 mm saturated with NaCl solution (1.25 Molal). The sand column was mounted on a digital balance connected to a computer to record the evaporation rate automatically. We studied dynamics of salt concentration at 30°C under relative humidity of 30%, 45% and 60% and also under the constant relative humidity of 45% at 30°C and 35°C . The experimentally-determined salt profiles were in a good agreement with the analytical and numerical predictions. Results revealed the preferential salt
Choi, H.; Lim, H-N; Kang, J-W; Hwang, T-M; Kim, J.; Environmental Research; Kwangju Inst. of Science and Technology; Yonsei Univ.
2002-07-01
Laboratory column experiments were conducted by employing various porous media to delineate the characteristics of gaseous ozone transport in the unsaturated zone under various conditions. Water content, soil organic matter (SOM), and metal oxides (MOs) were found to be the factors most influential in the fate and transport of gaseous ozone in unsaturated porous media. The migration velocity of the gaseous ozone front was inversely proportional to the MO content of the porous media. Increased water content at fixed gas flux decreased the ozone breakthrough time proportionally as a result of reduced gas pore volume (PV) in the column, and increased pore water interfered with reactions of gaseous ozone with SOM and MOs on the surface of porous media. The feasibility of in-situ ozone injection for the remediation of unsaturated soils contaminated with either phenanthrene or diesel-range organics (DROs) was investigated under various conditions. The maximum removal after 1 h of ozone injection was achieved in columns packed with baked sand, followed, in descending order, by glass beads and by sand, indicating that catalytic ozone decomposition with MOs in columns packed with baked sand enhanced hydroxyl radical formation and resulted in increased contaminant removal. Overall removal efficiency of multicomponent C{sub 10}-C{sub 24} DROs after 14 h of ozonation was 78.7%. Ozone transport was retarded considerably because of the high ozone demand of DROs, requiring more than 6 h for the gaseous ozone to initially break through the soil column under the experimental conditions tested in this study. Overall, gaseous ozone was readily delivered and transported to remediate unsaturated soils contaminated with phenanthrene and DROs.
Interplay between oxygen demand reactions and kinetic gas-water transfer in porous media.
Oswald, Sascha E; Griepentrog, Marco; Schirmer, Mario; Balcke, Gerd U
2008-08-01
Gas-water phase transfer associated with the dissolution of trapped gas in porous media is a key process that occurs during pulsed gas sparging operations in contaminated aquifers. Recently, we applied a numerical model that was experimentally validated for abiotic situations, where multi-species kinetic inter-phase mass transfer and dissolved gas transport occurred during pulsed gas penetration-dissolution events [Balcke, G.U., Meenken, S., Hoefer, C. and Oswald, S.E., 2007. Kinetic gas-water transfer and gas accumulation in porous media during pulsed oxygen sparging. Environmental Science & Technology 41(12), 4428-4434]. Here we extend the model by using a reactive term to describe dissolved oxygen demand reactions via the formation of a reaction product, and to study the effects of such an aerobic degradation process on gas-water mass transfer and dissolution of trapped gas in porous media. As a surrogate for microbial oxygen reduction, first-order oxygen demand reactions were based on the measured oxidation of alkaline pyrogallol in column experiments. This reaction allows for adjusting the rate to values close to expected biodegradation rates and detection of the reaction product. The experiments and model consistently demonstrated accelerated oxygen gas-water mass transfer with increasing oxygen demand rates associated with an influence on the partitioning of other gases. Thus, as the oxygen demand accelerates, less gas phase residues, consisting mainly of nitrogen, are observed, which is in general beneficial to the performance of field biosparging operations. Model results additionally predict how oxygen demand influences oxygen mass transfer for a range of biodegradation rates. A typical field case scenario was simulated to illustrate the observed coupling of oxygen consumption and gas bubble dissolution. The model provides a tool to improve understanding of trapped gas behavior in porous media and contributes to a model-assisted biosparging.
