An Amorphous Network Model for Capillary Flow and Dispersion in a Partially Saturated Porous Medium

Science.gov (United States)

Simmons, C. S.; Rockhold, M. L.

2013-12-01

Network models of capillary flow are commonly used to represent conduction of fluids at pore scales. Typically, a flow system is described by a regular geometric lattice of interconnected tubes. Tubes constitute the pore throats, while connection junctions (nodes) are pore bodies. Such conceptualization of the geometry, however, is questionable for the pore scale, where irregularity clearly prevails, although prior published models using a regular lattice have demonstrated successful descriptions of the flow in the bulk medium. Here a network is allowed to be amorphous, and is not subject to any particular lattice structure. Few network flow models have treated partially saturated or even multiphase conditions. The research trend is toward using capillary tubes with triangular or square cross sections that have corners and always retain some fluid by capillarity when drained. In contrast, this model uses only circular capillaries, whose filled state is controlled by a capillary pressure rule for the junctions. The rule determines which capillary participate in the flow under an imposed matric potential gradient during steady flow conditions. Poiseuille's Law and Laplace equation are used to describe flow and water retention in the capillary units of the model. A modified conjugate gradient solution for steady flow that tracks which capillary in an amorphous network contribute to fluid conduction was devised for partially saturated conditions. The model thus retains the features of classical capillary models for determining hydraulic flow properties under unsaturated conditions based on distribution of non-interacting tubes, but now accounts for flow exchange at junctions. Continuity of the flow balance at every junction is solved simultaneously. The effective water retention relationship and unsaturated permeability are evaluated for an extensive enough network to represent a small bulk sample of porous medium. The model is applied for both a hypothetically

Tracer transfer in consolidated porous medium and fractured porous medium: experimentations and modelling

International Nuclear Information System (INIS)

Dalla Costa, C.

2007-07-01

We try to identify and model physical and chemical mechanisms governing the water flow and the solute transport in fractured consolidated porous medium. An original experimental device was built. The 'cube' consists of an idealized fractured medium reproduced by piling up consolidated porous cubes of 5 cm edge. Meanwhile, columns of the homogeneous consolidated porous medium are studied. The same anionic tracing technique is used in both cases. Using a system analysis approach, we inject concentration pulses in the device to obtain breakthrough curves. After identifying the mass balance and the residence time, we fit the CD and the MIM models to the experimental data. The MIM model is able to reproduce experimental curves of the homogeneous consolidated porous medium better than the CD model. The mobile water fraction is in accordance with the porous medium geometry. The study of the flow rate influence highlights an interference dispersion regime. It was not possible to highlight the observation length influence in this case. On the contrary, we highlight the effect of the observation scale on the fractured and porous medium, comparing the results obtained on a small 'cube' and a big 'cube'. The CD model is not satisfactory in this case. Even if the MIM model can fit the experimental breakthrough curves, it was not possible to obtain unique parameters for the set of experiments. (author)

Numerical investigation of heat transfer in a laminar flow in a helical pipe filled with a fluid saturated porous medium: the sensitivity to parameter variations

International Nuclear Information System (INIS)

Cheng, L.; Kuznetsov, A.V.

2005-01-01

This paper presents the first attempt to investigate numerically heat transfer in a helical pipe filled with a fluid saturated porous medium; the analysis is based on the full momentum equation for porous media that accounts for the Brinkman and Forchheimer extensions of the Darcy law as well as for the flow inertia. Numerical computations are performed in an orthogonal helical coordinate system. The effects of the Darcy number, the Forchheimer coefficient as well as the Dean and Germano numbers on the axial flow velocity, secondary flow, temperature distribution, and the Nusselt number are investigated. (authors)

Numerical investigation of heat transfer in a laminar flow in a helical pipe filled with a fluid saturated porous medium: the sensitivity to parameter variations

Energy Technology Data Exchange (ETDEWEB)

Cheng, L.; Kuznetsov, A.V. [North Carolina State Univ., Raleigh, NC (United States). Dept. of Mechanical and Aerospace Engineering

2005-07-01

This paper presents the first attempt to investigate numerically heat transfer in a helical pipe filled with a fluid saturated porous medium; the analysis is based on the full momentum equation for porous media that accounts for the Brinkman and Forchheimer extensions of the Darcy law as well as for the flow inertia. Numerical computations are performed in an orthogonal helical coordinate system. The effects of the Darcy number, the Forchheimer coefficient as well as the Dean and Germano numbers on the axial flow velocity, secondary flow, temperature distribution, and the Nusselt number are investigated. (authors)

Configuration de piégeage dans un milieu poreux à saturation résiduelle en huile Configuration of Trapping in a Porous Medium with Residual Oil Saturation

Directory of Open Access Journals (Sweden)

Sylvestre L.

2006-11-01

ainsi, d'une part, situer le comportement du milieu poreux par rapport aux deux états de référence précédemment définis et d'autre part, nous avons pu estimer la fraction du volume poreux en écoulement, la composition des zones stagnantes et leur taille moyenne, en fonction de la saturation en huile. L'analyse critique de ces résultats nous permet de conclure que, si certains comportements sont vraisemblablement caractéristiques de notre mode opératoire expérimental et du milieu poreux étudié, la technique mise au point (traçage et interprétation par un modèle PDE pourrait être utilisée avec succès dans le cas de milieux poreux réels. This article analyzes the hydrodynamics and spatial distribution of liquid phases in a porous medium with residual oil saturation. Experiments were performed in a porous medium made up of glass beads piled up in a column. Water drive was used to achieve decane saturations of up to 30% pore volume. The sweep water was traced during each experiment by a dyestuff that was insoluble in oil. The distribution curves of the tracer residence time, obtained upon issuing from the medium, were analyzed by a chromatographic model of the piston-dispersion type with exchange (PDE. This model covers all the pores in which the sweeping phase is flowing as well as the stagnant sections containing trapped water and oil. In the first phase an analysis of equations led to a definition, in the form of adimensional variables, of the penetrability of the porous medium and of the time constants respectively characterizing flow in the mobile phase and diffusion in stagnant zones. An examination of the influence of these variables on the flows transferred led to a definition of the state of distribution equilibrium of the solute between the stagnant and mobile phases. Two reference situations were chosen: (i equilibrium almost reached, and (ii negligible penetration of stagnant zones. On these bases, correlations were established between the

A Conditionally Stable Scheme for a Transient Flow of a Non-Newtonian Fluid Saturating a Porous Medium

KAUST Repository

El-Amin, Mohamed

2012-06-02

The problem of thermal dispersion effects on unsteady free convection from an isothermal horizontal circular cylinder to a non-Newtonian fluid saturating a porous medium is examined numerically. The Darcy-Brinkman-Forchheimer model is employed to describe the flow field. The thermal diffusivity coefficient has been assumed to be the sum of the molecular diffusivity and the dynamic diffusivity due to mechanical dispersion. The simultaneous development of the momentum and thermal boundary layers are obtained by using finite difference method. The stability conditions are determined for each difference equation. Using an explicit finite difference scheme, solutions at each time-step have been found and then stepped forward in time until reaching steady state solution. Velocity and temperature profiles are shown graphically. It is found that as time approaches infinity, the values of friction factor and heat transfer coefficient approach the steady state values.

A Conditionally Stable Scheme for a Transient Flow of a Non-Newtonian Fluid Saturating a Porous Medium

KAUST Repository

El-Amin, Mohamed; Salama, Amgad; Sun, Shuyu

2012-01-01

The problem of thermal dispersion effects on unsteady free convection from an isothermal horizontal circular cylinder to a non-Newtonian fluid saturating a porous medium is examined numerically. The Darcy-Brinkman-Forchheimer model is employed to describe the flow field. The thermal diffusivity coefficient has been assumed to be the sum of the molecular diffusivity and the dynamic diffusivity due to mechanical dispersion. The simultaneous development of the momentum and thermal boundary layers are obtained by using finite difference method. The stability conditions are determined for each difference equation. Using an explicit finite difference scheme, solutions at each time-step have been found and then stepped forward in time until reaching steady state solution. Velocity and temperature profiles are shown graphically. It is found that as time approaches infinity, the values of friction factor and heat transfer coefficient approach the steady state values.

Radiative properties effects on unsteady natural convection inside a saturated porous medium. Application for porous heat exchangers

International Nuclear Information System (INIS)

Abdesslem, Jbara; Khalifa, Slimi; Abdelaziz, Nasr; Abdallah, Mhimid

2013-01-01

The present article deals with a numerical study of coupled fluid flow and heat transfer by transient natural convection and thermal radiation in a porous bed confined between two-vertical hot plates and saturated by a homogeneous and isotropic fluid phase. The main objective is to study the effects of radiative properties on fluid flow and heat transfer behavior inside the porous material. The numerical results show that the temperature, the axial velocity, the volumetric flow rate and the convective heat flux exchanged at the channel's exit are found to be increased when the particle emissivity (ε) and/or the absorption coefficient (κ) increase or when the scattering coefficient (σ s ) and/or the single scattering albedo (ω) decrease. Furthermore, the amount of heat (Q c ) transferred to fluid and the energetic efficiency E c are found to be increased when there is a raise in the particle emissivity values. In order to improve the performance of heat exchanger, we proposed the model of a porous heat exchanger which includes a porous bed of large spherical particles with high emissivity as a practical application of the current study. - Highlights: • The temperature increases with the particle emissivity ε. • The volumetric flow rate and the convective heat flux exchanged increase with the particle emissivity ε. • The amount of heat transferred to fluid and the energetic efficiency increase with the particle emissivity ε. • A heat exchanger including a porous bed of spherical particles with high emissivity is proposed like a practical application

Effective medium approximation for elastic constants of porous solids with microscopic heterogeneity

International Nuclear Information System (INIS)

Berryman, J.G.

1986-01-01

Formulas for the scattering from an inhomogeneous sphere in a fluid-saturated porous medium are used to construct a self-consistent effective medium approximation for the coefficients in Biot's equations of poroelasticity [J. Acoust. Soc. Am. 28, 168 (1956)] when the material constituting the porous solid frame is not homogeneous on the microscopic scale. The discussion is restricted to porous materials exhibiting both macroscopic and microscopic isotropy. Brown and Korringa [Geophysics 40, 608 (1975)] have previously found the general form of these coefficients. The present results give explicit estimates of all the coefficients in terms of the moduli of the solid constituents. The results are also shown to be completely consistent with the well-known results of Gassmann and of Biot and Willis, as well as those of Brown and Korringa

Microstructural effects on the overall poroelastic properties of saturated porous media

International Nuclear Information System (INIS)

Bouhlel, M; Jamei, M; Geindreau, C

2010-01-01

At the macroscopic scale, the quasi-static deformation of an elastic porous medium saturated by an incompressible Newtonian fluid is described by the well-known Biot's model, which involves four effective parameters. In this work, the three effective poroelastic properties and the permeability of two periodic microstructures of saturated cohesive granular media, i.e. simple cubic (SC) and body-centered cubic (BCC) arrays of overlapping spheres, are computed by solving, over the representative elementary volume, boundary-value problems arising from the homogenization process. The influence of microstructure properties, i.e. solid volume fraction, arrangement of spheres, number of contacts as well as the intrinsic properties of the solid phase on the overall properties, is highlighted. Numerical results are then compared with rigorous bounds, self-consistent estimations, exact expansions and experimental results on ceramics and metals available in the literature. Finally, the capability of the obtained results on such periodic microstructures to describe the poroelastic properties of real porous media is discussed

Analysis of the laminar Newtonian fluid flow through a thin fracture modelled as a fluid-saturated sparsely packed porous medium

Energy Technology Data Exchange (ETDEWEB)

Pazanin, Igor [Zagreb Univ. (Croatia). Dept. of Mathematics; Siddheshwar, Pradeep G. [Bangalore Univ., Bengaluru (India). Dept. of Mathematics

2017-06-01

In this article we investigate the fluid flow through a thin fracture modelled as a fluid-saturated porous medium. We assume that the fracture has constrictions and that the flow is governed by the prescribed pressure drop between the edges of the fracture. The problem is described by the Darcy-Lapwood-Brinkman model acknowledging the Brinkman extension of the Darcy law as well as the flow inertia. Using asymptotic analysis with respect to the thickness of the fracture, we derive the explicit higher-order approximation for the velocity distribution. We make an error analysis to comment on the order of accuracy of the method used and also to provide rigorous justification for the model.

Numerical simulation for a two-phase porous medium flow problem with rate independent hysteresis

KAUST Repository

Brokate, M.; Botkin, N.D.; Pykhteev, O.A.

2012-01-01

The paper is devoted to the numerical simulation of a multiphase flow in porous medium with a hysteretic relation between the capillary pressures and the saturations of the phases. The flow model we use is based on Darcys law. The hysteretic

Non-Darcy Mixed Convection in a Doubly Stratified Porous Medium with Soret-Dufour Effects

Directory of Open Access Journals (Sweden)

D. Srinivasacharya

2014-01-01

Full Text Available This paper presents the nonsimilarity solutions for mixed convection heat and mass transfer along a semi-infinite vertical plate embedded in a doubly stratified fluid saturated porous medium in the presence of Soret and Dufour effects. The flow in the porous medium is described by employing the Darcy-Forchheimer based model. The nonlinear governing equations and their associated boundary conditions are initially cast into dimensionless forms and then solved numerically. The influence of pertinent parameters on dimensionless velocity, temperature, concentration, heat, and mass transfer in terms of the local Nusselt and Sherwood numbers is discussed and presented graphically.

Hydrocarbons biodegradation in unsaturated porous medium

International Nuclear Information System (INIS)

Gautier, C.

2007-12-01

Biological processes are expected to play an important role in the degradation of petroleum hydrocarbons in contaminated soils. However, factors influencing the kinetics of biodegradation are still not well known, especially in the unsaturated zone. To address these biodegradation questions in the unsaturated zone an innovative experimental set up based on a physical column model was developed. This experimental set up appeared to be an excellent tool for elaboration of a structured porous medium, with well defined porous network and adjusted water/oil saturations. Homogeneous repartition of both liquid phases (i.e., aqueous and non aqueous) in the soil pores, which also contain air, was achieved using ceramic membranes placed at the bottom of the soil column. Reproducible interfaces (and connectivity) are developed between gas, and both non mobile water and NAPL phases, depending on the above-defined characteristics of the porous media and on the partial saturations of these three phases (NAPL, water and gas). A respirometric apparatus was coupled to the column. Such experimental set up have been validated with hexadecane in dilution in an HMN phase. This approach allowed detailed information concerning n-hexadecane biodegradation, in aerobic condition, through the profile of the oxygen consumption rate. We have taken benefit of this technique, varying experimental conditions, to determine the main parameters influencing the biodegradation kinetics and compositional evolution of hydrocarbons, under steady state unsaturated conditions and with respect to aerobic metabolism. Impacts of the nitrogen quantity and of three different grain sizes have been examined. Biodegradation of petroleum cut, as diesel cut and middle distillate without aromatic fraction, were, also studied. (author)

Experimental study of mass boiling in a porous medium model

International Nuclear Information System (INIS)

Sapin, Paul

2014-01-01

This manuscript presents a pore-scale experimental study of convective boiling heat transfer in a two-dimensional porous medium. The purpose is to deepen the understanding of thermohydraulics of porous media saturated with multiple fluid phases, in order to enhance management of severe accidents in nuclear reactors. Indeed, following a long-lasting failure in the cooling system of a pressurized water reactor (PWR) or a boiling water reactor (BWR) and despite the lowering of the control rods that stops the fission reaction, residual power due to radioactive decay keeps heating up the core. This induces water evaporation, which leads to the drying and degradation of the fuel rods. The resulting hot debris bed, comparable to a porous heat-generating medium, can be cooled down by reflooding, provided a water source is available. This process involves intense boiling mechanisms that must be modelled properly. The experimental study of boiling in porous media presented in this thesis focuses on the influence of different pore-scale boiling regimes on local heat transfer. The experimental setup is a model porous medium made of a bundle of heating cylinders randomly placed between two ceramic plates, one of which is transparent. Each cylinder is a resistance temperature detector (RTD) used to give temperature measurements as well as heat generation. Thermal measurements and high-speed image acquisition allow the effective heat exchanges to be characterized according to the observed local boiling regimes. This provides precious indications precious indications for the type of correlations used in the non-equilibrium macroscopic model used to model reflooding process. (author) [fr

On natural convection in enclosures filled with fluid-saturated porous media including viscous dissipation

Energy Technology Data Exchange (ETDEWEB)

Costa, V.A.F. [Departamento de Engenharia Mecanica, Universidade de Aveiro, Campus Universitario de Santiago, 3810-193 Aveiro (Portugal)

2006-07-15

Care needs to be taken when considering the viscous dissipation in the energy conservation formulation of the natural convection problem in fluid-saturated porous media. The unique energy formulation compatible with the First Law of Thermodynamics informs us that if the viscous dissipation term is taken into account, also the work of pressure forces term needs to be taken into account. In integral terms, the work of pressure forces must equal the energy dissipated by viscous effects, and the net energy generation in the overall domain must be zero. If only the (positive) viscous dissipation term is considered in the energy conservation equation, the domain behaves as a heat multiplier, with an heat output greater than the heat input. Only the energy formulation consistent with the First Law of Thermodynamics leads to the correct flow and temperature fields, as well as of the heat transfer parameters characterizing the involved porous device. Attention is given to the natural convection problem in a square enclosure filled with a fluid-saturated porous medium, using the Darcy Law to describe the fluid flow, but the main ideas and conclusions apply equally for any general natural or mixed convection heat transfer problem. It is also analyzed the validity of the Oberbeck-Boussinesq approximation when applied to natural convection problems in fluid-saturated porous media. (author)

Stability Analysis and Internal Heating Effect on Oscillatory Convection in a Viscoelastic Fluid Saturated Porous Medium Under Gravity Modulation

Science.gov (United States)

Bhadauria, B. S.; Singh, M. K.; Singh, A.; Singh, B. K.; Kiran, P.

2016-12-01

In this paper, we investigate the combined effect of internal heating and time periodic gravity modulation in a viscoelastic fluid saturated porous medium by reducing the problem into a complex non-autonomous Ginzgburg-Landau equation. Weak nonlinear stability analysis has been performed by using power series expansion in terms of the amplitude of gravity modulation, which is assumed to be small. The Nusselt number is obtained in terms of the amplitude for oscillatory mode of convection. The influence of viscoelastic parameters on heat transfer has been discussed. Gravity modulation is found to have a destabilizing effect at low frequencies and a stabilizing effect at high frequencies. Finally, it is found that overstability advances the onset of convection, more with internal heating. The conditions for which the complex Ginzgburg-Landau equation undergoes Hopf bifurcation and the amplitude equation undergoes supercritical pitchfork bifurcation are studied.

Hydromagnetic Flow and Heat Transfer over a Porous Oscillating Stretching Surface in a Viscoelastic Fluid with Porous Medium.

Science.gov (United States)

Khan, Sami Ullah; Ali, Nasir; Abbas, Zaheer

2015-01-01

An analysis is carried out to study the heat transfer in unsteady two-dimensional boundary layer flow of a magnetohydrodynamics (MHD) second grade fluid over a porous oscillating stretching surface embedded in porous medium. The flow is induced due to infinite elastic sheet which is stretched periodically. With the help of dimensionless variables, the governing flow equations are reduced to a system of non-linear partial differential equations. This system has been solved numerically using the finite difference scheme, in which a coordinate transformation is used to transform the semi-infinite physical space to a bounded computational domain. The influence of the involved parameters on the flow, the temperature distribution, the skin-friction coefficient and the local Nusselt number is shown and discussed in detail. The study reveals that an oscillatory sheet embedded in a fluid-saturated porous medium generates oscillatory motion in the fluid. The amplitude and phase of oscillations depends on the rheology of the fluid as well as on the other parameters coming through imposed boundary conditions, inclusion of body force term and permeability of the porous medium. It is found that amplitude of flow velocity increases with increasing viscoelastic and mass suction/injection parameters. However, it decreases with increasing the strength of the applied magnetic field. Moreover, the temperature of fluid is a decreasing function of viscoelastic parameter, mass suction/injection parameter and Prandtl number.

Borehole guided waves in a non-Newtonian (Maxwell) fluid-saturated porous medium

International Nuclear Information System (INIS)

Zhi-Wen, Cui; Jin-Xia, Liu; Ke-Xie, Wang; Gui-Jin, Yao

2010-01-01

The property of acoustic guided waves generated in a fluid-filled borehole surrounded by a non-Newtonian (Maxwell) fluid-saturated porous formation with a permeable wall is investigated. The influence of non-Newtonian effects on acoustic guided waves such as Stoneley waves, pseudo-Rayleigh waves, flexural waves, and screw waves propagations in a fluid-filled borehole is demonstrated based on the generalized Biot–Tsiklauri model by calculating their velocity dispersion and attenuation coefficients. The corresponding acoustic waveforms illustrate their properties in time domain. The results are also compared with those based on generalized Biot's theory. The results show that the influence of non-Newtonian effect on acoustic guided wave, especially on the attenuation coefficient of guided wave propagation in borehole is noticeable. (classical areas of phenomenology)

Stability Analysis and Internal Heating Effect on Oscillatory Convection in a Viscoelastic Fluid Saturated Porous Medium Under Gravity Modulation

Directory of Open Access Journals (Sweden)

Bhadauria B.S.

2016-12-01

Full Text Available In this paper, we investigate the combined effect of internal heating and time periodic gravity modulation in a viscoelastic fluid saturated porous medium by reducing the problem into a complex non-autonomous Ginzgburg-Landau equation. Weak nonlinear stability analysis has been performed by using power series expansion in terms of the amplitude of gravity modulation, which is assumed to be small. The Nusselt number is obtained in terms of the amplitude for oscillatory mode of convection. The influence of viscoelastic parameters on heat transfer has been discussed. Gravity modulation is found to have a destabilizing effect at low frequencies and a stabilizing effect at high frequencies. Finally, it is found that overstability advances the onset of convection, more with internal heating. The conditions for which the complex Ginzgburg-Landau equation undergoes Hopf bifurcation and the amplitude equation undergoes supercritical pitchfork bifurcation are studied.

Numerical simulation for a two-phase porous medium flow problem with rate independent hysteresis

International Nuclear Information System (INIS)

Brokate, M.; Botkin, N.D.; Pykhteev, O.A.

2012-01-01

The paper is devoted to the numerical simulation of a multiphase flow in porous medium with a hysteretic relation between the capillary pressures and the saturations of the phases. The flow model we use is based on Darcy's law. The hysteretic relation between the capillary pressures and the saturations is described by a play-type hysteresis operator. We propose a numerical algorithm for treating the arising system of equations, discuss finite element schemes and present simulation results for the case of two phases.

Film condensation on a porous vertical surface in a porous media

International Nuclear Information System (INIS)

Ebinuma, C.D.; Liu, C.Y.; Ismail, K.A.R.

1983-01-01

The problem of dry saturated steam film condensation by natural convection on a porous surface in a porous medium is presented. Through the classical Darcy law for flow in porous medium and the approximations considered in the Boundary layer theory, it is shown that the analytical solution exists only when the normal velocity to the porous wall is inversly proportional to the square root of the distance along the plate. (E.G.) [pt

Benchmarking variable-density flow in saturated and unsaturated porous media

Science.gov (United States)

Guevara Morel, Carlos Roberto; Cremer, Clemens; Graf, Thomas

2015-04-01

In natural environments, fluid density and viscosity can be affected by spatial and temporal variations of solute concentration and/or temperature. These variations can occur, for example, due to salt water intrusion in coastal aquifers, leachate infiltration from waste disposal sites and upconing of saline water from deep aquifers. As a consequence, potentially unstable situations may exist in which a dense fluid overlies a less dense fluid. This situation can produce instabilities that manifest as dense plume fingers that move vertically downwards counterbalanced by vertical upwards flow of the less dense fluid. Resulting free convection increases solute transport rates over large distances and times relative to constant-density flow. Therefore, the understanding of free convection is relevant for the protection of freshwater aquifer systems. The results from a laboratory experiment of saturated and unsaturated variable-density flow and solute transport (Simmons et al., Transp. Porous Medium, 2002) are used as the physical basis to define a mathematical benchmark. The HydroGeoSphere code coupled with PEST are used to estimate the optimal parameter set capable of reproducing the physical model. A grid convergency analysis (in space and time) is also undertaken in order to obtain the adequate spatial and temporal discretizations. The new mathematical benchmark is useful for model comparison and testing of variable-density variably saturated flow in porous media.

Uniqueness of specific interfacial area-capillary pressure-saturation relationship under non-equilibrium conditions in two-phase porous media flow

NARCIS (Netherlands)

Joekar-Niasar, V.; Hassanizadeh, S.M.

2012-01-01

The capillary pressure–saturation (P c–S w) relationship is one of the central constitutive relationships used in two-phase flow simulations. There are two major concerns regarding this relation. These concerns are partially studied in a hypothetical porous medium using a dynamic pore-network model

Numerical simulation for a two-phase porous medium flow problem with rate independent hysteresis

KAUST Repository

Brokate, M.

2012-05-01

The paper is devoted to the numerical simulation of a multiphase flow in porous medium with a hysteretic relation between the capillary pressures and the saturations of the phases. The flow model we use is based on Darcys law. The hysteretic relation between the capillary pressures and the saturations is described by a play-type hysteresis operator. We propose a numerical algorithm for treating the arising system of equations, discuss finite element schemes and present simulation results for the case of two phases. © 2011 Elsevier B.V. All rights reserved.

Fem Formulation of Heat Transfer in Cylindrical Porous Medium

Science.gov (United States)

Azeem; Khaleed, H. M. T.; Soudagar, Manzoor Elahi M.

2017-08-01

Heat transfer in porous medium can be derived from the fundamental laws of flow in porous region ass given by Henry Darcy. The fluid flow and energy transport inside the porous medium can be described with the help of momentum and energy equations. The heat transfer in cylindrical porous medium differs from its counterpart in radial and axial coordinates. The present work is focused to discuss the finite element formulation of heat transfer in cylindrical porous medium. The basic partial differential equations are derived using Darcy law which is the converted into a set of algebraic equations with the help of finite element method. The resulting equations are solved by matrix method for two solution variables involved in the coupled equations.

Combined effect of thermal dispersion and variable viscosity of non-darcy convection heat transfer in a fluidsaturated porous medium

KAUST Repository

El-Amin, Mohamed; Salama, Amgad; El-Amin, Ammaarah A.; Gorla, Rama Subba Reddy

2013-01-01

In this paper, the effects of thermal dispersion and variable viscosity on the non-Darcy free, mixed, and forced convection heat transfer along a vertical flat plate embedded in a fluid-saturated porous medium are investigated. Forchheimer extension

Natural convection in square cavity filled with ferrofluid saturated porous medium in the presence of uniform magnetic field

Energy Technology Data Exchange (ETDEWEB)

Javed, Tariq [Department of Mathematics and Statistics, FBAS, International Islamic University, Islamabad 44000 (Pakistan); Mehmood, Z., E-mail: rajaziafat@yahoo.com [Department of Mathematics and Statistics, FBAS, International Islamic University, Islamabad 44000 (Pakistan); Abbas, Z. [Department of Mathematics, The Islamia University, Bahawalpur (Pakistan)

2017-02-01

This article contains numerical results for free convection through square enclosure enclosing ferrofluid saturated porous medium when uniform magnetic field is applied upon the flow along x-axis. Heat is provided through bottom wall and a square blockage placed near left or right bottom corner of enclosure as a heat source. Left and right vertical boundaries of the cavity are considered insulated while upper wall is taken cold. The problem is modelled in terms of system of nonlinear partial differential equations. Finite element method has been adopted to compute numerical simulations of mathematical problem for wide range of pertinent flow parameters including Rayleigh number, Hartman number, Darcy number and Prandtl number. Analysis of results reveals that the strength of streamline circulation is an increasing function of Darcy and Prandtl number where convection heat transfer is dominant for large values of these parameters whereas increase in Hartman number has opposite effects on isotherms and streamline circulations. Thermal conductivity and hence local heat transfer rate of fluid gets increased when ferroparticles are introduced in the fluid. Average Nusselt number increases with increase in Darcy and Rayleigh numbers while it is decreases when Hartman number is increased.

Natural convection in square cavity filled with ferrofluid saturated porous medium in the presence of uniform magnetic field

International Nuclear Information System (INIS)

Javed, Tariq; Mehmood, Z.; Abbas, Z.

2017-01-01

This article contains numerical results for free convection through square enclosure enclosing ferrofluid saturated porous medium when uniform magnetic field is applied upon the flow along x-axis. Heat is provided through bottom wall and a square blockage placed near left or right bottom corner of enclosure as a heat source. Left and right vertical boundaries of the cavity are considered insulated while upper wall is taken cold. The problem is modelled in terms of system of nonlinear partial differential equations. Finite element method has been adopted to compute numerical simulations of mathematical problem for wide range of pertinent flow parameters including Rayleigh number, Hartman number, Darcy number and Prandtl number. Analysis of results reveals that the strength of streamline circulation is an increasing function of Darcy and Prandtl number where convection heat transfer is dominant for large values of these parameters whereas increase in Hartman number has opposite effects on isotherms and streamline circulations. Thermal conductivity and hence local heat transfer rate of fluid gets increased when ferroparticles are introduced in the fluid. Average Nusselt number increases with increase in Darcy and Rayleigh numbers while it is decreases when Hartman number is increased.

On the Onset of Thermal Convection in a Layer of Oldroydian Visco-Elastic Fluid Saturated by Brinkman–Darcy Porous Medium

Directory of Open Access Journals (Sweden)

Chand Ramesh

2015-12-01

Full Text Available Thermal instability in a horizontal layer of Oldroydian visco-elastic fluid in a porous medium is investigated. For porous medium the Brinkman–Darcy model is considered. A linear stability analysis based upon perturbation method and normal mode technique is used to find solution of the fluid layer confined between two free-free boundaries. The onset criterion for stationary and oscillatory convection is derived analytically. The influence of the Brinkman–Darcy, Prandtl–Darcy number, stress relaxation parameter on the stationary and oscillatory convection is studied both analytically and graphically. The sufficient condition for the validity of PES has also been derived.

NUMERICAL STUDY OF NON-DARCIAN NATURAL CONVECTION HEAT TRANSFER IN A RECTANGULAR ENCLOSURE FILLED WITH POROUS MEDIUM SATURATED WITH VISCOUS FLUID

Directory of Open Access Journals (Sweden)

Mahmood H. Ali

2015-02-01

Full Text Available A numerical study of non-Darcian natural convection heat transfer in a rectangular enclosure filled with porous medium saturated with viscous fluid was carried out. The effects of medium Rayleigh number, porosity, particle to fluid thermal conductivity ratio, Darcy number and enclosure aspect ratio on heat transfer were examined to demonstrate the ability of using this construction in thermal insulation of buildings walls.A modified Brinkman-Forchheimer-extended Darcy flow model was used and no-slip boundary conditions were imposed for velocity at the walls and the governing equations were expressed in dimensionless stream function, vorticity, and temperature formulation. The resulting algebraic equations obtained from finite difference discritization of vorticity and temperature equations are solved using (ADI method which uses Three Diagonal Matrix Algorithm (TDMA in each direction, while that of the stream function equation solved using successive iteration method.The study was done for the range of enclosure aspect ratio ( which is in the tall layers region at medium Rayleigh number ( , Darcy number (Da=10-3, 10-4, 10-5 , porosity (e=0.35, 0.45, 0.55, particle to fluid thermal conductivity (kS/kf=5.77, 38.5, 1385.5.The results showed that the Nusselt number is direct proportional to medium Rayleigh number and porosity and reversely proportional to Darcy number, ratio of particle to fluid thermal conductivity and enclosure aspect ratio. The variables that affect the heat transfer in the above arrangement was correlated in a mathematical equation that account better for their affects on heat transfer which is represented by mean Nusselt number (Nu.

Scaling behavior of microbubbles rising in water-saturated porous media

Science.gov (United States)

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

Reflection of processes of non-equilibrium two-phase filtration in oil-saturated hierarchical medium in data of active wave geophysical monitoring

Science.gov (United States)

Hachay, Olga; Khachay, Andrey; Khachay, Oleg

2016-04-01

The processes of oil extraction from deposit are linked with the movement of multi-phase multi-component media, which are characterized by non-equilibrium and non-linear rheological features. The real behavior of layered systems is defined by the complexity of the rheology of moving fluids and the morphology structure of the porous medium, and also by the great variety of interactions between the fluid and the porous medium [Hasanov and Bulgakova, 2003]. It is necessary to take into account these features in order to informatively describe the filtration processes due to the non-linearity, non-equilibrium and heterogeneity that are features of real systems. In this way, new synergetic events can be revealed (namely, a loss of stability when oscillations occur, and the formation of ordered structures). This allows us to suggest new methods for the control and management of complicated natural systems that are constructed on account of these phenomena. Thus the layered system, from which it is necessary to extract the oil, is a complicated dynamical hierarchical system. A comparison is provided of non-equilibrium effects of the influence of independent hydrodynamic and electromagnetic induction on an oil layer and the medium which it surrounds. It is known that by drainage and steeping the hysteresis effect on curves of the relative phase permeability in dependence on the porous medium's water saturation in some cycles of influence (drainage-steep-drainage) is observed. Using the earlier developed 3D method of induction electromagnetic frequency geometric monitoring, we showed the possibility of defining the physical and structural features of a hierarchical oil layer structure and estimating the water saturation from crack inclusions. This effect allows managing the process of drainage and steeping the oil out of the layer by water displacement. An algorithm was constructed for 2D modeling of sound diffraction on a porous fluid-saturated intrusion of a hierarchical

Development of finite element code for the analysis of coupled thermo-hydro-mechanical behaviors of saturated-unsaturated medium

International Nuclear Information System (INIS)

Ohnishi, Y.; Shibata, H.; Kobayashi, A.

1985-01-01

A model is presented which describes fully coupled thermo-hydro-mechanical behavior of porous geologic medium. The mathematical formulation for the model utilizes the Biot theory for the consolidation and the energy balance equation. The medium is in the condition of saturated-unsaturated flow, then the free surfaces are taken into consideration in the model. The model, incorporated in a finite element numerical procedure, was implemented in a two-dimensional computer code. The code was developed under the assumptions that the medium is poro-elastic and in plane strain condition; water in the ground does not change its phase; heat is transferred by conductive and convective flow. Analytical solutions pertaining to consolidation theory for soils and rocks, thermoelasticity for solids and hydrothermal convection theory provided verification of stress and fluid flow couplings, respectively in the coupled model. Several types of problems are analyzed. The one is a study of some of the effects of completely coupled thermo-hydro-mechanical behavior on the response of a saturated-unsaturated porous rock containing a buried heat source. Excavation of an underground opening which has radioactive wastes at elevated temperatures is modeled and analyzed. The results shows that the coupling phenomena can be estimated at some degree by the numerical procedure. The computer code has a powerful ability to analyze of the repository the complex nature of the repository

A coupled deformation-diffusion theory for fluid-saturated porous solids

Science.gov (United States)

Henann, David; Kamrin, Ken; Anand, Lallit

2012-02-01

Fluid-saturated porous materials are important in several familiar applications, such as the response of soils in geomechanics, food processing, pharmaceuticals, and the biomechanics of living bone tissue. An appropriate constitutive theory describing the coupling of the mechanical behavior of the porous solid with the transport of the fluid is a crucial ingredient towards understanding the material behavior in these varied applications. In this work, we formulate and numerically implement in a finite-element framework a large-deformation theory for coupled deformation-diffusion in isotropic, fluid-saturated porous solids. The theory synthesizes the classical Biot theory of linear poroelasticity and the more-recent Coussy theory of poroplasticity in a large deformation framework. In this talk, we highlight several salient features of our theory and discuss representative examples of the application of our numerical simulation capability to problems of consolidation as well as deformation localization in granular materials.

On the viscous dissipation modeling of thermal fluid flow in a porous medium

KAUST Repository

Salama, Amgad

2011-02-24

The problem of viscous dissipation and thermal dispersion in saturated porous medium is numerically investigated for the case of non-Darcy flow regime. The fluid is induced to flow upward by natural convection as a result of a semi-infinite vertical wall that is immersed in the porous medium and is kept at constant higher temperature. The boundary layer approximations were used to simplify the set of the governing, nonlinear partial differential equations, which were then non-dimensionalized and solved using the finite elements method. The results for the details of the governing parameters are presented and investigated. It is found that the irreversible process of transforming the kinetic energy of the moving fluid to heat energy via the viscosity of the moving fluid (i.e.; viscous dissipation) resulted in insignificant generation of heat for the range of parameters considered in this study. On the other hand, thermal dispersion has shown to disperse heat energy normal to the wall more effectively compared with the normal diffusion mechanism. © 2011 Springer-Verlag.

Modelling and simulation of a natural convection flow in a saturated porous cavity

International Nuclear Information System (INIS)

Costa, M.L.M.; Sampaio, R.; Gama, R.M.S. da.

1991-09-01

The natural convection flow in a two-dimensional fluid-saturated porous cavity is modelled by means of a Theory of Mixtures viewpoint in which fluid and porous medium are regarded as continuous constituents of a binary mixture, coexisting superposed. A local description, that allows distinct temperature profiles for both fluid and solid constituents is obtained. The model, simplified by the Boussinesq approximation, is simulated with the help of the Control Volumes Method. The effect of some usual parameters like Rayleigh, Darcy and Prandtl numbers and of a new dimensionless number, relating coefficients associated to the heat exchange between fluid and solid constituents (due to its temperature difference) and coefficients of heat conduction for each constituent, is considered. Stream lines for the fluid constituent and isotherms for both fluid and solid constituents are presented for some cases. Qualitative agreement with results using the classical approach (Darcy's law and additional terms to account for boundary and inertia effects, used as momentum equation) was obtained. (author)

Transport of Escherichia coli phage through saturated porous media considering managed aquifer recharge.

Science.gov (United States)

Zhang, Wenjing; Li, Shuo; Wang, Shuang; Lei, Liancheng; Yu, Xipeng; Ma, Tianyi

2018-03-01

Virus is one of the most potentially harmful microorganisms in groundwater. In this paper, the effects of hydrodynamic and hydrogeochemical conditions on the transportation of the colloidal virus considering managed aquifer recharge were systematically investigated. Escherichia coli phage, vB_EcoM-ep3, has a broad host range and was able to lyse pathogenic Escherichia coli. Bacteriophage with low risk to infect human has been found extensively in the groundwater environment, so it is considered as a representative model of groundwater viruses. Laboratory studies were carried out to analyze the transport of the Escherichia coli phage under varying conditions of pH, ionic strength, cation valence, flow rate, porous media, and phosphate buffer concentration. The results indicated that decreasing the pH will increase the adsorption of Escherichia coli phage. Increasing the ionic strength, either Na + or Ca 2+ , will form negative condition for the migration of Escherichia coli phage. A comparison of different cation valence tests indicated that changes in transport and deposition were more pronounced with divalent Ca 2+ than monovalent Na + . As the flow rate increases, the release of Escherichia coli phage increases and the retention of Escherichia coli phage in the aquifer medium reduces. Changes in porous media had a significant effect on Escherichia coli phage migration. With increase of phosphate buffer concentration, the suspension stability and migration ability of Escherichia coli phage are both increased. Based on laboratory-scale column experiments, a one-dimensional transport model was established to quantitatively describe the virus transport in saturated porous medium.