Pore-scale dynamics of salt transport and distribution in drying porous media
NASA Astrophysics Data System (ADS)
Shokri, Nima
2014-01-01
Understanding the physics of water evaporation from saline porous media is important in many natural and engineering applications such as durability of building materials and preservation of monuments, water quality, and mineral-fluid interactions. We applied synchrotron x-ray micro-tomography to investigate the pore-scale dynamics of dissolved salt distribution in a three dimensional drying saline porous media using a cylindrical plastic column (15 mm in height and 8 mm in diameter) packed with sand particles saturated with CaI2 solution (5% concentration by mass) with a spatial and temporal resolution of 12 μm and 30 min, respectively. Every time the drying sand column was set to be imaged, two different images were recorded using distinct synchrotron x-rays energies immediately above and below the K-edge value of Iodine. Taking the difference between pixel gray values enabled us to delineate the spatial and temporal distribution of CaI2 concentration at pore scale. Results indicate that during early stages of evaporation, air preferentially invades large pores at the surface while finer pores remain saturated and connected to the wet zone at bottom via capillary-induced liquid flow acting as evaporating spots. Consequently, the salt concentration increases preferentially in finer pores where evaporation occurs. Higher salt concentration was observed close to the evaporating surface indicating a convection-driven process. The obtained salt profiles were used to evaluate the numerical solution of the convection-diffusion equation (CDE). Results show that the macro-scale CDE could capture the overall trend of the measured salt profiles but fail to produce the exact slope of the profiles. Our results shed new insight on the physics of salt transport and its complex dynamics in drying porous media and establish synchrotron x-ray tomography as an effective tool to investigate the dynamics of salt transport in porous media at high spatial and temporal resolution.
Considerations for developing models of multiphase flow in deformable porous media.
Martinez, Mario J.; Stone, Charles Michael
2008-09-01
This document summarizes research and planning for the development of a numerical simulation capability for nonisothermal multiphase, multicomponent transport in heterogeneous deformable porous materials. Particular attention is given to describing a mathematical formulation for flow in deformable media and for numerical techniques for dealing with phase transitions. A development plan is formulated to provide a computational capability motivated by current and future needs in geosystems management for energy security.
A Pore-Network Model of In-Situ Combustion in Porous Media
Lu, Chuan; Yortsos, Y.C.
2001-01-29
This report the use of dual pore networks (pores and solid sites) for modeling the effect of the microstructure on combustion processes in porous media is considered. The model accounts for flow and transport of the gas phase in the porespace, where convection predominates, and for heat transfer by conduction in the solid phase. Gas phase flow in the pore and throats is governed by Darcy's law.
Pore-scale dynamics of salt transport and distribution in drying porous media
Shokri, Nima
2014-01-15
Understanding the physics of water evaporation from saline porous media is important in many natural and engineering applications such as durability of building materials and preservation of monuments, water quality, and mineral-fluid interactions. We applied synchrotron x-ray micro-tomography to investigate the pore-scale dynamics of dissolved salt distribution in a three dimensional drying saline porous media using a cylindrical plastic column (15 mm in height and 8 mm in diameter) packed with sand particles saturated with CaI{sub 2} solution (5% concentration by mass) with a spatial and temporal resolution of 12 μm and 30 min, respectively. Every time the drying sand column was set to be imaged, two different images were recorded using distinct synchrotron x-rays energies immediately above and below the K-edge value of Iodine. Taking the difference between pixel gray values enabled us to delineate the spatial and temporal distribution of CaI{sub 2} concentration at pore scale. Results indicate that during early stages of evaporation, air preferentially invades large pores at the surface while finer pores remain saturated and connected to the wet zone at bottom via capillary-induced liquid flow acting as evaporating spots. Consequently, the salt concentration increases preferentially in finer pores where evaporation occurs. Higher salt concentration was observed close to the evaporating surface indicating a convection-driven process. The obtained salt profiles were used to evaluate the numerical solution of the convection-diffusion equation (CDE). Results show that the macro-scale CDE could capture the overall trend of the measured salt profiles but fail to produce the exact slope of the profiles. Our results shed new insight on the physics of salt transport and its complex dynamics in drying porous media and establish synchrotron x-ray tomography as an effective tool to investigate the dynamics of salt transport in porous media at high spatial and temporal
An alternative smooth particle hydrodynamics formulation to simulate chemotaxis in porous media.
Avesani, Diego; Dumbser, Michael; Chiogna, Gabriele; Bellin, Alberto
2016-08-27
Chemotaxis, the microorganisms autonomous motility along or against the concentration gradients of a chemical species, is an important, yet often neglected factor controlling the transport of bacteria through saturated porous media. For example, chemotactic bacteria could enhance bioremediation by directing their own motion to residual contaminants trapped in low hydraulic conductive zones of contaminated aquifers. The aim of the present work is to develop an accurate numerical scheme to model chemotaxis in saturated porous media and other advective dominating flow systems. We propose to model chemotaxis by using a new class of meshless Lagrangian particle methods we recently developed for applications in fluid mechanics. The method is based on the Smooth Particle Hydrodynamics (SPH) formulation of (Ben Moussa et al., Int Ser Numer Math, 13(1):29-62, 2006), combined with a new Weighted Essentially Non-Oscillatory (WENO) reconstruction technique on moving point clouds in multiple space dimensions. The purpose of this new numerical scheme is to fully exploit the advantages of SPH among traditional mesh-based and mesh-free schemes and to overcome drawbacks related to the use of standard SPH for modeling chemotaxis in porous media. First, we test the new scheme against analytical reference solutions. Then, under the assumption of complete mixing at the Darcy scale, we perform two-dimensional conservative solute transport simulations under steady-state flow conditions, to show the capability of the proposed new scheme to model chemotaxis.
Study of Gas Flow Characteristics in Tight Porous Media with a Microscale Lattice Boltzmann Model
NASA Astrophysics Data System (ADS)
Zhao, Jianlin; Yao, Jun; Zhang, Min; Zhang, Lei; Yang, Yongfei; Sun, Hai; An, Senyou; Li, Aifen
2016-09-01
To investigate the gas flow characteristics in tight porous media, a microscale lattice Boltzmann (LB) model with the regularization procedure is firstly adopted to simulate gas flow in three-dimensional (3D) digital rocks. A shale digital rock and a sandstone digital rock are reconstructed to study the effects of pressure, temperature and pore size on microscale gas flow. The simulation results show that because of the microscale effect in tight porous media, the apparent permeability is always higher than the intrinsic permeability, and with the decrease of pressure or pore size, or with the increase of temperature, the difference between apparent permeability and intrinsic permeability increases. In addition, the Knudsen numbers under different conditions are calculated and the results show that gas flow characteristics in the digital rocks under different Knudsen numbers are quite different. With the increase of Knudsen number, gas flow in the digital rocks becomes more uniform and the effect of heterogeneity of the porous media on gas flow decreases. Finally, two commonly used apparent permeability calculation models are evaluated by the simulation results and the Klinkenberg model shows better accuracy. In addition, a better proportionality factor in Klinkenberg model is proposed according to the simulation results.
Effects of temperature on graphene oxide deposition and transport in saturated porous media.
Wang, Mei; Gao, Bin; Tang, Deshan; Sun, Huimin; Yin, Xianqiang; Yu, Congrong
2017-06-05
Laboratory batch sorption and sand column experiments were conducted to examine the effects of temperature (6 and 24°C) on the retention and transport of GO in water-saturated porous media with different combination of solution ionic strength (IS, 1 and 10mM), sand type (natural and acid-cleaned), and grain size (coarse and fine). Although results from batch sorption experiment showed that temperature affected the sorption of GO onto the sand grains at the low IS, the interactions between GO and the sand were relatively weak, which did make the temperature effect prominent. When the IS was 1mM, experimental temperature showed little effect on GO retention and transport regardless of the medium properties. GO was highly mobile in the sand columns with mass recovery rates ranged from 77.3% to 92.4%. When the IS increased to 10mM, temperature showed notable effects on GO retention and transport in saturated porous media. For all the combinations of sand type and grain size, the higher the temperature was, the less mobile GO particles were. The effects of temperature on GO retention and transport in saturated porous media were further verified though simulations from an advection-dispersion-reaction model.
Colloid release and transport processes in natural and model porous media
Roy, S.B.; Dzombak, D.A.