Irreversibility analysis of hydromagnetic flow of couple stress fluid with radiative heat in a channel filled with a porous medium

Directory of Open Access Journals (Sweden)

A.S. Eegunjobi

Full Text Available Numerical analysis of the intrinsic irreversibility of a mixed convection hydromagnetic flow of an electrically conducting couple stress fluid through upright channel filled with a saturated porous medium and radiative heat transfer was carried out. The thermodynamics first and second laws were employed to examine the problem. We obtained the dimensionless nonlinear differential equations and solves numerically with shooting procedure joined with a fourth order Runge-Kutta-Fehlberg integration scheme. The temperature and velocity obtained, used to analyse the entropy generation rate together with some various physical parameters of the flow. Our results are presented graphically and talk over. Keywords: MHD channel flow, Couple stress fluid, Porous medium, Thermal radiation, Entropy generation, Injection/suction

A Finite Difference Scheme for Double-Diffusive Unsteady Free Convection from a Curved Surface to a Saturated Porous Medium with a Non-Newtonian Fluid

KAUST Repository

El-Amin, Mohamed

2011-05-14

In this paper, a finite difference scheme is developed to solve the unsteady problem of combined heat and mass transfer from an isothermal curved surface to a porous medium saturated by a non-Newtonian fluid. The curved surface is kept at constant temperature and the power-law model is used to model the non-Newtonian fluid. The explicit finite difference method is used to solve simultaneously the equations of momentum, energy and concentration. The consistency of the explicit scheme is examined and the stability conditions are determined for each equation. Boundary layer and Boussinesq approximations have been incorporated. Numerical calculations are carried out for the various parameters entering into the problem. Velocity, temperature and concentration profiles are shown graphically. It is found that as time approaches infinity, the values of wall shear, heat transfer coefficient and concentration gradient at the wall, which are entered in tables, approach the steady state values.

Numerical Study of Frequency-dependent Seismoelectric Coupling in Partially-saturated Porous Media

Directory of Open Access Journals (Sweden)

Djuraev Ulugbek

2017-01-01

Full Text Available The seismoelectric phenomenon associated with propagation of seismic waves in fluid-saturated porous media has been studied for many decades. The method has a great potential to monitor subsurface fluid saturation changes associated with production of hydrocarbons. Frequency of the seismic source has a significant impact on measurement of the seismoelectric effects. In this paper, the effects of seismic wave frequency and water saturation on the seismoelectric response of a partially-saturated porous media is studied numerically. The conversion of seismic wave to electromagnetic wave was modelled by extending the theoretically developed seismoelectric coupling coefficient equation. We assumed constant values of pore radius and zeta-potential of 80 micrometers and 48 microvolts, respectively. Our calculations of the coupling coefficient were conducted at various water saturation values in the frequency range of 10 kHz to 150 kHz. The results show that the seismoelectric coupling is frequency-dependent and decreases exponentially when frequency increases. Similar trend is seen when water saturation is varied at different frequencies. However, when water saturation is less than about 0.6, the effect of frequency is significant. On the other hand, when the water saturation is greater than 0.6, the coupling coefficient shows monotonous trend when water saturation is increased at constant frequency.

Forced convection on a heated horizontal flat plate with finite thermal conductivity in a non-Darcian porous medium

Energy Technology Data Exchange (ETDEWEB)

Luna, N. [Direccion de Operacion Petrolera, Direccion General de Exploracion y Explotacion de Hidrocarburos, Secretaria de Energia, 03100 Mexico DF (Mexico); Mendez, F. [Facultad de Ingenieria, UNAM, 04510 Mexico DF (Mexico)

2005-07-01

The steady-state analysis of conjugated heat transfer process for the hydrodynamically developed forced convection flow on a heated flat plate embedded in a porous medium is studied. The governing equations for the fluid-saturated porous medium are solved analytically using the integral boundary layer approximation. This integral solution is coupled to the energy equation for the flat plate, where the longitudinal heat conduction effects are taken into account. The resulting equations are then reduced to an integro-differential equation which is solved by regular perturbation techniques and numerical methods. The analytical and numerical predictions for the temperature profile of the plate and appropriate local and average Nusselt numbers are plotted for finite values of the conduction parameter, {alpha}, which represents the presence of the longitudinal heat conduction effects. (authors)

Freezing heat transfer within water-saturated porous media

International Nuclear Information System (INIS)

Sasaki, Akira; Aiba, Shinya; Fukusako, Shoichiro.

1990-01-01

In the present study, analytical and experimental investigations were performed so as to clarify the characteristics of freezing heat transfer in porous media saturated with water in a vertical rectangular cavity. In order to establish the momentum equation, the law of conservation of momentum was applied to the fluid in our control volume, and the equation took into account Forchheimer's extension as the resistance to flow in the porous media. Three different sizes of glass, iron and copper beads were used as the porous media in this study. The temperature of the cold wall was kept at -10degC, while that of the hot wall was varied from 2degC to 22 degC. Comparisons between the analytical results and the experimental ones show good agreement with the exception of the copper bead results. (author)

Efficiency improvement of a concentrated solar receiver for water heating system using porous medium

Science.gov (United States)

Prasartkaew, Boonrit

2018-01-01

This experimental study aims at investigating on the performance of a high temperature solar water heating system. To approach the high temperature, a porous-medium concentrated solar collector equipped with a focused solar heliostat were proposed. The proposed system comprised of two parts: a 0.7x0.7-m2 porous medium receiver, was installed on a 3-m tower, and a focused multi-flat-mirror solar heliostat with 25-m2 aperture area. The porous medium used in this study was the metal swarf or metal waste from lathing process. To know how the system efficiency could be improved by using such porous medium, the proposed system with- and without-porous medium were tested and the comparative study was performed. The experimental results show that, using porous medium for enhancing the heat transfer mechanism, the system thermal efficiency was increased about 25%. It can be concluded that the efficiency of the proposed system can be substantially improved by using the porous medium.

Steam injection into water-saturated porous rock

NARCIS (Netherlands)

Bruining, J.; Marchesin, D.; Duijn, van C.J.

2003-01-01

We formulate conservation laws governing steam injection in a linear porous medium containing water. Heat losses to the outside are neglected. We find a complete and systematic description of all solutions of the Riemann problem for the injection of a mixture of steam and water into a

Computed tomography for the quantitative characterization of flow through a porous medium

International Nuclear Information System (INIS)

Auzerais, F.M.; Dussan, E.B.; Reischer, A.J.

1991-01-01

X-ray computer tomography (CT) has become an increasingly popular research tool in petroleum engineering for characterizing porous media. Its highly detailed images have been used to construct maps of porosity, saturation and atomic composition, and to visualize the displacement of fluids. However, extracting data necessary to characterize flow through porous media is both time consuming and dependent on the availability of extensive computational resources - - a consequence of the large size of the image files. The authors of this paper applied to known technique, based upon the ability to recognize regions with similar features, which avoids these difficulties. It allows the authors to substitute for the image, the pixel location of the boundaries of the recognized regions, reducing considerably the computer storage requirements. The authors this technique to study the dynamics of two miscible liquids of different densities flowing through a porous medium where buoyancy plays an important role. The authors' specific concern is the movement of mud filtrate as it penetrates a permeable formation in the vicinity of a recently drilled wellbore. The authors quantify the manner in which impermeable horizontal barriers influence the movement of the filtrate

Continued development of a semianalytical solution for two-phase fluid and heat flow in a porous medium

Energy Technology Data Exchange (ETDEWEB)

Doughty, C.; Pruess, K. [Lawrence Berkeley Lab., CA (United States)

1991-06-01

Over the past few years the authors have developed a semianalytical solution for transient two-phase water, air, and heat flow in a porous medium surrounding a constant-strength linear heat source, using a similarity variable {eta} = r/{radical}t. Although the similarity transformation approach requires a simplified geometry, all the complex physical mechanisms involved in coupled two-phase fluid and heat flow can be taken into account in a rigorous way, so that the solution may be applied to a variety of problems of current interest. The work was motivated by adverse to predict the thermohydrological response to the proposed geologic repository for heat-generating high-level nuclear wastes at Yucca Mountain, Nevada, in a partially saturated, highly fractured volcanic formation. The paper describes thermal and hydrologic conditions near the heat source; new features of the model; vapor pressure lowering; and the effective-continuum representation of a fractured/porous medium.

Double-diffusive convection in a Darcy porous medium saturated with a couple-stress fluid

International Nuclear Information System (INIS)

Malashetty, M S; Kollur, Premila; Pal, Dulal

2010-01-01

The onset of double-diffusive convection in a couple-stress fluid-saturated horizontal porous layer is studied using linear and weak nonlinear stability analyses. The modified Darcy equation that includes the time derivative term and the inertia term is used to model the momentum equation. The expressions for stationary, oscillatory and finite-amplitude Rayleigh number are obtained as a function of the governing parameters. The effect of couple-stress parameter, solute Rayleigh number, Vadasz number and diffusivity ratio on stationary, oscillatory and finite-amplitude convection is shown graphically. It is found that the couple-stress parameter and the solute Rayleigh number have a stabilizing effect on stationary, oscillatory and finite-amplitude convection. The diffusivity ratio has a destabilizing effect in the case of stationary and finite-amplitude modes, with a dual effect in the case of oscillatory convection. The Vadasz number advances the onset of oscillatory convection. The heat and mass transfer decreases with an increase in the values of couple-stress parameter and diffusivity ratio, while both increase with an increase in the value of the solute Rayleigh number.

A medium-independent variational macroscopic theory of two-phase porous media – Part I: Derivation of governing equations and stress partitioning laws

OpenAIRE

Serpieri , Roberto; Travascio , Francesco

2016-01-01

A macroscopic continuum theory of two-phase saturated porous media is derived by a purely variational deduction based on the least Action principle. The proposed theory proceeds from the consideration of a minimal set of kinematic descriptors and keeps a specific focus on the derivation of most general medium-independent governing equations, which have a form independent from the particular constitutive relations and thermodynamic constraints characterizing a specific medium. The kinematics o...

Bulk elastic wave propagation in partially saturated porous solids

International Nuclear Information System (INIS)

Berryman, J.G.; Thigpen, L.; Chin, R.C.Y.

1988-01-01

The linear equations of motion that describe the behavior of small disturbances in a porous solid containing both liquid and gas are solved for bulk wave propagation. The equations have been simplified by neglecting effects due to changes in capillary pressure. With this simplifying assumption, the equations reduce to two coupled (vector) equations of the form found in Biot's equations (for full saturation) but with more complicated coefficients. As in fully saturated solids, two shear waves with the same speed but different polarizations exist as do two compressional waves with distinct speeds. Attenuation effects can be enhanced in the partially saturated solid, depending on the distribution of gas in the pore space. Two models of the liquid/gas spatial distribution are considered: a segregated-fluids model and a mixed-fluids model. The two models predict comparable attentuation when the gas saturation is low, but the segregated-fluids model predicts a more rapid roll-off of attenuation as the gas saturation increases

Infiltration behaviour of elemental mercury DNAPL in fully and partially water saturated porous media

Science.gov (United States)

D'Aniello, Andrea; Hartog, Niels; Sweijen, Thomas; Pianese, Domenico

2018-02-01

Mercury is a contaminant of global concern due to its harmful effects on human health and for the detrimental consequences of its release in the environment. Sources of liquid elemental mercury are usually anthropogenic, such as chlor-alkali plants. To date insight into the infiltration behaviour of liquid elemental mercury in the subsurface is lacking, although this is critical for assessing both characterization and remediation approaches for mercury DNAPL contaminated sites. Therefore, in this study the infiltration behaviour of elemental mercury in fully and partially water saturated systems was investigated using column experiments. The properties affecting the constitutive relations governing the infiltration behaviour of liquid Hg0, and PCE for comparison, were determined using Pc(S) experiments with different granular porous media (glass beads and sands) for different two- and three-phase configurations. Results showed that, in water saturated porous media, elemental mercury, as PCE, acted as a non-wetting fluid. The required entry head for elemental mercury was higher (from about 5 to 7 times). However, due to the almost tenfold higher density of mercury, the required NAPL entry heads of 6.19 cm and 12.51 cm for mercury to infiltrate were 37.5% to 20.7% lower than for PCE for the same porous media. Although Leverett scaling was able to reproduce the natural tendency of Hg0 to be more prone than PCE to infiltrate in water saturated porous media, it considerably underestimated Hg0 infiltration capacity in comparison with the experimental results. In the partially water saturated system, in contrast with PCE, elemental mercury also acted as a nonwetting fluid, therefore having to overcome an entry head to infiltrate. The required Hg0 entry heads (10.45 and 15.74 cm) were considerably higher (68.9% and 25.8%) than for the water saturated porous systems. Furthermore, in the partially water saturated systems, experiments showed that elemental mercury displaced

A practical approach in porous medium combustion for domestic application: A review

Science.gov (United States)

Ismail, A. K.; Ibrahim, N. H.; Shamsuddin, K. A.; Abdullah, M. Z.; Zubair, M.

2018-05-01

Combustion in porous media has been widely studied. Many application involving the combustion of porous media has been reported in various way with most consider on numerical works and industrial application. Besides, recent application of porous medium combustion for domestic is the topic of interest among researchers. In this paper, a review was conducted on the combustion of porous media in term of practical application for domestic consumers. Details on the type of fuel used including bio fuel and their system have been search thoroughly. Most of the system have utilized compressed air system to provide lean combustion in domestic application. Some self-aspirating system of porous medium burner was also reported. The application of new technology such as cogeneration by using thermoelectric cells in tandem with porous medium combustion is also revised according to recent work which have already been published. Besides, the recent advances which include coating of porous material is also considered at the end of this paper.

On the propagation of a coupled saturation and pressure front

Energy Technology Data Exchange (ETDEWEB)

Vasco, D. W.

2010-12-01

Using an asymptotic technique, valid for a medium with smoothly varying heterogeneity, I derive an expression for the velocity of a propagating, coupled saturation and pressure front. Due to the nonlinearity of the governing equations, the velocity of the propagating front depends upon the magnitude of the saturation and pressure changes across the front in addition to the properties of the medium. Thus, the expression must be evaluated in conjunction with numerical reservoir simulation. The propagation of the two-phase front is governed by the background saturation distribution, the saturation-dependent component of the fluid mobility, the porosity, the permeability, the capillary pressure function, the medium compressibility, and the ratio of the slopes of the relative permeability curves. Numerical simulation of water injection into a porous layer saturated with a nonaqueous phase liquid indicates that two modes of propagation are important. The fastest mode of propagation is a pressure-dominated disturbance that travels through the saturated layer. This is followed, much later, by a coupled mode with a large saturation change. These two modes are also observed in a simulation using a heterogeneous porous layer. A comparison between the propagation times estimated from the results of the numerical simulation and predictions from the asymptotic expression indicates overall agreement.

The nonlinear interaction of convection modes in a box of a saturated porous medium

Science.gov (United States)

Florio, Brendan J.; Bassom, Andrew P.; Fowkes, Neville; Judd, Kevin; Stemler, Thomas

2015-05-01

A plethora of convection modes may occur within a confined box of porous medium when the associated dimensionless Rayleigh number R is above some critical value dependent on the geometry. In many cases the crucial Rayleigh number Rc for onset is different for each mode, and in practice the mode with the lowest associated Rc is likely to be the dominant one. For particular sizes of box, however, it is possible for multiple modes (typically three) to share a common Rc. For box shapes close to these special geometries the modes interact and compete nonlinearly near the onset of convection. Here this mechanism is explored and it is shown that generically the dynamics of the competition takes on one of two possible structures. A specific example of each is described, while the general properties of the system enables us to compare our results with some previous calculations for particular box dimensions.

Convective hydromagnetic instabilities of a power-law liquid saturating a porous medium: Flux conditions

Science.gov (United States)

Chahtour, C.; Ben Hamed, H.; Beji, H.; Guizani, A.; Alimi, W.

2018-01-01

We investigate how an external imposed magnetic field affects thermal instability in a horizontal shallow porous cavity saturated by a non-Newtonian power-law liquid. The magnetic field is assumed to be constant and parallel to the gravity. A uniform heat flux is applied to the horizontal walls of the layer while the vertical walls are adiabatic. We use linear stability analysis to find expressions for the critical Rayleigh number as a function of the power-law index and the intensity of the magnetic field. We use nonlinear parallel flow theory to find some explicit solutions of the problem, and we use finite difference numerical simulations to solve the full nonlinear equations. We show how the presence of magnetic field alters the known hydrodynamical result of Newtonian flows and power-law flows and how it causes the presence of subcritical finite amplitude convection for both pseudoplastic and dilatant fluids. We also show that in the limit of very strong magnetic field, the dissipation of energy by Joule effect dominates the dissipation of energy by shear stress and gives to the liquid an inviscid character.

Tracer transfer in consolidated porous medium and fractured porous medium: experimentations and modelling; Transferts d'un traceur en milieu poreux consolide et en milieu poreux fissure: experimentations et modelisations

Energy Technology Data Exchange (ETDEWEB)

Dalla Costa, C

2007-07-15

We try to identify and model physical and chemical mechanisms governing the water flow and the solute transport in fractured consolidated porous medium. An original experimental device was built. The 'cube' consists of an idealized fractured medium reproduced by piling up consolidated porous cubes of 5 cm edge. Meanwhile, columns of the homogeneous consolidated porous medium are studied. The same anionic tracing technique is used in both cases. Using a system analysis approach, we inject concentration pulses in the device to obtain breakthrough curves. After identifying the mass balance and the residence time, we fit the CD and the MIM models to the experimental data. The MIM model is able to reproduce experimental curves of the homogeneous consolidated porous medium better than the CD model. The mobile water fraction is in accordance with the porous medium geometry. The study of the flow rate influence highlights an interference dispersion regime. It was not possible to highlight the observation length influence in this case. On the contrary, we highlight the effect of the observation scale on the fractured and porous medium, comparing the results obtained on a small 'cube' and a big 'cube'. The CD model is not satisfactory in this case. Even if the MIM model can fit the experimental breakthrough curves, it was not possible to obtain unique parameters for the set of experiments. (author)

Effect of partial heating at mid of vertical plate adjacent to porous medium

Science.gov (United States)

Mulla, Mohammed Fahimuddin; Pallan, Khalid. M.; Al-Rashed, A. A. A. A.

2018-05-01

Heat and mass transfer in porous medium due to heating of vertical plate at mid-section is analyzed for various physical parameters. The heat and mass transfer in porous medium is modeled with the help of momentum, energy and concentration equations in terms of non-dimensional partial differential equations. The partial differential equations are converted into simpler form of algebraic equations with the help of finite element method. A computer code is developed to assemble the matrix form of algebraic equations into global matrices and then to solve them in an iterative manner to obtain the temperature, concentration and streamline distribution inside the porous medium. It is found that the heat transfer behavior of porous medium heated at middle section is considerably different from other cases.

Hydrocarbons biodegradation in unsaturated porous medium; Biodegradation des hydrocarbures en milieu poreux insature

Energy Technology Data Exchange (ETDEWEB)

Gautier, C

2007-12-15

Biological processes are expected to play an important role in the degradation of petroleum hydrocarbons in contaminated soils. However, factors influencing the kinetics of biodegradation are still not well known, especially in the unsaturated zone. To address these biodegradation questions in the unsaturated zone an innovative experimental set up based on a physical column model was developed. This experimental set up appeared to be an excellent tool for elaboration of a structured porous medium, with well defined porous network and adjusted water/oil saturations. Homogeneous repartition of both liquid phases (i.e., aqueous and non aqueous) in the soil pores, which also contain air, was achieved using ceramic membranes placed at the bottom of the soil column. Reproducible interfaces (and connectivity) are developed between gas, and both non mobile water and NAPL phases, depending on the above-defined characteristics of the porous media and on the partial saturations of these three phases (NAPL, water and gas). A respirometric apparatus was coupled to the column. Such experimental set up have been validated with hexadecane in dilution in an HMN phase. This approach allowed detailed information concerning n-hexadecane biodegradation, in aerobic condition, through the profile of the oxygen consumption rate. We have taken benefit of this technique, varying experimental conditions, to determine the main parameters influencing the biodegradation kinetics and compositional evolution of hydrocarbons, under steady state unsaturated conditions and with respect to aerobic metabolism. Impacts of the nitrogen quantity and of three different grain sizes have been examined. Biodegradation of petroleum cut, as diesel cut and middle distillate without aromatic fraction, were, also studied. (author)

Unsteady MHD blood flow through porous medium in a parallel plate channel

Science.gov (United States)

Latha, R.; Rushi Kumar, B.

2017-11-01

In this study, we have analyzed heat and mass transfer effects on unsteady blood flow through parallel plate channel in a saturated porous medium in the presence of a transverse magnetic field with thermal radiation. The governing higher order nonlinear PDE’S are converted to dimensionless equations using dimensionless variables. The dimensionless equations are then solved analytically using boundary conditions by choosing the axial flow transport and the fields of concentration and temperature apart from the normal velocity as a function of y and t. The effects of different pertinent parameters appeared in this model viz thermal radiation, Prandtl number, Heat source parameter, Hartmann number, Permeability parameter, Decay parameter on axial flow transport and the normal velocity are analyzed in detail.

Influence of gas hydrates crystals or ice crystals on the permeability of a porous medium; Influence de cristaux d'hydrates de gaz ou de glace sur la permeabilite d'un milieu poreux

Energy Technology Data Exchange (ETDEWEB)

Bonnefoy, O

2005-03-15

The first part is a bibliographic study. We study the conditions for thermodynamic equilibrium of the hydrates as a bulk medium and the composition of the liquid and solid phases. We then describe the basics of fluid dynamics in a porous medium. Eventually, we merge the two approaches and study the influence of the porous medium on the hydrate stability. An off-shore hydrate field (Blake Ridge) and an on-shore field (Mallik) are precisely described. The latter will be used as a reference case for subsequent numerical simulations. The second part is devoted to the experiments. Their goal is to measure the permeability of a sediment containing crystals. To get closer to natural geologic conditions, crystals are synthesized in absence of free gas. It turns out that hydrates form in a very heterogeneous way in the porous medium, which makes the measurements non representative. We believe that this result has a general character and that, at the laboratory time-scale, it is difficult, to say the least to achieve a uniform distribution of gas hydrates grown from dissolved gas. To circumvent this difficulty, we show, with a theoretical approach, that ice crystals behave much the same way as the hydrate crystals, concerning the Van der Waals forces that govern the agglomeration. This allows us to calculate the Hamaker constant of the hydrates. The second series of experiments focuses on the permeability of a non consolidated porous medium under mechanical stress, where the pores are filled with ice crystals. Two silica beads populations are used to form a porous medium: 3 mm and 0.2 mm. With the large grains, results show two thresholds: for saturations below the lower threshold, the presence of crystals does not modify the permeability. For saturations above the upper threshold, the permeability vanishes almost completely (percolation phenomenon). Between these two limits, the permeability decreases exponentially with the saturation. With the fine grains, the permeability

Application of porous medium for efficiency improvement of a concentrated solar air heating system

Science.gov (United States)

Prasartkaew, Boonrit

2018-01-01

The objective of this study is to evaluate the thermal efficiency of a concentrated solar collector for a high temperature air heating system. The proposed system consists of a 25-m2 focused multi-flat-mirror solar heliostat equipped with a porous medium solar collector/receiver which was installed on the top of a 3-m tower, called ‘tower receiver’. To know how the system efficiency cloud be improved by using porous medium, the proposed system with and without porous medium were tested and the comparative study was performed. The experimental results reveal that, for the proposed system, application of porous medium is promising, the efficiency can be increased about 2 times compared to the conventional one. In addition, due to the porous medium used in this study was the waste material with very low cost. It can be summarized that the substantial efficiency improvement with very low investment cost of the proposed system seem to be a vital measures for addressing the energy issues.

Geochemical thermodynamic and kinetic modeling that take into account the mass transfer phenomena in saturated porous medium

International Nuclear Information System (INIS)

Gerard, Frederic

1996-01-01

The mass transport mechanisms (advection. mechanical dispersion and molecular diffusion) have been introduced into the thermodynamic and kinetic geochemical code KINDIS. This innovative approach to couple chemical and transport mass transfers has allowed us to develop a reactive transport or hydrochemical code named KIRMAT, which naturally preserve the comprehensive geochemical functions of KINDIS. Mass transport phenomena through the total connected porosity of a water-saturated porous medium are solved over one spatial dimension (ID). The finite difference method is used. An explicit or forward time scheme is computed. The advective finite difference expression may be either centered or upstream weighted. Thus, ail of the hydrodynamic conditions may be modeled (from the pure advection to pure diffusion). The mass transport and geochemical flux are solved simultaneously (one-step algorithm). Moreover. the code KIRMAT is designed to quantify reactive mass transport through a double or dual porosity medium, in which the flow porosity (filled by free water) and the diffusion porosity (containing stagnant water) are viewed as two distinct sub mediums or Systems. Under some given conditions, the need to solve one or the other mass transport equation is a function of the water-rock System size. The accuracy of the kinetic constraint has been improved in KIRMAT. Two new kinetic rate laws have been introduced for the dissolution of the most abundant silicates (alkali feldspars, silica. etc.). These rate laws integrate the quantitatively important inhibitor and catalytic effects involved with some dissolved chemical elements that are ubiquitous in natural aqueous solutions. The basic step. the numerical verification of the code, has been tackled with two complementary approaches. The numerical results from KIRMAT have been compared to those calculated from an exact solution and a new method has been developed and used. We have compared the numerical results of KIRMAT in

Modelling critical degrees of saturation of porous building materials subjected to freezing

DEFF Research Database (Denmark)

Hansen, Ernst Jan De Place

1996-01-01

of SCR based on fracture mechanics and phase geometry of two-phase materials has been developed.The degradation is modelled as being caused by different eigenstrains of the pore phase and the solid phase when freezing, leading to stress concentrations and crack propagation. Simplifications are made......Frost resistance of porous materials can be characterized by the critical degree of saturation, SCR, and the actual degree of saturation, SACT. An experimental determination of SCR is very laborious and therefore only seldom used when testing frost resistance. A theoretical model for prediction...... to describe the development of stresses and the pore structure, because a mathematical description of the physical theories explaining the process of freezing of water in porous materials is lacking.Calculations are based on porosity, modulus of elasticity and tensile strength, and parameters characterizing...

A porous medium model for predicting the duct wall temperature of sodium fast reactor fuel assembly

Energy Technology Data Exchange (ETDEWEB)

Yu, Yiqi, E-mail: yyu@anl.gov [Nuclear Engineering Division, Argonne National Laboratory, Lemont, IL 60439 (United States); Merzari, Elia; Obabko, Aleksandr [Mathematics and Computer Science Division, Argonne National Laboratory, Lemont, IL 60439 (United States); Thomas, Justin [Nuclear Engineering Division, Argonne National Laboratory, Lemont, IL 60439 (United States)

2015-12-15

Highlights: • The proposed models are 400 times less computationally expensive than CFD simulations. • The proposed models show good duct wall temperature agreement with CFD simulations. • The paper provides an efficient tool for coupled radial core expansion calculation. - Abstract: Porous medium models have been established for predicting duct wall temperature of sodium fast reactor rod bundle assembly, which is much less computationally expensive than conventional CFD simulations that explicitly represent the wire-wrap and fuel pin geometry. Three porous medium models are proposed in this paper. Porous medium model 1 takes the whole assembly as one porous medium of uniform characteristics in the conventional approach. Porous medium model 2 distinguishes the pins along the assembly's edge from those in the interior with two distinct regions, each with a distinct porosity, resistance, and volumetric heat source. This accounts for the different fuel-to-coolant volume ratio in the two regions, which is important for predicting the temperature of the assembly's exterior duct wall. In Porous medium model 3, a precise resistance distribution was employed to define the characteristic of the porous medium. The results show that both porous medium model 2 and 3 can capture the average duct wall temperature well. Furthermore, the local duct wall variations due to different sub-channel patterns in bare rod bundles are well captured by porous medium model 3, although the wire effect on the duct wall temperature in wire wrap rod bundle has not been fully reproduced yet.

Hydrologic mechanisms governing fluid flow in partially saturated, fractured, porous tuff at Yucca Mountain

International Nuclear Information System (INIS)

Wang, J.S.Y.; Narasimhan, T.N.

1984-10-01

In contrast to the saturated zone where fluid moves rapidly along fractures, the fractures (with apertures large relative to the size of matrix pores) will desaturate first during drainage process and the bulk of fluid flow would be through interconnected pores in the matrix. Within a partially drained fracture, the presence of a relatively continuous air phase will produce practically an infinite resistance to liquid flow in the direction parallel to the fracture. The residual liquid will be held by capillary force in regions around fracture contact areas where the apertures are small. Normal to the fracture surfaces, the drained portion of the fractures will reduce the effective area for liquid flow from one matrix block to another matrix block. A general statistical theory is constructed for flow along the fracture and for flow between the matrix blocks to the fractures under partially saturated conditions. Results are obtained from an aperture distribution model for fracture saturation, hydraulic conductivity, and effective matrix-fracture flow areas as functions of pressure. Drainage from a fractured tuff column is simulated. The parameters for the simulations are deduced from fracture surface characteristics, spacings and orientations based on core analyses, and from matrix characteristics curve based on laboratory measurements. From the cases simulated for the fractured, porous column with discrete vertical and horizontal fractures and porous matrix blocks explicitly taken into account, it is observed that the highly transient changes from fully saturated conditions to partially saturated conditions are extremely sensitive to the fracture properties. However, the quasi-steady changes of the fluid flow of a partially saturated, fractured, porous system could be approximately simulated without taking the fractures into account. 22 references, 16 figures

Thermal non-equilibrium in porous medium adjacent to vertical plate: ANN approach

Science.gov (United States)

Ahmed, N. J. Salman; Ahamed, K. S. Nazim; Al-Rashed, Abdullah A. A. A.; Kamangar, Sarfaraz; Athani, Abdulgaphur

2018-05-01

Thermal non-equilibrium in porous medium is a condition that refers to temperature discrepancy in solid matrix and fluid of porous medium. This type of flow is complex flow requiring complex set of partial differential equations that govern the flow behavior. The current work is undertaken to predict the thermal non-equilibrium behavior of porous medium adjacent to vertical plate using artificial neural network. A set of neurons in 3 layers are trained to predict the heat transfer characteristics. It is found that the thermal non-equilibrium heat transfer behavior in terms of Nusselt number of fluid as well as solid phase can be predicted accurately by using well-trained neural network.

Evaluation of Colloid Retention Site Dominance in Variably Saturated Porous Media: An All Pores Pore-Scale Analysis

Science.gov (United States)

Morales, Veronica; Perez-Reche, Francisco; Holzner, Markus; Kinzelbach, Wolfgang

2016-04-01

It is well accepted that colloid and nanoparticle transport processes in porous media differ substantially between water saturated and unsaturated conditions. Differences are frequently ascribed to particle immobilization by association with interfaces with the gas, as well as to restrictions of the liquid medium through which colloids are transported. Yet, the current understanding of the importance of particle 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 Silver particles were transported for conditions of varying water content and water chemistry. 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 main locations where colloids can become retained (interfaces with the water-solid, air-water, air-solid, and air-water-solid, grain-grain contacts, and the bulk liquid), ii) deposition profiles of colloids along the column classified by the available retention location, and iii) channel widths of 3-dimensional pore-water network representations. The results presented provide a direct statistical evaluation on the significance of colloid retention by attachment to interfaces or by strainig at contact points where multiple interfaces meet.

Perturbation analysis of magnetohydrodynamics oscillatory flow on convective-radiative heat and mass transfer of micropolar fluid in a porous medium with chemical reaction

Directory of Open Access Journals (Sweden)

Dulal Pal

2016-03-01

Full Text Available This paper deals with the perturbation analysis of mixed convection heat and mass transfer of an oscillatory viscous electrically conducting micropolar fluid over an infinite moving permeable plate embedded in a saturated porous medium in the presence of transverse magnetic field. Analytical solutions are obtained for the governing basic equations. The effects of permeability, chemical reaction, viscous dissipation, magnetic field parameter and thermal radiation on the velocity distribution, micro-rotation, skin friction and wall couple stress coefficients are analyzed in detail. The results indicate that the effect of increasing the chemical reaction has a tendency to decrease the skin friction coefficient at the wall, while opposite trend is seen by increasing the permeability parameter of the porous medium. Also micro-rotational velocity distribution increases with an increase in the magnetic field parameter.

Influence of gas hydrates crystals or ice crystals on the permeability of a porous medium; Influence de cristaux d'hydrates de gaz ou de glace sur la permeabilite d'un milieu poreux

Energy Technology Data Exchange (ETDEWEB)

Bonnefoy, O.

2005-03-15

The first part is a bibliographic study. We study the conditions for thermodynamic equilibrium of the hydrates as a bulk medium and the composition of the liquid and solid phases. We then describe the basics of fluid dynamics in a porous medium. Eventually, we merge the two approaches and study the influence of the porous medium on the hydrate stability. An off-shore hydrate field (Blake Ridge) and an on-shore field (Mallik) are precisely described. The latter will be used as a reference case for subsequent numerical simulations. The second part is devoted to the experiments. Their goal is to measure the permeability of a sediment containing crystals. To get closer to natural geologic conditions, crystals are synthesized in absence of free gas. It turns out that hydrates form in a very heterogeneous way in the porous medium, which makes the measurements non representative. We believe that this result has a general character and that, at the laboratory time-scale, it is difficult, to say the least to achieve a uniform distribution of gas hydrates grown from dissolved gas. To circumvent this difficulty, we show, with a theoretical approach, that ice crystals behave much the same way as the hydrate crystals, concerning the Van der Waals forces that govern the agglomeration. This allows us to calculate the Hamaker constant of the hydrates. The second series of experiments focuses on the permeability of a non consolidated porous medium under mechanical stress, where the pores are filled with ice crystals. Two silica beads populations are used to form a porous medium: 3 mm and 0.2 mm. With the large grains, results show two thresholds: for saturations below the lower threshold, the presence of crystals does not modify the permeability. For saturations above the upper threshold, the permeability vanishes almost completely (percolation phenomenon). Between these two limits, the permeability decreases exponentially with the saturation. With the fine grains, the permeability

Modeling of strongly heat-driven flow in partially saturated fractured porous media

International Nuclear Information System (INIS)

Pruess, K.; Tsang, Y.W.; Wang, J.S.Y.

1985-01-01

The authors have performed modeling studies on the simultaneous transport of heat, liquid water, vapor, and air in partially saturated fractured porous media, with particular emphasis on strongly heat-driven flow. The presence of fractures makes the transport problem very complex, both in terms of flow geometry and physics. The numerical simulator used for their flow calculations takes into account most of the physical effects which are important in multi-phase fluid and heat flow. It has provisions to handle the extreme non-linearities which arise in phase transitions, component disappearances, and capillary discontinuities at fracture faces. They model a region around an infinite linear string of nuclear waste canisters, taking into account both the discrete fractures and the porous matrix. From an analysis of the results obtained with explicit fractures, they develop equivalent continuum models which can reproduce the temperature, saturation, and pressure variation, and gas and liquid flow rates of the discrete fracture-porous matrix calculations. The equivalent continuum approach makes use of a generalized relative permeability concept to take into account the fracture effects. This results in a substantial simplification of the flow problem which makes larger scale modeling of complicated unsaturated fractured porous systems feasible. Potential applications for regional scale simulations and limitations of the continuum approach are discussed. 27 references, 13 figures, 2 tables

Modeling of strongly heat-driven flow in partially saturated fractured porous media

International Nuclear Information System (INIS)

Pruess, K.; Tsang, Y.W.; Wang, J.S.Y.

1984-10-01

We have performed modeling studies on the simultaneous transport of heat, liquid water, vapor, and air in partially saturated fractured porous media, with particular emphasis on strongly heat-driven flow. The presence of fractures makes the transport problem very complex, both in terms of flow geometry and physics. The numerical simulator used for our flow calculations takes into account most of the physical effects which are important in multi-phase fluid and heat flow. It has provisions to handle the extreme non-linearities which arise in phase transitions, component disappearances, and capillary discontinuities at fracture faces. We model a region around an infinite linear string of nuclear waste canisters, taking into account both the discrete fractures and the porous matrix. From an analysis of the results obtained with explicit fractures, we develop equivalent continuum models which can reproduce the temperature, saturation, and pressure variation, and gas and liquid flow rates of the discrete fracture-porous matrix calculations. The equivalent continuum approach makes use of a generalized relative permeability concept to take into account for fracture effects. This results in a substantial simplification of the flow problem which makes larger scale modeling of complicated unsaturated fractured porous systems feasible. Potential applications for regional scale simulations and limitations of the continuum approach are discussed. 27 references, 13 figures, 2 tables

Integrated compartmental model for describing the transport of solute in a fractured porous medium. [FRACPORT

Energy Technology Data Exchange (ETDEWEB)

DeAngelis, D.L.; Yeh, G.T.; Huff, D.D.

1984-10-01

This report documents a model, FRACPORT, that simulates the transport of a solute through a fractured porous matrix. The model should be useful in analyzing the possible transport of radionuclides from shallow-land burial sites in humid environments. The use of the model is restricted to transport through saturated zones. The report first discusses the general modeling approach used, which is based on the Integrated Compartmental Method. The basic equations of solute transport are then presented. The model, which assumes a known water velocity field, solves these equations on two different time scales; one related to rapid transport of solute along fractures and the other related to slower transport through the porous matrix. FRACPORT is validated by application to a simple example of fractured porous medium transport that has previously been analyzed by other methods. Then its utility is demonstrated in analyzing more complex cases of pulses of solute into a fractured matrix. The report serves as a user's guide to FRACPORT. A detailed description of data input, along with a listing of input for a sample problem, is provided. 16 references, 18 figures, 3 tables.

Development of finite element code for the analysis of coupled thermo-hydro-mechanical behaviors of a saturated-unsaturated medium

International Nuclear Information System (INIS)

Ohnishi, Y.; Shibata, H.; Kobsayashi, A.

1987-01-01

A model is presented which describes fully coupled thermo-hydro-mechanical behavior of a porous geologic medium. The mathematical formulation for the model utilizes the Biot theory for the consolidation and the energy balance equation. If the medium is in the condition of saturated-unsaturated flow, then the free surfaces are taken into consideration in the model. The model, incorporated in a finite element numerical procedure, was implemented in a two-dimensional computer code. The code was developed under the assumptions that the medium is poro-elastic and in the plane strain condition; that water in the ground does not change its phase; and that heat is transferred by conductive and convective flow. Analytical solutions pertaining to consolidation theory for soils and rocks, thermoelasticity for solids and hydrothermal convection theory provided verification of stress and fluid flow couplings, respectively, in the coupled model. Several types of problems are analyzed

Natural Convection Heat Transfer in Concentric Horizontal Annuli Containing a Saturated Porous Medi

Directory of Open Access Journals (Sweden)

Ahmed F. Alfahaid, R.Y. Sakr

2012-10-01

Full Text Available Natural convection in horizontal annular porous media has become a subject receiving increasing attention due to its practical importance in the problem of insulators, such as ducting system in high temperature gas-cooled reactors, heating systems, thermal energy storage systems, under ground cable systems, etc. This paper presents a numerical study for steady state thermal convection in a fully saturated porous media bounded by two horizontal concentric cylinders, the cylinders are impermeable to fluid motion and maintained at different, uniform temperatures.  The solution scheme is based on two-dimensional model, which is governed by Darcy-Oberbeck-Boussinesq equations. The finite element method using Galerkin technique is developed and employed to solve the present problem. A numerical simulation is carried out to examine the parametric effects of Rayleigh number and radius ratio on the role played by natural convection heat transfer in the porous annuli. The numerical results obtained from the present model were compared with the available published results and good agreement is observed. The average Nusselt number at the heating surface of the inner cylinder is correlated to Rayleigh number and radius ratio.Keywords: Natural convection, numerical investigation, saturated porous media, finite element method, concentric horizontal annuli.