1995-12-01
Colloidal particles present in porous media may be released and transported over significant distances when contacted with water at low ionic strength. An understanding of this process is of environmental interest because suspended colloidal particles in groundwater may enhance the subsurface transport of contaminants that are sorbed on their surfaces. This research focused on the processes of colloid release and transport in natural porous media of interest in contaminant transport, i.e., high permeability materials with low fines contents. Our objective in this study was to examine the mechanisms of colloid release and transport in a natural sand, and two model systems: latex particles attached on glass beads, and kaolinite particles attached on glass beads. For the appropriate electrolyte conditions, the release of attached colloids from all three porous media was found to be substantial. The total amount of colloids released depended upon the electrolyte composition and concentration. Column effluent data could be described with an advective-dispersive transport equation for colloidal particles with first-order terms for colloid release and deposition rates, by changing the mass of colloids available for release at each electrolyte concentrations.
NASA Astrophysics Data System (ADS)
Perlin, Marc; Gose, James W.; Golovin, Kevin; Ceccio, Steven L.; Tuteja, Anish
2015-11-01
Super-hydrophobic (SH) materials have been used successfully to generate reduced skin-friction in laminar flows. Success in the laminar regime has led researchers to try SH materials in turbulent flows. More often than not, this has been unsuccessful at providing meaningful skin-friction drag reduction, and has even generated increased drag. This failure is frequently attributed to the wetting of an SH surface or equivalently the transition from the Cassie-Baxter to the Wenzel state. The result is fluid flow over an essentially roughened surface. In this investigation the researchers aim to perfuse small amounts of gas through porous media, including sintered and foam metals, to attain skin-friction drag reduction in a fully-developed turbulent channel flow. As air is perfused through porous media, the solid - liquid interaction at the interface transitions to a solid - liquid - gas interaction. This can result in an interface that functions similarly to SH materials. Controlled air perfusion that provides the necessary replenishment of lost gas at the interface might prevent wetting, and thus eliminate or reduce the effect of the roughness on the flow. This latter possibility is investigated by perfusing small amounts of gas through porous media with and without SH coatings. To quantify the effectiveness of this method, pressure drop is used to infer friction drag along the surface in a fully-developed turbulent channel flow. The authors recognize the support of ONR.
Behavior of CO2/water flow in porous media for CO2 geological storage.
Jiang, Lanlan; Yu, Minghao; Liu, Yu; Yang, Mingjun; Zhang, Yi; Xue, Ziqiu; Suekane, Tetsuya; Song, Yongchen
2017-04-01
A clear understanding of two-phase fluid flow properties in porous media is of importance to CO2 geological storage. The study visually measured the immiscible and miscible displacement of water by CO2 using MRI (magnetic resonance imaging), and investigated the factor influencing the displacement process in porous media which were filled with quartz glass beads. For immiscible displacement at slow flow rates, the MR signal intensity of images increased because of CO2 dissolution; before the dissolution phenomenon became inconspicuous at flow rate of 0.8mLmin(-1). For miscible displacement, the MR signal intensity decreased gradually independent of flow rates, because supercritical CO2 and water became miscible in the beginning of CO2 injection. CO2 channeling or fingering phenomena were more obviously observed with lower permeable porous media. Capillary force decreases with increasing particle size, which would increase permeability and allow CO2 and water to invade into small pore spaces more easily. The study also showed CO2 flow patterns were dominated by dimensionless capillary number, changing from capillary finger to stable flow. The relative permeability curve was calculated using Brooks-Corey model, while the results showed the relative permeability of CO2 slightly decreases with the increase of capillary number.
Measuring miscible fluid displacement in porous media with magnetic resonance imaging
NASA Astrophysics Data System (ADS)
Muir, Colleen E.; Petrov, Oleg V.; Romanenko, Konstantin V.; Balcom, Bruce J.
2014-03-01
The development of new quantitative magnetic resonance imaging (MRI) technologies open new opportunities for measurements of mass transport in porous media. The current work examines a simple miscible displacement process of H2O and D2O in porous media samples. Laboratory measurements of dispersion in porous media traditionally monitor the effluent intensity of an injected tracer. We employ MRI to obtain quantitative water saturation profiles, and to measure dispersion in rock core plugs. The saturation profiles are modeled with PHREEQC, a fluid transport modeling program. We demonstrate how independent magnetic resonance measurements can be employed to estimate three important input parameters for PHREEQC, mobile porosity, immobile porosity, and dispersivity. Bulk Carr Purcell Meiboom Gill (CPMG) T2 distribution measurements were undertaken to estimate mobile and immobile porosity. Bulk alternating-pulsed-gradient-stimulated-echo (APGSTE) measurements were undertaken to measure dispersivity. The imaging method employed, T2 mapping Spin Echo Single Point Imaging (SE-SPI), also provides information about the pore size distributions in the rock cores, and how the fluid occupancy of the pores changes during the displacement process.
Study of Displacement Efficiency and Flow Behavior of Foamed Gel in Non-Homogeneous Porous Media
Bai, Baojun; Wei, Mingzhen
2015-01-01
Field trials have demonstrated that foamed gel is a very cost-effective technology for profile modification and water shut-off. However, the mechanisms of profile modification and flow behavior of foamed gel in non-homogeneous porous media are not yet well understood. In order to investigate these mechanisms and the interactions between foamed gel and oil in porous media, coreflooding and pore-scale visualization waterflooding experiments were performed in the laboratory. The results of the coreflooding experiment in non-homogeneous porous media showed that the displacement efficiency improved by approximately 30% after injecting a 0.3 pore volume of foamed gel, and was proportional to the pore volumes of the injected foamed gel. Additionally, the mid-high permeability zone can be selectively plugged by foamed gel, and then oil located in the low permeability zone will be displaced. The visualization images demonstrated that the amoeba effect and Jamin effect are the main mechanisms for enhancing oil recovery by foamed gel. Compared with conventional gel, a unique benefit of foamed gel is that it can pass through micropores by transforming into arbitrary shapes without rupturing, this phenomenon has been named the amoeba effect. Additionally, the stability of foam in the presence of crude oil also was investigated. Image and statistical analysis showed that these foams boast excellent oil resistance and elasticity, which allows them to work deep within formations. PMID:26030282
Enhanced transport of Si-coated nanoscale zero-valent iron particles in porous media.
HonetschlÄgerová, Lenka; Janouškovcová, Petra; Kubal, Martin
2016-01-01
Laboratory column experiments were conducted to evaluate the effect of previously described silica coating method on the transport of nanoscale zero-valent iron (nZVI) in porous media. The silica coating method showed the potential to prevent the agglomeration of nZVI. Transport experiments were conducted using laboratory-scale sand-packed columns at conditions that were very similar of natural groundwater. Transport properties of non-coated and silica-coated nZVI are investigated in columns of 40 cm length, which were filled with porous media. A suspension was injected in three different Fe particle concentrations (100, 500, and 1000 mg/L) at flow 5 mL/min. Experimental results were compared using nanoparticle attachment efficiency and travel distances which were calculated by classical particle filtration theory. It was found that non-coated particles were essentially immobile in porous media. In contrast, silica-coated particles showed significant transport distances at the tested conditions. Results of this study suggest that silica can increase nZVI mobility in the subsurface.
Roth, Eric J; Gilbert, Benjamin; Mays, David C
2015-10-20
Experiments reveal a wide discrepancy between the permeability of porous media containing colloid deposits and the available predictive equations. Evidence suggests that this discrepancy results, in part, from the predictive equations failing to account for colloid deposit morphology. This article reports a series of experiments using static light scattering (SLS) to characterize colloid deposit morphology within refractive index matched (RIM) porous media during flow through a column. Real time measurements of permeability, specific deposit, deposit fractal dimension, and deposit radius of gyration, at different vertical positions, were conducted with initially clean porous media at various ionic strengths and fluid velocities. Decreased permeability (i.e., increased clogging) corresponded with higher specific deposit, lower fractal dimension, and smaller radius of gyration. During deposition, fractal dimension, radius of gyration, and permeability decreased with increasing specific deposit. During flushing with colloid-free fluid, these trends reversed, with increased fractal dimension, radius of gyration, and permeability. These observations suggest a deposition scenario in which large and uniform aggregates become deposits, which reduce porosity, lead to higher fluid shear forces, which then decompose the deposits, filling the pore space with small and dendritic fragments of aggregate.