Hydrodynamic instability of compressible fluid in porous medium

International Nuclear Information System (INIS)

Argal, Shraddha; Tiwari, Anita; Sharma, P K; Prajapati, R P

2014-01-01

The hydrodynamic Rayleigh -Taylor instability of two superposed compressible fluids in porous medium has been studied. The dispersion relation is derived for such a medium by using normal mode analysis. The RT instability is discussed for various simplified configuration. The effect of porosity and dynamic viscosity has been analyzed and it is observed that porosity and dynamic viscosity have stabilizing effect on the Rayleigh- Taylor instability of compressible fluids.

Propagation des ondes acoustiques dans les milieux poreux saturés Propagation of Acoustic Waves in Saturated Porous Media

Directory of Open Access Journals (Sweden)

Coussy O.

2006-11-01

Full Text Available Ce travail comporte deux parties. La première partie concerne la théorie de la propagation des ondes acoustiques dans les milieux poreux saturés. Une revue des différentes méthodes existantes est faite et un développement critique de la théorie de Biot est exposé en détail. On examine en particulier les différents résultats auxquels cette théorie conduit et on regarde, dans quelles conditions et sur quels problèmes géophysiques, les phénomènes physiques mis en évidence peuvent jouer de manière notable. Dans la deuxième partie, on présente une vérification expérimentale due à Plona (1980 de la théorie de Biot. Après une introduction qualitative de l'expérience mise en place, on expose les résultats obtenus pour un grand nombre de matériaux de porosités différentes. La notion de tortuosité d'un milieu poreux est introduite théoriquement et discutée expérimentalement. This article is in two parts. The first part has to do with the theory of acoustic wave propagation in saturated porous media. Different existing methods are reviewed, and Biot's theory is critically developed in detail. In particular, the different results to which this theory leads are examined, and the conditions and geophysical problems on which the physical phenomena involved may have an appreciable effect are considered. The second part is devoted to the experimental check made by Plona (1980 of Biot's theory. After a qualitative introduction of the experimental procedure, the results obtained for many materials of different porosities are described. The concept of the tortuosity of a porous medium is introduced theoretically and discussed experimentally.

Homogeneous-heterogeneous reactions in curved channel with porous medium

Science.gov (United States)

Hayat, T.; Ayub, Sadia; Alsaedi, A.

2018-06-01

Purpose of the present investigation is to examine the peristaltic flow through porous medium in a curved conduit. Problem is modeled for incompressible electrically conducting Ellis fluid. Influence of porous medium is tackled via modified Darcy's law. The considered model utilizes homogeneous-heterogeneous reactions with equal diffusivities for reactant and autocatalysis. Constitutive equations are formulated in the presence of viscous dissipation. Channel walls are compliant in nature. Governing equations are modeled and simplified under the assumptions of small Reynolds number and large wavelength. Graphical results for velocity, temperature, heat transfer coefficient and homogeneous-heterogeneous reaction parameters are examined for the emerging parameters entering into the problem. Results reveal an activation in both homogenous-heterogenous reaction effect and heat transfer rate with increasing curvature of the channel.

Sensitivity and inversion of full seismic waveforms in stratified porous medium

International Nuclear Information System (INIS)

Barros, L. de

2007-12-01

Characterization of porous media parameters, and particularly the porosity, permeability and fluid properties are very useful in many applications (hydrologic, natural hazards or oil industry). The aim of my research is to evaluate the possibility to determine these properties from the full seismic wave fields. First, I am interested in the useful parameters and the specific properties of the seismic waves in the poro-elastic theory, often called Biot (1956) theory. I then compute seismic waves propagation in fluid saturated stratified porous media with a reflectivity method coupled with the discrete wavenumber integration method. I first used this modeling to study the possibilities to determine the carbon dioxide concentration and localization thanks to the reflected P-waves in the case of the deep geological storage of Sleipner (North Sea). The sensitivity of the seismic response to the poro-elastic parameters are then generalized by the analytical computation of the Frechet derivatives which are expressed in terms of the Green's functions of the unperturbed medium. The numerical tests show that the porosity and the consolidation are the main parameters to invert. The sensitivity operators are then introduced in a inversion algorithm based on iterative modeling of the full waveform. The classical algorithm of generalized least-square inverse problem is solved by the quasi-Newton technique (Tarantola, 1984). The inversion of synthetic data show that we can invert for the porosity and the fluid and solid parameters (densities and mechanical modulus, or volume rate of fluid and mineral) can be correctly rebuilt if the other parameters are well known. However, the strong seismic coupling of the porous parameters leads to difficulties to invert simultaneously for several parameters. One way to get round these difficulties is to use additional information and invert for one single parameter for the fluid properties (saturating rate) or for the lithology. An other way

Geometric and Hydrodynamic Characteristics of Three-dimensional Saturated Prefractal Porous Media Determined with Lattice Boltzmann Modeling

Science.gov (United States)

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...

Transport of vanadium (V in saturated porous media: effects of pH, ionic-strength and clay mineral

Directory of Open Access Journals (Sweden)

Yulu Wang

2016-10-01

Full Text Available Vanadium, a hazardous pollutant, has been frequently detected in soil and groundwater, however, its transport behavior in porous media were not clearly understood. In this study, the effects of solution pH, ionic strength (IS and the effect of clay mineral on the transport of vanadium in saturated porous media were investigated. Laboratory experiments using a series of columns packed with quartz sand were carried out to explore the retention and transport of vanadium with a range of ionic-strength (0.001–0.1 M and pH (4–8 and two different types of clay minerals montmorillonite and kaolinite. Results of the breakthrough experiments showed that vanadium was highly mobile in the saturated porous media. The increase in pH rendered a higher transport of vanadium in saturated porous media. The study also indicated an easier transfer of vanadium with an increase in IS. Montmorillonite enhanced the mobility of vanadium in the column when compared to kaolinite. A mathematical model based on advection-dispersion equation coupled with equilibrium and kinetic reactions was used to describe the retention and transport of vanadium in the columns very well.

Experimental studies on solar parabolic dish cooker with porous medium

International Nuclear Information System (INIS)

Lokeswaran, S.; Eswaramoorthy, M.

2012-01-01

The solar cooking is the alternate method of cooking to reduce consumptions of fossil fuels. An affordable, energy efficient solar cooking technology is much need due to the fossil fuels increasing cost and it is the hottest research topic in all over the world. This paper presents an experimental analysis of the heat transfer enhancement of solar parabolic dish cookers by a porous medium made of scrap material. Using the stagnation temperature test and water boiling test are conducted on the cooking vessel with and without porous medium. Experimental results are compared for both cases in terms of thermal performance, optical efficiency, heat loss factor and cooking power. (authors)

Heat transfer through natural convection in a porous saturated medium between two vertical cylinders

Energy Technology Data Exchange (ETDEWEB)

Hasnaoui, M. [Faculte des Sciences Semlalia, Marrakech (Morocco); Vasseur, P.; Bilgen, E.; Robillard, L. [Ecole Polytechnique, Montreal, PQ (Canada)

1993-12-31

A numerical and analytical study of two dimensional, laminar and near steady convection in a vertical porous annular region. The mathematical model was established, basing on Darcy-Oberbeck-Boussinesq equations. The analytical resolution is in the limit where the width of the porous layer is small compared to the cylinders height and it is based on the hypothesis of the parallel flow. (Authors). 4 refs., 4 figs.

A simplified transfer function for estimating saturated hydraulic conductivity of porous drainage filters

DEFF Research Database (Denmark)

Canga, Eriona; Iversen, Bo Vangsø; Kjærgaard, Charlotte

2013-01-01

Knowledge of the saturated hydraulic conductivity (Ksat) of porous filters used in water treatment technologies is important for optimizing the retention of nutrients and pollutants. This parameter determines the hydraulic capacity, which together with the Chemical properties of the filter media...

Nonlinear throughflow and internal heating effects on vibrating porous medium

Directory of Open Access Journals (Sweden)

Palle Kiran

2016-06-01

Full Text Available The effect of vertical throughflow and internal heating effects on fluid saturated porous medium under gravity modulation is investigated. The amplitude of modulation is considered to be very small and the disturbances are expanded in terms of power series of amplitude of convection. A weakly nonlinear stability analysis is proposed to study stationary convection. The Nusselt number is obtained numerically to present the results of heat transfer while using Ginzburg–Landau equation. The vertical throughflow has dual effect either to destabilize or to stabilize the system for downward or upward directions. The effect of internal heat source (Ri>0 enhances or sink (Ri<0 diminishes heat transfer in the system. The amplitude and frequency of modulation have the effects of increasing or diminishing heat transport. For linear model Venezian approach suggested that throughflow and internal heating have both destabilizing and stabilizing effects for suitable ranges of Ω. Further, the study establishes that heat transport can be controlled effectively by a mechanism that is external to the system throughflow and gravity modulation.

Generation of reactive oxygen species from porous silicon microparticles in cell culture medium.

Science.gov (United States)

Low, Suet Peng; Williams, Keryn A; Canham, Leigh T; Voelcker, Nicolas H

2010-06-01

Nanostructured (porous) silicon is a promising biodegradable biomaterial, which is being intensively researched as a tissue engineering scaffold and drug-delivery vehicle. Here, we tested the biocompatibility of non-treated and thermally-oxidized porous silicon particles using an indirect cell viability assay. Initial direct cell culture on porous silicon determined that human lens epithelial cells only poorly adhered to non-treated porous silicon. Using an indirect cell culture assay, we found that non-treated microparticles caused complete cell death, indicating that these particles generated a toxic product in cell culture medium. In contrast, thermally-oxidized microparticles did not reduce cell viability significantly. We found evidence for the generation of reactive oxygen species (ROS) by means of the fluorescent probe 2',7'-dichlorofluorescin. Our results suggest that non-treated porous silicon microparticles produced ROS, which interacted with the components of the cell culture medium, leading to the formation of cytotoxic species. Oxidation of porous silicon microparticles not only mitigated, but also abolished the toxic effects.

Fluid-Driven Deformation of a Soft Porous Medium

Science.gov (United States)

Lutz, Tyler; Wilen, Larry; Wettlaufer, John

2017-11-01

Viscous drag forces resisting the flow of fluid through a soft porous medium are maintained by restoring forces associated with deformations in the solid matrix. We describe experimental measurements of the deformation of foam under a pressure-driven flow of water along a single axis. Image analysis techniques allow tracking of the foam displacement while pressure sensors allow measurement of the fluid pressure. Experiments are performed for a series of different pressure heads ranging from 10 to 90 psi, and the results are compared to theory. This work builds on previous measurements of the fluid-induced deformation of a bed of soft hydrogel spheres. Compared to the hydrogel system, foams have the advantage that the constituents of the porous medium do not rearrange during an experiment, but they have the disadvantage of having a high friction coefficient with any boundaries. We detail strategies to characterize and mitigate the effects of friction on the observed foam deformations.

Transport of titanium dioxide nanoparticles in saturated porous media under various solution chemistry conditions

International Nuclear Information System (INIS)

Wang Yu; Gao Bin; Morales, Verónica L.; Tian Yuan; Wu Lei; Gao Jie; Bai Wei; Yang Liuyan

2012-01-01

Because of its wide applications, nanosized titanium dioxide may become a potential environmental risk to soil and groundwater system. It is therefore important to improve current understanding of the environmental fate and transport of titanium oxides nanoparticles (TONPs). In this work, the effect of solution chemistry (i.e., pH, ionic strength, and natural organic matter (NOM) concentration) on the deposition and transport of TONPs in saturated porous media was examined in detail. Laboratory columns packed with acid-cleaned quartz sand were used in the experiment as porous media. Transport experiments were conducted with various chemistry combinations, including four ionic strengths, three pH levels, and two NOM concentrations. The results showed that TONP mobility increased with increasing solution pH, but decreased with increasing solution ionic strength. It is also found that the presence of NOM in the system enhanced the mobility of TONPs in the saturated porous media. The Derjaguin–Landau–Verwey–Overbeek (DLVO) theory was used to justify the mobility trends observed in the experimental data. Predictions from the theory agreed excellently with the experimental data.

Bistable enhanced total reflection in Kretschmann configuration containing a saturable gain medium.

Science.gov (United States)

Zhou, Haichun; Guo, Jie; Xu, Kun; Li, Zhe; Tang, Junqi; Man, Shiqing

2018-03-05

The reflection of a TM-polarized light beam from a Kretschmann configuration with a saturable gain medium is investigated theoretically. Here, the dielectric constant of the gain medium is described by a classical Lorentzian oscillator model. When surface plasmon polaritons are effectively excited in this structure, it is demonstrated that the curves of enhanced total reflection (ETR) show different shaped hysteresis loops associated with optical bistability owing to gain saturation effect. The effects of the angle of incidence, the thickness of metal film, and the value of small-signal gain on bistable ETR are discussed in detail in a homogeneously broadened (HB) gain medium at line center. Analogous results can also be obtained in an inhomogeneously broadened (inHB) gain medium, while the two switch thresholds and the width of optical bistability hysteresis in an inHB gain medium are significantly different from those in a HB gain medium.

Centrifuge modeling of LNAPL transport in partially saturated sand

NARCIS (Netherlands)

Esposito, G.; Allersma, H.G.B.; Selvadurai, A.P.S.

1999-01-01

Model tests were performed at the Geotechnical Centrifuge Facility of Delft University of Technology, The Netherlands, to examine the mechanics of light nonaqueous phase liquid (LNAPL) movement in a partially saturated porous granular medium. The experiment simulated a 2D spill of LNAPL in an

Two-phase flow in porous media: power-law scaling of effective permeability

Energy Technology Data Exchange (ETDEWEB)

Groeva, Morten; Hansen, Alex, E-mail: Morten.Grova@ntnu.no, E-mail: Alex.Hansen@ntnu.no [Department of Physics, NTNU, NO-7491 Trondheim (Norway)

2011-09-15

A recent experiment has reported power-law scaling of effective permeability of two-phase flow with respect to capillary number for a two-dimensional model porous medium. In this paper, we consider the simultaneous flow of two phases through a porous medium under steady-state conditions, fixed total flow-rate and saturation, using a two-dimensional network simulator. We obtain power-law exponents for the scaling of effective permeability with respect to capillary number. The simulations are performed both for viscosity matched fluids and for a high viscosity ratio resembling that of air and water. Good power-law behaviour is found for both cases. Different exponents are found, depending on saturation.

A generalized power-law scaling law for a two-phase imbibition in a porous medium

KAUST Repository

El-Amin, Mohamed

2013-11-01

Dimensionless time is a universal parameter that may be used to predict real field behavior from scaled laboratory experiments in relation to imbibition processes in porous media. Researchers work to nondimensionalize the time has been through the use of parameters that are inherited to the properties of the moving fluids and the porous matrix, which may be applicable to spontaneous imbibition. However, in forced imbibition, the dynamics of the process depends, in addition, on injection velocity. Therefore, we propose the use of scaling velocity in the form of a combination of two velocities, the first of which (the characteristic velocity) is defined by the fluid and the porous medium parameters and the second is the injection velocity, which is a characteristic of the process. A power-law formula is suggested for the scaling velocity such that it may be used as a parameter to nondimensionalize time. This may reduce the complexities in characterizing two-phase imbibition through porous media and works well in both the cases of spontaneous and forced imbibition. The proposed scaling-law is tested against some oil recovery experimental data from the literature. In addition, the governing partial differential equations are nondimensionalized so that the governing dimensionless groups are manifested. An example of a one-dimensional countercurrent imbibition is considered numerically. The calculations are carried out for a wide range of Ca and Da to illustrate their influences on water saturation as well as relative water/oil permeabilities. © 2013 Elsevier B.V.

A generalized power-law scaling law for a two-phase imbibition in a porous medium

KAUST Repository

El-Amin, Mohamed; Salama, Amgad; Sun, Shuyu

2013-01-01

Dimensionless time is a universal parameter that may be used to predict real field behavior from scaled laboratory experiments in relation to imbibition processes in porous media. Researchers work to nondimensionalize the time has been through the use of parameters that are inherited to the properties of the moving fluids and the porous matrix, which may be applicable to spontaneous imbibition. However, in forced imbibition, the dynamics of the process depends, in addition, on injection velocity. Therefore, we propose the use of scaling velocity in the form of a combination of two velocities, the first of which (the characteristic velocity) is defined by the fluid and the porous medium parameters and the second is the injection velocity, which is a characteristic of the process. A power-law formula is suggested for the scaling velocity such that it may be used as a parameter to nondimensionalize time. This may reduce the complexities in characterizing two-phase imbibition through porous media and works well in both the cases of spontaneous and forced imbibition. The proposed scaling-law is tested against some oil recovery experimental data from the literature. In addition, the governing partial differential equations are nondimensionalized so that the governing dimensionless groups are manifested. An example of a one-dimensional countercurrent imbibition is considered numerically. The calculations are carried out for a wide range of Ca and Da to illustrate their influences on water saturation as well as relative water/oil permeabilities. © 2013 Elsevier B.V.

Fem Formulation for Heat and Mass Transfer in Porous Medium

Science.gov (United States)

Azeem; Soudagar, Manzoor Elahi M.; Salman Ahmed, N. J.; Anjum Badruddin, Irfan

2017-08-01

Heat and mass transfer in porous medium can be modelled using three partial differential equations namely, momentum equation, energy equation and mass diffusion. These three equations are coupled to each other by some common terms that turn the whole phenomenon into a complex problem with inter-dependable variables. The current article describes the finite element formulation of heat and mass transfer in porous medium with respect to Cartesian coordinates. The problem under study is formulated into algebraic form of equations by using Galerkin's method with the help of two-node linear triangular element having three nodes. The domain is meshed with smaller sized elements near the wall region and bigger size away from walls.

Thermo-hydric characterization of partially saturated porous media; Caracterisation thermo-hydrique de milieux poreux partiellement satures d'eau

Energy Technology Data Exchange (ETDEWEB)

Simon Salager; Frederic Jamin; Moulay Said El Youssoufi; Christian Saix [Laboratoire de Mecanique et Genie Civil, Universite Montpellier II, cc 048, Place Eugene Bataillon, 34095 Montpellier (France)

2005-07-01

We present a contribution to the thermo-hydric characterization of partially saturated porous media by water, through the characteristic curve. This curve defines the relation between suction and degree of saturation. Using this curve for a given temperature, a model is used to predict it for other temperatures. An experimental device called pressure cell was made in a thermo-regulated environment. The model was validated by several tests on a ceramic and silty clayey sand, at 20 and 60 C. The results obtained lead to a characteristic surface which can be considered as a generalization of the classical characteristic curve. (authors)

Transport of Silica Colloid through Saturated Porous Media under Different Hydrogeochemical and Hydrodynamic Conditions Considering Managed Aquifer Recharge

Directory of Open Access Journals (Sweden)

Zhuo Wang

2016-11-01

Full Text Available Colloids may have an important role in regulating the structure and function of groundwater ecosystems, and may influence the migration of low solubility contaminants in groundwater. There is, however, a degree of uncertainty about how colloids behave under the variable hydrogeochemical and hydrodynamic conditions that occur during managed aquifer recharge. We used an online monitoring system to monitor the transport of silica colloid in saturated porous media under different hydrogeochemical conditions, including a range of pH values (5, 7, and 9, ionic strengths (<0.0005, 0.02, and 0.05 M, cation valences (Na+, Ca2+, flow rates (0.1, 0.2, and 0.4 mL/min. The results showed that silica colloid was more likely to deposit on the surface of porous media in acidic conditions (pH = 5 than in alkaline conditions (pH = 9, indicating that the risks of pollution from colloidal interactions would be higher when the pH of the recharge water was higher. Colloid deposition occurred when the ionic strength of the colloidal suspension increased, and bivalent cations had a greater effect than monovalent cations. This suggests that bivalent cation-rich recharge water might affect the porosity of the porous medium because of colloid deposition during the managed aquifer recharge process. As the flow rate increased, the migration ability of silica colloid increased. We simulated the migration of silica colloid in porous media with the COMSOL Multiphysics model.

Heat Transfer to Pulsatile Slip Flow in a Porous Channel Filled With ...

African Journals Online (AJOL)

This paper investigate the effect of slip on the hydromagnetic pulsatile flow through a porous channel filled with saturated porous medium with time dependent boundary condition on the heated wall. Based on the pulsatile flow nature, the dimensionless flow governing equations are resolved to harmonic and non-harmonic ...

Existence and Uniqueness of Solutions to the Stochastic Porous Media Equations of Saturated Flows

International Nuclear Information System (INIS)

Ciotir, Ioana

2010-01-01

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 3 .

Diffusion, Coulombic interactions and multicomponent ionic transport of charged species in saturated porous media

DEFF Research Database (Denmark)

Rolle, Massimo; Muniruzzaman, Muhammad

water are cross-coupled due to the effects of Coulombic interactions. Such effects are illustrated in flow-through experiments in saturated porous media. Simple strong electrolytes (i.e., salts and strong acid solutions) were selected as tracers and their transport was studied under different advection......-dominated conditions in homogeneous and heterogeneous porous media [2-3]. The model-based interpretation of the experimental results is challenging since it requires a multicomponent ionic formulation with an accurate description of local hydrodynamic dispersion and explicitly accounting for the cross-coupling...

Unsteady flow of an incompressible fluid in a horizontal porous medium with suction

International Nuclear Information System (INIS)

Bestman, A.R.

1988-04-01

A theoretical analysis of two-dimensional unsteady flow in a porous medium bounded by a horizontal wall is presented as a perturbation on a basic flow. It is assumed that the perturbation is occasioned by a sudden suction at the wall. Even for a highly permeable medium the characteristic Reynolds number in porous media flow is usually small and asymptotic solutions are developed by the Laplace transform technique. It is observed that the perturbed shear stress at the wall decays exponentially with time. (author). 5 refs

Effect of flow on bacterial transport and biofilm formation in saturated porous media

Science.gov (United States)

Rusconi, R.

2016-12-01

Understanding the transport of bacteria in saturated porous media is crucial for many applications ranging from the management of pumping wells subject to bio-clogging to the design of new bioremediation schemes for subsurface contamination. However, little is known about the spatial distribution of bacteria at the pore scale, particularly when small-scale heterogeneities - always present even in seemingly homogeneous aquifers - lead to preferential pathways for groundwater flow. In particular, the coupling of flow and motility has recently been shown to strongly affect bacterial transport1, and this leads us to predict that subsurface flow may strongly affect the dispersal of bacteria and the formation of biofilms in saturated aquifers. I present here microfluidic experiments combined with numerical simulations to show how the topological features of the flow correlate with bacterial concentration and promote the attachment of bacteria to specific regions of the pore network, which will ultimately influence the formations of biofilms. These results highlight the intimate link between small-scale biological processes and transport in porous media.

A general approach for defining the macroscopic free energy density of saturated porous media at finite strains under non-isothermal conditions

International Nuclear Information System (INIS)

Gajo, A.

2011-01-01

A general approach is proposed for defining the macroscopic free energy density function (and its complement, the free enthalpy) of a saturated porous medium submitted to finite deformations under non-isothermal conditions, in the case of compressible fluid and solid constituents. Reference is made to an elementary volume treated as an 'open system', moving with the solid skeleton. The proposed free energy depends on the generalised strains (namely an appropriate measure of the strain of the solid skeleton and the variation in fluid mass content) and the absolute temperatures of the solid and fluid phases (which are assumed to differ from each other for the sake of generality). This macroscopic energy proves to be a potential for the generalised stresses (namely the associated measure of the total stress and the free enthalpy of the pore fluid per unit mass) and the entropies of the solid and fluid phases. In contrast with mixture theories, the resulting free energy is not the simple sum of the free energies of the single constituents. Two simplified cases are examined in detail, i.e. the semi-linear theory (originally proposed for isothermal conditions and extended here to non-isothermal problems) and the linear theory. The proposed approach paves the way to the consistent non-isothermal-hyper-elastic-plastic modelling of saturated porous media with a compressible fluid and solid constituents. (authors)

Comparison study between the effects of different terms contributing to viscous dissipation in saturated porous media

KAUST Repository

Salama, Amgad

2013-02-01

Some sort of controversy is associated with the problem of viscous dissipation in saturated porous media for which we try to present a comparison study between the influences of the different terms contributing to this phenomenon. We consider viscous dissipation by studying the case of semi-infinite flat plate embedded in saturated porous medium and is kept at constant, higher temperature compared with the surrounding fluid. The fluid is induced to move upwards by natural convection during which viscous dissipation is considered. The boundary layer assumptions are considered to simplify the treatment and to highlight the influencing parameters. The behavior of temperature, and velocity fields in the neighborhood of the vertical flat plate were used to highlight the effects of these parameters. Three terms were considered to contribute to viscous dissipation, namely Darcy\\'s term, the Forchheimer term and Al-Hadharami\\'s term. Although there are no unanimous agreements between researchers to include the Forchhemier term in the dissipation function, some researchers argued it might have an indirect effect and hence for this sake and for completion purposes, we include it in this comparison study. Dimensional considerations reveal that Darcy\\'s term is influenced by Gebhart number, the Forchheimer term is controlled by the non-Darcy parameter and Al-Hadharami\\'s term is influenced by Darcy\\'s number. The governing, non-dimensional set of equations together with the imposed boundary conditions is numerically investigated by finite element method. The results for the details of the governing parameters are presented and investigated. It is found that the irreversible process of transforming the kinetic energy of the moving fluid to heat energy via the viscosity of the moving fluid (i.e., viscous dissipation) is very much influenced by the relative magnitude of these dimensionless parameters. © 2012 Elsevier Masson SAS. All rights reserved.

LLUVIA-II: A program for two-dimensional, transient flow through partially saturated porous media

International Nuclear Information System (INIS)

Eaton, R.R.; Hopkins, P.L.

1992-08-01

LLUVIA-II is a program designed for the efficient solution of two- dimensional transient flow of liquid water through partially saturated, porous media. The code solves Richards equation using the method-of-lines procedure. This document describes the solution procedure employed, input data structure, output, and code verification

Experimental study on distributed optical fiber-based approach monitoring saturation line in levee engineering

Science.gov (United States)

Su, Huaizhi; Li, Hao; Kang, Yeyuan; Wen, Zhiping

2018-02-01

Seepage is one of key factors which affect the levee engineering safety. The seepage danger without timely detection and rapid response may likely lead to severe accidents such as seepage failure, slope instability, and even levee break. More than 90 percent of levee break events are caused by the seepage. It is very important for seepage behavior identification to determine accurately saturation line in levee engineering. Furthermore, the location of saturation line has a major impact on slope stability in levee engineering. Considering the structure characteristics and service condition of levee engineering, the distributed optical fiber sensing technology is introduced to implement the real-time observation of saturation line in levee engineering. The distributed optical fiber temperature sensor system (DTS)-based monitoring principle of saturation line in levee engineering is investigated. An experimental platform, which consists of DTS, heating system, water-supply system, auxiliary analysis system and levee model, is designed and constructed. The monitoring experiment of saturation line in levee model is implemented on this platform. According to the experimental results, the numerical relationship between moisture content and thermal conductivity in porous medium is identified. A line heat source-based distributed optical fiber method obtaining the thermal conductivity in porous medium is developed. A DTS-based approach is proposed to monitor the saturation line in levee engineering. The embedment pattern of optical fiber for monitoring saturation line is presented.

Biogenic Cracks in Porous Rock

Science.gov (United States)

Hemmerle, A.; Hartung, J.; Hallatschek, O.; Goehring, L.; Herminghaus, S.

2014-12-01

Microorganisms growing on and inside porous rock may fracture it by various processes. Some of the mechanisms of biofouling and bioweathering are today identified and partially understood but most emphasis is on chemical weathering, while mechanical contributions have been neglected. However, as demonstrated by the perseverance of a seed germinating and cracking up a concrete block, the turgor pressure of living organisms can be very significant. Here, we present results of a systematic study of the effects of the mechanical forces of growing microbial populations on the weathering of porous media. We designed a model porous medium made of glass beads held together by polydimethylsiloxane (PDMS), a curable polymer. The rheological properties of the porous medium, whose shape and size are tunable, can be controlled by the ratio of crosslinker to base used in the PDMS (see Fig. 1). Glass and PDMS being inert to most chemicals, we are able to focus on the mechanical processes of biodeterioration, excluding any chemical weathering. Inspired by recent measurements of the high pressure (~0.5 Mpa) exerted by a growing population of yeasts trapped in a microfluidic device, we show that yeast cells can be cultured homogeneously within porous medium until saturation of the porous space. We investigate then the effects of such an inner pressure on the mechanical properties of the sample. Using the same model system, we study also the complex interplay between biofilms and porous media. We focus in particular on the effects of pore size on the penetration of the biofilm within the porous sample, and on the resulting deformations of the matrix, opening new perspectives into the understanding of life in complex geometry. Figure 1. Left : cell culture growing in a model porous medium. The white spheres represent the grains, bonds are displayed in grey, and microbes in green. Right: microscopy picture of glass beads linked by PDMS bridges, scale bar: 100 μm.

A Physically Based Analytical Model to Describe Effective Excess Charge for Streaming Potential Generation in Water Saturated Porous Media

Science.gov (United States)

Guarracino, L.; Jougnot, D.

2018-01-01

Among the different contributions generating self-potential, the streaming potential is of particular interest in hydrogeology for its sensitivity to water flow. Estimating water flux in porous media using streaming potential data relies on our capacity to understand, model, and upscale the electrokinetic coupling at the mineral-solution interface. Different approaches have been proposed to predict streaming potential generation in porous media. One of these approaches is the flux averaging which is based on determining the excess charge which is effectively dragged in the medium by water flow. In this study, we develop a physically based analytical model to predict the effective excess charge in saturated porous media using a flux-averaging approach in a bundle of capillary tubes with a fractal pore size distribution. The proposed model allows the determination of the effective excess charge as a function of pore water ionic concentration and hydrogeological parameters like porosity, permeability, and tortuosity. The new model has been successfully tested against different set of experimental data from the literature. One of the main findings of this study is the mechanistic explanation to the empirical dependence between the effective excess charge and the permeability that has been found by several researchers. The proposed model also highlights the link to other lithological properties, and it is able to reproduce the evolution of effective excess charge with electrolyte concentrations.

Nonlinear radiative peristaltic flow of hydromagnetic fluid through porous medium

Directory of Open Access Journals (Sweden)

Q. Hussain

2018-06-01

Full Text Available The radiative heat and mass transfer in wall induced flow of hydromagnetic fluid through porous medium in an asymmetric channel is analyzed. The fluid viscosity is considered temperature dependent. In the theory of peristalsis, the radiation effects are either ignored or taken as linear approximation of radiative heat flux. Such approximation is only possible when there is sufficiently small temperature differences in the flow field; however, nonlinear radiation effects are valid for large temperature differences as well (the new feature added in the present study. Mathematical modeling of the problems include the complicated system of highly nonlinear differential equations. Semi-analytical solutions are established in the wave reference frame. Results are displayed graphically and discussed in detail for the variation of various physical parameters with the special attention to viscosity, radiation, and temperature ratio parameters. Keywords: Nonlinear thermal radiation, Variable viscosity, Porous medium, Soret and Dufour effects, Peristalsis

Thermal convection and nonlinear effects of a superfluid 3He-4He mixture in a porous medium

International Nuclear Information System (INIS)

Chien, L.C.L.

1986-01-01

The convective instability of one-component classical fluids in a porous medium confined between two unbounded slabs was studied. This system behaves like a high Prandtl number bulk fluid. It has boundary conditions similar to the stress-free boundary conditions of bulk one-component classical fluids. Both the amplitude expansion method and the Galerkin method were used to investigate the nonlinear steady convection. Two dimensional rolls are the only stable motion at the onset of convection. Beyond threshold, the steady convection rolls become unstable to formation of cross-roll and zigzag instabilities. Applying the phase-dynamics approach for the zigzag instability, the author obtained the diffusion coefficient D, which can signal the onset of instability. Also investigated was the convective instability of superfluid 3 He- 4 He mixtures in porous media. Assuming no interaction between the average superflow and the porous medium and treating the normal flow in the equation of motion like a classical fluid in a porous medium, it was found that the superfluid mixtures in a porous medium. To investigate the effects of a lateral boundary, the convective instability of classical one-component fluids in porous media inside a box was studied. The zigzag instability does not exist because of the boundary conditions at the side of the box

Solidification of porous medium saturated with aqueous solution in a rectangular cell. ; Discussion on influence of initial concentration of solution and mean diameter of beads. Kukei sonai no suiyoeki de mitasareta takoshitsutai no gyoko. ; Shoki nodo to beads no heikin chokkei no eikyo ni kansuru kento

Energy Technology Data Exchange (ETDEWEB)

Matsumoto, K [Miyazaki University, Miyazaki (Japan). Faculty of engineering; Okada, M [Aoyama Gakuin University, Tokyo (Japan). School of Science and Engineering; Murakami, M [Toshiba Corp., Tokyo (Japan); Yabushita, Y [Sony Corp., Tokyo (Japan)

1993-11-25

Studies have been made for the purpose of analyzing solidification phenomenon of ground in relation to freezing construction method used in subway, water supply, and sewage constructions. Experimental studies have been carried out on solidification process of porous medium saturated with aqueous solution to discover influence of initial concentration of the solution and diameter of beads that constitute a porous medium. The experiment was performed by solidifying the porous medium sequentially from a side wall with lower temperature in a rectangular experimental tank with a height and a width of 100 mm filled with NaCl aqueous solution and beads. As a result, it was discovered that, if the initial concentration is low, the temperature difference is little between the upper part and the lower part of the experimental tank, and natural convection in the liquid-phase region is suppressed because of rising solidification temperature; the natural convection is suppressed in the liquid-phase region; and the boundary face between the mushy region and the liquid-phase region moves quickly. Further, the concentration rise in the liquid-phase region has slowed down despite that the solidification region is large enough. The smaller the mean diameter of beads, the faster the growth rate on the boundary face, hence the natural convection in the tank has been suppressed, and the growth rate on the boundary face has increased. In addition, the concentration stratification in the liquid-phase region does not expand, but is formed only on the bottom. 6 refs., 12 figs.

A free boundary problem describing the saturated-unsaturated flow in a porous medium

Directory of Open Access Journals (Sweden)

Gabriela Marinoschi

2004-01-01

Full Text Available This paper presents a functional approach to a nonlinear model describing the complete physical process of water infiltration into an unsaturated soil, including the saturation occurrence and the advance of the wetting front. The model introduced in this paper involves a multivalued operator covering the simultaneous saturated and unsaturated flow behaviors and enhances the study of the displacement of the free boundary between these two flow regimes. The model resides in Richards' equation written in pressure form with an initial condition and boundary conditions which in this work express the inflow due to the rain on the soil surface on the one hand, and characterize a certain permeability corresponding to the underground boundary, on the other hand. Existence, uniqueness, and regularity results for the transformed model in diffusive form, that is, for the moisture of the soil, and the existence of the weak solution for the pressure form are proved in the 3D case. The main part of the paper focuses on the existence of the free boundary between the saturated and unsaturated parts of the soil, and this is proved, in the 1D case, for certain stronger assumptions on the initial data and boundary conditions.

FEMWASTE: a Finite-Element Model of Waste transport through porous saturated-unsaturated media

International Nuclear Information System (INIS)

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

A multi-scale computational scheme for anisotropic hydro-mechanical couplings in saturated heterogeneous porous media

NARCIS (Netherlands)

Mercatoris, B.C.N.; Massart, T.J.; Sluys, L.J.

2013-01-01

This contribution discusses a coupled two-scale framework for hydro-mechanical problems in saturated heterogeneous porous geomaterials. The heterogeneous nature of such materials can lead to an anisotropy of the hydro-mechanical couplings and non-linear effects. Based on an assumed model of the

A numerical model for self-compacting concrete flow through reinforced sections. A porous medium analogy

International Nuclear Information System (INIS)

Vasilic, Ksenija

2016-01-01

This thesis addresses numerical simulations of self-compacting concrete (SCC) castings and suggests a novel modelling approach that treats reinforcement zones in a formwork as porous media. As a relatively new field in concrete technology, numerical simulations of fresh concrete flow can be a promising aid to optimise casting processes and to avoid on-site casting incidents by predicting the flow behaviour of concrete during the casting process. The simulations of fresh concrete flow generally involve complex mathematical modelling and time-consuming computations. In case of a casting prediction, the simulation time is additionally significantly increased because each reinforcement bar occurring in succession has to be considered one by one. This is particularly problematic when simulating SCC casting, since this type of concrete is typically used for heavily reinforced structural members. However, the wide use of numerical tools for casting prediction in practice is possible only if the tools are user-friendly and simulations are time-saving. In order to shorten simulation time and to come closer to a practical tool for casting prediction, instead to model steel bars one by one, this thesis suggests to model zones with arrays of steel bars as porous media. Consequently, one models the flow of SCC through a reinforcement zone as a free-surface flow of a non-Newtonian fluid, propagating through the medium. By defining characteristic parameters of the porous medium, the influence on the flow and the changed (apparent) behaviour of concrete in the porous matrix can be predicted. This enables modelling of any reinforcement network as a porous zone and thus significantly simplifies and fastens simulations of reinforced components' castings. Within the thesis, a computational model for SCC flow through reinforced sections was developed. This model couples a fluid dynamics model for fresh concrete and the macroscopic approach for the influence of the porous medium

A numerical model for self-compacting concrete flow through reinforced sections. A porous medium analogy

Energy Technology Data Exchange (ETDEWEB)

Vasilic, Ksenija

2016-05-01

This thesis addresses numerical simulations of self-compacting concrete (SCC) castings and suggests a novel modelling approach that treats reinforcement zones in a formwork as porous media. As a relatively new field in concrete technology, numerical simulations of fresh concrete flow can be a promising aid to optimise casting processes and to avoid on-site casting incidents by predicting the flow behaviour of concrete during the casting process. The simulations of fresh concrete flow generally involve complex mathematical modelling and time-consuming computations. In case of a casting prediction, the simulation time is additionally significantly increased because each reinforcement bar occurring in succession has to be considered one by one. This is particularly problematic when simulating SCC casting, since this type of concrete is typically used for heavily reinforced structural members. However, the wide use of numerical tools for casting prediction in practice is possible only if the tools are user-friendly and simulations are time-saving. In order to shorten simulation time and to come closer to a practical tool for casting prediction, instead to model steel bars one by one, this thesis suggests to model zones with arrays of steel bars as porous media. Consequently, one models the flow of SCC through a reinforcement zone as a free-surface flow of a non-Newtonian fluid, propagating through the medium. By defining characteristic parameters of the porous medium, the influence on the flow and the changed (apparent) behaviour of concrete in the porous matrix can be predicted. This enables modelling of any reinforcement network as a porous zone and thus significantly simplifies and fastens simulations of reinforced components' castings. Within the thesis, a computational model for SCC flow through reinforced sections was developed. This model couples a fluid dynamics model for fresh concrete and the macroscopic approach for the influence of the porous medium

Heat transfer in porous medium embedded with vertical plate: Non-equilibrium approach - Part A

Energy Technology Data Exchange (ETDEWEB)

Badruddin, Irfan Anjum [Dept. of Mechanical Engineering, University of Malaya, Kuala Lumpur, 50603 (Malaysia); Quadir, G. A. [School of Mechatronic Engineering, University Malaysia Perlis, Pauh Putra, 02600 Arau, Perlis (Malaysia)

2016-06-08

Heat transfer in a porous medium embedded with vertical flat plate is investigated by using thermal non-equilibrium model. Darcy model is employed to simulate the flow inside porous medium. It is assumed that the heat transfer takes place by natural convection and radiation. The vertical plate is maintained at isothermal temperature. The governing partial differential equations are converted into non-dimensional form and solved numerically using finite element method. Results are presented in terms of isotherms and streamlines for various parameters such as heat transfer coefficient parameter, thermal conductivity ratio, and radiation parameter.