The Role of Biofilms and Curli in Salmonella Transport Through Porous Media
NASA Astrophysics Data System (ADS)
Salvucci, A. E.; Zhang, W.; Morales, V. L.; Cakmak, M. E.; Hay, A. G.; Steenhuis, T. S.
2008-12-01
Microbial pathogens, such as Salmonella and E. coli, are continually deposited in the environment and have been shown to contaminate the groundwater by leaching through the vadose zone. Therefore, understanding the mechanisms controlling the transport of these microbial pathogens through porous media is critical to protecting drinking water supplies. As previous research has shown, retention of microbial pathogens in porous media can be influenced by numerous biological factors. Consequently, this experiment specifically investigated the role of biofilm formation and curli production on the transport of environmental Salmonella through porous media. Environmental Salmonella strains used in the experiment were isolated from tile drains on dairy farms. In addition, two well-characterized E. coli strains with known high and low biofilm and curli producing capabilities were tested as controls alongside the Salmonella isolates throughout the experiment. The isolates were first assayed for their ability to form biofilms and produce curli, and then a subset of these isolates, representing range of high and low biofilm and curli formation capabilities, were simultaneously examined for transport characteristics through packed sand columns. Transport characteristics were tested for correlation with biofilm and curli-forming capabilities. Unlike the E. coli strains in which column retention correlated with biofilm formation and curli production, no obvious correlation between Salmonella phenotypes was observed. The results indicate that while transport of well-characterized laboratory E. coli strains can often be hindered by the presence of curli and biofilms, such assumptions are not fully representative of the behavior exhibited by environmental isolates of Salmonella.
An Initial Non-Equilibrium Porous-Media Model for CFD Simulation of Stirling Regenerators
NASA Technical Reports Server (NTRS)
Tew, Roy C.; Simon, Terry; Gedeon, David; Ibrahim, Mounir; Rong, Wei
2006-01-01
The objective of this paper is to define empirical parameters for an initial thermal non-equilibrium porous-media model for use in Computational Fluid Dynamics (CFD) codes for simulation of Stirling regenerators. The two codes currently used at Glenn Research Center for Stirling modeling are Fluent and CFD-ACE. The codes porous-media models are equilibrium models, which assume solid matrix and fluid are in thermal equilibrium. This is believed to be a poor assumption for Stirling regenerators; Stirling 1-D regenerator models, used in Stirling design, use non-equilibrium regenerator models and suggest regenerator matrix and gas average temperatures can differ by several degrees at a given axial location and time during the cycle. Experimentally based information was used to define: hydrodynamic dispersion, permeability, inertial coefficient, fluid effective thermal conductivity, and fluid-solid heat transfer coefficient. Solid effective thermal conductivity was also estimated. Determination of model parameters was based on planned use in a CFD model of Infinia's Stirling Technology Demonstration Converter (TDC), which uses a random-fiber regenerator matrix. Emphasis is on use of available data to define empirical parameters needed in a thermal non-equilibrium porous media model for Stirling regenerator simulation. Such a model has not yet been implemented by the authors or their associates.
NASA Astrophysics Data System (ADS)
Chiogna, Gabriele; Herrera, Paulo
2015-04-01
Several studies have demonstrated how plume deformation induced by flow heterogeneity in porous media can enhance mixing of reactants. This enhancement can have important impact on mixing controlled reactions such a biodegradation of plumes of organic compounds. On the other hand, recent studies have indicated the possibility of observing complex flow topology on groundwater flow that occurs in anisotropic yet homogenous porous media. Moreover, it has been demonstrated that those complex flow topologies can also enhance solute mixing. We study the effect of medium anisotropy on reactive solute transport for the case of a chemical reactor composed of two homogeneous anisotropic layers. We simulate different injection strategies for different chemical reactions that involve two reactants. We demonstrate the effect of the medium anisotropy by analyzing the results of the simulations and identify best strategies for the operation and design of the system to maximize reaction rates. These findings could have potential application in the design of new remediation systems for contaminated groundwater, chemical reactors and other engineering problems that involve flow through porous media.