Heat transfer in porous medium embedded with vertical plate: Non-equilibrium approach - Part A

International Nuclear Information System (INIS)

Badruddin, Irfan Anjum; Quadir, G. A.

2016-01-01

Heat transfer in a porous medium embedded with vertical flat plate is investigated by using thermal non-equilibrium model. Darcy model is employed to simulate the flow inside porous medium. It is assumed that the heat transfer takes place by natural convection and radiation. The vertical plate is maintained at isothermal temperature. The governing partial differential equations are converted into non-dimensional form and solved numerically using finite element method. Results are presented in terms of isotherms and streamlines for various parameters such as heat transfer coefficient parameter, thermal conductivity ratio, and radiation parameter

Graphene Oxide Affects Mobility and Antibacterial Ability of Levofloxacin and Ciprofloxacin in Saturated and Unsaturated Porous Media

Science.gov (United States)

Kaixuan, S.

2017-12-01

Understand the fate and impact of fluoroquinolone antibiotics (FQs) in soil and groundwater systems is critical to the safety of ecosystem and public health. In this work, laboratory batch sorption, column transport, and bacterial growth experiments were conducted to improve current understanding of the interactions between two typical FQs (levofloxacin (LEV) and ciprofloxacin (CIP)) and graphene oxide (GO) in quartz sand media under various conditions. Studies showed that both GO and quartz sand adsorbed LEV and CIP in aqueous solutions and sand was capable to compete with GO for the antibiotics. While GO showed much larger sorption capacity, the sand had stronger sorption affinity to the two antibiotics. As a result, neither LEV nor CIP showed any signs of breakthrough in saturated or unsaturated porous media. When the two antibiotics were premixed with GO, their mobility in porous media increased for both saturate and unsaturated conditions and the amount of LEV or CIP in the effluents increased with the increasing of initial GO concentration. During their transport in saturated porous media, some of the GO-bound antibiotics, especially those sorbed via relatively weak interactions, transferred from GO to the quartz sand. Under unsaturated conditions, GO-bound LEV might also transfer from GO to the air-water interface due to the strong affiliation between LEV and air-water interface. Sorption onto GO reduced the antibacterial ability of LEV and CIP, however, the GO-bound antibiotics still effectively inhibited the growth of E coli. Findings from this work indicated that mobile GO affected not only the mobility but also the ecotoxicity of LEV and CIP in porous media.

Experimental Study on Water Sensitivity Difference Based on Oiliness of Porous Medium Rock

Directory of Open Access Journals (Sweden)

Jie Li

2017-01-01

Full Text Available This study presents the differences of water sensitivity experiment of porous medium rock between conventional dry core samples and oil-bearing core. The comparison was made to analyze the impact of single-phase fluid and multiphase fluid on the actual sensitivity of rock. The nuclear magnetic resonance (NMR test was carried out to reveal the distribution of oil in porous medium and the microscopic influence mechanism of oil phase. The study shows that the initial oil in place could isolate the clay from water, and then the expansion and the migration of the clay were prevented to reduce the decrease of degree of damage.

Boundary Layer Flows in Porous Media with Lateral Mass Flux

DEFF Research Database (Denmark)

Nemati, H; H, Bararnia; Noori, F

2015-01-01

Solutions for free convection boundary layers on a heated vertical plate with lateral mass flux embedded in a saturated porous medium are presented using the Homotopy Analysis Method and Shooting Numerical Method. Homotopy Analysis Method yields an analytic solution in the form of a rapidly...

Effects of key factors on solar aided methane steam reforming in porous medium thermochemical reactor

International Nuclear Information System (INIS)

Wang, Fuqiang; Tan, Jianyu; Ma, Lanxin; Leng, Yu

2015-01-01

Highlights: • Effects of key factors on chemical reaction for solar methane reforming are studied. • MCRT and FVM method coupled with UDFs is used to establish numerical model. • Heat and mass transfer model coupled with thermochemical reaction is established. • LTNE model coupled with P1 approximation is used for porous matrix solar reactor. • A formula between H 2 production and conductivity of porous matrix is put forward. - Abstract: With the aid of solar energy, methane reforming process can save up to 20% of the total methane consumption. Monte Carlo Ray Tracing (MCRT) method and Finite Volume Method (FVM) combined method are developed to establish the heat and mass transfer model coupled with thermochemical reaction kinetics for porous medium solar thermochemical reactor. In order to provide more temperature information, local thermal non-equilibrium (LTNE) model coupled with P1 approximation is established to investigate the thermal performance of porous medium solar thermochemical reaction. Effects of radiative heat loss and thermal conductivity of porous matrix on temperature distribution and thermochemical reaction for solar driven steam methane reforming process are numerically studied. Besides, the relationship between hydrogen production and thermal conductivity of porous matrix are analyzed. The results illustrate that hydrogen production shows a 3 order polynomial relation with thermal conductivity of porous matrix

Deposition and release kinetics of nano-TiO2 in saturated porous media: Effects of solution ionic strength and surfactants

International Nuclear Information System (INIS)

Godinez, Itzel G.; Darnault, Christophe J.G.; Khodadoust, Amid P.; Bogdan, Dorin

2013-01-01

The aggregation, transport and deposition kinetics (i.e. attachment and release) of TiO 2 nanoparticles (nano-TiO 2 ) were investigated as a function of ionic strength and the presence of anionic (sodium dodecylbenzene sulfonate, SDBS) and non-ionic (Triton X-100) surfactants in 100% critical micelle concentration (CMC). The electrolyte concentration of the suspensions dictated the kinetic stability of nano-TiO 2 thus influencing the transport and retention of the nanoaggregates in the saturated porous medium. With increasing ionic strength, the interaction between approaching nano-TiO 2 and nano-TiO 2 already deposited onto collectors surfaces seemed to be more favorable than the interaction between approaching nano-TiO 2 and bare collectors surfaces. The abrupt and gradual reduction in electrolyte concentration during the flushing cycles of the column experiments induced the release of previously deposited nano-TiO 2 suggesting attachment of nano-TiO 2 through secondary energy minimum. Highlights: ► This study focuses on aggregation, transport and deposition kinetics of nano-TiO 2 . ► Ionic strength and surfactants impact nano-TiO 2 transport in saturated porous media. ► Previously deposited nano-TiO 2 serve as preferential sites for subsequent deposition. ► Changes in solution chemistry cause nanodeposits to release a portion of nano-TiO 2 . -- Previously deposited nano-TiO 2 serve as preferential sites for subsequent deposition and changes in solution chemistry cause nanodeposits to release a portion of nano-TiO 2

ACOUSTIC WAVES EMISSION IN THE TWO-COMPONENT HEREDITARY-ELASTIC MEDIUM

Directory of Open Access Journals (Sweden)

V. S. Polenov

2014-01-01

Full Text Available Summary. On the dynamics of two-component media a number of papers, which address the elastic waves in a homogeneous, unbounded fluid-saturated porous medium. In other studies address issues of dissipative processes in harmonic deformation hereditary elastic medium. In the article the dissipative processes of the viscoelastic porous medium, which hereditary properties are described by the core relaxation fractional exponential function U.N. Rabotnova integro-differential Boltzmann-Volterr ratio, harmonic deformation by the straining saturated incompressible liquid are investigated. Speed of wave propagation, absorption coefficient, mechanical loss tangent, logarithmic decrement, depending on fractional parameter γ, determining formulas received. The frequency logarithm and temperature graph dependences with the goal fractional parameter are constructed. Shows the dependences velocity and attenuation coefficient of the tangent of the phase angle of the logarithm of the temperature, and the dependence of the attenuation coefficient of the logarithm of the frequency. Dependencies the speed and the tangent of the phase angle of the frequency identical function of the logarithm of temperature.

Simulation of water flow in fractured porous medium by using discretized virtual internal bond

Science.gov (United States)

Peng, Shujun; Zhang, Zhennan; Li, Chunfang; He, Guofu; Miao, Guoqing

2017-12-01

The discretized virtual internal bond (DVIB) is adopted to simulate the water flow in fractured porous medium. The intact porous medium is permeable because it contains numerous micro cracks and pores. These micro discontinuities construct a fluid channel network. The representative volume of this fluid channel network is modeled as a lattice bond cell with finite number of bonds in statistical sense. Each bond serves as a fluid channel. In fractured porous medium, many bond cells are cut by macro fractures. The conductivity of the fracture facet in a bond cell is taken over by the bonds parallel to the flow direction. The equivalent permeability and volumetric storage coefficient of a micro bond are calibrated based on the ideal bond cell conception, which makes it unnecessary to consider the detailed geometry of a specific element. Such parameter calibration method is flexible and applicable to any type of element. The accuracy check results suggest this method has a satisfying accuracy in both the steady and transient flow simulation. To simulate the massive fractures in rockmass, the bond cells intersected by fracture are assigned aperture values, which are assumed random numbers following a certain distribution law. By this method, any number of fractures can be implicitly incorporated into the background mesh, avoiding the setup of fracture element and mesh modification. The fracture aperture heterogeneity is well represented by this means. The simulation examples suggest that the present method is a feasible, simple and efficient approach to the numerical simulation of water flow in fractured porous medium.

Impact of small-scale saline tracer heterogeneity on electrical resistivity monitoring in fully and partially saturated porous media: Insights from geoelectrical milli-fluidic experiments

Science.gov (United States)

Jougnot, Damien; Jiménez-Martínez, Joaquín; Legendre, Raphaël; Le Borgne, Tanguy; Méheust, Yves; Linde, Niklas

2018-03-01

Time-lapse electrical resistivity tomography (ERT) is a geophysical method widely used to remotely monitor the migration of electrically-conductive tracers and contaminant plumes in the subsurface. Interpretations of time-lapse ERT inversion results are generally based on the assumption of a homogeneous solute concentration below the resolution limits of the tomogram depicting inferred electrical conductivity variations. We suggest that ignoring small-scale solute concentration variability (i.e., at the sub-resolution scale) is a major reason for the often-observed apparent loss of solute mass in ERT tracer studies. To demonstrate this, we developed a geoelectrical milli-fluidic setup where the bulk electric conductivity of a 2D analogous porous medium, consisting of cylindrical grains positioned randomly inside a Hele-Shaw cell, is monitored continuously in time while saline tracer tests are performed through the medium under fully and partially saturated conditions. High resolution images of the porous medium are recorded with a camera at regular time intervals, and provide both the spatial distribution of the fluid phases (aqueous solution and air), and the saline solute concentration field (where the solute consists of a mixture of salt and fluorescein, the latter being used as a proxy for the salt concentration). Effective bulk electrical conductivities computed numerically from the measured solute concentration field and the spatial distributions of fluid phases agree well with the measured bulk conductivities. We find that the effective bulk electrical conductivity is highly influenced by the connectivity of high electrical conductivity regions. The spatial distribution of air, saline tracer fingering, and mixing phenomena drive temporal changes in the effective bulk electrical conductivity by creating preferential paths or barriers for electrical current at the pore-scale. The resulting heterogeneities in the solute concentrations lead to strong anisotropy

An agent-based method for simulating porous fluid-saturated structures with indistinguishable components

Science.gov (United States)

Kashani, Jamal; Pettet, Graeme John; Gu, YuanTong; Zhang, Lihai; Oloyede, Adekunle

2017-10-01

Single-phase porous materials contain multiple components that intermingle up to the ultramicroscopic level. Although the structures of the porous materials have been simulated with agent-based methods, the results of the available methods continue to provide patterns of distinguishable solid and fluid agents which do not represent materials with indistinguishable phases. This paper introduces a new agent (hybrid agent) and category of rules (intra-agent rule) that can be used to create emergent structures that would more accurately represent single-phase structures and materials. The novel hybrid agent carries the characteristics of system's elements and it is capable of changing within itself, while also responding to its neighbours as they also change. As an example, the hybrid agent under one-dimensional cellular automata formalism in a two-dimensional domain is used to generate patterns that demonstrate the striking morphological and characteristic similarities with the porous saturated single-phase structures where each agent of the ;structure; carries semi-permeability property and consists of both fluid and solid in space and at all times. We conclude that the ability of the hybrid agent to change locally provides an enhanced protocol to simulate complex porous structures such as biological tissues which could facilitate models for agent-based techniques and numerical methods.

On the importance of aqueous diffusion and electrostatic interactions in advection-dominated transport in saturated porous media

DEFF Research Database (Denmark)

Rolle, Massimo

2015-01-01

to multicomponent ionic dispersion: the dispersive fluxes of the different ions are cross-coupled due to the effects of Coulombic interactions. Such effects are illustrated in flow-through experiments in saturated porous media. Simple strong electrolytes were selected as tracers and their transport was studied...... under different advection-dominated conditions and in homogeneous and heterogeneous porous media. The interpretation of the experimental results requires a multicomponent modeling approach with an accurate description of local hydrodynamic dispersion and explicitly accounting for the cross-coupling...

CFD prediction of mixing in a steam generator mock-up: Comparison between full geometry and porous medium approaches

International Nuclear Information System (INIS)

Dehbi, A.; Badreddine, H.

2013-01-01

Highlights: • CFD is used to simulate single phase mixing in a model steam generator. • Motive of the work is to compare porous media approach with full geometry representation of tubes. • Porous media approach is found to compare favorably with full representation in steady states. - Abstract: In CFD simulations of single phase flow mixing in a steam generator (SG) during a station blackout severe accident, one is faced with the problem of representing the thousands of SG U-tubes. Typically simplifications are made to render the problem computationally tractable. In particular, one or a number of tubes are lumped in one volume that is treated as a single porous medium which replicates the pressure loss and heat transfer characteristics of the real tube. This approach significantly reduces the computational size of the problem and hence simulation time. In this work, we endeavor to investigate the adequacy of this approach by performing a series of simulations. We first validate the porous medium approach against results of the 1/7th scale Westinghouse SG-S3 test. In a second step, we make two separate simulations of flow in the PSI SG mock-up, i.e. one in which the porous medium model is used for the tube bundle, and another in which the full geometry is represented. In all simulations, the Reynolds Stress (RSM) model of turbulence is used. We show that in steady state conditions, the porous medium treatment yields results which are comparable to those of the full geometry representation (temperature distribution, recirculation ratio, hot plume spread, etc.). Hence, the porous medium approach can be extended with a good degree of confidence to model single phase mixing in the full scale SG

Experimental investigation of clogging dynamics in homogeneous porous medium

Science.gov (United States)

Shen, Jikang; Ni, Rui

2017-03-01

A 3-D refractive-index matching Lagrangian particle tracking (3D-RIM-LPT) system was developed to study the filtration and the clogging process inside a homogeneous porous medium. A small subset of particles flowing through the porous medium was dyed and tracked. As this subset was randomly chosen, its dynamics is representative of all the rest. The statistics of particle locations, number, and velocity were obtained as functions of different volumetric concentrations. It is found that in our system the clogging time decays with the particle concentration following a power law relationship. As the concentration increases, there is a transition from depth filtration to cake filtration. At high concentration, more clogged pores lead to frequent flow redirections and more transverse migrations of particles. In addition, the velocity distribution in the transverse direction is symmetrical around zero, and it is slightly more intermittent than the random Gaussian curve due to particle-particle and particle-grain interactions. In contrast, as clogging develops, the longitudinal velocity of particles along the mean flow direction peaks near zero because of many trapped particles. But at the same time, the remaining open pores will experience larger pressure and, as a result, particles through those pores tend to have larger longitudinal velocities.

Transformation of seismic velocity data to extract porosity and saturation values for rocks

International Nuclear Information System (INIS)

Berryman, James G.; Berge, Patricia A.; Bonner, Brian P.

2000-01-01

For wave propagation at low frequencies in a porous medium, the Gassmann-Domenico relations are well-established for homogeneous partial saturation by a liquid. They provide the correct relations for seismic velocities in terms of constituent bulk and shear moduli, solid and fluid densities, porosity and saturation. It has not been possible, however, to invert these relations easily to determine porosity and saturation when the seismic velocities are known. Also, the state (or distribution) of saturation, i.e., whether or not liquid and gas are homogeneously mixed in the pore space, is another important variable for reservoir evaluation. A reliable ability to determine the state of saturation from velocity data continues to be problematic. It is shown how transforming compressional and shear wave velocity data to the (ρ/λ,μ/λ)-plane (where λ and μ are the Lame parameters and ρ is the total density) results in a set of quasi-orthogonal coordinates for porosity and liquid saturation that greatly aids in the interpretation of seismic data for the physical parameters of most interest. A second transformation of the same data then permits isolation of the liquid saturation value, and also provides some direct information about the state of saturation. By thus replotting the data in the (λ/μ, ρ/μ)-plane, inferences can be made concerning the degree of patchy (inhomogeneous) versus homogeneous saturation that is present in the region of the medium sampled by the data. Our examples include igneous and sedimentary rocks, as well as man-made porous materials. These results have potential applications in various areas of interest, including petroleum exploration and reservoir characterization, geothermal resource evaluation, environmental restoration monitoring, and geotechnical site characterization. (c) 2000 Acoustical Society of America

Thermosolutal convection in saturated porous enclosure with concentrated energy and solute sources

Energy Technology Data Exchange (ETDEWEB)

Liu, Di; Zhao, Fu-Yun; Tang, Guang-Fa [College of Civil Engineering, Hunan University, Changsha (China)

2008-01-15

Double diffusive natural convection within a vertical porous enclosure with localized heating and salting from one side is numerically studied by the finite element based finite volume method. In the formulation of the problem, use is made of the Darcy model, which allows the slip boundary condition on a solid wall to be satisfied. Comparisons with benchmark solutions for natural convection in fluid saturated porous enclosures are first presented to validate the code. Following that, an extensive series of numerical simulations is conducted in the range of -55 {<=} N {<=} + 55 and 0.125 {<=} L {<=} 0.875, where N and L are the buoyancy ratio and the element location, respectively. Streamlines, heatlines, masslines, isotherms and iso-concentrations in the system are produced to illustrate the flow structure transition from solutal dominated opposing to thermal dominated and solutal dominated aiding flows, respectively. The computed average Nusselt and Sherwood numbers provide guidance for locating the heating and salting element. (author)

Thermosolutal convection in saturated porous enclosure with concentrated energy and solute sources

Energy Technology Data Exchange (ETDEWEB)

Liu Di [College of Civil Engineering, Hunan University, Changsha (China)], E-mail: liudi66@163.com; Zhao Fuyun [College of Civil Engineering, Hunan University, Changsha (China)], E-mail: zfycfdnet@163.com; Tang Guangfa [College of Civil Engineering, Hunan University, Changsha (China)], E-mail: gftangcfd@163.com

2008-01-15

Double diffusive natural convection within a vertical porous enclosure with localized heating and salting from one side is numerically studied by the finite element based finite volume method. In the formulation of the problem, use is made of the Darcy model, which allows the slip boundary condition on a solid wall to be satisfied. Comparisons with benchmark solutions for natural convection in fluid saturated porous enclosures are first presented to validate the code. Following that, an extensive series of numerical simulations is conducted in the range of -55 {<=} N {<=} + 55 and 0.125 {<=} L {<=} 0.875, where N and L are the buoyancy ratio and the element location, respectively. Streamlines, heatlines, masslines, isotherms and iso-concentrations in the system are produced to illustrate the flow structure transition from solutal dominated opposing to thermal dominated and solutal dominated aiding flows, respectively. The computed average Nusselt and Sherwood numbers provide guidance for locating the heating and salting element.

Application of the finite volume method in the simulation of saturated flows of binary mixtures

International Nuclear Information System (INIS)

Murad, M.A.; Gama, R.M.S. da; Sampaio, R.

1989-12-01

This work presents the simulation of saturated flows of an incompressible Newtonian fluid through a rigid, homogeneous and isotropic porous medium. The employed mathematical model is derived from the Continuum Theory of Mixtures and generalizes the classical one which is based on Darcy's Law form of the momentum equation. In this approach fluid and porous matrix are regarded as continuous constituents of a binary mixture. The finite volume method is employed in the simulation. (author) [pt

Multi-level adaptive simulation of transient two-phase flow in heterogeneous porous media

KAUST Repository

Chueh, C.C.

2010-10-01

An implicit pressure and explicit saturation (IMPES) finite element method (FEM) incorporating a multi-level shock-type adaptive refinement technique is presented and applied to investigate transient two-phase flow in porous media. Local adaptive mesh refinement is implemented seamlessly with state-of-the-art artificial diffusion stabilization allowing simulations that achieve both high resolution and high accuracy. Two benchmark problems, modelling a single crack and a random porous medium, are used to demonstrate the robustness of the method and illustrate the capabilities of the adaptive refinement technique in resolving the saturation field and the complex interaction (transport phenomena) between two fluids in heterogeneous media. © 2010 Elsevier Ltd.

The effect of Coriolis force on nonlinear convection in a porous medium

Directory of Open Access Journals (Sweden)

D. H. Riahi

1994-01-01

Full Text Available Nonlinear convection in a porous medium and rotating about vertical axis is studied in this paper. An upper bound to the heat flux is calculated by the method initiated first by Howard [6] for the case of infinite Prandtl number.

Simulation of CO2 Injection in Porous Media with Structural Deformation Effect

KAUST Repository

Negara, Ardiansyah

2011-06-18

Carbon dioxide (CO2) sequestration is one of the most attractive methods to reduce the amount of CO2 in the atmosphere by injecting it into the geological formations. Furthermore, it is also an effective mechanism for enhanced oil recovery. Simulation of CO2 injection based on a suitable modeling is very important for explaining the fluid flow behavior of CO2 in a reservoir. Increasing of CO2 injection may cause a structural deformation of the medium. The structural deformation modeling in carbon sequestration is useful to evaluate the medium stability to avoid CO2 leakage to the atmosphere. Therefore, it is important to include such effect into the model. The purpose of this study is to simulate the CO2 injection in a reservoir. The numerical simulations of two-phase flow in homogeneous and heterogeneous porous media are presented. Also, the effects of gravity and capillary pressure are considered. IMplicit Pressure Explicit Saturation (IMPES) and IMplicit Pressure-Displacements and an Explicit Saturation (IMPDES) schemes are used to solve the problems under consideration. Various numerical examples were simulated and divided into two parts of the study. The numerical results demonstrate the effects of buoyancy and capillary pressure as well as the permeability value and its distribution in the domain. Some conclusions that could be derived from the numerical results are the buoyancy of CO2 is driven by the density difference, the CO2 saturation profile (rate and distribution) are affected by the permeability distribution and its value, and the displacements of the porous medium go to constant values at least six to eight months (on average) after injection. Furthermore, the simulation of CO2 injection provides intuitive knowledge and a better understanding of the fluid flow behavior of CO2 in the subsurface with the deformation effect of the porous medium.

Graphene oxide-facilitated transport of levofloxacin and ciprofloxacin in saturated and unsaturated porous media.

Science.gov (United States)

Sun, Kaixuan; Dong, Shunan; Sun, Yuanyuan; Gao, Bin; Du, Wenchao; Xu, Hongxia; Wu, Jichun

2018-04-15

In this work, effects of graphene oxide (GO) on the co-transport of the two typical Fluoroquinolones (FQs) - levofloxacin (LEV) and ciprofloxacin (CIP) in saturated and unsaturated quartz sand media were studied. The adsorption isotherms showed that GO had much larger sorption capacities to LEV and CIP than sand with the largest Langmuir adsorption capacity of 409 mg g -1 (CIP-GO); while the sorption affinity of the two FQs onto the two adsorbents might follow the order of CIP-sand > LEV-sand > LEV-GO > CIP-GO. GO promoted the mobility of the two FQs in both saturated and unsaturated porous media due to its strong mobility and sorption capacity. The GO-bound LEV/CIP was responsible for the LEV/CIP transport in the porous media, and transport of GO-bound FQs increased with the increasing of initial GO concentration. Under unsaturated conditions, moisture showed little effect on the transport of GO-bound CIP; however, the mobility of GO-bound LEV reduced with the decreasing of moisture content, suggesting the transport of adsorbed LEV from GO to air-water interface. GO sorption reduced the antibacterial ability of the two FQs, but they were still effective in inhibiting E. coli growth. Copyright © 2018 Elsevier B.V. All rights reserved.

Description of regional blow-up in a porous-medium equation

Directory of Open Access Journals (Sweden)

Carmen Cortazar

2002-10-01

Full Text Available We describe the (finite-time blow-up phenomenon for a non-negative solution of a porous medium equation of the form $$ u_t = Delta u^m + u^m $$ in the entire space. Here $m>1$ and the initial condition is assumed compactly supported. Blow-up takes place exactly inside a finite number of balls with same radii and exhibiting the same self-similar profile.

Transport of water and ions in partially water-saturated porous media. Part 2. Filtration effects

Science.gov (United States)

Revil, A.

2017-05-01

A new set of constitutive equations describing the transport of the ions and water through charged porous media and considering the effect of ion filtration is applied to the problem of reverse osmosis and diffusion of a salt. Starting with the constitutive equations derived in Paper 1, I first determine specific formula for the osmotic coefficient and effective diffusion coefficient of a binary symmetric 1:1 salt (such as KCl or NaCl) as a function of a dimensionless number Θ corresponding to the ratio between the cation exchange capacity (CEC) and the salinity. The modeling is first carried with the Donnan model used to describe the concentrations of the charge carriers in the pore water phase. Then a new model is developed in the thin double layer approximation to determine these concentrations. These models provide explicit relationships between the concentration of the ionic species in the pore space and those in a neutral reservoir in local equilibrium with the pore space and the CEC. The case of reverse osmosis and diffusion coefficient are analyzed in details for the case of saturated and partially saturated porous materials. Comparisons are done with experimental data from the literature obtained on bentonite. The model predicts correctly the influence of salinity (including membrane behavior at high salinities), porosity, cation type (K+ versus Na+), and water saturation on the osmotic coefficient. It also correctly predicts the dependence of the diffusion coefficient of the salt with the salinity.

Homogenization of one-dimensional draining through heterogeneous porous media including higher-order approximations

Science.gov (United States)

Anderson, Daniel M.; McLaughlin, Richard M.; Miller, Cass T.

2018-02-01

We examine a mathematical model of one-dimensional draining of a fluid through a periodically-layered porous medium. A porous medium, initially saturated with a fluid of a high density is assumed to drain out the bottom of the porous medium with a second lighter fluid replacing the draining fluid. We assume that the draining layer is sufficiently dense that the dynamics of the lighter fluid can be neglected with respect to the dynamics of the heavier draining fluid and that the height of the draining fluid, represented as a free boundary in the model, evolves in time. In this context, we neglect interfacial tension effects at the boundary between the two fluids. We show that this problem admits an exact solution. Our primary objective is to develop a homogenization theory in which we find not only leading-order, or effective, trends but also capture higher-order corrections to these effective draining rates. The approximate solution obtained by this homogenization theory is compared to the exact solution for two cases: (1) the permeability of the porous medium varies smoothly but rapidly and (2) the permeability varies as a piecewise constant function representing discrete layers of alternating high/low permeability. In both cases we are able to show that the corrections in the homogenization theory accurately predict the position of the free boundary moving through the porous medium.

Viscoelastic Waves Simulation in a Blocky Medium with Fluid-Saturated Interlayers Using High-Performance Computing

Science.gov (United States)

Sadovskii, Vladimir; Sadovskaya, Oxana

2017-04-01

A thermodynamically consistent approach to the description of linear and nonlinear wave processes in a blocky medium, which consists of a large number of elastic blocks interacting with each other via pliant interlayers, is proposed. The mechanical properties of interlayers are defined by means of the rheological schemes of different levels of complexity. Elastic interaction between the blocks is considered in the framework of the linear elasticity theory [1]. The effects of viscoelastic shear in the interblock interlayers are taken into consideration using the Pointing-Thomson rheological scheme. The model of an elastic porous material is used in the interlayers, where the pores collapse if an abrupt compressive stress is applied. On the basis of the Biot equations for a fluid-saturated porous medium, a new mathematical model of a blocky medium is worked out, in which the interlayers provide a convective fluid motion due to the external perturbations. The collapse of pores is modeled within the generalized rheological approach, wherein the mechanical properties of a material are simulated using four rheological elements. Three of them are the traditional elastic, viscous and plastic elements, the fourth element is the so-called rigid contact [2], which is used to describe the behavior of materials with different resistance to tension and compression. Thermodynamic consistency of the equations in interlayers with the equations in blocks guarantees fulfillment of the energy conservation law for a blocky medium in a whole, i.e. kinetic and potential energy of the system is the sum of kinetic and potential energies of the blocks and interlayers. As a result of discretization of the equations of the model, robust computational algorithm is constructed, that is stable because of the thermodynamic consistency of the finite difference equations at a discrete level. The splitting method by the spatial variables and the Godunov gap decay scheme are used in the blocks, the

Full-field dye concentration measurement within saturated/unsaturated thin slabs of porous media

International Nuclear Information System (INIS)

Norton, D.L.; Glass, R.J.

1993-01-01

This paper presents a full-field dye concentration measurement technique that extends our experimental capabilities to the measurement of transient dye concentration fields within steady state flow fields under unsaturated or saturated conditions. Simple light absorption theory provides a basis for translating images into high resolution dye concentration fields. A series of dye pulse experiments that demonstrate the combined use of the full-field saturation and dye concentration techniques was conducted at four different degrees of saturation. Each of these experimental sequences was evaluated with respect to mass balance, the results being within 5% of the known dye mass input. An image windowing technique allowed us to see increased dispersion due to decreasing moisture content, tailing of concentration at the rear of the dye pulse and slight velocity changes of the dispersive front due to changes in moisture content. The exceptional resolution of dye concentration in space and time provided by this laboratory technique allows systematic experimentation for examining basic processes affecting solute transport within saturated/unsaturated porous media. Future challenges for this work will be to use these techniques to analyze more complex systems involving heterogeneities, scaling laws, and detailed investigations of the relationship between transverse and longitudinal dispersion in unsaturated media

Growth of fingers at an unstable diffusing interface in a porous medium or hele-shaw cell

Energy Technology Data Exchange (ETDEWEB)

Wooding, R A

1969-11-27

Waves at an unstable horizontal interface, between 2 fluids moving vertically through a saturated porous medium, are observed to grow rapidly to become fingers (i.e., the amplitude greatly exceeds the wavelength). For a diffusing interface, in experiments using a Hele-Shaw cell, the mean amplitude taken over many fingers grows approx. as (time)U2D, followed by a transition to a growth proportional to time. Correspondingly, the mean wave number decreases approx. as (time)U-1/2D. Because of the rapid increase in amplitude, longitudinal dispersion ultimately becomes negligible relative to wave growth. To represent the observed quantities at large time, the transport equation is suitably weighted and averaged over the horizontal plane. Hyperbolic equations result, and the ascending and descending zones containing the fronts of the fingers are replaced by discontinuities. These averaged equations form an open set, but closure is achieved by assuming a law for the mean wave number based on similarity. (22 refs.)

Theoretical Study of Heat Transfer through a Sun Space Filled with a Porous Medium

Directory of Open Access Journals (Sweden)

Ahmed Tawfeeq Ahmed Al-Sammarraie

2016-10-01

Full Text Available A theoretical study had been conducted to detect the effect of using a porous medium in sunspace to reduce  heating  load  and  overcoming  coldness  of  winter  in  the  cold  regions.  In  this  work,  the  heat transferred and stored in the storage wall was investigated. The mathematical model was unsteady, heat conduction equation with nonlinear boundary conditions was solved by using finite difference method and the solution technique  of heat conduction had based  on the  Crank Nicholson method. The results had adopted  on  the  aspect  ratio  (H/L=30,  Darcy  number  (Da=10-3,  porosity  (φ=0.35  and  particle  to  fluid thermal conductivity ratio (kp/kf=38.5. The results showed that using the porous medium had enhanced the heat transferred and stored in the storage wall. For   the outside storage wall temperature, an increase of 19.7%  was achieved by using the porous medium instead of the air, while it was 20.3%  for the inside storage wall temperature.

Effect of Variable Viscosity on Vortex Instability of Non-Darcy Mixed Convection Boundary Layer Flow Adjacent to a Nonisothermal Horizontal Surface in a Porous Medium

Directory of Open Access Journals (Sweden)

A. M. Elaiw

2012-01-01

Full Text Available We study the effect of variable viscosity on the flow and vortex instability for non-Darcy mixed convection boundary layer flow on a nonisothermal horizontal plat surface in a saturated porous medium. The variation of viscosity is expressed as an exponential function of temperature. The analysis of the disturbance flow is based on linear stability theory. The base flow equations and the resulting eigenvalue problem are solved using finite difference schemes. It is found that the variable viscosity effect enhances the heat transfer rate and destabilizes the flow for liquid heating, while the opposite trend is true for gas heating.

On the viscous dissipation modeling of thermal fluid flow in a porous medium

KAUST Repository

Salama, Amgad; El-Amin, Mohamed; Abbas, Ibrahim A A; Sun, Shuyu

2011-01-01

wall that is immersed in the porous medium and is kept at constant higher temperature. The boundary layer approximations were used to simplify the set of the governing, nonlinear partial differential equations, which were then non

Long-wave equivalent viscoelastic solids for porous rocks saturated by two-phase fluids

Science.gov (United States)

Santos, J. E.; Savioli, G. B.

2018-04-01

Seismic waves traveling across fluid-saturated poroelastic materials with mesoscopic-scale heterogeneities induce fluid flow and Biot's slow waves generating energy loss and velocity dispersion. Using Biot's equations of motion to model these type of heterogeneities would require extremely fine meshes. We propose a numerical upscaling procedure to determine the complex and frequency dependent P-wave and shear moduli of an effective viscoelastic medium long-wave equivalent to a poroelastic solid saturated by a two-phase fluid. The two-phase fluid is defined in terms of capillary pressure and relative permeability flow functions. The P-wave and shear effective moduli are determined using harmonic compressibility and shear experiments applied on representative samples of the bulk material. Each experiment is associated with a boundary value problem that is solved using the finite element method. Since a poroelastic solid saturated by a two-phase fluid supports the existence of two slow waves, this upscaling procedure allows to analyze their effect on the mesoscopic-loss mechanism in hydrocarbon reservoir formations. Numerical results show that a two-phase Biot medium model predicts higher attenuation than classic Biot models.

Numerical analysis of gas transfer by natural convection in a fluid saturated porous medium

International Nuclear Information System (INIS)

Akbal, S.; Filiz Baytas, A.

2005-01-01

The concentration distribution of a radioactive gas in a square porous cavity is investigated in this study. The decay of the radioactive gas is taken into account in the concentration equation. The governing equations are solved using alternating direction implicit method (ADI) and Finite volume method. Numerical results for velocity and concentration profiles are presented for an extensive range of parameter like Grashof number (Gr c ), Schmidt number (Sc) and the non-dimensional constant of radioactive decay. (authors)

Numerical analysis of gas transfer by natural convection in a fluid saturated porous medium

Energy Technology Data Exchange (ETDEWEB)

Akbal, S. [Cekmece Nuclear Research and Training Center (Turkey); Filiz Baytas, A. [Istanbul Technical Univ. (Turkey). Inst. for Energy

2005-07-01

The concentration distribution of a radioactive gas in a square porous cavity is investigated in this study. The decay of the radioactive gas is taken into account in the concentration equation. The governing equations are solved using alternating direction implicit method (ADI) and Finite volume method. Numerical results for velocity and concentration profiles are presented for an extensive range of parameter like Grashof number (Gr{sub c}), Schmidt number (Sc) and the non-dimensional constant of radioactive decay. (authors)

Effect of radiation on the laminar convective heat transfer through a layer of highly porous medium

International Nuclear Information System (INIS)

Lee, K.; Howell, J.R.

1986-01-01

A numerical investigation is reported of the coupled forced convective and radiative transfer through a highly porous medium. The porosity range investigated is high enough that the fluid inertia terms in the momentum equation cannot be neglected; i.e., the simple form of Darcy's law is invalid. The geometry studied is a plane layer of highly porous medium resting on one impermeable boundary and exposed to a two-dimensional laminar external flow field. The objective is to determine the effective overall heat transfer coefficients for such a geometry. The results are applicable to diverse situations, including insulation batts exposed to external flow, the heat loss and drying rates of grain fields and forest areas, and the drying of beds of porous material exposed to convective and radiative heating

A note on similarity in single-phase and porous-medium natural convection

International Nuclear Information System (INIS)

Lyall, H.G.

1981-03-01

The similarity laws for single-phase and porous-medium natural convection are developed. For single-phase flow Nu = Nu(Ra) implies that inertial effects are negligible, while Nu = Nu(Ra.Pr) implies that viscous effects are. The first correlation is adequate for Pr>10, while the second applies for Pr<0.01. For intermediate values of Pr, a more general correlation, Nu = Nu(Ra,Pr) is necessary. For a porous-medium, if inertial effects and dispersion are negligible, Nu* = Nu*(Ra*). However dispersion will only be negligible if the ratio of grain size d to the width of the region L is very small (d/L<< l). If this condition does not hold it is necessary to model d/L. If inertial effects are significant, i.e. the Reynolds number is too large for Darcy's law to apply, a group containing the effective Prandtl number, Pr*, also needs to be modelled for similarity. (author)

Differentiated-effect shims for medium field levels and saturation

International Nuclear Information System (INIS)

Richie, A.

1976-01-01

The arrangement of shims on the upstream and downstream ends of magnets may be based on the independent effects of variations in the geometric length and degree of saturation at the edges of the poles. This technique can be used to match the bending strength of an accelerator's magnets at two field levels (medium fields and maximum fields) and thus save special procedures (mixing the laminations, local compensation for errors by arranging the magnets in the appropriate order) and special devices (for instance, correcting dipoles) solely for correcting bending strengths at low field levels. (Auth.)

Natural convection in a porous medium: External flows

International Nuclear Information System (INIS)

Cheng, P.