Study of Gas Flow Characteristics in Tight Porous Media with a Microscale Lattice Boltzmann Model
Zhao, Jianlin; Yao, Jun; Zhang, Min; Zhang, Lei; Yang, Yongfei; Sun, Hai; An, Senyou; Li, Aifen
2016-01-01
To investigate the gas flow characteristics in tight porous media, a microscale lattice Boltzmann (LB) model with the regularization procedure is firstly adopted to simulate gas flow in three-dimensional (3D) digital rocks. A shale digital rock and a sandstone digital rock are reconstructed to study the effects of pressure, temperature and pore size on microscale gas flow. The simulation results show that because of the microscale effect in tight porous media, the apparent permeability is always higher than the intrinsic permeability, and with the decrease of pressure or pore size, or with the increase of temperature, the difference between apparent permeability and intrinsic permeability increases. In addition, the Knudsen numbers under different conditions are calculated and the results show that gas flow characteristics in the digital rocks under different Knudsen numbers are quite different. With the increase of Knudsen number, gas flow in the digital rocks becomes more uniform and the effect of heterogeneity of the porous media on gas flow decreases. Finally, two commonly used apparent permeability calculation models are evaluated by the simulation results and the Klinkenberg model shows better accuracy. In addition, a better proportionality factor in Klinkenberg model is proposed according to the simulation results. PMID:27587293
Conceptual Design of a Condensing Heat Exchanger for Space Systems Using Porous Media
NASA Technical Reports Server (NTRS)
Hasan, Mohammad M.; Khan, Lutful I.; Nayagam, Vedha; Balasubramaniam, Ramaswamy
2006-01-01
Condensing heat exchangers are used in many space applications in the thermal and humidity control systems. In the International Space Station (ISS), humidity control is achieved by using a water cooled fin surface over which the moist air condenses, followed by "slurper bars" that take in both the condensate and air into a rotary separator and separates the water from air. The use of a cooled porous substrate as the condensing surface provides and attractive alternative that combines both heat removal as well as liquid/gas separation into a single unit. By selecting the pore sizes of the porous substrate a gravity independent operation may also be possible with this concept. Condensation of vapor into and on the porous surface from the flowing air and the removal of condensate from the porous substrate are the critical processes involved in the proposed concept. This paper describes some preliminary results of the proposed condensate withdrawal process and discusses the on-going design and development work of a porous media based condensing heat exchanger at the NASA Glenn Research Center in collaboration with NASA Johnson Space Center.
Microscale simulations of NMR relaxation in porous media
NASA Astrophysics Data System (ADS)
Mohnke, Oliver; Klitzsch, Norbert
2010-05-01
In petrophysical applications of nuclear magnetic resonance (NMR), the measured relaxation signals originate from the fluid filled pore space. Hence, in rocks or sediments the water content directly corresponds to the initial amplitude of the recorded NMR relaxation signals. The relaxation rate (longitudinal/transversal decay time T1, T2) is sensitive to pore sizes and physiochemical properties of rock-fluid interfaces (surface relaxivity), as well as the concentration of paramagnetic ions in the fluid phases (bulk relaxivity). In the subproject A2 of the TR32 we aim at improving the basic understanding of these processes at the pore scale and thereby advancing the interpretation of NMR data by reducing the application of restrictive approximated interpretation schemes, e.g. for deriving pore size distributions, connectivity or permeability. In this respect we numerically simulate NMR relaxation data at the micro sale to study the impact of physical and hydrological parameters such as internal field gradients or pore connectivities on NMR signals. Joint numerical simulations of the NMR relaxation behavior (Bloch equations) in the presence of internal gradients (Ampere's law) and fluid flow (Navier-Stokes) on a pore scale dimension have been implemented in a finite element (FE) model using Comsol Multiphysics. Processes governing the time and spatial behavior of the nuclear magnetization density in a porous medium are diffusion and surface interactions at the rock-fluid interface. Based on Fick's law of diffusive motion Brownstein and Tarr (1979) introduced differential equations that describe the relaxation behavior of the Spin magnetization in single isolated pores and derived analytical solutions for simple geometries, i.e. spherical, cylindrical and planar. However, by numerically solving these equ