1985-01-01

Early theoretical work on heat transfer in porous media focussed its attention on the onset of natural convection and cellular convection in rectangular enclosures with heating from below. Recently, increased attention has been directed to the study of natural convection in a porous medium external to heated surfaces and bodies. Boundary layer approximations were introduced, and similarly solutions have been obtained for steady natural convection boundary layers adjacent to a heated flat plate, a horizontal cylinder and a sphere as well as other two-dimensional and axisymmetric bodies of arbitrary shape. Higher order boundary layer theories have been carried out to assess the accuracy of the boundary layer approximation. The effects of entrainments at the edge of the boundary layer, the inclination angle of the heated inclined plate, and the upstream geometry on the heat transfer characteristics have been investigated based on the method of matched asymptotic expansions. The conditions for the onset of vortex instability in porous layers heated from below were determined based on linear stability analyses. The effects of no-slip boundary conditions, non-Darcy and thermal dispersion, which were neglected in all of the previous theoretical investigations, have recently been re-examined. Experimental investigations on natural convection about a vertical and inclined heated plate, a horizontal cylinder, as well as plume rise from a horizontal line source of heat have been conducted. All of this work is reviewed in this paper

Uniqueness of Specific Interfacial Area–Capillary Pressure–Saturation Relationship Under Non-Equilibrium Conditions in Two-Phase Porous Media Flow

KAUST Repository

Joekar-Niasar, Vahid

2012-02-23

The capillary pressure-saturation (P c-S w) relationship is one of the central constitutive relationships used in two-phase flow simulations. There are two major concerns regarding this relation. These concerns are partially studied in a hypothetical porous medium using a dynamic pore-network model called DYPOSIT, which has been employed and extended for this study: (a) P c-S w relationship is measured empirically under equilibrium conditions. It is then used in Darcy-based simulations for all dynamic conditions. This is only valid if there is a guarantee that this relationship is unique for a given flow process (drainage or imbibition) independent of dynamic conditions; (b) It is also known that P c-S w relationship is flow process dependent. Depending on drainage and imbibition, different curves can be achieved, which are referred to as "hysteresis". A thermodynamically derived theory (Hassanizadeh and Gray, Water Resour Res 29: 3389-3904, 1993a) suggests that, by introducing a new state variable, called the specific interfacial area (a nw, defined as the ratio of fluid-fluid interfacial area to the total volume of the domain), it is possible to define a unique relation between capillary pressure, saturation, and interfacial area. This study investigates these two aspects of capillary pressure-saturation relationship using a dynamic pore-network model. The simulation results imply that P c-S w relation not only depends on flow process (drainage and imbibition) but also on dynamic conditions for a given flow process. Moreover, this study attempts to obtain the first preliminary insights into the global functionality of capillary pressure-saturation-interfacial area relationship under equilibrium and non-equilibrium conditions and the uniqueness of P c-S w-a nw relationship. © 2012 The Author(s).

A physically-based analytical model to describe effective excess charge for streaming potential generation in saturated porous media

Science.gov (United States)

Jougnot, D.; Guarracino, L.

2016-12-01

The self-potential (SP) method is considered by most researchers the only geophysical method that is directly sensitive to groundwater flow. One source of SP signals, the so-called streaming potential, results from the presence of an electrical double layer at the mineral-pore water interface. When water flows through the pore space, it gives rise to a streaming current and a resulting measurable electrical voltage. Different approaches have been proposed to predict streaming potentials in porous media. One approach is based on the excess charge which is effectively dragged in the medium by the water flow. Following a recent theoretical framework, we developed a physically-based analytical model to predict the effective excess charge in saturated porous media. In this study, the porous media is described by a bundle of capillary tubes with a fractal pore-size distribution. First, an analytical relationship is derived to determine the effective excess charge for a single capillary tube as a function of the pore water salinity. Then, this relationship is used to obtain both exact and approximated expressions for the effective excess charge at the Representative Elementary Volume (REV) scale. The resulting analytical relationship allows the determination of the effective excess charge as a function of pore water salinity, fractal dimension and hydraulic parameters like porosity and permeability, which are also obtained at the REV scale. This new model has been successfully tested against data from the literature of different sources. One of the main finding of this study is that it provides a mechanistic explanation to the empirical dependence between the effective excess charge and the permeability that has been found by various researchers. The proposed petrophysical relationship also contributes to understand the role of porosity and water salinity on effective excess charge and will help to push further the use of streaming potential to monitor groundwater flow.

A hierarchy of models for simulating experimental results from a 3D heterogeneous porous medium

Science.gov (United States)

Vogler, Daniel; Ostvar, Sassan; Paustian, Rebecca; Wood, Brian D.

2018-04-01

In this work we examine the dispersion of conservative tracers (bromide and fluorescein) in an experimentally-constructed three-dimensional dual-porosity porous medium. The medium is highly heterogeneous (σY2 = 5.7), and consists of spherical, low-hydraulic-conductivity inclusions embedded in a high-hydraulic-conductivity matrix. The bimodal medium was saturated with tracers, and then flushed with tracer-free fluid while the effluent breakthrough curves were measured. The focus for this work is to examine a hierarchy of four models (in the absence of adjustable parameters) with decreasing complexity to assess their ability to accurately represent the measured breakthrough curves. The most information-rich model was (1) a direct numerical simulation of the system in which the geometry, boundary and initial conditions, and medium properties were fully independently characterized experimentally with high fidelity. The reduced-information models included; (2) a simplified numerical model identical to the fully-resolved direct numerical simulation (DNS) model, but using a domain that was one-tenth the size; (3) an upscaled mobile-immobile model that allowed for a time-dependent mass-transfer coefficient; and, (4) an upscaled mobile-immobile model that assumed a space-time constant mass-transfer coefficient. The results illustrated that all four models provided accurate representations of the experimental breakthrough curves as measured by global RMS error. The primary component of error induced in the upscaled models appeared to arise from the neglect of convection within the inclusions. We discuss the necessity to assign value (via a utility function or other similar method) to outcomes if one is to further select from among model options. Interestingly, these results suggested that the conventional convection-dispersion equation, when applied in a way that resolves the heterogeneities, yields models with high fidelity without requiring the imposition of a more

Heat and mass transfer by free convection in a porous medium along a surface of arbitrary shape

International Nuclear Information System (INIS)

Hossain, M.A.; Nakayama, A.

1993-06-01

Free convection flow of a viscous incompressible fluid in the presence of species concentration along a surface of arbitrary shape embedded in a saturated porous medium is investigated with non-uniform surface temperature and surface concentration distributions. The equations governing the flow, derived in the form of local similarity and nonsimilarity equations, are integrated numerically using the implicit finite difference approximation together with the Keller box method. Exact solutions of the local similarity equations are also obtained and compared with the finite difference solutions. All the solutions are shown graphically in terms of local Nusselt number, Nu χ , and local Sherwood number, Sh χ , against the physical parameter ξ (which characterizes the streamwise distance along the surface from the leading edge) taking the value of the Lewis number, Le, equals 1 0, 5, and 10 while N (which defines the ratio between the buoyancy forces arise due to thermal and mass diffusion) is unity. (author). Refs, 5 figs, 1 tab

Thermodynamic analysis of the heat regenerative cycle in porous medium engine

International Nuclear Information System (INIS)

Liu Hongsheng; Xie Maozhao; Wu Dan

2009-01-01

The advantages of homogeneous combustion in internal combustion engines are well known all over the world. Recent years, porous medium (PM) engine has been proposed as a new type engine based on the technique of combustion in porous medium, which can fulfils all requirements to perform homogeneous combustion. In this paper, working processes of a PM engine are briefly introduced and an ideal thermodynamic model of the PM heat regeneration cycle in PM engine is developed. An expression for the relation between net work output and thermal efficiency is derived for the cycle. In order to evaluate of the cycle, the influences of the expansion ratio, initial temperature and limited temperature on the net work and efficiency are discussed, and the availability terms of the cycle are analyzed. Comparing the PM heat regenerative cycle of the PM engine against Otto cycle and Diesel cycle shows that PM heat regenerative cycle can improve net work output greatly with little drop of efficiency. The aim of this paper is to predict the thermodynamic performance of PM heat regeneration cycle and provide a guide to further investigations of the PM engine

Dispersion of extensional waves in fluid-saturated porous cylinders at ultrasonic frequencies

International Nuclear Information System (INIS)

Berryman, J.G.

1983-01-01

Ultrasonic dispersion of extensional waves in fluid-saturated porous cylinders is studied by analyzing generalized Pochhammer equations derived using Biot's theory. Cases with open-pore surface and closed-pore surface boundary conditions are considered. For both cases, the dispersion of the fast extensional wave does not differ much qualitatively from the dispersion expected for extensional waves in isotropic elastic cylinders. A slow extensional wave propagates in the case with a closed-pore surface but not in the case with an open-pore surface. The propagating slow wave has very weak dispersion and its speed is always lower than, but close to, the bulk slow wave speed

Heat transfer prediction in a square porous medium using artificial neural network

Science.gov (United States)

Ahamad, N. Ameer; Athani, Abdulgaphur; Badruddin, Irfan Anjum

2018-05-01

Heat transfer in porous media has been investigated extensively because of its applications in various important fields. Neural network approach is applied to analyze steady two dimensional free convection flows through a porous medium fixed in a square cavity. The backpropagation neural network is trained and used to predict the heat transfer. The results are compared with available information in the literature. It is found that the heat transfer increases with increase in Rayleigh number. It is further found that the local Nusselt number decreases along the height of cavity. The neural network is found to predict the heat transfer behavior accurately for given parameters.

Concurrent freezing and sublimation of a liquid-saturated porous slab

International Nuclear Information System (INIS)

Vaidyanathan, N.; Shamsundar, N.

1991-01-01

In this paper analytical models are formulated for describing heat and mass transport during concurrent freezing and sublimation of a one-dimensional liquid-saturated porous slab. The models are based on transient heat transfer in the frozen and wet regions, and quasi-steady heat and mass transfer in the dried region. The enthalpy method in conjunction with a fully implicit finite-difference scheme is employed to obtain the solution in the frozen and wet regions. A quasi-steady solution is used in the dried region. The governing equations are nondimensionalized and parametric studies are performed. The results indicate that the Luikov number, the ambient vapor pressure, and the heat transfer Biot number are important parameters. The results also confirm that the sublimation interface temperature may show significant variations, in contrast to earlier studies in which it was assumed constant

Transport and fate of Herbaspirillum chlorophenolicum FA1 in saturated porous media

Science.gov (United States)

Li, X.; Xu, H.; Wu, J.

2016-12-01

For the bioremediation of contaminated groundwater, sufficient dispersal of functional microorganisms is one of the most important factors that determine the remediation efficiency. There are extensive studies on the transport of microbes in porous media, while most of them focus on pathogenic bacteria and little attention has been given toward functional bacteria that being used in bioremediation process. Therefore, accurate knowledge of the mechanisms that govern the transport and distribution of such bacteria in groundwater is needed to develop efficient treatment techniques. Herbaspirillum chlorophenolicum FA1, a pure bacterial strain capable of absorbing heavy metals and degrading polycyclic aromatic hydrocarbons (PAHs), was selected as the representative functional bacterium in this study. A series of batch and column experiments were conducted to investigate the transport and deposition behavior of strain FA1 in saturated porous media. The effects of physical (grain size), chemical (ionic strength, humic acid), and biological factors (living/dead cells) were studied in detail. In addition, numerical simulations of breakthrough curve (BTC) data were also performed for information gathering. Results of this study could advance our understanding of functional bacteria transport and help to develop successful bioremediation strategies. This work was financially supported by the National Natural Science Foundation of China -Xinjiang Project (U1503282), the National Natural Science Foundation of China (41030746, 41102148), and the Natural Science Foundation of Jiangsu Province (BK20151385). Keywords: Herbaspirillum chlorophenolicum FA1, bacteria, porous media, transport, modeling

Saturated poroelastic actuators generated by topology optimization

DEFF Research Database (Denmark)

Andreasen, Casper Schousboe; Sigmund, Ole

2011-01-01

the coupling of internal fluid pressure and elastic shear stresses a slab of the optimized porous material deflects/deforms when a pressure is imposed and an actuator is created. Several phenomenologically based constraints are imposed in order to get a stable force transmitting actuator.......In this paper the fluid-structure interaction problem of a saturated porous media is considered. The pressure coupling properties of porous saturated materials change with the microstructure and this is utilized in the design of an actuator using a topology optimized porous material. By maximizing...

Monolithic multigrid method for the coupled Stokes flow and deformable porous medium system

NARCIS (Netherlands)

P. Luo (Peiyao); C. Rodrigo (Carmen); F.J. Gaspar Lorenz (Franscisco); C.W. Oosterlee (Cornelis)

2018-01-01

textabstractThe interaction between fluid flow and a deformable porous medium is a complicated multi-physics problem, which can be described by a coupled model based on the Stokes and poroelastic equations. A monolithic multigrid method together with either a coupled Vanka smoother or a decoupled

Crystal precipitation and dissolution in a porous medium: Effective equations and numerical experiments

NARCIS (Netherlands)

Noorden, van T.L.

2009-01-01

We investigate a two-dimensional microscale model for crystal dissolution and precipitation in a porous medium. The model contains a free boundary and allows for changes in the pore volume. Using a level set formulation of the free boundary, we apply a formal homogenization procedure to obtain

Modeling seismic stimulation: Enhanced non-aqueous fluid extraction from saturated porous media under pore-pressure pulsing at low frequencies

Science.gov (United States)

Lo, Wei-Cheng; Sposito, Garrison; Huang, Yu-Han

2012-03-01

Seismic stimulation, the application of low-frequency stress-pulsing to the boundary of a porous medium containing water and a non-aqueous fluid to enhance the removal of the latter, shows great promise for both contaminated groundwater remediation and enhanced oil recovery, but theory to elucidate the underlying mechanisms lag significantly behind the progress achieved in experimental research. We address this conceptual lacuna by formulating a boundary-value problem to describe pore-pressure pulsing at seismic frequencies that is based on the continuum theory of poroelasticity for an elastic porous medium permeated by two immiscible fluids. An exact analytical solution is presented that is applied numerically using elasticity parameters and hydraulic data relevant to recent proof-of-principle laboratory experiments investigating the stimulation-induced mobilization of trichloroethene (TCE) in water flowing through a compressed sand core. The numerical results indicated that significant stimulation-induced increases of the TCE concentration in effluent can be expected from pore-pressure pulsing in the frequency range of 25-100 Hz, which is in good agreement with what was observed in the laboratory experiments. Sensitivity analysis of our numerical results revealed that the TCE concentration in the effluent increases with the porous medium framework compressibility and the pulsing pressure. Increasing compressibility also leads to an optimal stimulation response at lower frequencies, whereas changing the pulsing pressure does not affect the optimal stimulation frequency. Within the context of our model, the dominant physical cause for enhancement of non-aqueous fluid mobility by seismic stimulation is the dilatory motion of the porous medium in which the solid and fluid phases undergo opposite displacements, resulting in stress-induced changes of the pore volume.

Intermittent Lagrangian velocities and accelerations in three-dimensional porous medium flow.

Science.gov (United States)

Holzner, M; Morales, V L; Willmann, M; Dentz, M

2015-07-01

Intermittency of Lagrangian velocity and acceleration is a key to understanding transport in complex systems ranging from fluid turbulence to flow in porous media. High-resolution optical particle tracking in a three-dimensional (3D) porous medium provides detailed 3D information on Lagrangian velocities and accelerations. We find sharp transitions close to pore throats, and low flow variability in the pore bodies, which gives rise to stretched exponential Lagrangian velocity and acceleration distributions characterized by a sharp peak at low velocity, superlinear evolution of particle dispersion, and double-peak behavior in the propagators. The velocity distribution is quantified in terms of pore geometry and flow connectivity, which forms the basis for a continuous-time random-walk model that sheds light on the observed Lagrangian flow and transport behaviors.

Combined effect of thermal dispersion and variable viscosity of non-darcy convection heat transfer in a fluidsaturated porous medium

KAUST Repository

El-Amin, Mohamed

2013-01-01

In this paper, the effects of thermal dispersion and variable viscosity on the non-Darcy free, mixed, and forced convection heat transfer along a vertical flat plate embedded in a fluid-saturated porous medium are investigated. Forchheimer extension is employed in the flow equation to express the non-Darcy model. The fluid viscosity varies as an inverse linear function of temperature. The coefficient of thermal diffusivity has been assumed to be the sum of the molecular diffusivity and the dynamic diffusivity due to mechanical dispersion. Similarity solutions of the governing equations, for an isothermally heated plate, are obtained. Effects of the physical parameters, which govern the problem, on the rate of heat transfer in terms of Nusselt number, the slip velocity, and the boundary layer thickness, for the two cases Darcy and non-Darcy, are shown on graphs or entered in tables. © 2013 by Begell House, Inc.

Standing torsional waves in a fully saturated, porous, circular cylinder

CERN Document Server

Solorza, S; 10.1111/j.1365-246X.2004.02198.x

2004-01-01

For dynamic measurement of the elastic moduli of a porous material saturated with viscous fluid using the resonance-bar technique, one also observes attenuation. In this article we have carried out the solution of the boundary-value problem associated with standing torsional oscillations of a finite, poroelastic, circular cylinder cast in the framework of volume-averaged theory of poroelasticity. Analysing this solution by eigenvalue perturbation approach we are able to develop expressions for torsional resonance and temporal attenuation frequencies in which the dependence upon the material properties are transparent. It shows how the attenuation is controlled by the permeability and the fluid properties, and how the resonance frequency drops over its value for the dry solid-frame due to the drag effect of fluid mass. Based upon this work we have a firm basis to determine solid-frame shear modulus, permeability, and tortuosity factor from torsional oscillation experiments.

Debris bed coolability using a 3-D two phase model in a porous medium

Energy Technology Data Exchange (ETDEWEB)

Bechaud, C.; Duval, F.; Fichot, F. [CEA Cadarache, Inst. de Protection et de Surete Nucleaire13 - Saint-Paul-lez-Durance (France); Quintard, M. [Institut de Mecanique des Fluides de Toulouse, 31 (France); Parent, M. [CEA Grenoble, Dept. de Thermohydraulique et de Physique, 38 (France)

2001-07-01

During a severe nuclear accident, a part of the molten corium resulting from the core degradation may relocate in the lower plenum of the reactor vessel. In order to predict the safety margin of the reactor under such conditions, the coolability of this porous heat-generating medium is evaluated in this study and compared with other investigations. In this work, conservation equations derived for debris beds are implemented in the three dimensional thermal-hydraulic module of the CATHARE code. The coolant flow is a two phase flow with phase change. The momentum balance equation for each fluid phase is an extension of Darcy's law. This extension takes into account the capillary effects between the two phases, the relative permeabilities and passabilities of each phase, the interfacial drag force between liquid and gas, and the porous bed configuration (porosity, particle diameter,... ). The model developed is three-dimensional which is important to better predict the flow in configuration such as counter-current flow or to emphasize preferential ways induced by porous geometry. The energy balance equations of the three phases (liquid, gas and solid phase) are obtained by a volume averaging process of the local conservation equations. In this method, the local thermal non-equilibrium between the three phases is considered and the heat exchanges, the phase change rate as well as the thermal dispersion coefficients are calculated as a function of the local geometry of the porous medium. Such a method allows the numerical estimation of these thermal properties which are very difficult to determine experimentally. This feature is a great advantage of this approach. After a brief description of the thermal-hydraulic model, one-dimensional predictions of critical dryout fluxes are presented and compared with results from the literature. Reasonable agreement is obtained. Then a two-dimensional calculation is presented and shows the influence of the porous medium

Heat Transfer and Flows of Thermal Convection in a Fluid-Saturated Rotating Porous Medium

Directory of Open Access Journals (Sweden)

Jianhong Kang

2015-01-01

Full Text Available Thermal convection at the steady state for high Rayleigh number in a rotating porous half space is investigated. Taking into account the effect of rotation, Darcy equation is extended to incorporate the Coriolis force term in a rotating reference frame. The velocity and temperature fields of thermal convection are obtained by using the homotopy analysis method. The influences of Taylor number and Rayleigh number on the Nusselt number, velocity profile, and temperature distribution are discussed in detail. It is found that the Nusselt number decreases rapidly with the increase of Taylor number but tends to have an asymptotic value. Besides, the rotation can give rise to downward flow in contrast with the upward thermal convection.

The diverse nature of saturated fats and the case of medium-chain triglycerides: how one recommendation may not fit all.

Science.gov (United States)

Bhavsar, Nilam; St-Onge, Marie-Pierre

2016-03-01

The adverse cardiovascular health effects of saturated fats have been debated recently since the publication of studies reporting no increase in cardiovascular risk with saturated fat intakes. We purport that this may be because of the varied nature of saturated fats, which range in length from 2 to over 20 carbon atoms, and review evidence surrounding the cardiovascular health effects of medium-chain triglycerides (MCT). MCTs are saturated fats of shorter chain length than other, more readily consumed saturated fats. Studies have reported that consumption of MCT may lead to improvements in body composition without adversely affecting cardio-metabolic risk factors. There may also be synergistic actions between MCT and n-3 polyunsaturated fats that may lead to improvements in cardiovascular health. It is clinically relevant to distinguish between sources of saturated fats for cardiovascular health. Medium, and possibly shorter chain, saturated fats behave differently than long-chain saturated fats and should not be judged similarly when it comes to their cardio-metabolic health effects. Given their neutral, and potentially beneficial cardiovascular health effects, they should not be categorized together.

Analytical and numerical investigation of double diffusion in thermally anisotropy multilayer porous medium

Energy Technology Data Exchange (ETDEWEB)

Bennacer, R. [Neuville sur Oise, LEEVAM 5 mail Gay Lussac, Cergy-Pontoise Cedex (France); Mohamad, A.A. [CEERE University of Calgary, Department of Mechanical and Manufacturing Engineering, Calgary, Alberta (Canada); Ganaoui, M.El [Faculte des Sciences et Techniques de Limoges, Limoges (France)

2005-02-01

Double-diffusive natural convection within a multilayer anisotropic porous medium is studied numerically and analytically. The domain composed of two horizontal porous layers is subjected to a uniform horizontal heat flux and a vertical mass flux, where only the lower one is thermally anisotropic. Darcy model with classical Boussinesq approximation is used in formulating the mathematical model. The effect of thermal anisotropy and the relative width of the two layers on the flow and transfers is illustrated with characterising the transitions from the diffusive to the convective solution. Results were well compared with respect to a developed analytical approach, based on a parallel flow approximation for thermally anisotropic multilayer media. (orig.)

The Riemann Solution for the Injection of Steam and Nitrogen in a Porous Medium

NARCIS (Netherlands)

Lambert, W.; Marchesin, D.; Bruining, J.

2009-01-01

We solve the model for the flow of nitrogen, vapor, and water in a porous medium, neglecting compressibility, heat conductivity, and capillary effects. Our choice of injection conditions is determined by the application to clean up polluted sites. We study all mathematical structures, such as

Time-dependent electrophoresis of a dielectric spherical particle embedded in Brinkman medium

Science.gov (United States)

Saad, E. I.; Faltas, M. S.

2018-04-01

An expression for electrophoretic apparent velocity slip in the time-dependent flow of an electrolyte solution saturated in a charged porous medium within an electric double layer adjacent to a dielectric plate under the influence of a tangential uniform electric field is derived. The velocity slip is used as a boundary condition to solve the electrophoretic motion of an impermeable dielectric spherical particle embedded in an electrolyte solution saturated in porous medium under the unsteady Darcy-Brinkman model. Throughout the system, a uniform electric field is applied and maintains with constant strength. Two cases are considered, when the electric double layer enclosing the particle is thin, but finite and when of a particle with a thick double layer. Expressions for the electrophoretic mobility of the particle as functions of the relevant parameters are found. Our results indicate that the time scale for the growth of mobility is significant and small for high permeability. Generally, the effect of the relaxation time for starting electrophoresis is negligible, irrespective of the thickness of the double layer and permeability of the medium. The effects of the elapsed time, permeability, mass density and Debye length parameters on the fluid velocity, the electrophoretic mobility and the acceleration are shown graphically.

The two-phase flow IPTT method for measurement of nonwetting-wetting liquid interfacial areas at higher nonwetting saturations in natural porous media.

Science.gov (United States)

Zhong, Hua; Ouni, Asma El; Lin, Dan; Wang, Bingguo; Brusseau, Mark L

2016-07-01

Interfacial areas between nonwetting-wetting (NW-W) liquids in natural porous media were measured using a modified version of the interfacial partitioning tracer test (IPTT) method that employed simultaneous two-phase flow conditions, which allowed measurement at NW saturations higher than trapped residual saturation. Measurements were conducted over a range of saturations for a well-sorted quartz sand under three wetting scenarios of primary drainage (PD), secondary imbibition (SI), and secondary drainage (SD). Limited sets of experiments were also conducted for a model glass-bead medium and for a soil. The measured interfacial areas were compared to interfacial areas measured using the standard IPTT method for liquid-liquid systems, which employs residual NW saturations. In addition, the theoretical maximum interfacial areas estimated from the measured data are compared to specific solid surface areas measured with the N 2 /BET method and estimated based on geometrical calculations for smooth spheres. Interfacial areas increase linearly with decreasing water saturation over the range of saturations employed. The maximum interfacial areas determined for the glass beads, which have no surface roughness, are 32±4 and 36±5 cm -1 for PD and SI cycles, respectively. The values are similar to the geometric specific solid surface area (31±2 cm -1 ) and the N 2 /BET solid surface area (28±2 cm -1 ). The maximum interfacial areas are 274±38, 235±27, and 581±160 cm -1 for the sand for PD, SI, and SD cycles, respectively, and ~7625 cm -1 for the soil for PD and SI. The maximum interfacial areas for the sand and soil are significantly larger than the estimated smooth-sphere specific solid surface areas (107±8 cm -1 and 152±8 cm -1 , respectively), but much smaller than the N 2 /BET solid surface area (1387±92 cm -1 and 55224 cm -1 , respectively). The NW-W interfacial areas measured with the two-phase flow method compare well to values measured using the standard

An Interface Tracking Algorithm for the Porous Medium Equation.

Science.gov (United States)

1983-03-01

equation (1.11). N [v n n 2(2) = n . AV k + wk---IY" 2] +l~ x A t K Ax E E 2+ VeTA i;- 2k1 n- o (nr+l) <k-<.(n+l) N [Av] [ n+l <Ax Z m(v ) I~+lIAxAt...RD-R127 685 AN INTERFACE TRACKING ALGORITHM FOR THE POROUS MEDIUM / EQURTION(U) WISCONSIN UNIV-MRDISON MATHEMATICS RESEARCH CENTER E DIBENEDETTO ET...RL. MAR 83 NRC-TSR-249 UNCLASSIFIED DAG29-88-C-8041 F/G 12/1i N E -EEonshhhhI EhhhMhhhhhhhhE mhhhhhhhhhhhhE mhhhhhhhhhhhhI IMhhhhhhhMhhhE

Permeability of model porous medium formed by random discs

Science.gov (United States)

Gubaidullin, A. A.; Gubkin, A. S.; Igoshin, D. E.; Ignatev, P. A.

2018-03-01

Two-dimension model of the porous medium with skeleton of randomly located overlapping discs is proposed. The geometry and computational grid are built in open package Salome. Flow of Newtonian liquid in longitudinal and transverse directions is calculated and its flow rate is defined. The numerical solution of the Navier-Stokes equations for a given pressure drop at the boundaries of the area is realized in the open package OpenFOAM. Calculated value of flow rate is used for defining of permeability coefficient on the base of Darcy law. For evaluating of representativeness of computational domain the permeability coefficients in longitudinal and transverse directions are compered.

Mathematical modeling of deformation of a porous medium, considering its strengthening due to pore collapse

Energy Technology Data Exchange (ETDEWEB)

Sadovskii, V. M., E-mail: sadov@icm.krasn.ru; Sadovskaya, O. V., E-mail: o-sadov@icm.krasn.ru [Institute of Computational Modeling, SB RAS, Akademgorodok 50/44, 660036 Krasnoyarsk (Russian Federation)

2015-10-28

Based on the generalized rheological method, the mathematical model describing small deformations of a single-phase porous medium without regard to the effects of a fluid or gas in pores is constructed. The change in resistance of a material to the external mechanical impacts at the moment of pore collapse is taken into account by means of the von Mises–Schleicher strength condition. In order to consider irreversible deformations, alongside with the classical yield conditions by von Mises and Tresca– Saint-Venant, the special condition modeling the plastic loss of stability of a porous skeleton is used. The random nature of the pore size distribution is taken into account. It is shown that the proposed mathematical model satisfies the principles of thermodynamics of irreversible processes. Phenomenological parameters of the model are determined on the basis of the approximate calculation of the problem on quasi-static loading of a cubic periodicity cell with spherical voids. In the framework of the obtained model, the process of propagation of plane longitudinal waves of the compression in a homogenous porous medium, accompanied by the plastic deformation of a skeleton and the collapse of pores, is analyzed.

Estimation of Knudsen diffusion coefficients from tracer experiments conducted with a binary gas system and a porous medium

Science.gov (United States)

Hibi, Yoshihiko; Kashihara, Ayumi

2018-03-01

A previous study has reported that Knudsen diffusion coefficients obtained by tracer experiments conducted with a binary gas system and a porous medium are consistently smaller than those obtained by permeability experiments conducted with a single-gas system and a porous medium. To date, however, that study is the only one in which tracer experiments have been conducted with a binary gas system. Therefore, to confirm this difference in Knudsen diffusion coefficients, we used a method we had developed previously to conduct tracer experiments with a binary carbon dioxide-nitrogen gas system and five porous media with permeability coefficients ranging from 10-13 to 10-11 m2. The results showed that the Knudsen diffusion coefficient of N2 (DN2) (cm2/s) was related to the effective permeability coefficient ke (m2) as DN2 = 7.39 × 107ke0.767. Thus, the Knudsen diffusion coefficients of N2 obtained by our tracer experiments were consistently 1/27 of those obtained by permeability experiments conducted with many porous media and air by other researchers. By using an inversion simulation to fit the advection-diffusion equation to the distribution of concentrations at observation points calculated by mathematically solving the equation, we confirmed that the method used to obtain the Knudsen diffusion coefficient in this study yielded accurate values. Moreover, because the Knudsen diffusion coefficient did not differ when columns with two different lengths, 900 and 1500 mm, were used, this column property did not influence the flow of gas in the column. The equation of the dusty gas model already includes obstruction factors for Knudsen diffusion and molecular diffusion, which relate to medium heterogeneity and tortuosity and depend only on the structure of the porous medium. Furthermore, there is no need to take account of any additional correction factor for molecular diffusion except the obstruction factor because molecular diffusion is only treated in a multicomponent

Modeling the transport of engineered nanoparticles in saturated porous media - an experimental setup

Science.gov (United States)

Braun, A.; Neukum, C.; Azzam, R.

2011-12-01

The accelerating production and application of engineered nanoparticles is causing concerns regarding their release and fate in the environment. For assessing the risk that is posed to drinking water resources it is important to understand the transport and retention mechanisms of engineered nanoparticles in soil and groundwater. In this study an experimental setup for analyzing the mobility of silver and titanium dioxide nanoparticles in saturated porous media is presented. Batch and column experiments with glass beads and two different soils as matrices are carried out under varied conditions to study the impact of electrolyte concentration and pore water velocities. The analysis of nanoparticles implies several challenges, such as the detection and characterization and the preparation of a well dispersed sample with defined properties, as nanoparticles tend to form agglomerates when suspended in an aqueous medium. The analytical part of the experiments is mainly undertaken with Flow Field-Flow Fractionation (FlFFF). This chromatography like technique separates a particulate sample according to size. It is coupled to a UV/Vis and a light scattering detector for analyzing concentration and size distribution of the sample. The advantage of this technique is the ability to analyze also complex environmental samples, such as the effluent of column experiments including soil components, and the gentle sample treatment. For optimization of the sample preparation and for getting a first idea of the aggregation behavior in soil solutions, in sedimentation experiments the effect of ionic strength, sample concentration and addition of a surfactant on particle or aggregate size and temporal dispersion stability was investigated. In general the samples are more stable the lower the concentration of particles is. For TiO2 nanoparticles, the addition of a surfactant yielded the most stable samples with smallest aggregate sizes. Furthermore the suspension stability is

A generalised porous medium approach to study thermo-fluid dynamics in human eyes.

Science.gov (United States)

Mauro, Alessandro; Massarotti, Nicola; Salahudeen, Mohamed; Romano, Mario R; Romano, Vito; Nithiarasu, Perumal

2018-03-22

The present work describes the application of the generalised porous medium model to study heat and fluid flow in healthy and glaucomatous eyes of different subject specimens, considering the presence of ocular cavities and porous tissues. The 2D computational model, implemented into the open-source software OpenFOAM, has been verified against benchmark data for mixed convection in domains partially filled with a porous medium. The verified model has been employed to simulate the thermo-fluid dynamic phenomena occurring in the anterior section of four patient-specific human eyes, considering the presence of anterior chamber (AC), trabecular meshwork (TM), Schlemm's canal (SC), and collector channels (CC). The computational domains of the eye are extracted from tomographic images. The dependence of TM porosity and permeability on intraocular pressure (IOP) has been analysed in detail, and the differences between healthy and glaucomatous eye conditions have been highlighted, proving that the different physiological conditions of patients have a significant influence on the thermo-fluid dynamic phenomena. The influence of different eye positions (supine and standing) on thermo-fluid dynamic variables has been also investigated: results are presented in terms of velocity, pressure, temperature, friction coefficient and local Nusselt number. The results clearly indicate that porosity and permeability of TM are two important parameters that affect eye pressure distribution. Graphical abstract Velocity contours and vectors for healthy eyes (top) and glaucomatous eyes (bottom) for standing position.

Analysis of heat transfer for unsteady MHD free convection flow of rotating Jeffrey nanofluid saturated in a porous medium

Directory of Open Access Journals (Sweden)

Nor Athirah Mohd Zin

Full Text Available In this article, the influence of thermal radiation on unsteady magnetohydrodynamics (MHD free convection flow of rotating Jeffrey nanofluid passing through a porous medium is studied. The silver nanoparticles (AgNPs are dispersed in the Kerosene Oil (KO which is chosen as conventional base fluid. Appropriate dimensionless variables are used and the system of equations is transformed into dimensionless form. The resulting problem is solved using the Laplace transform technique. The impact of pertinent parameters including volume fraction φ, material parameters of Jeffrey fluid λ1, λ, rotation parameter r, Hartmann number Ha, permeability parameter K, Grashof number Gr, Prandtl number Pr, radiation parameter Rd and dimensionless time t on velocity and temperature profiles are presented graphically with comprehensive discussions. It is observed that, the rotation parameter, due to the Coriolis force, tends to decrease the primary velocity but reverse effect is observed in the secondary velocity. It is also observed that, the Lorentz force retards the fluid flow for both primary and secondary velocities. The expressions for skin friction and Nusselt number are also evaluated for different values of emerging parameters. A comparative study with the existing published work is provided in order to verify the present results. An excellent agreement is found. Keywords: Jeffrey nanofluid, AgNPs, MHD and Porosity, Rotating flow, Laplace transform technique

Effect of deformability on fluid flow through a fractured-porous medium

International Nuclear Information System (INIS)

Tsang, C.F.; Noorishad, J.; Witherspoon, P.A.

1985-01-01

A permeable geologic medium containing interstitial fluids generally undergoes deformation as the fluid pressure changes. Depending on the nature of the medium, the strain ranges from infinitesimal to finite quantities. This response is the result of a coupled hydraulic-mechanical phenomenon which can basically be formulated in the generalized three-dimensional theory of consolidation. Dealing mainly with media of little deformability, traditional hydrogeology accounts for medium deformability as far as it affects the volume of pore spaces, through the introduction of a coefficient of specific storage in the fluid flow equation. This treatment can be justified on the basis of a one-dimensional effective stress law and the assumption of homogeneity of the total stress field throughout the medium. The present paper uses a numerical model called ROCMAS (Noorishad et al., 1982; Noorishad e al., 1984) which was developed to calculate fluid flow through a deformable fractured-porous medium. The code employs the Finite Element Method based on a variational approach. It has been verified against a number of simple analytic solutions. In this work, the code is used to address the role of medium deformability in continuous and pulse testing techniques. The errors that may result because of application of traditional fluid flow methods are discussed. It is found that low pressure continuous well testing or pulse testing procedures can reduce such errors. 16 references, 9 figures, 1 table

Oxidative stabilization of mixed mayonnaises made with linseed oil and saturated medium-chain triglyceride oil

NARCIS (Netherlands)

Raudsepp, P.; Brüggemann, D.A.; Lenferink, Aufrid T.M.; Otto, Cornelis; Andersen, M.L.

2014-01-01

Mayonnaises, made with either saturated medium chain triglyceride (MCT) oil or unsaturated purified linseed oil (LSO), were mixed. Raman confocal microspectrometry demonstrated that lipid droplets in mixed mayonnaise remained intact containing either MCT oil or LSO. Peroxide formation during storage

Fluid flow in a porous medium with transverse permeability discontinuity

Science.gov (United States)

Pavlovskaya, Galina E.; Meersmann, Thomas; Jin, Chunyu; Rigby, Sean P.

2018-04-01

Magnetic resonance imaging (MRI) velocimetry methods are used to study fully developed axially symmetric fluid flow in a model porous medium of cylindrical symmetry with a transverse permeability discontinuity. Spatial mapping of fluid flow results in radial velocity profiles. High spatial resolution of these profiles allows estimating the slip in velocities at the boundary with a permeability discontinuity zone in a sample. The profiles are compared to theoretical velocity fields for a fully developed axially symmetric flow in a cylinder derived from the Beavers-Joseph [G. S. Beavers and D. D. Joseph, J. Fluid Mech. 30, 197 (1967), 10.1017/S0022112067001375] and Brinkman [H. C. Brinkman, Appl. Sci. Res. A 1, 27 (1947), 10.1007/BF02120313] models. Velocity fields are also computed using pore-scale lattice Boltzmann modeling (LBM) where the assumption about the boundary could be omitted. Both approaches give good agreement between theory and experiment, though LBM velocity fields follow the experiment more closely. This work shows great promise for MRI velocimetry methods in addressing the boundary behavior of fluids in opaque heterogeneous porous media.

Steady Boundary Layer Slip Flow along with Heat and Mass Transfer over a Flat Porous Plate Embedded in a Porous Medium

Science.gov (United States)

Aziz, Asim; Siddique, J. I.; Aziz, Taha

2014-01-01

In this paper, a simplified model of an incompressible fluid flow along with heat and mass transfer past a porous flat plate embedded in a Darcy type porous medium is investigated. The velocity, thermal and mass slip conditions are utilized that has not been discussed in the literature before. The similarity transformations are used to transform the governing partial differential equations (PDEs) into a nonlinear ordinary differential equations (ODEs). The resulting system of ODEs is then reduced to a system of first order differential equations which was solved numerically by using Matlab bvp4c code. The effects of permeability, suction/injection parameter, velocity parameter and slip parameter on the structure of velocity, temperature and mass transfer rates are examined with the aid of several graphs. Moreover, observations based on Schmidt number and Soret number are also presented. The result shows, the increase in permeability of the porous medium increase the velocity and decrease the temperature profile. This happens due to a decrease in drag of the fluid flow. In the case of heat transfer, the increase in permeability and slip parameter causes an increase in heat transfer. However for the case of increase in thermal slip parameter there is a decrease in heat transfer. An increase in the mass slip parameter causes a decrease in the concentration field. The suction and injection parameter has similar effect on concentration profile as for the case of velocity profile. PMID:25531301

Steady boundary layer slip flow along with heat and mass transfer over a flat porous plate embedded in a porous medium.

Science.gov (United States)

Aziz, Asim; Siddique, J I; Aziz, Taha

2014-01-01

In this paper, a simplified model of an incompressible fluid flow along with heat and mass transfer past a porous flat plate embedded in a Darcy type porous medium is investigated. The velocity, thermal and mass slip conditions are utilized that has not been discussed in the literature before. The similarity transformations are used to transform the governing partial differential equations (PDEs) into a nonlinear ordinary differential equations (ODEs). The resulting system of ODEs is then reduced to a system of first order differential equations which was solved numerically by using Matlab bvp4c code. The effects of permeability, suction/injection parameter, velocity parameter and slip parameter on the structure of velocity, temperature and mass transfer rates are examined with the aid of several graphs. Moreover, observations based on Schmidt number and Soret number are also presented. The result shows, the increase in permeability of the porous medium increase the velocity and decrease the temperature profile. This happens due to a decrease in drag of the fluid flow. In the case of heat transfer, the increase in permeability and slip parameter causes an increase in heat transfer. However for the case of increase in thermal slip parameter there is a decrease in heat transfer. An increase in the mass slip parameter causes a decrease in the concentration field. The suction and injection parameter has similar effect on concentration profile as for the case of velocity profile.

Three-dimensional Rayleigh-Taylor convection of miscible fluids in a porous medium

Science.gov (United States)

Suekane, Tetsuya; Nakanishi, Yuji; Wang, Lei

2017-11-01

Natural convection of miscible fluids in a porous medium is relevant for fields, such as geoscience and geoengineering, and for the geological storage of CO2. In this study, we use X-ray computer tomography to visualize 3D fingering structures associated with the Rayleigh-Taylor instability between miscible fluids in a porous medium. In the early stages of the onset of the Rayleigh-Taylor instability, a fine crinkling pattern gradually appears at the interface. As the wavelength and amplitude increase, descending fingers form on the interface and extend vertically downward; moreover, ascending and highly symmetric fingers form. The adjacent fingers are cylindrical in shape and coalesce to form large fingers. Fingers appearing on the interface tend to become finer with increasing Rayleigh number, which is consistent with linear perturbation theory. If the Péclet number exceeds 10, the transverse dispersion increases the finger diameter and enhances finger coalescence, strongly impacting the decay in finger number density. When mechanical dispersion is negligible, the finger-extension velocity, the mass-transfer rate, and the onset time scale with Rayleigh number. Mechanical dispersion not only reduces the onset time but also enhances mass transport, which indicates that mechanical dispersion influences the long-term dissolution process of CO2 injected into aquifers.

An experimental study of dielectric dispersion in porous media and its dependence on pore geometry

Energy Technology Data Exchange (ETDEWEB)

Haslund, E.

1996-12-31

Understanding water saturated composite media are important in the study of oil reservoirs. This doctoral thesis discusses measurements of the frequency dependent permittivity and conductivity of water saturated porous glass specimens. The experiments are designed to investigate the dispersion resulting from the geometrical properties of the pore space. Measurements are presented of the effective complex dielectric constant of water saturated porous glass specimens for frequencies below 13 MHz. The specimens are made from sintered glass spheres, and in some specimens thin plates are mixed in with the spheres. Low-conductivity water is used to saturate the pore space in order to scale the frequency range of the Maxwell-Wagner dispersion into the measurement range. The experiments are compared with two different effective medium approaches. One approach is the Mendelson and Cohen theory with randomly oriented spheroidal grains in addition to spherical grains, the other the Local porosity theory due to Hilfer. Both theories were found to be in good agreement with the experimental observations. 175 refs., 59 figs., 1 table

Determination of saturation functions and wettability for chalk based on measured fluid saturations

Energy Technology Data Exchange (ETDEWEB)

Olsen, D.; Bech, N.; Moeller Nielsen, C.

1998-08-01

The end effect of displacement experiments on low permeable porous media is used for determination of relative permeability functions and capillary pressure functions. Saturation functions for a drainage process are determined from a primary drainage experiment. A reversal of the flooding direction creates an intrinsic imbibition process in the sample, which enables determination if imbibition saturation functions. The saturation functions are determined by a parameter estimation technique. Scanning effects are modelled by the method of Killough. Saturation profiles are determined by NMR. (au)

On the description of the properties of fractured rock using the concept of a porous medium

International Nuclear Information System (INIS)

Stokes, J.

1980-05-01

In order to describe the flow of groundwater through fractured rock, water is either assumed to flow through a pervious continuum of through descrete fractures between impervious blocks of rock. The latter approach being the one demanding more information on the rock, problems on groundwater flow are usually discussed using the porous medium approach. It is often a question of debate wether the continuum approach is applicable to the fractured rock under consideration. Therefore, it is essential that after assuming that a certain flow region acts as a porous medium, we use a procedure for measuring the properties that at the same time gives a test of this assumption. When giving a description of groundwater flow, the goal is often a presentation of pathlines and flowtimes between points of interest and the ground surface. Using a porous medium approach, this means that hydraulic conductivity and porosity must be known through the medium. In order to cope with transient flow, we must also know the time constant governing the development of the flow. The pathlines depend to a great extent on the variation of conductivity through space. A conductivity decreasing with depth will force the pathlines to the surface giving local flow. If instead the conductivity is constant, the flow is regional. It is therefore important to know the gradient of hydraulic conductivity. Finally, as we know that the flow takes place through a geological structure, the anisotropic behaviour of the rock must be known in order to describe the flow. In this report a procedure to measure the properties listed above is developed. (author)

Flow visualization in heat-generating porous media

International Nuclear Information System (INIS)

Lee, D.O.; Nilson, R.H.

1977-11-01

The work reported is in support of the Sandia Post-Accident Heat Removal Program, in which simulated LMFBR beds will be subjected to in-pile heating in the ACPR (Annular Core Pulsed Reactor). Flow visualization experiments were performed to gain some insight into the flow patterns and temperature distributions in a fluid-saturated heat-generating porous medium. Although much of the information presented is of a qualitative nature, it is useful in the recognition of the controlling transport process and in the formulation of analytic and numerical models

Unsaturated and Saturated Permeabilities of Fiber Reinforcement: Critics and Suggestions

Directory of Open Access Journals (Sweden)

Chung Hae ePARK

2015-04-01

Full Text Available In general, permeability measurement results show a strong scattering according to the measurement method, the type of test fluid and the fluid injection condition, even though permeability is regarded as a unique property of porous medium. In particular, the discrepancy between the unsaturated and saturated permeabilities for the same fabric has been widely reported. In the literature, relative permeability has been adopted to model the unsaturated flow. This approach has some limits in the modeling of double-scale porosity medium. We address this issue of permeability measurement by rigorously examining the mass conservation condition. Finally, we identify that the pressure gradient is non-linear with positive curvature in the unsaturated flow and a misinterpretation of pressure gradient is the main reason for the difference between the saturated and unsaturated permeabilities of the same fiber reinforcement. We propose to use a fixed value of permeability and to modify the mass conservation equation if there are air voids which are entrapped inside the fiber tow. Finally, we also suggest some guidelines and future perspectives to obtain more consistent permeability measurement results.

A model to analyse the flow of an incompressible Newtonian fluid through a rigid, homogeneous, isotropic and infinite porous medium

International Nuclear Information System (INIS)

Gama, R.M.S. da; Sampaio, R.

1985-01-01

The flow of an incompressible Newtonian fluid through a rigid, homogeneous, isotropic and infinite porous medium which has a given inicial distribuition of the mentioned fluid, is analyzed. It is proposed a model that assumes that the motion is caused by concentration gradient, but it does not consider the friction between the porous medium and the fluid. We solve an onedimensional case where the mathematical problem is reduced to the solution of a non-linear hyperbolic system of differential equations, subjected to an inicial condition given by a step function, called 'Riemann Problem'. (Author) [pt

Natural convection of nanofluids over a convectively heated vertical plate embedded in a porous medium

Energy Technology Data Exchange (ETDEWEB)

Ghalambaz, M.; Noghrehabadi, A.; Ghanbarzadeh, A., E-mail: m.ghalambaz@gmail.com, E-mail: ghanbarzadeh.a@scu.ac.ir [Department of Mechanical Engineering, Shahid Chamran University of Ahvaz, Ahvaz (Iran, Islamic Republic of)

2014-04-15

In this paper, the natural convective flow of nanofluids over a convectively heated vertical plate in a saturated Darcy porous medium is studied numerically. The governing equations are transformed into a set of ordinary differential equations by using appropriate similarity variables, and they are numerically solved using the fourth-order Runge-Kutta method associated with the Gauss-Newton method. The effects of parametric variation of the Brownian motion parameter (Nb), thermophoresis parameter (Nt) and the convective heating parameter (Nc) on the boundary layer profiles are investigated. Furthermore, the variation of the reduced Nusselt number and reduced Sherwood number, as important parameters of heat and mass transfer, as a function of the Brownian motion, thermophoresis and convective heating parameters is discussed in detail. The results show that the thickness of the concentration profiles is much lower than the temperature and velocity profiles. For low values of the convective heating parameter (Nc), as the Brownian motion parameter increases, the non-dimensional wall temperature increases. However, for high values of Nc, the effect of the Brownian motion parameter on the non-dimensional wall temperature is not significant. As the Brownian motion parameter increases, the reduced Sherwood number increases and the reduced Nusselt number decreases. (author)

The transport behaviour of elemental mercury DNAPL in saturated porous media: analysis of field observations and two-phase flow modelling.

Science.gov (United States)

Sweijen, Thomas; Hartog, Niels; Marsman, Annemieke; Keijzer, Thomas J S

2014-06-01

Mercury is a contaminant of global concern. The use of elemental mercury in various (former) industrial processes, such as chlorine production at chlor-alkali plants, is known to have resulted in soil and groundwater contaminations worldwide. However, the subsurface transport behaviour of elemental mercury as an immiscible dense non-aqueous phase liquid (DNAPL) in porous media has received minimal attention to date. Even though, such insight would aid in the remediation effort of mercury contaminated sites. Therefore, in this study a detailed field characterization of elemental mercury DNAPL distribution with depth was performed together with two-phase flow modelling, using STOMP. This is to evaluate the dynamics of mercury DNAPL migration and the controls on its distribution in saturated porous media. Using a CPT-probe mounted with a digital camera, in-situ mercury DNAPL depth distribution was obtained at a former chlor-alkali-plant, down to 9 m below ground surface. Images revealing the presence of silvery mercury DNAPL droplets were used to quantify its distribution, characteristics and saturation, using an image analysis method. These field-observations with depth were compared with results from a one-dimensional two-phase flow model simulation for the same transect. Considering the limitations of this approach, simulations reasonably reflected the variability and range of the mercury DNAPL distribution. To further explore the impact of mercury's physical properties in comparison with more common DNAPLs, the migration of mercury and PCE DNAPL in several typical hydrological scenarios was simulated. Comparison of the simulations suggest that mercury's higher density is the overall controlling factor in controlling its penetration in saturated porous media, despite its higher resistance to flow due to its higher viscosity. Based on these results the hazard of spilled mercury DNAPL to cause deep contamination of groundwater systems seems larger than for any other

Fluid dynamics and mass transfer in variably saturated porous media: formulation and applications of a mathematical model

International Nuclear Information System (INIS)

Sharma, D.

1982-01-01

This paper presents the formulation and applications of a mathematical model designed to predict the fluid dynamics and associated mass transfers in variably saturated porous media. Novelties in the formulation are emphasized and demonstrated to provide several computational advantages. The numerical procedure employed is of the integrated finite-difference variety which employs a hybrid differencing scheme. This procedure, while solving the coupled governing equations in conservative form, permits accommodation of substantial heterogeneities and anisotropies in material properties of the porous media. Accordingly, it is capable of making reliable predictions of steeply varying moisture and chemical-specie concentration fronts. The paper provides several examples of application of the model to the solution of practical problems. It is demonstrated that economical solutions to highly non-linear problems associated with solid and liquid waste disposal practices can be obtained

Effect of flood conditions on the deterioration of porous clay-based brick

Science.gov (United States)

Mol, L.; Tomor, A.

2017-12-01

Man-made materials represent an increasingly large proportion of geomaterials that are used to build up a rapidly expanding urbanised landscape. The deterioration of such materials is of increasing concern, in particular in light of the projected increase in storm and flood events and their associated high water levels. The effect of prolonged saturation in porous materials, man-made as well as natural, can lead to accelerated deterioration. This can be of particular concern for load-bearing structural materials, for example bridges. In this study, the effect of moisture movement has been investigated for brick masonry, as one of the most commonly used porous building materials. Saturation of brick masonry can be of particular concern for historical masonry, such as masonry arch bridges in conjunction with under increasing levels of long-term traffic loading. While flooding can lead to scour and sudden collapse of bridges, saturation can also lead to accelerated medium and long-term deterioration. A series of small-scale laboratory tests have been carried out on brick masonry to identify the effects of saturation on the material properties and changes in the rate of deterioration. Brick masonry prisms have been loaded to failure under quasi-static and long-term cyclic compression and monitored with the help of acoustic emission technique, accelerometers, linear variable differential transformers (LVDTs), permeametry and brick surface hardness measurements. Under quasi-static loading saturated samples showed significant reduction in the load capacity and increased fracture development. Under fatigue loading the number of cycles to failure reduced significantly for saturated specimens and characteristic changes in material parameters have been related to stages of fatigue deterioration. Test results indicated that increasing flood events can accelerate moisture-related deterioration in porous brick masonry.

Dynamic characterization of partially saturated engineered porous media and gas diffusion layers using hydraulic admittance

Science.gov (United States)

Cheung, Perry; Fairweather, Joseph D.; Schwartz, Daniel T.

2012-09-01

Simple laboratory methods for determining liquid water distribution in polymer electrolyte membrane fuel cell gas diffusion layers (GDLs) are needed to engineer better GDL materials. Capillary pressure vs. liquid saturation measurements are attractive, but lack the ability to probe the hydraulic interconnectivity and distribution within the pore structure. Hydraulic admittance measurements of simple capillary bundles have recently been shown to nicely measure characteristics of the free-interfaces and hydraulic path. Here we examine the use of hydraulic admittance with a succession of increasingly complex porous media, starting with a laser-drilled sample with 154 asymmetric pores and progress to the behavior of Toray TGP-H090 carbon papers. The asymmetric laser-drilled sample clearly shows hydraulic admittance measurements are sensitive to sample orientation, especially when examined as a function of saturation state. Finite element modeling of the hydraulic admittance is consistent with experimental measurements. The hydraulic admittance spectra from GDL samples are complex, so we examine trends in the spectra as a function of wet proofing (0% and 40% Teflon loadings) as well as saturation state of the GDL. The presence of clear peaks in the admittance spectra for both GDL samples suggests a few pore types are largely responsible for transporting liquid water.

Natural convection flow and heat transfer between a fluid layer and a porous layer inside a rectangular enclosure

International Nuclear Information System (INIS)

Beckermann, C.; Ramadhyani, S.; Viskanta, R.

1986-01-01

A numerical and experimental study is performed to analyze the steady-state natural convection fluid flow and heat transfer in a vertical rectangular enclosure that is partially filled with a vertical layer of a fluid-saturated porous medium. The flow in the porous layer is modeled utilizing the Brinkman-Forchheimer-extended Darcy equations. The numerical model is verified by conducting a number of experiments with spherical glass beads as the porous medium and water and glycerin as the fluids in rectangular test-cells. The agreement between the flow visualization results and temperature measurements and the numerical model is, in general, good. It is found that the amount of fluid penetrating from the fluid region into the porous layer depends strongly on the Darcy (Da) and Rayleigh (Ra) numbers. For a relatively low product of Ra x Da, the flow takes place primarily in the fluid layer, and heat transfer in the porous layer is by conduction only. On the other hand, fluid penetrating into a relatively highly permeable porous layer has a significant impact on the natural convection flow patterns in the entire enclosure

Chemical reaction effects on unsteady MHD free convective flow in a rotating porous medium with mass transfer

Directory of Open Access Journals (Sweden)

Govindarajan Arunachalam

2014-01-01

Full Text Available An investigation of unsteady MHD free convective flow and mass transfer during the motion of a viscous incompressible fluid through a porous medium, bounded by an infinite vertical porous surface, in a rotating system is presented. The porous plane surface and the porous medium are assumed to rotate in a solid body rotation. The vertical surface is subjected to uniform constant suction perpendicular to it and the temperature at this surface fluctuates in time about a non-zero constant mean. Analytical expressions for the velocity, temperature and concentration fields are obtained using the perturbation technique. The effects of R (rotation parameter, k0 (permeability parameter, M (Hartmann number and w (frequency parameter on the flow characteristics are discussed. It is observed that the primary velocity component decreases with the increase in either of the rotation parameter R, the permeability parameter k0, or the Hartmann number M. It is also noted that the primary skin friction increases whenever there is an increase in the Grashof number Gr or the modified Grashof number Gm. It is clear that the heat transfer coefficient in terms of the Nusselt number decreases in the case of both air and water when there is an increase in the Hartmann number M. It is observed that the magnitude of the secondary velocity profiles increases whenever there is an increase in either of the Grashof number or the modified Grashof number for mass transfer or the permeability of the porous media. Concentration profiles decreases with an increase in the Schmidt number.

Diffusive–Dispersive and Reactive Fronts in Porous Media

DEFF Research Database (Denmark)

Haberer, Christina M.; Muniruzzaman, Muhammad; Grathwohl, Peter

2015-01-01

, across the unsaturated–saturated interface, under both conservative and reactive transport conditions. As reactive system we considered the abiotic oxidation of Fe2+ in the presence of O2. We studied the reaction kinetics in batch experiments and its coupling with diffusive and dispersive transport...... processes by means of one-dimensional columns and two-dimensional flow-through experiments, respectively. A noninvasive optode technique was used to track O2 transport into the initially anoxic porous medium at highly resolved spatial and temporal scales. The results show significant differences...

Non-Darcy Free Convection of Power-Law Fluids Over a Two-Dimensional Body Embedded in a Porous Medium

KAUST Repository

El-Amin, Mohamed

2010-11-27

A boundary layer analysis was presented to study the non-Darcy-free convection of a power-law fluid over a non-isothermal two-dimensional body embedded in a porous medium. The Ostwald-de Waele power-law model was used to characterize the non-Newtonian fluid behavior. Similarity solutions were obtained with variations in surface temperature or surface heat flux. In view of the fact that most of the non-Newtonian fluids have large Prandtl numbers, this study was directed toward such fluids. The effects of the porous medium parameters, k1 and k2, body shape parameter, m, and surface thermal variations parameter, p, as well as the power-law index, n, were examined. © 2010 Springer Science+Business Media B.V.

Non-Darcy Free Convection of Power-Law Fluids Over a Two-Dimensional Body Embedded in a Porous Medium

KAUST Repository

El-Amin, Mohamed; Sun, Shuyu; El-Ameen, M. A.; Jaha, Y. A.; Gorla, Rama Subba Reddy

2010-01-01

A boundary layer analysis was presented to study the non-Darcy-free convection of a power-law fluid over a non-isothermal two-dimensional body embedded in a porous medium. The Ostwald-de Waele power-law model was used to characterize the non-Newtonian fluid behavior. Similarity solutions were obtained with variations in surface temperature or surface heat flux. In view of the fact that most of the non-Newtonian fluids have large Prandtl numbers, this study was directed toward such fluids. The effects of the porous medium parameters, k1 and k2, body shape parameter, m, and surface thermal variations parameter, p, as well as the power-law index, n, were examined. © 2010 Springer Science+Business Media B.V.

Transient heat characteristics of water-saturated porous media with freezing; Toketsu wo tomonau gansui takoshitsu sonai no hiteijo netsu tokusei

Energy Technology Data Exchange (ETDEWEB)

Sasaki, A [Akita National College of Technology, Akita (Japan)

1998-02-25

Analytical and experimental investigations were performed to examine the transient heat characteristics of water-saturated porous media with freezing. As a physical model, a two-dimensional vertical cavity was considered. One vertical wall was abruptly cooled below the fusion temperature. Other three walls were thermally insulated. Three different sizes of glass, and iron, alumina and copper beads were used as the porous media in this study. The cold energy stored up in the porous media and the average thickness of frozen layer were measured in the experiments. Comparisons of the analytical results with the experimental ones were made, and the effects of Darcy number, Stefan number and modified Prandtl number on the transient heat characteristics were discussed. The dimensionless equations for predicting the averaged frozen layer thickness and the stored cold energy were obtained as a function of various dimensionless parameters. 8 refs., 16 figs., 1 tab.

Heat transfer in a Couette flow with part of the space between the plates filled with porous medium

International Nuclear Information System (INIS)

Carrocci, L.R.; Liu, C.Y.; Ismail, K.A.R.

1982-01-01

The effect of various parameters in the temperature profile is shown under boundary conditions for the Couette flow between infinite plates with part of the space filled with porous medium. The parameters observed are: pressure gradient, permeability, the non-dimensional product PE (Prandtl number x Eckert number), the relation between the thermal conductibility coefficient between porous region and pure fluid, and finally the non-dimensional product PR (Prandtl number x Reynolds number). (E.G.) [pt

Analytical and numerical stability analysis of Soret-driven convection in a horizontal porous layer: the effect of conducting bounding plates

Energy Technology Data Exchange (ETDEWEB)

Ouattara, B; Khouzam, A; Mojtabi, A [Universite de Toulouse (France); INPT, UPS (France); IMFT (Institut de Mecanique des Fluides de Toulouse), Allee Camille Soula, F-31400 Toulouse (France); Charrier-Mojtabi, M C, E-mail: bouattar@imft.fr, E-mail: akhouzam@imft.fr, E-mail: mojtabi@imft.fr, E-mail: cmojtabi@cict.fr [PHASE, EA 810, UFR PCA, Universite Paul Sabatier, 118 route de Narbonne, 31062 Toulouse cedex (France)

2012-06-01

The aim of this study was to investigate the effect of conducting boundaries on the onset of convection in a binary fluid-saturated porous layer. The isotropic saturated porous layer is bounded by two impermeable but thermally conducting plates, subjected to a constant heat flux. These plates have identical conductivity. Moreover, the conductivity of the plates is generally different from the porous layer conductivity. The overall layer is of large extent in both horizontal directions. The problem is governed by seven dimensionless parameters, namely the normalized porosity of the medium {epsilon}, the ratio of plates over the porous layer thickness {delta} and their relative thermal conductivities ratio d, the separation ratio {delta}, the Lewis number Le and thermal Rayleigh number Ra. In this work, an analytical and numerical stability analysis is performed. The equilibrium solution is found to lose its stability via a stationary bifurcation or a Hopf bifurcation depending on the values of the dimensionless parameters. For the long-wavelength mode, the critical Rayleigh number is obtained as Ra{sub cs}=12(1+2d{delta} )/[1+{psi} (2d{delta}Le+Le+1)] and k{sub cs}=0 for {psi}> {psi} {sub uni}> 0. This work extends an earlier paper by Mojtabi and Rees (2011 Int. J. Heat Mass Transfer 54 293-301) who considered a configuration where the porous layer is saturated by a pure fluid.

Natural convection boundary layer with suction and mass transfer in a porous medium

International Nuclear Information System (INIS)

Bestman, A.R.

1989-03-01

The free convection boundary layer flow with simultaneous heat and mass transfer in a porous medium is studied when the boundary wall moves in its own plane with suction. The study also incorporates chemical reaction for the very simple model of a binary reaction with Arrhenius activation energy. For large suction asymptotic approximate solutions are obtained for the flow variables for various values of the activation energy. (author). 10 refs, 2 figs

Ultimate regime of high Rayleigh number convection in a porous medium.

Science.gov (United States)

Hewitt, Duncan R; Neufeld, Jerome A; Lister, John R

2012-06-01

Well-resolved direct numerical simulations of 2D Rayleigh-Bénard convection in a porous medium are presented for Rayleigh numbers Ra≤4×10(4) which reveal that, contrary to previous indications, the linear classical scaling for the Nusselt number, Nu~Ra, is attained asymptotically. The flow dynamics are analyzed, and the interior of the vigorously convecting system is shown to be increasingly well described as Ra→∞ by a simple columnar "heat-exchanger" model with a single horizontal wave number k and a linear background temperature field. The numerical results are approximately fitted by k~Ra(0.4).

Transport of radionuclides by concentrated brine in a porous medium with micropore-macropore structure

International Nuclear Information System (INIS)

Hassanizadeh, S.M.

1987-01-01

This work concerns itself with the study of effects of soil aggregation and high salt concentrations on the transport of radionuclides by concentrated brine flowing through an aggregated porous medium. The medium is considered to be composed of porous rock aggregates separated by macropores through which the brine flows and transport of salt and radionuclides takes place. The aggregates contain dead-end pores, cracks, and stationary pockets collectively called micropores. The micropore space does not contribute to the flow, but it serves as a storage for salt and radionuclides. Adsorption of radionuclides takes place at internal surfaces of aggregates where they assume that a linear equilibrium isotherm describes the process. A one-dimensional numerical model is developed which is based on two sets of equations: one set for the flow and transport of salt and another set for transport of radionuclides. Results of numerical experiments clearly indicate that the existence of high salt concentrations markedly reduces the peak of nuclides concentration and slows down their movement. Also, it is found that diffusive mass exchange between macropores and aggregates results in a pronounced lowering of the radionuclides concentration peaks. 9 references, 7 figures

VS2DRTI: Simulating Heat and Reactive Solute Transport in Variably Saturated Porous Media.

Science.gov (United States)

Healy, Richard W; Haile, Sosina S; Parkhurst, David L; Charlton, Scott R

2018-01-29

Variably saturated groundwater flow, heat transport, and solute transport are important processes in environmental phenomena, such as the natural evolution of water chemistry of aquifers and streams, the storage of radioactive waste in a geologic repository, the contamination of water resources from acid-rock drainage, and the geologic sequestration of carbon dioxide. Up to now, our ability to simulate these processes simultaneously with fully coupled reactive transport models has been limited to complex and often difficult-to-use models. To address the need for a simple and easy-to-use model, the VS2DRTI software package has been developed for simulating water flow, heat transport, and reactive solute transport through variably saturated porous media. The underlying numerical model, VS2DRT, was created by coupling the flow and transport capabilities of the VS2DT and VS2DH models with the equilibrium and kinetic reaction capabilities of PhreeqcRM. Flow capabilities include two-dimensional, constant-density, variably saturated flow; transport capabilities include both heat and multicomponent solute transport; and the reaction capabilities are a complete implementation of geochemical reactions of PHREEQC. The graphical user interface includes a preprocessor for building simulations and a postprocessor for visual display of simulation results. To demonstrate the simulation of multiple processes, the model is applied to a hypothetical example of injection of heated waste water to an aquifer with temperature-dependent cation exchange. VS2DRTI is freely available public domain software. © 2018, National Ground Water Association.

Numerical Simulation of Transient Free Convection Flow and Heat Transfer in a Porous Medium

Directory of Open Access Journals (Sweden)

Rajesh Sharma

2013-01-01

Full Text Available The coupled momentum and heat transfer in unsteady, incompressible flow along a semi-infinite vertical porous moving plate adjacent to an isotropic porous medium with viscous dissipation effect are investigated. The Darcy-Forchheimer nonlinear drag force model which includes the effects of inertia drag forces is employed. The governing differential equations of the problem are transformed into a system of nondimensional differential equations which are solved numerically by the finite element method (FEM. The non-dimensional velocity and temperature profiles are presented for the influence of Darcy number, Forchheimer number, Grashof number, Eckert number, Prandtl number, plate velocity, and time. The Nusselt number is also evaluated and compared with finite difference method (FDM, which shows excellent agreement.

Influence of pH on the Transport of Silver Nanoparticles in Saturated Porous Media: Laboratory Experiments and Modeling

Science.gov (United States)

2012-03-01

the potential toxic effects of AgNPs (USEPA 2010). Recent in vitro and in vivo studies using various cell lines, algae , zooplankton, fish, rats and... TiO2 in Saturated Porous Media: Effects of pH, Surfactants and Flow Velocity.” Water Research, 45(2), 839-851. He, F., Zhang, M., Qian, T., and Zhao...of silver nanoparticles (AgNPs), the largest and fastest growing category of nanomaterials, and their potential for toxic effects to both humans

Transfers in porous medium, drying; Transferts en milieu poreux, sechage

Energy Technology Data Exchange (ETDEWEB)

Ferrasse, J.H.; Arlabosse, P.; Puaux, J.P. [Ecole des Mines d' Albi-Carnaux, Centre Energetique Environnement, 81 - Albi (France)] (and others)

2000-07-01

This congress, on thermology, took place at Lyon in France, the 15-17 may 2000 with a presentation of 143 papers on the recent researches and specialized discussions. The talks published in this book are sorted out in ten thema. One of the thema concerns the transfers in porous medium and the drying, with seven talks presented. They can be applied to many natural domains as the residual waters filtering, the hydrocarbons extraction, the soil utilization for energy source or reserve, the thermal insulation improvement. In the drying domain, two papers are presented, one on the development of the drying of sewage sludges, the other on a drying process for superheated steam. (A.L.B.)

Particles and solutes migration in porous medium : radionuclides and clayey particles simultaneous transport under the effect of a salinity gradient

International Nuclear Information System (INIS)

Faure, M.H.

1994-01-01

This work deals with the radiation protection of high-level and long-life radioactive waste storages. The colloids presence in ground waters can accelerate the radionuclides migration in natural geological deposits. The aim of this thesis is then to control particularly the particles motion in porous medium in order to anticipate quantitatively their migration. Liquid chromatography columns are filled with a clayey sand and fed with a decreasing concentration sodium chloride solution in order to study the particles outlet under a salinity gradient. When the porous medium undergoes a decrease of salinity it deteriorates. The adsorption of the cations : sodium 22, calcium 45, cesium 137 and neptunium 237 is then studied by the ions exchange method. The radionuclide solution is injected before the decrease of the feed solution salinity. The decrease of the sodium chloride concentration leads to the decrease of the radionuclides concentration because the adsorption competition between the sodium ion and the injected cation is lower. The particles transport, without fouling of the porous medium, is carried out in particular physical and chemical conditions which are described. (O.L.). 71 refs., 105 figs., 26 tabs

Comparison of Experimental and Numerical Two-Phase Flows in a Porous Micro-Model

Directory of Open Access Journals (Sweden)

Dustin Crandall

2009-12-01

Full Text Available Characterizing two-phase flow in porous media is important to provide estimates of sweep efficiency in enhanced oil recovery and storage estimates in potential geological CO2 sequestration repositories. To further the current understanding of two-phase flow in porous media a micro-model of interconnected channels was designed and fabricated using stereolithography to experimentally study gas-liquid flows. This flowcell was created with a wide variability of throat dimensions to represent naturally occurring porous media. Low flow rate experiments of immiscible two-phase drainage were performed within this cell. Additionally, a computational model for analyzing two-phase flows in the same flowcell was developed and used to simulate conditions not possible with our laboratory settings. The computational model was first tested for the identical conditions used in the experimental studies, and was shown to be in good agreement with the experimentally determined fractal dimension of the invading gas structure, time until breakthrough, and fluid saturation. The numerical model was then used to study two-phase air-water flows in flowcells with the same geometry and different gas-liquid-solid contact angles. The percent saturation of air and the motion of the fluids through the cell were found to vary with changes in these parameters. Finally, to simulate flows expected during geologic carbon sequestration, the fluid properties and interface conditions were set to model the flow of CO2 into a brine-saturated porous medium at representative subsurface conditions. The CO2 flows were shown to have larger gas saturations than the previous air into water studies. Thus the accuracy of the computational model was supported by the flowcell experiments, and the computational model extended the laboratory results to conditions not possible with the apparatus used in the experiments.

Capillary pressure-saturation relationships for porous granular materials: Pore morphology method vs. pore unit assembly method

Science.gov (United States)

Sweijen, Thomas; Aslannejad, Hamed; Hassanizadeh, S. Majid

2017-09-01

In studies of two-phase flow in complex porous media it is often desirable to have an estimation of the capillary pressure-saturation curve prior to measurements. Therefore, we compare in this research the capability of three pore-scale approaches in reproducing experimentally measured capillary pressure-saturation curves. To do so, we have generated 12 packings of spheres that are representative of four different glass-bead packings and eight different sand packings, for which we have found experimental data on the capillary pressure-saturation curve in the literature. In generating the packings, we matched the particle size distributions and porosity values of the granular materials. We have used three different pore-scale approaches for generating the capillary pressure-saturation curves of each packing: i) the Pore Unit Assembly (PUA) method in combination with the Mayer and Stowe-Princen (MS-P) approximation for estimating the entry pressures of pore throats, ii) the PUA method in combination with the hemisphere approximation, and iii) the Pore Morphology Method (PMM) in combination with the hemisphere approximation. The three approaches were also used to produce capillary pressure-saturation curves for the coating layer of paper, used in inkjet printing. Curves for such layers are extremely difficult to determine experimentally, due to their very small thickness and the presence of extremely small pores (less than one micrometer in size). Results indicate that the PMM and PUA-hemisphere method give similar capillary pressure-saturation curves, because both methods rely on a hemisphere to represent the air-water interface. The ability of the hemisphere approximation and the MS-P approximation to reproduce correct capillary pressure seems to depend on the type of particle size distribution, with the hemisphere approximation working well for narrowly distributed granular materials.

Porous media heat transfer for injection molding

Science.gov (United States)

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.

Numerical simulation of flow boiling for organic fluid with high saturation temperature in vertical porous coated tube

Energy Technology Data Exchange (ETDEWEB)

Yang Dong, E-mail: dyang@mail.xjtu.edu.cn [State Key Laboratory of Multiphase Flow in Power Engineering, Xi' an Jiaotong University, Xi' an, Shaanxi Province 710049 (China); Pan Jie; Wu Yanhua; Chen Tingkuan [State Key Laboratory of Multiphase Flow in Power Engineering, Xi' an Jiaotong University, Xi' an, Shaanxi Province 710049 (China); Zhou, Chenn Q. [Department of Mechanical Engineering, Purdue University Calumet, Hammond, IN 46323 (United States)

2011-08-15

Highlights: > A model is developed for the prediction of flow boiling in vertical porous tubes. > The model assumes that the nucleate boiling plays an important role. > The present model can predict most of the experimental values within {+-}20%. > The results indicate the nucleate boiling contribution decreases from 50% to 15%. - Abstract: A semi-analytical model is developed for the prediction of flow boiling heat transfer inside vertical porous coated tubes. The model assumes that the forced convection and nucleate boiling coexist together in the annular flow regime. Conservations of mass, momentum, and energy are used to solve for the liquid film thickness and temperature. The heat flux due to nucleate boiling consists of those inside and outside micro-tunnels. To close the equations, a detailed analysis of various forces acting on the bubble is presented to predict its mean departure diameter. The active nucleation site density of porous layer is determined from the pool boiling correlation by introducing suppression factor. The flow boiling heat transfer coefficients of organic fluid (cumene) with high saturation temperature in a vertical flame-spraying porous coated tube are studied numerically. It is shown that the present model can predict most of the experimental values within {+-}20%. The numerical results also indicate that the nucleate boiling contribution to the overall heat transfer coefficient decreases from 50% to 15% with vapor quality increasing from 0.1 to 0.5.

The Role of GPR84 in Medium-chain Saturated Fatty Acid Taste Transduction

OpenAIRE

Liu, Yan

2016-01-01

Previous research has shown the gustatory recognition of the long-chain unsaturated fatty acids. In this study, I showed for the first time that medium-chain saturated fatty acids (MCFAs) are effective taste stimuli at both the cellular and behavioral levels. The mechanisms of gustatory recognition of MCFAs in mice were also partially elucidated using pharmaceutical approaches. The inward currents induced by capric acid in mouse taste cells were significantly inhibited by the antagonists of G...

Hydro-mechanical coupling in non-saturated medium with phase change. Application to desiccation shrinkage

International Nuclear Information System (INIS)

Lassabatere, Thierry

1994-01-01

The target of this research is to set up a unified and coherent working frame based upon the rigorous principles of thermodynamics and making it possible to model a large class of physical phenomena acting in unsaturated porous media, as well as the related interactions with the mechanical state of the structures. This class corresponds to reactive phenomena among which one finds the phase change (desiccation) for which the whole of its subsequent actions (creep but essentially shrinkage) is modelled and which will be treated as a specific application example. The first chapter recalls the bases of the adopted description of the porous medium as well as the global thermodynamical frame which underlays the whole modelling. Chapter II deals with the mainly new formulation and the identification of a non linear elastic constitutive law of the medium involved. Various reflexion elements related to the microscopic behaviours of the components and to experiments have orientated the model towards some more limitative hypotheses making it possible to have a complete and explicit determination of a law for the macroscopic behaviour. Chapter IV and V are examples of application: chapter IV studies the problem of shrinkage and creep in a coupled linear elastic behaviour. Chapter V is limited to the case of shrinkage treated by a numerical application of the whole non-linear elastic model. The results obtained are in good agreement with the corresponding experiments. (author) [fr

Autonomous Sensors for Measuring Continuously the Moisture and Salinity of a Porous Medium

Science.gov (United States)

Chavanne, Xavier; Frangi, Jean-Pierre

2017-01-01

The article describes a new field sensor to monitor continuously in situ moisture and salinity of a porous medium via measurements of its dielectric permittivity, conductivity and temperature. It intends to overcome difficulties and biases encountered with sensors based on the same sensitivity principle. Permittivity and conductivity are determined simultaneously by a self-balanced bridge, which measures directly the admittance of sensor electrodes in medium. All electric biases are reduced and their residuals taken into account by a physical model of the instrument, calibrated against reference fluids. Geometry electrode is optimized to obtain a well representative sample of the medium. The sensor also permits acquiring a large amount of data at high frequency (six points every hour, and even more) and to access it rapidly, even in real time, owing to autonomy capabilities and wireless communication. Ongoing developments intend to simplify and standardize present sensors. Results of field trials of prototypes in different environments are presented. PMID:28492471

Autonomous Sensors for Measuring Continuously the Moisture and Salinity of a Porous Medium.

Science.gov (United States)

Chavanne, Xavier; Frangi, Jean-Pierre

2017-05-11

The article describes a new field sensor to monitor continuously in situ moisture and salinity of a porous medium via measurements of its dielectric permittivity, conductivity and temperature. It intends to overcome difficulties and biases encountered with sensors based on the same sensitivity principle. Permittivity and conductivity are determined simultaneously by a self-balanced bridge, which measures directly the admittance of sensor electrodes in medium. All electric biases are reduced and their residuals taken into account by a physical model of the instrument, calibrated against reference fluids. Geometry electrode is optimized to obtain a well representative sample of the medium. The sensor also permits acquiring a large amount of data at high frequency (six points every hour, and even more) and to access it rapidly, even in real time, owing to autonomy capabilities and wireless communication. Ongoing developments intend to simplify and standardize present sensors. Results of field trials of prototypes in different environments are presented.

Magnetogravitational stability of resistive plasma through porous medium with thermal conduction and FLR corrections

International Nuclear Information System (INIS)

Vaghela, D.S.; Chhajlani, R.K.

1989-01-01

The problem of stability of self gravitating magnetized plasma in porous medium is studied incorporating electrical resistivity, thermal conduction and FLR corrections. Normal mode analysis is applied to derive the dispersion relation. Wave propagation is discussed for parallel and perpendicular directions to the magnetic field. Applying Routh Hurwitz Criterion the stability of the medium is discussed and it is found that Jeans' criterion determines the stability of the medium. Magnetic field, porosity and resistivity of the medium have no effect on Jeans' Criterion in longitudinal direction. For perpendicular direction, in case of resistive medium Jeans' expression remains unaffected by magnetic field but for perfectly conducting medium magnetic field modifies the Jeans' expression to show the stabilizing effect. Thermal conductivity affects the sonic mode by making the process isothermal instead of adiabatic. Porosity of the medium is effective only in case of perpendicular direction to magnetic field for perfectly conducting plasma as it reduces the stabilizing effect of magnetic field. For longitudinal wave propagation, though Finite Larmor Radius (FLR) corrections have no effect on sonic mode but it changes the growth rate for Alfven mode. For transverse wave propagation FLR corrections and porosity affect the Jeans' expression in case of non-viscous medium but viscosity of the medium removes the effect of FLR and porosity on Jeans' condition. (author)

Finite medium Green's function solutions to nuclide transport in porous media

International Nuclear Information System (INIS)

Oston, S.G.

1979-01-01

Current analytical techniques for predicting the transport of nuclides in porous materials center on the Green's function approach - i.e., determining the response characteristics of a geologic pathway to an impulse function input. To data, the analyses all have set the boundary conditions needed to solve the 1-D transport equation as though each pathway were infinite in length. The purpose of this work is to critically examine the effect that this infinite pathway assumption has on Green's function models of nuclide transport in porous media. The work described herein has directly attacked the more difficult problem of obtaining suitable Green's functions for finite pathways whose dimensions, in fact, may not be much greater than the diffusion length. Two different finite media Green's functions describing the nuclide mass flux have been determined, depending on whether the pathway is terminated by a high or a low flow resistance at the outlet end. Pulse shapes and peak amplitudes have been computed for each Green's function over a wide range of geohydrologic parameters. These results have been compared to both infinite and semi-infinite medium solutions. It was found that predicted pulse shapes are quite sensitive to selection of a Green's function model for short pathways only. For long pathways all models tend toward a symmetric Gaussian flux-time history at the outlet. Thus, the results of our previous waste transport studies using the infinite pathway assumption are still generally valid because they always included at least one long pathway. It was also found that finite medium models offer some unique computational advantages for evaluating nuclide transport in a series of connecting pathways

Thermo-diffusion effect on free convection heat and mass transfer in a thermally linearly stratified non-darcy porous media

KAUST Repository

Murthy, P.V.S.N.

2011-12-26

Thermo-diffusion effect on free convection heat and mass transfer from a vertical surface embedded in a liquid saturated thermally stratified non - Darcy porous medium has been analyzed using a local non-similar procedure. The wall temperature and concentration are constant and the medium is linearly stratified in the vertical direction with respect to the thermal conditions. The fluid flow, temperature and concentration fields are affected by the complex interactions among the diffusion ratio Le, buoyancy ratio N, thermo-diffusion parameter Sr and stratification parameter ?. Non-linear interactions of all these parameters on the convective transport has been analyzed and variation of heat and mass transfer coefficients with thermo-diffusion parameter in the thermally stratified non-Darcy porous media is presented through computer generated plots.

Thermo-diffusion effect on free convection heat and mass transfer in a thermally linearly stratified non-darcy porous media

KAUST Repository

Murthy, P.V.S.N.; El-Amin, Mohamed

2011-01-01

Thermo-diffusion effect on free convection heat and mass transfer from a vertical surface embedded in a liquid saturated thermally stratified non - Darcy porous medium has been analyzed using a local non-similar procedure. The wall temperature and concentration are constant and the medium is linearly stratified in the vertical direction with respect to the thermal conditions. The fluid flow, temperature and concentration fields are affected by the complex interactions among the diffusion ratio Le, buoyancy ratio N, thermo-diffusion parameter Sr and stratification parameter ?. Non-linear interactions of all these parameters on the convective transport has been analyzed and variation of heat and mass transfer coefficients with thermo-diffusion parameter in the thermally stratified non-Darcy porous media is presented through computer generated plots.

Multiscale Adapted Time-Splitting Technique for Nonisothermal Two-Phase Flow and Nanoparticles Transport in Heterogenous Porous Media

KAUST Repository

El-Amin, Mohamed F.

2017-05-05

This paper is devoted to study the problem of nonisothermal two-phase flow with nanoparticles transport in heterogenous porous media, numerically. For this purpose, we introduce a multiscale adapted time-splitting technique to simulate the problem under consideration. The mathematical model consists of equations of pressure, saturation, heat, nanoparticles concentration in the water–phase, deposited nanoparticles concentration on the pore–walls, and entrapped nanoparticles concentration in the pore–throats. We propose a multiscale time splitting IMplicit Pressure Explicit Saturation–IMplicit Temperature Concentration (IMPES-IMTC) scheme to solve the system of governing equations. The time step-size adaptation is achieved by satisfying the stability Courant–Friedrichs–Lewy (CFL<1) condition. Moreover, numerical test of a highly heterogeneous porous medium is provided and the water saturation, the temperature, the nanoparticles concentration, the deposited nanoparticles concentration, and the permeability are presented in graphs.

Conjugate heat transfer in a porous cavity filled with nano-fluids and heated by a triangular thick wall

International Nuclear Information System (INIS)

Chamkha, Ali J.; Ismael, Muneer A.

2013-01-01

The conjugate natural convection-conduction heat transfer in a square domain composed of nano-fluids filled porous cavity heated by a triangular solid wall is studied under steady-state conditions. The vertical and horizontal walls of the triangular solid wall are kept isothermal and at the same hot temperature Th. The other boundaries surrounding the porous cavity are kept adiabatic except the right vertical wall where it is kept isothermally at the lower temperature T c . Equations governing the heat transfer in the triangular wall and heat and nano-fluid flow, based on the Darcy model, in the nano-fluid-saturated porous medium together with the derived relation of the interface temperature are solved numerically using the over-successive relaxation finite-difference method. A temperature independent nano-fluids properties model is adopted. Three nano-particle types dispersed in one base fluid (water) are investigated. The investigated parameters are the nano-particles volume fraction φ (0-0.2), Rayleigh number Ra (10-1000), solid wall to base-fluid saturated porous medium thermal conductivity ratio K ro (0.44, 1, 23.8), and the triangular wall thickness D (0.1-1). The results are presented in the conventional form; contours of streamlines and isotherms and the local and average Nusselt numbers. At a very low Rayleigh number Ra = 10, a significant enhancement in heat transfer within the porous cavity with φ is observed. Otherwise, the heat transfer may be enhanced or deteriorated with φ depending on the wall thickness D and the Rayleigh number Ra. At high Rayleigh numbers and low conductivity ratios, critical values of D, regardless of 4, are observed and accounted. (authors)

Effect of magnetic field on Rayleigh-Taylor instability of quantum and stratified plasma in porous medium

International Nuclear Information System (INIS)

Sharma, P.K.; Tiwari, Anita; Argal, Shraddha; Chhajlani, R.K.

2013-01-01

This paper is devoted to an investigation of Quantum effects and magnetic field effects on the Rayleigh Taylor instability of two superposed incompressible fluids in bounded porous medium. The Quantum magneto hydrodynamic equations are solved by using normal mode method and a dispersion relation is obtained. The dispersion relation is derived for the case where plasma is bounded by two rigid planes z = 0 and z = h. The Rayleigh Taylor instability growth rate and stability condition of the medium is discussed in the presence of quantum effect, magnetic field, porosity and permeability. It is found that the magnetic field and medium porosity have stabilizing influence while permeability has destabilizing influence on the Rayleigh Taylor instability. (author)

Analysis of the processes defining radionuclide migration from deep geological repositories in porous medium

International Nuclear Information System (INIS)

Brazauskaite, A.; Poskas, P.

2004-01-01

Due to the danger of exposure arising from long-lived radionuclides to humans and environment, spent nuclear fuel (SNF) and high level waste (HLW) are not allowed to be disposed of in near surface repositories. There exists an international consensus that such high level and long-lived radioactive wastes are best disposed of in geological repositories using a system of engineered and natural barriers. At present, the geological repository of SNF and HLW has not been realized yet in any country but there is a lot of experience in the assessment of radionuclide migration from deep repositories, investigations of different processes related to the safety of a disposal system. The aim of this study was to analyze the processes related to the radionuclide migration from deep geological repositories in porous medium such as SNF matrix dissolution, release mechanism of radionuclides from SNF matrix, radionuclide solubility, sorption, diffusive, advective transport of radionuclides from the canister and through the engineered and natural barriers. It has been indicated that SNF matrix dissolution, radionuclide solubility and sorption are sensitive to ambient conditions prevailing in the repository. The approaches that could be used for modeling the radionuclide migration from deep repositories in porous medium are also presented. (author)

Carbofuran biodegradation in brackish groundwater and its effect on the hydraulic properties of the porous medium

Science.gov (United States)

Amiaz, Yanai; Ronen, Zeev; Adar, Eilon; Weisbrod, Noam

2015-04-01

A chalk fractured aquitard beneath an industrial site is subjected to intense contamination due to percolation of contaminants from the different facilities operating at the site. In order to reduce further contamination, draining trenches were excavated and filled with coarse gravel (3-4 cm in diameter) forming a porous medium, to which the contaminated groundwater discharges from the fractures surrounding the trenches. This research is aimed at establishing a biodegrading process of high efficiency and performance within the draining trenches. The research includes both field and laboratory experiments. An experimental setup of five columns (50 cm length and 4.5 cm in diameter) was constructed under highly controlled conditions. Over the course of the experiments, the columns were filled with different particle sizes and placed in a temperature controlled chamber. Filtered groundwater (0.2 µm) from the site groundwater, enriched by a model contaminant carbofuran (CRF), was injected to the columns; as two of the columns were inoculated by CRF degrading microorganisms native in the site's groundwater, two columns were inoculated by CRF degrading bacteria from the external environment, and one column was used as a control. During the experiment, measurements were taken from different locations along each column. These include: (a) CRF concentration and (b) hydraulic pressure and solution viscosity (in order to obtain the changes in permeability). A tracer test using uranine was carried out in parallel, in order to obtain the changes in hydraulic parameters. Correlating CRF concentration variations to changes of hydraulic parameters enable the deduction due to the effect that biological activity (under different temperature regimes) has on the hydraulic properties of the porous medium and its effect on the process of contaminant groundwater bodies' remediation. Preliminary results suggest that although biodegradation occurs, microbial activity has minor effect on

Influence of yield stress on free convective boundary-layer flow of a non-Newtonian nanofluid past a vertical plate in a porous medium

International Nuclear Information System (INIS)

Hady, F. M.; Ibrahim, F. S.; Abdel-Gaied, S. M.; Eid, M. R.

2011-01-01

The effect of yield stress on the free convective heat transfer of dilute liquid suspensions of nanofluids flowing on a vertical plate saturated in porous medium under laminar conditions is investigated considering the nanofluid obeys the mathematical model of power-law. The model used for non-Newtonian nanofluid incorporates the effects of Brownian motion and thermophoresis. The governing boundary- layer equations are cast into dimensionless system which is solved numerically using a deferred correction technique and Newton iteration. This solution depends on yield stress parameter Ω, a power-law index n, Lewis number Le, a buoyancy-ratio number Nr, a Brownian motion number Nb, and a thermophoresis number Nt. Analyses of the results found that the reduced Nusselt and Sherwood numbers are decreasing functions of the higher yield stress parameter for each dimensionless numbers, n and Le, except the reduced Sherwood number is an increasing function of higher Nb for different values of yield stress parameter

Observation of a new surface mode on a fluid-saturated permeable solid

International Nuclear Information System (INIS)

Nagy, P.B.

1992-01-01

Almost ten years ago, S. Feng and D. L. Johnson predicted the presence of a new surface mode on a fluid/fluid-saturated porous solid interface with closed surface pores [J. Acoust. Soc. Am. 74, 906 (1983)]. We found that, due to surface tension, practically closed-pore boundary conditions can prevail at an interface between a nonwetting fluid (e.g., air) and a porous solid saturated with a wetting fluid (e.g., water or alcohol). Surface wave velocity and attenuation measurements were made on alcohol-saturated porous sintered glass at 100 kHz. The experimental results show clear evidence of the new ''slow'' surface mode predicted by Feng and Johnson

Mixed convection in fluid superposed porous layers

CERN Document Server

Dixon, John M

2017-01-01

This Brief describes and analyzes flow and heat transport over a liquid-saturated porous bed. The porous bed is saturated by a liquid layer and heating takes place from a section of the bottom. The effect on flow patterns of heating from the bottom is shown by calculation, and when the heating is sufficiently strong, the flow is affected through the porous and upper liquid layers. Measurements of the heat transfer rate from the heated section confirm calculations. General heat transfer laws are developed for varying porous bed depths for applications to process industry needs, environmental sciences, and materials processing. Addressing a topic of considerable interest to the research community, the brief features an up-to-date literature review of mixed convection energy transport in fluid superposed porous layers.

Modeling of filtration of 2-types particles suspension in a porous medium

Directory of Open Access Journals (Sweden)

Galaguz Yuri

2017-01-01

Full Text Available The filtration problem describes the process of concreting loose soil with a liquefied concrete solution. The filtration of 2-types particles suspension in a homogeneous porous medium with a size-exclusion particles retention mechanism is considered. The difference in the filtration coefficients of 2-types particles leads to the separation of the filtration domain into two zones, in one of which two types of particles are deposited and in another – only particles of one type are deposited. In this paper, the mobile boundary of two zones is calculated, and numerical solution of the problem is calculated.

Surface wave propagation in a fluid-saturated incompressible ...

Indian Academy of Sciences (India)

dilatational and one rotational elastic waves in fluid-saturated porous solids. Biot theory ..... If the pore liquid is absent or gas is filled in the pores, then ρF ..... Biot M A (1962) Mechanics of deformation and acoustic propagation in porous media.

Nonlinear radiative peristaltic flow of hydromagnetic fluid through porous medium

Science.gov (United States)

Hussain, Q.; Latif, T.; Alvi, N.; Asghar, S.

2018-06-01

The radiative heat and mass transfer in wall induced flow of hydromagnetic fluid through porous medium in an asymmetric channel is analyzed. The fluid viscosity is considered temperature dependent. In the theory of peristalsis, the radiation effects are either ignored or taken as linear approximation of radiative heat flux. Such approximation is only possible when there is sufficiently small temperature differences in the flow field; however, nonlinear radiation effects are valid for large temperature differences as well (the new feature added in the present study). Mathematical modeling of the problems include the complicated system of highly nonlinear differential equations. Semi-analytical solutions are established in the wave reference frame. Results are displayed graphically and discussed in detail for the variation of various physical parameters with the special attention to viscosity, radiation, and temperature ratio parameters.

Modeling of the pollutant transport in fissured-porous media under consideration of colloids using the transport codes FRAME and COFRAME; Modellierung des Schadstofftransports in geklueftet-poroesen Medien unter Beruecksichtigung von Kolloiden mit den Transportprogrammen FRAME und COFRAME

Energy Technology Data Exchange (ETDEWEB)

Reiche, Tatiana; Noseck, Ulrich; Wolf, Jens Wilhelm

2014-05-15

For the long-term safety analysis of final nuclear waste repositories the transport of pollutants from the repository into the biosphere three mostly independent subsystems are considered: the near field, the geosphere and the biosphere. Normally rocks include fissures or other disturbances. Porous materials in the rock matrix have usually a high water content and acts as storage for pollutants due to sorption and diffusion processes. The aim of the project is the development of calculation modules for the code RepoTREND that simulate the pollutant transport in saturated fissured-porous media taking into account the effect of colloids. FRAME describes the pollutant dispersion in a fissured-porous medium and COFRAME the colloid influenced transport in a fissured-porous medium.

Analytical Solution of Flow and Heat Transfer over a Permeable Stretching Wall in a Porous Medium

Directory of Open Access Journals (Sweden)

M. Dayyan

2013-01-01

Full Text Available Boundary layer flow through a porous medium over a stretching porous wall has seen solved with analytical solution. It has been considered two wall boundary conditions which are power-law distribution of either wall temperature or heat flux. These are general enough to cover the isothermal and isoflux cases. In addition to momentum, both first and second laws of thermodynamics analyses of the problem are investigated. The governing equations are transformed into a system of ordinary differential equations. The transformed ordinary equations are solved analytically using homotopy analysis method. A comprehensive parametric study is presented, and it is shown that the rate of heat transfer increases with Reynolds number, Prandtl number, and suction to the surface.

MHD convective flow through porous medium in a horizontal channel with insulated and impermeable bottom wall in the presence of viscous dissipation and Joule heating

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K.V.S. Raju

2014-06-01

Full Text Available This paper deals with a steady MHD forced convective flow of a viscous fluid of finite depth in a saturated porous medium over a fixed horizontal channel with thermally insulated and impermeable bottom wall in the presence of viscous dissipation and joule heating. The governing equations are solved in the closed form and the exact solutions are obtained for velocity and temperature distributions when the temperatures on the fixed bottom and on the free surface are prescribed. The expressions for flow rate, mean velocity, temperature, mean temperature, mean mixed temperature in the flow region and the Nusselt number on the free surface have been obtained. The cases of large and small values of porosity coefficients have been obtained as limiting cases. Further, the cases of small depth (shallow fluid and large depth (deep fluid are also discussed. The results are presented and discussed with the help of graphs.

Sensitivity and inversion of full seismic waveforms in stratified porous medium; Sensibilite et inversion de formes d'ondes completes en milieu poreux stratifie

Energy Technology Data Exchange (ETDEWEB)

Barros, L. de

2007-12-15

Characterization of porous media parameters, and particularly the porosity, permeability and fluid properties are very useful in many applications (hydrologic, natural hazards or oil industry). The aim of my research is to evaluate the possibility to determine these properties from the full seismic wave fields. First, I am interested in the useful parameters and the specific properties of the seismic waves in the poro-elastic theory, often called Biot (1956) theory. I then compute seismic waves propagation in fluid saturated stratified porous media with a reflectivity method coupled with the discrete wavenumber integration method. I first used this modeling to study the possibilities to determine the carbon dioxide concentration and localization thanks to the reflected P-waves in the case of the deep geological storage of Sleipner (North Sea). The sensitivity of the seismic response to the poro-elastic parameters are then generalized by the analytical computation of the Frechet derivatives which are expressed in terms of the Green's functions of the unperturbed medium. The numerical tests show that the porosity and the consolidation are the main parameters to invert. The sensitivity operators are then introduced in a inversion algorithm based on iterative modeling of the full waveform. The classical algorithm of generalized least-square inverse problem is solved by the quasi-Newton technique (Tarantola, 1984). The inversion of synthetic data show that we can invert for the porosity and the fluid and solid parameters (densities and mechanical modulus, or volume rate of fluid and mineral) can be correctly rebuilt if the other parameters are well known. However, the strong seismic coupling of the porous parameters leads to difficulties to invert simultaneously for several parameters. One way to get round these difficulties is to use additional information and invert for one single parameter for the fluid properties (saturating rate) or for the lithology. An other

Laboratory analysis of fluid flow and solute transport through a variably saturated fracture embedded in porous tuff

International Nuclear Information System (INIS)

Chuang, Y.; Haldeman, W.R.; Rasmussen, T.C.; Evans, D.D.

1990-02-01

Laboratory techniques are developed that allow concurrent measurement of unsaturated matrix hydraulic conductivity and fracture transmissivity of fractured rock blocks. Two Apache Leap tuff blocks with natural fractures were removed from near Superior, Arizona, shaped into rectangular prisms, and instrumented in the laboratory. Porous ceramic plates provided solution to block tops at regulated pressures. Infiltration tests were performed on both test blocks. Steady flow testing of the saturated first block provided estimates of matrix hydraulic conductivity and fracture transmissivity. Fifteen centimeters of suction applied to the second block top showed that fracture flow was minimal and matrix hydraulic conductivity was an order of magnitude less than the first block saturated matrix conductivity. Coated-wire ion-selective electrodes monitored aqueous chlorided breakthrough concentrations. Minute samples of tracer solution were collected with filter paper. The techniques worked well for studying transport behavior at near-saturated flow conditions and also appear to be promising for unsaturated conditions. Breakthrough curves in the fracture and matrix, and a concentration map of chloride concentrations within the fracture, suggest preferential flows paths in the fracture and substantial diffusion into the matrix. Average travel velocity, dispersion coefficient and longitudinal dispersivity in the fracture are obtained. 67 refs., 54 figs., 23 tabs

Ultrasonic Characterization of Water Saturated Double Porosity Media

Science.gov (United States)

Bai, Ruonan; Tinel, Alain; Alem, Abdellah; Franklin, Hervé; Wang, Huaqing

Wave propagation through a multilayered structure consisting of a water saturated double porosity medium in an aluminum rectangular box immersed in water is studied. By assuming a plane incident wave from water onto the structure, the reflection and transmission coefficients are derived by application of the boundary conditions at each interface. Numerical computations are done for two particular double porosity media, ROBU® and Tobermorite 11 Å, that are assumed to obey Berryman's extension of Biot's theory [Berryman 1995, 2000]. The influence of the thickness of double porosity medium is investigated. To compare experiments to computations, two comparison coefficients Cnum and Cexp are introduced. The theoretical one Cnum is defined as the ratio of the transmission coefficient of the structure to the transmission coefficient of the box filled exclusively with water. The experimental comparison coefficient Cexp is defined as the ratio of the Fourier transforms of the transmitted signals by the box filled with the double porous medium to that of the transmitted signals by the box filled with water. A method of minimization based on a gradient descent algorithm is used to optimize some of the parameters of the double porosity media such as the bulk moduli.

A mathematical model for two-phase water, air, and heat flow around a linear heat source emplaced in a permeable medium

International Nuclear Information System (INIS)

Doughty, C.; Pruess, K.

1991-03-01

A semianalytical solution for transient two-phase water, air, and heat flow in a uniform porous medium surrounding a constant-strength linear heat source has been developed, using a similarity variable η=r/√t (r is radial distance, t is time). Although the similarity transformation requires a simplified radial geometry, all the physical mechanisms involved in two-phase fluid and heat flow may be taken into account in a rigorous way. The solution includes nonlinear thermophysical fluid and material properties, such as relative permeability and capillary pressure variations with saturation, and density and viscosity variations with temperature and pressure. The resulting governing equations form a set of coupled nonlinear ODEs, necessitating numerical integration. The solution has been applied to a partially saturated porous medium initially at a temperature well below the saturation temperature, which is the setting for the potential nuclear waste repository site at Yucca Mountain, Nevada. The resulting heat and fluid flows provide a stringent test of many of the capabilities of numerical simulation models, making the similarity solution a useful tool for model verification. Comparisons to date have shown excellent agreement between the TOUGH2 simulator and the similarity solution for a variety of conditions. 13 refs., 6 figs., 1 tab

Peristaltic Flow of Carreau Fluid in a Rectangular Duct through a Porous Medium

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R. Ellahi

2012-01-01

Full Text Available We have examined the peristaltic flow of Carreau fluid in a rectangular channel through a porous medium. The governing equations of motion are simplified by applying the long wavelength and low Reynolds number approximations. The reduced highly nonlinear partial differential equations are solved jointly by homotopy perturbation and Eigen function expansion methods. The expression for pressure rise is computed numerically by evaluating the numerical integration. The physical features of pertinent parameters have been discussed by plotting graphs of velocity, pressure rise, pressure gradient, and stream functions.

A novel direct-fired porous-medium boiler

Science.gov (United States)

Prasartkaew, Boonrit

2018-01-01

Nowadays, power and heat generation systems pay an important role in all economic sectors. These systems are mainly based on combustion reaction and operated under the second law of thermodynamics. A conventional boilers, a main component of heat and power generators, have thermal efficiency in the range of 70 to 85%, mainly owing to they have flue gas heat loss. This paper proposes a novel type of boiler, called a Direct-fired Porous-medium Boiler (DPB). Due to being operated without flue gas heat loss, its thermal efficiency cloud be approximately close to 100%. The steam produced from the proposed boiler; however, is not pure water steam. It is the composite gases of steam and combustion-product-gases. This paper aims at presenting the working concept and reporting the experimental results on the performance of the proposed boiler. The experiments of various operating parameters were performed and collected data were used for the performance analysis. The experimental results demonstrated that the proposed boiler can be operated as well as the conceptual design and then it is promising. It can be possibly further developed to be a high efficiency boiler by means of reducing or suppressing the surface heat loss with better insulator and/or refractory lined.

MHD flow of a dusty viscoelastic liquid through a porous medium between two inclined parallel plates

International Nuclear Information System (INIS)

Singh, A.K.; Singh, N.P.

1996-01-01

Magnetohydrodynamic flow of a dusty viscoelastic liquid (Oldroyd B-liquid) through a porous medium between two parallel plates inclined to the horizon has been studied. The liquid velocity, dust particle velocity and flux of flow have been obtained. Earlier results have been deduced as particular cases of the present investigation. The physical situation of the motion has been discussed graphically. (author)

Modeling and simulation of nanoparticles transport in a two-phase flow in porous media

KAUST Repository

El-Amin, Mohamed; Salama, Amgad; Sun, Shuyu

2012-01-01

In the current paper, a mathematical model to describe the nanoparticles transport carried by a two-phase flow in a porous medium is presented. Both capillary forces as well as Brownian diffusion are considered in the model. A numerical example of countercurrent water-oil imbibition is considered. We monitor the changing of the fluid and solid properties due to the addition of the nanoparticles using numerical experiments. Variation of water saturation, nanoparticles concentration and porosity ratio are investigated.

Chaotic Darcy-Brinkman convection in a fluid saturated porous layer subjected to gravity modulation

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Moli Zhao

2018-06-01

Full Text Available On the basis of Darcy-Brinkman model, the chaotic convection in a couple stress fluid saturated porous media under gravity modulation is investigated using the nonlinear stability analyses. The transition from steady convection to chaos is analysed with the effect of Darcy-Brinkman couple stress parameter and the gravity modulation. The results show that the chaotic behavior is connected with the critical value of Rayleigh number which is dependent upon the oscillation frequency and the Darcy-Brinkman couple stress parameter. If the oscillation frequency Ω is not zero, the Rayleigh number value R of the chaotic behavior increases with the increase of the Darcy-Brinkman couple stress parameter. The Darcy-Brinkman couple stress parameter and the gravity modulation decrease the rate of heat transfer. Keywords: Darcy-Brinkman model, Gravity modulation, Nonlinear stability, Chaotic convection

Capillary-driven flow in a fracture located in a porous medium

International Nuclear Information System (INIS)

Martinez, M.J.

1988-09-01

Capillary-driven immiscible displacement of air by water along an isolated fracture located in a permeable medium is induced by an abrupt change in water saturation at the fracture inlet. The fracture is idealized as either a smooth slot with permeable walls or a high-permeability later. The penetration distance of moisture in the fracture permeability ratio and length scales for the problem. The models are applied to materials representative of the Yucca Mountain region of the Nevada Test Site. Fracture moisture-penetration histories are predicted for several units in Yucca Mountain and for representative fracture apertures. 18 refs., 20 figs., 6 tabs

Chaotic convection of viscoelastic fluids in porous media

Energy Technology Data Exchange (ETDEWEB)

Sheu, L.-J. [Department of Mechanical Engineering, Chung Hua University, Hsinchu, Taiwan (China)], E-mail: ljsheu@chu.edu.tw; Tam, L.-M. [Department of Electromechanical Engineering, University of Macau, Macau (China)], E-mail: fstlmt@umac.mo; Chen, J.-H. [Department of Mechanical Engineering, Chung Hua University, Hsinchu, Taiwan (China)], E-mail: chen@chu.edu.tw; Chen, H.-K. [Department of Industrial Engineering and Management, Hsiuping Institute of Technology, Taichung, Taiwan (China)], E-mail: kanechen@giga.net.tw; Lin, K.-T. [Department of Mechanical Engineering, Chung Yuan Christian University, Chung Li, Taiwan (China)], E-mail: willie@nanya.edu.tw; Kang Yuan [Department of Mechanical Engineering, Chung Yuan Christian University, Chung Li, Taiwan (China)], E-mail: yk@cycu.edu.tw

2008-07-15

Buoyancy-induced convection in a viscoelastic fluid-saturated porous medium was analyzed using an Oldroydian-type constitutive relation. An autonomous system with four differential equations was deduced by applying the truncated Galerkin expansion to the momentum and heat transfer equations. The four-dimensional system can be reduced to many systems provided in the literature such as the Lorenz system, Vadasz system, Khayat system, and Akhatov system. Depending on the flow parameters, the asymptotic behavior can be stationary, periodic, or chaotic. Generation of a four-scroll, or two-'butterfly', chaotic attractor was observed. Results also show that stress relaxation tends to precipitate the onset of chaos.

Numerical artifacts in the Generalized Porous Medium Equation: Why harmonic averaging itself is not to blame

Science.gov (United States)

Maddix, Danielle C.; Sampaio, Luiz; Gerritsen, Margot

2018-05-01

The degenerate parabolic Generalized Porous Medium Equation (GPME) poses numerical challenges due to self-sharpening and its sharp corner solutions. For these problems, we show results for two subclasses of the GPME with differentiable k (p) with respect to p, namely the Porous Medium Equation (PME) and the superslow diffusion equation. Spurious temporal oscillations, and nonphysical locking and lagging have been reported in the literature. These issues have been attributed to harmonic averaging of the coefficient k (p) for small p, and arithmetic averaging has been suggested as an alternative. We show that harmonic averaging is not solely responsible and that an improved discretization can mitigate these issues. Here, we investigate the causes of these numerical artifacts using modified equation analysis. The modified equation framework can be used for any type of discretization. We show results for the second order finite volume method. The observed problems with harmonic averaging can be traced to two leading error terms in its modified equation. This is also illustrated numerically through a Modified Harmonic Method (MHM) that can locally modify the critical terms to remove the aforementioned numerical artifacts.

The onset of double diffusive convection in a viscoelastic fluid-saturated porous layer with non-equilibrium model.

Directory of Open Access Journals (Sweden)

Zhixin Yang

Full Text Available The onset of double diffusive convection in a viscoelastic fluid-saturated porous layer is studied when the fluid and solid phase are not in local thermal equilibrium. The modified Darcy model is used for the momentum equation and a two-field model is used for energy equation each representing the fluid and solid phases separately. The effect of thermal non-equilibrium on the onset of double diffusive convection is discussed. The critical Rayleigh number and the corresponding wave number for the exchange of stability and over-stability are obtained, and the onset criterion for stationary and oscillatory convection is derived analytically and discussed numerically.

Transport and Retention of TiO2 Rutile Nanoparticles in Saturated Porous Media: Influence of Solution pH, Ionic Strength, and the Presence of Humic Acid

Science.gov (United States)

The influence of solution pH, ionic strength, and varying concentrations of the Suwannee River Humic Acid (SRHA) on the transport of titanium dioxide (TiO2, rutile) nanoparticle aggregates (nTiO2) in saturated porous media was investigated through systematically examining the tra...

Low-frequency asymptotic analysis of seismic reflection from afluid-saturated medium

Energy Technology Data Exchange (ETDEWEB)

Silin, D.B.; Korneev, V.A.; Goloshubin, G.M.; Patzek, T.W.

2004-04-14

Reflection of a seismic wave from a plane interface betweentwo elastic media does not depend on the frequency. If one of the mediais poroelastic and fluid-saturated, then the reflection becomesfrequency-dependent. This paper presents a low-frequency asymptoticformula for the reflection of seismic plane p-wave from a fluid-saturatedporous medium. The obtained asymptotic scaling of the frequency-dependentcomponent of the reflection coefficient shows that it is asymptoticallyproportional to the square root of the product of the reservoir fluidmobility and the frequency of the signal. The dependence of this scalingon the dynamic Darcy's law relaxation time is investigated as well.Derivation of the main equations of the theory of poroelasticity from thedynamic filtration theory reveals that this relaxation time isproportional to Biot's tortuosity parameter.

New concept to describe three-phase capillary pressure-degree of saturation relationship in porous media.

Science.gov (United States)

Nakamura, Keita; Kikumoto, Mamoru

2018-03-15

The Leverett concept is used conventionally to model the relationship between the capillary pressures and the degrees of saturation in the water-nonaqueous phase liquid (NAPL)-air three-phase system in porous media. In this paper, the limitation of the Leverett concept that the concept is not applicable in the case of nonspreading NAPLs is discussed through microscopic consideration. A new concept that can be applied in the case of nonspreading NAPLs as well as spreading NAPLs is then proposed. The validity of the proposed concept is confirmed by comparing with past experimental data and simulation results obtained using the conventional model based on the Leverett concept. It is confirmed that the proposed concept can correctly predict the observed distributions of NAPLs, including those of nonspreading ones. Copyright © 2018. Published by Elsevier B.V.

Color image analysis of contaminants and bacteria transport in porous media

Science.gov (United States)

Rashidi, Mehdi; Dehmeshki, Jamshid; Daemi, Mohammad F.; Cole, Larry; Dickenson, Eric

1997-10-01

Transport of contaminants and bacteria in aqueous heterogeneous saturated porous systems have been studied experimentally using a novel fluorescent microscopic imaging technique. The approach involves color visualization and quantification of bacterium and contaminant distributions within a transparent porous column. By introducing stained bacteria and an organic dye as a contaminant into the column and illuminating the porous regions with a planar sheet of laser beam, contaminant and bacterial transport processes through the porous medium can be observed and measured microscopically. A computer controlled color CCD camera is used to record the fluorescent images as a function of time. These images are recorded by a frame accurate high resolution VCR and are then analyzed using a color image analysis code written in our laboratories. The color images are digitized this way and simultaneous concentration and velocity distributions of both contaminant and bacterium are evaluated as a function of time and pore characteristics. The approach provides a unique dynamic probe to observe these transport processes microscopically. These results are extremely valuable in in-situ bioremediation problems since microscopic particle-contaminant- bacterium interactions are the key to understanding and optimization of these processes.

Dynamics of foam flow in porous media in the presence of oil

Science.gov (United States)

Shokri, N.; Osei-Bonsu, K.

2016-12-01

Foams demonstrate great potential for fluid displacement in porous media which is important in a number of subsurface operations such as the enhanced oil recovery and soil remediation. The application of foam in these processes is down to its unique ability to reduce gas mobility by increasing its effective viscosity and to divert gas to un-swept low permeability zones in porous media [1-4]. To investigate the fundamental aspects of foam flow in porous media, we have conducted a systematic series of experiment using a well-characterised porous medium manufactured by a high resolution 3D printer. This enabled us to design and control the properties of porous media with high accuracy. The model porous medium was initially saturated with oil. Then the pre-generated foam was injected into the model at well-defined injection rates to displace oil. The dynamics of foam-oil displacement in porous media was recorded using a digital camera controlled by a computer [5]. The recorded images were analysed in MATLAB to determine the dynamics of foam-oil displacement under different boundary conditions. Effects of the type of oil, foam quality and foam flow rate were investigated. Our results reveal that generation of stable foam is delayed in the presence of light oil in the porous medium compared to the heavy oil. Furthermore, higher foam quality appears to be less stable in the presence of oil lowering its recovery efficiency. Pore-scale inspection of foam-oil patterns formed during displacement revealed formation of a more stable front in the case of lower foam quality which affected the oil recovery efficiency. This study extends the physical understanding of governing mechanisms controlling oil displacement by foam in porous media. Grassia, P., E. Mas-Hernandez, N. Shokri, S.J. Cox, G. Mishuris, W.R. Rossen (2014), J. Fluid Mech., 751, 346-405. Grassia, P., C. Torres-Ulloa, S. Berres, E. Mas-Hernandez, N. Shokri (2016), European Physical Journal E, 39 (4), 42. Mas

Calibration-free quantification of interior properties of porous media with x-ray computed tomography

International Nuclear Information System (INIS)

Hussein, Esam M.A.; Agbogun, H.M.D.; Al, Tom A.

2015-01-01

A method is presented for interpreting the values of x-ray attenuation coefficients reconstructed in computed tomography of porous media, while overcoming the ambiguity caused by the multichromatic nature of x-rays, dilution by void, and material heterogeneity. The method enables determination of porosity without relying on calibration or image segmentation or thresholding to discriminate pores from solid material. It distinguishes between solution-accessible and inaccessible pores, and provides the spatial and frequency distributions of solid-matrix material in a heterogeneous medium. This is accomplished by matching an image of a sample saturated with a contrast solution with that saturated with a transparent solution. Voxels occupied with solid-material and inaccessible pores are identified by the fact that they maintain the same location and image attributes in both images, with voxels containing inaccessible pores appearing empty in both images. Fully porous and accessible voxels exhibit the maximum contrast, while the rest are porous voxels containing mixtures of pore solutions and solid. This matching process is performed with an image registration computer code, and image processing software that requires only simple subtraction and multiplication (scaling) processes. The process is demonstrated in dolomite (non-uniform void distribution, homogeneous solid matrix) and sandstone (nearly uniform void distribution, heterogeneous solid matrix) samples, and its overall performance is shown to compare favorably with a method based on calibration and thresholding. - Highlights: • A method is presented for quantifying x-ray CT data for porous media. • The method neither requires calibration nor segmentation nor thresholding. • We use voxel matching between images of a sample saturated with two distinct solutions. • Method is demonstrated for micro-CT images of dolomite and sandstone samples. • Overall performance compares favorably with a calibration

CALCULATION OF LONG-TERM FILTRATION IN A POROUS MEDIUM

Directory of Open Access Journals (Sweden)

Ludmila I. Kuzmina

2018-03-01

Full Text Available he filtration problem in a porous medium is an important part of underground hydromechanics. Filtration of suspensions and colloids determines the processes of strengthening the soil and creating waterproof walls in the ground while building the foundations of buildings and underground structures. It is assumed that the formation of a deposit is dominated by the size-exclusion mechanism of pore blocking: solid particles pass freely through large pores and get stuck at the inlet of pores smaller than the diameter of the particles. A one-dimensional mathematical model for the filtration of a monodisperse suspension includes the equation for the mass balance of suspended and retained particles and the kinetic equation for the growth of the deposit. For the blocking filtration coefficient with a double root, the exact solution is given implicitly. The asymptotics of the filtration problem is constructed for large time. The numerical calculation of the problem is carried out by the finite differences method. It is shown that asymptotic approximations rapidly converge to a solution with the increase of the expansion order.

Unsaturated medium hydrocarbons pollution evaluation

International Nuclear Information System (INIS)

Di Luise, G.

1991-01-01

When the so called porous unsaturated medium, that's the vertical subsoil section between both the ground and water-table level, is interested by a hydrocarbons spill, the problem to evaluate the pollution becomes difficult: considering, essentially, the natural coexistence in it of two fluids, air and water, and the interactions between them. This paper reports that the problems tend to increase when a third fluid, the pollutant, immiscible with water, is introduced into the medium: a three-phases flow, which presents several analogies with the flow conditions present in an oil-reservoir, will be established. In such a situation, it would be very useful to handle the matter by the commonly used parameters in the oil reservoirs studies such as: residual saturation, relative permeability, phases mobility, to derive a first semiquantitative estimation of the pollution. The subsoil pollution form hydrocarbons agents is one of the worldwide more diffused causes of contamination: such events are generally referable to two main effects: accidental (oil pipeline breakdowns, e.g.), and continuous (underground tanks breaks, industrial plants leakages, e.g.)

Analysis of Cattaneo-Christov heat and mass fluxes in the squeezed flow embedded in porous medium with variable mass diffusivity

Directory of Open Access Journals (Sweden)

M. Farooq

Full Text Available This research article investigates the squeezing flow of Newtonian fluid with variable viscosity over a stretchable sheet inserted in Darcy porous medium. Cattaneo-Christov double diffusion models are implemented to scrutinize the characteristics of heat and mass transfer via variable thermal conductivity and variable mass diffusivity. These models are the modification of conventional laws of Fourier’s and Fick’s via thermal and solutal relaxation times respectively. The homotopy analysis Method (HAM is being utilized to provide the solution of highly nonlinear system of coupled partial differential equations after converted into dimensionless governing equations. The behavior of flow parameters on velocity, concentration, and temperature distributions are sketched and analyzed physically. The result indicates that both concentration and temperature distributions decay for higher solutal and thermal relaxation parameters respectively. Keywords: Squeezing flow, Porous medium, Variable viscosity, Cattaneo-Christov heat and mass flux models, Variable thermal conductivity, Variable mass diffusivity

Anomalous solute transport in saturated porous media: Relating transport model parameters to electrical and nuclear magnetic resonance properties

Science.gov (United States)

Swanson, Ryan D; Binley, Andrew; Keating, Kristina; France, Samantha; Osterman, Gordon; Day-Lewis, Frederick D.; Singha, Kamini

2015-01-01

The advection-dispersion equation (ADE) fails to describe commonly observed non-Fickian solute transport in saturated porous media, necessitating the use of other models such as the dual-domain mass-transfer (DDMT) model. DDMT model parameters are commonly calibrated via curve fitting, providing little insight into the relation between effective parameters and physical properties of the medium. There is a clear need for material characterization techniques that can provide insight into the geometry and connectedness of pore spaces related to transport model parameters. Here, we consider proton nuclear magnetic resonance (NMR), direct-current (DC) resistivity, and complex conductivity (CC) measurements for this purpose, and assess these methods using glass beads as a control and two different samples of the zeolite clinoptilolite, a material that demonstrates non-Fickian transport due to intragranular porosity. We estimate DDMT parameters via calibration of a transport model to column-scale solute tracer tests, and compare NMR, DC resistivity, CC results, which reveal that grain size alone does not control transport properties and measured geophysical parameters; rather, volume and arrangement of the pore space play important roles. NMR cannot provide estimates of more-mobile and less-mobile pore volumes in the absence of tracer tests because these estimates depend critically on the selection of a material-dependent and flow-dependent cutoff time. Increased electrical connectedness from DC resistivity measurements are associated with greater mobile pore space determined from transport model calibration. CC was hypothesized to be related to length scales of mass transfer, but the CC response is unrelated to DDMT.

Approximation and stability of three-dimensional natural convection flows in a porous medium

International Nuclear Information System (INIS)

Janotto, Marie-Laurence

1991-01-01

The equations of the three-dimensional natural convection in a porous medium within a differentially heated horizontal walls cavity are solved by a pseudo-spectral method. First we will present the evolution of the two main modes according to two models of convection. A few asymptotic properties connected to the small and large eddies are set up and numerically validated. A new approximate inertial manifold is then proposed. The numerical scheme used is an exponential fitting algorithm the convergence of which is proved. We will present the physical mechanism at the origin of the un-stationary three-dimensional convection at high Rayleigh numbers. (author) [fr

Scaled particle theory for a hard spherocylinder fluid in a disordered porous medium: Carnahan-Starling and Parsons-Lee corrections

Directory of Open Access Journals (Sweden)

M.F. Holovko

2018-03-01

Full Text Available The scaled particle theory (SPT approximation is applied for the study of the influence of a porous medium on the isotropic-nematic transition in a hard spherocylinder fluid. Two new approaches are developed in order to improve the description in the case of small lengths of spherocylinders. In one of them, the so-called SPT-CS-PL approach, the Carnahan-Starling (CS correction is introduced to improve the description of thermodynamic properties of the fluid, while the Parsons-Lee (PL correction is introduced to improve the orientational ordering. The second approach, the so-called SPT-PL approach, is connected with generalization of the PL theory to anisotropic fluids in disordered porous media. The phase diagram is obtained from the bifurcation analysis of a nonlinear integral equation for the singlet distribution function and from the thermodynamic equilibrium conditions. The results obtained are compared with computer simulation data. Both ways and both approaches considerably improve the description in the case of spherocylinder fluids with smaller spherocylinder lengths. We did not find any significant differences between the results of the two developed approaches. We found that the bifurcation analysis slightly overestimates and the thermodynamical analysis underestimates the predictions of the computer simulation data. A porous medium shifts the phase diagram to smaller densities of the fluid and does not change the type of the transition.

Numerical Tools for Multicomponent, Multiphase, Reactive Processes: Flow of CO{sub 2} in Porous Medium

Energy Technology Data Exchange (ETDEWEB)

Khattri, Sanjay Kumar

2006-07-01

porous medium. We verify our simulator by comparing our results against available results. We analyze impact of fluid movement on long term CO{sub 2} migration at the Utsira. We analyze how flow of medium fluids affects important parameters such as the pH and evolution of CO{sub 2} saturation. The author's contributions to the paper include mesh generation in the Utsira formation, development of geometrical and lithological models, coupling of the Accrete and Athena code. Paper E: Control Volume Finite Difference On Adaptive Meshes. It is shown that discrete system formed on the adaptive meshes is not only more accurate but are also well conditioned compared to the one formed on the uniform meshes. Paper F: Grid Generation and Adaptation by Functionals Paper reviews various functionals for grid generation and adaptation. It is a well known fact that accuracy of a numerical simulation and quality of the grid are strongly related. In this article, we review various functionals for generating high quality structured quadrilateral meshes in two dimensional domains. Analysis of Winslow and Modified Liao functionals are presented. Numerical experiments are also reported to support our theoretical analysis. We demonstrate use of the Area functional for generating adaptive quadrilateral meshes. Paper G: CO{sub 2} storage in the Utsira Formation-ATHENA 3D reactive transport simulations Article presents 3D simulation of CO{sub 2} sequestration/deposition at the Utsira formation. Our model consists of fourteen chemical and sixteen mineral species. We present 1000 years simulation of CO{sub 2} deposition. In this work, the author prepared the geometrical model of the Utsira formation. He coupled the ACCRETE geochemistry module and the Athena simulator. Paper H: Numerical convergence on adaptive grids for control volume methods The article presents convergence of the Finite Volume Method on uniform and adaptive meshes. We also analyse convergence of the method in various norms on

Numerical Tools for Multicomponent, Multiphase, Reactive Processes: Flow of CO{sub 2} in Porous Medium

Energy Technology Data Exchange (ETDEWEB)

Khattri, Sanjay Kumar

2006-07-01

porous medium. We verify our simulator by comparing our results against available results. We analyze impact of fluid movement on long term CO{sub 2} migration at the Utsira. We analyze how flow of medium fluids affects important parameters such as the pH and evolution of CO{sub 2} saturation. The author's contributions to the paper include mesh generation in the Utsira formation, development of geometrical and lithological models, coupling of the Accrete and Athena code. Paper E: Control Volume Finite Difference On Adaptive Meshes. It is shown that discrete system formed on the adaptive meshes is not only more accurate but are also well conditioned compared to the one formed on the uniform meshes. Paper F: Grid Generation and Adaptation by Functionals Paper reviews various functionals for grid generation and adaptation. It is a well known fact that accuracy of a numerical simulation and quality of the grid are strongly related. In this article, we review various functionals for generating high quality structured quadrilateral meshes in two dimensional domains. Analysis of Winslow and Modified Liao functionals are presented. Numerical experiments are also reported to support our theoretical analysis. We demonstrate use of the Area functional for generating adaptive quadrilateral meshes. Paper G: CO{sub 2} storage in the Utsira Formation-ATHENA 3D reactive transport simulations Article presents 3D simulation of CO{sub 2} sequestration/deposition at the Utsira formation. Our model consists of fourteen chemical and sixteen mineral species. We present 1000 years simulation of CO{sub 2} deposition. In this work, the author prepared the geometrical model of the Utsira formation. He coupled the ACCRETE geochemistry module and the Athena simulator. Paper H: Numerical convergence on adaptive grids for control volume methods The article presents convergence of the Finite Volume Method on uniform and adaptive meshes. We also analyse convergence of the method in various norms

Low-Reynolds number flow of a viscous fluid in a channel partially filled with a porous medium

International Nuclear Information System (INIS)

Deng, C.; Martinez, D.M.

2003-01-01

Steady flow inside a rectangular channel with wall suction and partially filled with a porous material is examined. We solve the Navier-Stokes equations in the clear fluid region of the channel and the Brinkman extended Darcy's law in the porous material. The stress jump conditions outlined by Ochoa-Tapia and Whitaker are employed at the interface between these two regions. Ochoa-Tapia and Whitaker's conditions contain an empirical constant β which is unknown a priori. In this work we propose a method to estimate β. To do so, we solve for the flow field using two different approaches. In the first approach, the flow is assumed to be of similarity form and a new asymmetric solution is reported; β is retained in this formulation. In the second approach, we re-pose the equations of motion over the entire domain by considering the porous medium as a sink-term (which can be turned on and off); β is not required in this formulation. We estimate the value of β by comparing the resulting flow fields. (author)

Similarity Solution for Combined Free-Forced Convection Past a Vertical Porous Plate in a Porous Medium with a Convective Surface Boundary Condition

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Garg P.

2016-12-01

Full Text Available This paper studies the mathematical implications of the two dimensional viscous steady laminar combined free-forced convective flow of an incompressible fluid over a semi infinite fixed vertical porous plate embedded in a porous medium. It is assumed that the left surface of the plate is heated by convection from a hot fluid which is at a temperature higher than the temperature of the fluid on the right surface of the vertical plate. To achieve numerical consistency for the problem under consideration, the governing non linear partial differential equations are first transformed into a system of ordinary differential equations using a similarity variable and then solved numerically under conditions admitting similarity solutions. The effects of the physical parameters of both the incompressible fluid and the vertical plate on the dimensionless velocity and temperature profiles are studied and analysed and the results are depicted both graphically and in a tabular form. Finally, algebraic expressions and the numerical values are obtained for the local skin-friction coefficient and the local Nusselt number.

Effect of capillary forces on immiscible two-phase flow in heterogeneous porous media

Energy Technology Data Exchange (ETDEWEB)

van Duijn, C.J.; Molenaar, J.; de Neef, M.J.

1994-12-31

We consider the one-dimensional two-phase flow including capillary effects through a heterogeneous porous medium. The heterogeneity is due to the spatial variation of the absolute permeability and the porosity. Both these quantities are assumed to be piecewise constant. At interfaces where the rock properties are discontinuous, we derive, by a regularization technique, conditions to match the values of the saturation on both sides. There are two conditions: a flux condition and an extended pressure condition. Applying these conditions we show that trapping of the wetting phase may occur near hetergeneities. To illustrate the behavior of the saturation we consider a time-dependent diffusion problem without convection, a stationary convection-diffusion problem, and the full time-dependent convection-diffusion problem (numerically). In particular the last two problems explicitly show the trapping behavior.

On the propagation of a quasi-static disturbance in a heterogeneous, deformable, and porous medium with pressure-dependent properties

Energy Technology Data Exchange (ETDEWEB)

Vasco, D.W.

2011-10-01

Using an asymptotic technique, valid when the medium properties are smoothly-varying, I derive a semi-analytic expression for the propagation velocity of a quasi-static disturbance traveling within a nonlinear-elastic porous medium. The phase, a function related to the propagation time, depends upon the properties of the medium, including the pressure-sensitivities of the medium parameters, and on pressure and displacement amplitude changes. Thus, the propagation velocity of a disturbance depends upon its amplitude, as might be expected for a nonlinear process. As a check, the expression for the phase function is evaluated for a poroelastic medium, when the material properties do not depend upon the fluid pressure. In that case, the travel time estimates agree with conventional analytic estimates, and with values calculated using a numerical simulator. For a medium with pressure-dependent permeability I find general agreement between the semi-analytic estimates and estimates from a numerical simulation. In this case the pressure amplitude changes are obtained from the numerical simulator.

Fem Simulation of Triple Diffusive Natural Convection Along Inclined Plate in Porous Medium: Prescribed Surface Heat, Solute and Nanoparticles Flux

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Goyal M.

2017-12-01

Full Text Available In this paper, triple diffusive natural convection under Darcy flow over an inclined plate embedded in a porous medium saturated with a binary base fluid containing nanoparticles and two salts is studied. The model used for the nanofluid is the one which incorporates the effects of Brownian motion and thermophoresis. In addition, the thermal energy equations include regular diffusion and cross-diffusion terms. The vertical surface has the heat, mass and nanoparticle fluxes each prescribed as a power law function of the distance along the wall. The boundary layer equations are transformed into a set of ordinary differential equations with the help of group theory transformations. A wide range of parameter values are chosen to bring out the effect of buoyancy ratio, regular Lewis number and modified Dufour parameters of both salts and nanofluid parameters with varying angle of inclinations. The effects of parameters on the velocity, temperature, solutal and nanoparticles volume fraction profiles, as well as on the important parameters of heat and mass transfer, i.e., the reduced Nusselt, regular and nanofluid Sherwood numbers, are discussed. Such problems find application in extrusion of metals, polymers and ceramics, production of plastic films, insulation of wires and liquid packaging.

Characterization of thermal, hydraulic, and gas diffusion properties in variably saturated sand grades

DEFF Research Database (Denmark)

Deepagoda Thuduwe Kankanamge Kelum, Chamindu; Smits, Kathleen; Ramirez, Jamie

2016-01-01

porous media transport properties, key transport parameters such as thermal conductivity and gas diffusivity are particularly important to describe temperature-induced heat transport and diffusion-controlled gas transport processes, respectively. Despite many experimental and numerical studies focusing...... transport models (thermal conductivity, saturated hydraulic conductivity, and gas diffusivity). An existing thermal conductivity model was improved to describe the distinct three-region behavior in observed thermal conductivity–water saturation relations. Applying widely used parametric models for saturated......Detailed characterization of partially saturated porous media is important for understanding and predicting vadose zone transport processes. While basic properties (e.g., particle- and pore-size distributions and soil-water retention) are, in general, essential prerequisites for characterizing most...

History independence of steady state in simultaneous two-phase flow through two-dimensional porous media.

Science.gov (United States)

Erpelding, Marion; Sinha, Santanu; Tallakstad, Ken Tore; Hansen, Alex; Flekkøy, Eirik Grude; Måløy, Knut Jørgen

2013-11-01

It is well known that the transient behavior during drainage or imbibition in multiphase flow in porous media strongly depends on the history and initial condition of the system. However, when the steady-state regime is reached and both drainage and imbibition take place at the pore level, the influence of the evolution history and initial preparation is an open question. Here, we present an extensive experimental and numerical work investigating the history dependence of simultaneous steady-state two-phase flow through porous media. Our experimental system consists of a Hele-Shaw cell filled with glass beads which we model numerically by a network of disordered pores transporting two immiscible fluids. From measurements of global pressure evolution, histograms of saturation, and cluster-size distributions, we find that when both phases are flowing through the porous medium, the steady state does not depend on the initial preparation of the system or on the way it has been reached.

Thermal convection at low Rayleigh number from concentrated sources in porous media

International Nuclear Information System (INIS)

Hickox, C.E.

1980-01-01

A simple mathematical theory is proposed for the analysis of natural convective motion, at low Rayleigh number, from a concentrated source of heat in a fluid-saturated porous medium. The theory consists of retaining only the leading terms of series expansions of the dependent variables in terms of the Rayleigh number, is thus linear, and is valid only in the limit of small Rayleigh number. Based on fundamental results for a variety of isolated sources, superposition is used to provide solutions for situations of practical interest. Special emphasis is given to the analysis of sub-seabed disposal of nuclear waste. 8 figures

Oxidative stabilization of mixed mayonnaises made with linseed oil and saturated medium-chain triglyceride oil

DEFF Research Database (Denmark)

Raudsepp, Piret; Brüggemann, Dagmar A.; Lenferink, Aufried

2014-01-01

Mayonnaises, made with either saturated medium chain triglyceride (MCT) oil or unsaturated purified linseed oil (LSO), were mixed. Raman confocal microspectrometry demonstrated that lipid droplets in mixed mayonnaise remained intact containing either MCT oil or LSO. Peroxide formation during...... showed radicals are formed in the aqueous phase with the same rate independent of the lipids. This was also reflected in decay of α-tocopherol during storage being similar in MCT and LSO mayonnaises, but being stable in mixed oil mayonnaise and mixed mayonnaise. Results suggest that other effects than...

Passive flux meter measurement of water and nutrient flux in saturated porous media: bench-scale laboratory tests.

Science.gov (United States)

Cho, Jaehyun; Annable, Michael D; Jawitz, James W; Hatfield, Kirk

2007-01-01

The passive nutrient flux meter (PNFM) is introduced for simultaneous measurement of both water and nutrient flux through saturated porous media. The PNFM comprises a porous sorbent pre-equilibrated with a suite of alcohol tracers, which have different partitioning coefficients. Water flux was estimated based on the loss of loaded resident tracers during deployment, while nutrient flux was quantified based on the nutrient solute mass captured on the sorbent. An anionic resin, Lewatit 6328 A, was used as a permeable sorbent and phosphate (PO4(3-)) was the nutrient studied. The phosphate sorption capacity of the resin was measured in batch equilibration tests as 56 mg PO4(3-) g(-1), which was determined to be adequate capacity to retain PO4(3-) loads intercepted over typical PNFM deployment periods in most natural systems. The PNFM design was validated with bench-scale laboratory tests for a range of 9.8 to 28.3 cm d(-1) Darcy velocities and 6 to 43 h deployment durations. Nutrient and water fluxes measured by the PNFM averaged within 6 and 12% of the applied values, respectively, indicating that the PNFM shows promise as a tool for simultaneous measurement of water and nutrient fluxes.

Magnetohydrodynamic (MHD Jeffrey fluid over a stretching vertical surface in a porous medium

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Kartini Ahmad

2017-12-01

Full Text Available This paper presents the study of steady two-dimensional mixed convection boundary layer flow and heat transfer of a Jeffrey fluid over a stretched sheet immersed in a porous medium in the presence of a transverse magnetic field. The governing partial differential equations are reduced to nonlinear ordinary differential equations with the aid of similarity transformation, which are then solved numerically using an implicit finite difference scheme. The effects of some of the embedded parameters, such as Deborah number β, magnetic parameter M, mixed convection parameter λ, porosity parameter γ and Prandtl number Pr, on the flow and heat transfer characteristics, are given in forms of tables and graphs.

Modeling approaches to natural convection in porous media

CERN Document Server

Su, Yan

2015-01-01

This book provides an overview of the field of flow and heat transfer in porous medium and focuses on presentation of a generalized approach to predict drag and convective heat transfer within porous medium of arbitrary microscopic geometry, including reticulated foams and packed beds. Practical numerical methods to solve natural convection problems in porous media will be presented with illustrative applications for filtrations, thermal storage and solar receivers.

Chaotic dynamics of large-scale double-diffusive convection in a porous medium

Science.gov (United States)

Kondo, Shutaro; Gotoda, Hiroshi; Miyano, Takaya; Tokuda, Isao T.

2018-02-01

We have studied chaotic dynamics of large-scale double-diffusive convection of a viscoelastic fluid in a porous medium from the viewpoint of dynamical systems theory. A fifth-order nonlinear dynamical system modeling the double-diffusive convection is theoretically obtained by incorporating the Darcy-Brinkman equation into transport equations through a physical dimensionless parameter representing porosity. We clearly show that the chaotic convective motion becomes much more complicated with increasing porosity. The degree of dynamic instability during chaotic convective motion is quantified by two important measures: the network entropy of the degree distribution in the horizontal visibility graph and the Kaplan-Yorke dimension in terms of Lyapunov exponents. We also present an interesting on-off intermittent phenomenon in the probability distribution of time intervals exhibiting nearly complete synchronization.

Hall Currents and Heat Transfer Effects on Peristaltic Transport in a Vertical Asymmetric Channel through a Porous Medium

Directory of Open Access Journals (Sweden)

E. Abo-Eldahab

2012-01-01

a porous medium are investigated theoretically and graphically under assumptions of low Reynolds number and long wavelength. The flow is investigated in a wave frame of reference moving with the velocity of the wave. Analytical solutions have been obtained for temperature, axial velocity, stream function, pressure gradient, and shear stresses. The trapping phenomenon is discussed. Graphical results are sketched for various embedded parameters and interpreted.

FEMWATER: a finite-element model of water flow through saturated-unsaturated porous media

International Nuclear Information System (INIS)

Yeh, G.T.; Ward, D.S.

1980-10-01

Upon examining the Water Movement Through Saturated-Unsaturated Porous Media: A Finite-Element Galerkin Model, it was felt that the model should be modified and expanded. The modification is made in calculating the flow field in a manner consistent with the finite element approach, in evaluating the moisture-content increasing rate within the region of interest, and in numerically computing the nonlinear terms. With these modifications, the flow field is continuous everywhere in the flow regime, including element boundaries and nodal points, and the mass loss through boundaries is much reduced. Expansion is made to include four additional numerical schemes which would be more appropriate for many situations. Also, to save computer storage, all arrays pertaining to the boundary condition information are compressed to smaller dimension, and to ease the treatment of different problems, all arrays are variably dimensioned in all subroutines. This report is intended to document these efforts. In addition, in the derivation of finite-element equations, matrix component representation is used, which is believed more readable than the matrix representation in its entirety. Two identical sample problems are simulated to show the difference between the original and revised models

The foam drainage equation for drainage dynamics in unsaturated porous media

Science.gov (United States)

Lehmann, P.; Hoogland, F.; Assouline, S.; Or, D.

2017-07-01

Similarity in liquid-phase configuration and drainage dynamics of wet foam and gravity drainage from unsaturated porous media expands modeling capabilities for capillary flows and supplements the standard Richards equation representation. The governing equation for draining foam (or a soil variant termed the soil foam drainage equation—SFDE) obviates the need for macroscopic unsaturated hydraulic conductivity function by an explicit account of diminishing flow pathway sizes as the medium gradually drains. The study provides new and simple analytical expressions for drainage rates and volumes from unsaturated porous media subjected to different boundary conditions. Two novel analytical solutions for saturation profile evolution were derived and tested in good agreement with a numerical solution of the SFDE. The study and the proposed solutions rectify the original formulation of foam drainage dynamics of Or and Assouline (2013). The new framework broadens the scope of methods available for quantifying unsaturated flow in porous media, where the intrinsic conductivity and geometrical representation of capillary drainage could improve understanding of colloid and pathogen transport. The explicit geometrical interpretation of flow pathways underlying the hydraulic functions used by the Richards equation offers new insights that benefit both approaches.

An experimental method of characterization of deformable porous media

Directory of Open Access Journals (Sweden)

Sommier Alain

2012-04-01

Full Text Available A porous medium saturated with liquid and placed within a medium that undergoes a change in pressure reacts by shrinking. If the space contains the same liquid as the pores of the sample, then after a certain lapse of time the sample dilates. By measuring this dilation kinetic the specimen’s permeability can be approximated. This experimental method is called Dynamic Pressurisation. We set up an experimental apparatus to measure the permeability and the different agarose gel compressibility moduli. The liquid contained inside the gel pores is water. We have realized experiments in water and others in oil. In Scherer’s method the flow is considered only in the radial direction. To find the real permeability value we have built a numerical model considering that both the liquid and the solid are compressible. The simulations were compared to the experimental results and have allowed finding the real value of the permeability by considering the flow in both radial and axial directions.

Densification of porous bodies in a granular pressure-transmitting medium

International Nuclear Information System (INIS)

Olevsky, E.A.; Ma, J.; LaSalvia, J.C.; Meyers, M.A.

2007-01-01

Densification is a critical step in the manufacture of near-net-shaped components via powder processing. A non-isostatic stress state will in general result in shape distortion in addition to densification. In the quasi-isostatic pressing (QIP) process the green body is placed into a granular pressure-transmitting medium (i.e. PTM), which is itself contained in a rigid die. Upon the application of a uniaxial load, the PTM redistributes the tractions on the green body, thereby creating a stress state that is quasi-isostatic. The character of the deformation of the PTM is studied using model experiments on pressing of the PTM in a rigid die and a scanning electron microscopy analysis of the PTM powder. An important problem of the optimization of the PTM chemical composition enabling the maximum densification of a porous specimen with the minimum possible shape distortion is solved. The results of modeling agree satisfactorily with the experimental data on cold QIPing Ti and Ni powder samples and hot QIPing TiC-TiNi cermet composites

Evaluation of the dependence of heat transfer coefficient on the particle diameter of a metal porous medium in a heat removal system using liquid nitrogen

International Nuclear Information System (INIS)

Sasaki, Shunsuke; Ito, Satoshi; Hashizume, Hidetoshi

2015-01-01

Cryogenic cooling system using a bronze-particle-sintered porous medium has been studied for a re mountable high-temperature superconducting magnet. This study evaluates boiling curve of subcooled liquid nitrogen as flowing in a bronze porous medium as a function of the particle diameter of the medium. We obtained Departure from Nuclear Boiling (Dnb) point from the boiling curve and discussed growth of nitrogen vapor bubble inferred from measured pressure drop. The pressure drop decreased significantly at wall superheat before reaching the DNB point whereas that slightly decreased after reaching the DNB point compared to the smallest wall superheat. This result could consider DNB rises with an increase in the particle diameter because larger particle makes vapor to move easily from the heated pore region. The influence of the particle diameter on the heat transfer performance is larger than that of coolant's degree of subcooling. (author)

Mixed convection boundary layer flow over a vertical surface embedded in a thermally stratified porous medium

International Nuclear Information System (INIS)

Ishak, Anuar; Nazar, Roslinda; Pop, Ioan

2008-01-01

The mixed convection boundary layer flow through a stable stratified porous medium bounded by a vertical surface is investigated. The external velocity and the surface temperature are assumed to vary as x m , where x is measured from the leading edge of the vertical surface and m is a constant. Numerical solutions for the governing Darcy and energy equations are obtained. The results indicate that the thermal stratification significantly affects the surface shear stress as well as the surface heat transfer, besides delays the boundary layer separation

Solute transport in aggregated and layered porous media

International Nuclear Information System (INIS)

Koch, S.

1993-01-01

This work is a contribution to research in soil physics dealing with solute transport in porous media. The influence of structural inhomogeneities on solute transport is investigated. Detailed experiments at the laboratory scale are used to enlighten distinct processes which cannot be studied separately at field scale. Two main aspects are followed up: (i) to show the influence of aggregation of a porous medium on breakthrough time and spreading of an inert tracer and consequences on the estimation of parameter values of models describing solute transport in aggregated systems, (ii) to investigate the influences on the dispersion process when stratification is perpendicular to the direction of flow. Several concepts of modelling solute transport in soil are discussed. Models based on the convection-dispersion equation (CDE) are emphasized because they are used here to model solute transport experiments conducted with aggregated porous media. Stochastic concepts are introduced to show the limitations of the deterministic CDE approaches. Experiments are done in columns containing two kinds of solid phases and were saturated with water. The solid phases are porous and solid glass beads exhibiting a distinctly unimodal or bimodal pore size distribution. Experimental breakthrough curves (BTCs) are modelled with the CDE, a bicontinuum model with a phenomenological mass transfer rate and a bicontinuum spherical diffusion model. Experiments are also done in columns that are unsaturated containing porous materials that are layered. Flow is made at a steady rate. It is shown that layer boundaries have a severe influence on lateral mixing. They may force streamlines to converge or cause a lateral redistribution of solutes. (author) figs., tabs., 122 refs

Parametric study of boiling heat transfer in porous media

International Nuclear Information System (INIS)

Shi, B.; Jones, B.G.; Pan, C.

1996-01-01

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

Foam flow in a model porous medium: II. The effect of trapped gas.

Science.gov (United States)

Jones, S A; Getrouw, N; Vincent-Bonnieu, S

2018-05-09

Gas trapping is an important mechanism in both Water or Surfactant Alternating Gas (WAG/SAG) and foam injection processes in porous media. Foams for enhanced oil recovery (EOR) can increase sweep efficiency as they decrease the gas relative permeability, and this is mainly due to gas trapping. However, gas trapping mechanisms are poorly understood. Some studies have been performed during corefloods, but little work has been carried out to describe the bubble trapping behaviour at the pore scale. We have carried out foam flow tests in a micromodel etched with an irregular hexagonal pattern. Image analysis of the foam flow allowed the bubble centres to be tracked and local velocities to be obtained. It was found that the flow in the micromodel is dominated by intermittency and localized zones of trapped gas. The quantity of trapped gas was measured both by considering the fraction of bubbles that were trapped (via velocity thresholding) and by measuring the area fraction containing immobile gas (via image analysis). A decrease in the quantity of trapped gas was observed for both increasing total velocity and increasing foam quality. Calculations of the gas relative permeability were made with the Brooks Corey equation, using the measured trapped gas saturations. The results showed a decrease in gas relative permeabilities, and gas mobility, for increasing fractions of trapped gas. It is suggested that the shear thinning behaviour of foam could be coupled to the saturation of trapped gas.

Direct observation and determination of the mechanisms governing mobility of asbestos in porous media

Science.gov (United States)

Seiphoori, A.; Ortiz, C. P.; Jerolmack, D. J.

2017-12-01

Transport of asbestos through soil by groundwater is typically considered to be negligible. There are indications, however, that under some conditions of pore-water/soil chemistry asbestos may become mobile, implying that buried contaminants could migrate from a disposal site and surface elsewhere. Shape, size and surface charge may influence the physical and chemical interactions of colloids with the soil matrix, and asbestos consists of elongated particles with different size and unique surface charge properties. Although chemical factors such as pH and ionic strength of pore water may affect the transport properties, the presence of dissolved organic carbon (DOC) has been identified to remarkably enhance the mobility of colloids including asbestos. To date, there is no explanation for how the presence of DOC may facilitate the mobilization of asbestos in soil - mainly because the soil medium has been treated as a black box without the possibility of observing particles within the matrix. Here, we investigated the mobility of chrysotile asbestos particles ( 10 um long) in porous media by developing a flow cell with an optically-transparent porous medium composed of granules of a refractive-index matched material. This enabled us to observe and track the particles within the water-saturated porous medium using in situ microscopy. The aqueous suspension of asbestos fibers was passed through this artificial soil, while the physical and chemical interaction of asbestos particles with the medium and their pore-scale distribution were analyzed. We studied the effects of changing solution chemistry (e.g., ionic strength, pH, and DOC content) on transport, attachment and aggregation of chrysotile particles. Experiments revealed a novel mechanism where the DOC-associated nanoparticles attach to chrysotile fibers by an electrostatic attraction, which facilitates their mobilization through the porous medium while modulating aggregation among fibers. Although pH and ionic

Radiative mixed convection over an isothermal cone embedded in a porous medium with variable permeability

KAUST Repository

El-Amin, Mohamed; Ebrahiem, N.A.; Salama, Amgad; Sun, S.

2011-01-01

The interaction of mixed convection with thermal radiation of an optical dense viscous fluid adjacent to an isothermal cone imbedded in a porous medium with Rosseland diffusion approximation incorporating the variation of permeability and thermal conductivity is numerically investigated. The transformed conservation laws are solved numerically for the case of variable surface temperature conditions. Numerical results are given for the dimensionless temperature profiles and the local Nusselt number for various values of the mixed convection parameter , the cone angle parameter ?, the radiation-conduction parameter R d, and the surface temperature parameter H. Copyright 2011 M. F. El-Amin et al.

Calibration-free quantification of interior properties of porous media with x-ray computed tomography.

Science.gov (United States)

Hussein, Esam M A; Agbogun, H M D; Al, Tom A

2015-03-01

A method is presented for interpreting the values of x-ray attenuation coefficients reconstructed in computed tomography of porous media, while overcoming the ambiguity caused by the multichromatic nature of x-rays, dilution by void, and material heterogeneity. The method enables determination of porosity without relying on calibration or image segmentation or thresholding to discriminate pores from solid material. It distinguishes between solution-accessible and inaccessible pores, and provides the spatial and frequency distributions of solid-matrix material in a heterogeneous medium. This is accomplished by matching an image of a sample saturated with a contrast solution with that saturated with a transparent solution. Voxels occupied with solid-material and inaccessible pores are identified by the fact that they maintain the same location and image attributes in both images, with voxels containing inaccessible pores appearing empty in both images. Fully porous and accessible voxels exhibit the maximum contrast, while the rest are porous voxels containing mixtures of pore solutions and solid. This matching process is performed with an image registration computer code, and image processing software that requires only simple subtraction and multiplication (scaling) processes. The process is demonstrated in dolomite (non-uniform void distribution, homogeneous solid matrix) and sandstone (nearly uniform void distribution, heterogeneous solid matrix) samples, and its overall performance is shown to compare favorably with a method based on calibration and thresholding. Copyright © 2014 Elsevier Ltd. All rights reserved.

Definition of a facility for experimental studies of two-phase flows and heat transfer in porous materials

International Nuclear Information System (INIS)

Reda, D.C.; Eaton, R.R.

1981-01-01

A facility-development effort is currently underway at Sandia National Laboratories in order to create an experimental capability for the study of two-phase, steam/water flows through a variety of porous media. The facility definition phase of this project is described. Equations are derived for the steady, adiabatic, macroscopically-linear two-phase flow of a single-component fluid through a porous medium, including energy transfer both by convection and conduction. These equations are then solved to give relative permeabilities for the steam and water phases as functions of known and/or measurable quantities. A viable experimental approach was thereby formulated, leading to the definition of facility components and instrumentation requirements, including the application of gamma-beam densitometry for the measurement of liquid-saturation distributions in porous media. Finally, a state-of-the-art computer code was utilized to numerically simulate the proposed experiments, providing an estimate of the facility operating envelope

Seismic attenuation in fractured porous media: insights from a hybrid numerical and analytical model

International Nuclear Information System (INIS)

Ekanem, A M; Li, X Y; Chapman, M; Main, I G

2015-01-01

Seismic attenuation in fluid-saturated porous rocks can occur by geometric spreading, wave scattering or the internal dissipation of energy, most likely due to the squirt-flow mechanism. In principle, the pattern of seismic attenuation recorded on an array of sensors contains information about the medium, in terms of material heterogeneity and anisotropy, as well as material properties such as porosity, crack density, and pore-fluid composition and mobility. In practice, this inverse problem is challenging. Here we provide some insights into the effects of internal dissipation by analysing synthetic data produced by a hybrid numerical and analytical model for seismic wave propagation in a fractured medium embedded within a layered geological structure. The model is made up of one anisotropic and three isotropic horizontal layers. The anisotropic layer consists of a porous, fluid-saturated material containing vertically aligned inclusions representing a set of fractures. This combination allows squirt-flow to occur between the pores in the matrix and the model fractures. Our results show that the fluid mobility and the associated relaxation time of the fluid-pressure gradient control the frequency range over which attenuation occurs. This induced attenuation increases with incidence angle and azimuth away from the fracture strike-direction. Azimuthal variations in the induced attenuation are elliptical allowing the fracture orientations to be obtained from the axes of the ellipse. These observations hold out the potential of using seismic attenuation as an additional diagnostic in the characterisation of rock formations for a variety of applications including hydrocarbon exploration and production, subsurface storage of CO 2 , and geothermal energy extraction. (paper)

On a multigrid method for the coupled Stokes and porous media flow problem

Science.gov (United States)

Luo, P.; Rodrigo, C.; Gaspar, F. J.; Oosterlee, C. W.

2017-07-01

The multigrid solution of coupled porous media and Stokes flow problems is considered. The Darcy equation as the saturated porous medium model is coupled to the Stokes equations by means of appropriate interface conditions. We focus on an efficient multigrid solution technique for the coupled problem, which is discretized by finite volumes on staggered grids, giving rise to a saddle point linear system. Special treatment is required regarding the discretization at the interface. An Uzawa smoother is employed in multigrid, which is a decoupled procedure based on symmetric Gauss-Seidel smoothing for velocity components and a simple Richardson iteration for the pressure field. Since a relaxation parameter is part of a Richardson iteration, Local Fourier Analysis (LFA) is applied to determine the optimal parameters. Highly satisfactory multigrid convergence is reported, and, moreover, the algorithm performs well for small values of the hydraulic conductivity and fluid viscosity, that are relevant for applications.

Diffusion with condensation and evaporation in porous media

International Nuclear Information System (INIS)

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 τ = 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

Monolithic multigrid method for the coupled Stokes flow and deformable porous medium system

Science.gov (United States)

Luo, P.; Rodrigo, C.; Gaspar, F. J.; Oosterlee, C. W.

2018-01-01

The interaction between fluid flow and a deformable porous medium is a complicated multi-physics problem, which can be described by a coupled model based on the Stokes and poroelastic equations. A monolithic multigrid method together with either a coupled Vanka smoother or a decoupled Uzawa smoother is employed as an efficient numerical technique for the linear discrete system obtained by finite volumes on staggered grids. A specialty in our modeling approach is that at the interface of the fluid and poroelastic medium, two unknowns from the different subsystems are defined at the same grid point. We propose a special discretization at and near the points on the interface, which combines the approximation of the governing equations and the considered interface conditions. In the decoupled Uzawa smoother, Local Fourier Analysis (LFA) helps us to select optimal values of the relaxation parameter appearing. To implement the monolithic multigrid method, grid partitioning is used to deal with the interface updates when communication is required between two subdomains. Numerical experiments show that the proposed numerical method has an excellent convergence rate. The efficiency and robustness of the method are confirmed in numerical experiments with typically small realistic values of the physical coefficients.

Dietary medium-chain saturated fatty acids induce gene expression of energy metabolism-related pathways in adipose tissue of abdominally obese subjects

NARCIS (Netherlands)

Matualatupauw, J.C.; Bohl, Mette; Gregersen, Søren; Hermansen, K.; Afman, L.A.

2017-01-01

Background:Dietary medium-chain saturated fatty acids (MC-SFAs) have been shown to reduce total body fat. Previously, we showed that MC-SFAs prevent body fat accumulation, despite weight gain. Here, we aim to explore potential molecular mechanisms underlying the protective effect of MC-SFAs on body

MHD heat and mass diffusion flow by natural convection past a surface embedded in a porous medium

Directory of Open Access Journals (Sweden)

Chaudhary R.C.

2009-01-01

Full Text Available This paper presents an analytical study of the transient hydromagnetic natural convection flow past a vertical plate embedded in a porous medium, taking account of the presence of mass diffusion and fluctuating temperature about time at the plate. The governing equations are solved in closed form by the Laplace-transform technique. The results are obtained for temperature, velocity, penetration distance, Nusselt number and skin-friction. The effects of various parameters are discussed on the flow variables and presented by graphs.

Fully developed natural convection heat and mass transfer in a vertical annular porous medium with asymmetric wall temperatures and concentrations

International Nuclear Information System (INIS)

Cheng, C.-Y.

2006-01-01

This work examines the effects of the modified Darcy number, the buoyancy ratio and the inner radius-gap ratio on the fully developed natural convection heat and mass transfer in a vertical annular non-Darcy porous medium with asymmetric wall temperatures and concentrations. The exact solutions for the important characteristics of fluid flow, heat transfer, and mass transfer are derived by using a non-Darcy flow model. The modified Darcy number is related to the flow resistance of the porous matrix. For the free convection heat and mass transfer in an annular duct filled with porous media, increasing the modified Darcy number tends to increase the volume flow rate, total heat rate added to the fluid, and the total species rate added to the fluid. Moreover, an increase in the buoyancy ratio or in the inner radius-gap ratio leads to an increase in the volume flow rate, the total heat rate added to the fluid, and the total species rate added to the fluid

Water movement in glass bead porous media: 1. Experiments of capillary rise and hysteresis

Science.gov (United States)

Lu, T. X.; Biggar, J. W.; Nielsen, D. R.

1994-12-01

Experimental observations of capillary rise and hysteresis of water or ethanol in glass beads are presented to improve our understanding of those physical processes in porous media. The results provide evidence that capillary rise into porous media cannot be fully explained by a model of cylinders. They further demonstrate that the "Ink bottle" model does not provide an adequate explanation of hysteresis. Glass beads serving as a model for ideal soil are enclosed in a rectangular glass chamber model. A TV camera associated with a microscope was used to record the processes of capillary rise and drainage. It is clearly shown during capillary rise that the fluid exhibits a "jump" behavior at the neck of the pores in an initially dry profile or at the bottom of the water film in an initially wet profile. Under an initially dry condition, the jump initiates at the particle with smallest diameter. The jump process continues to higher elevations until at equilibrium the surface tensile force is balanced by the hydrostatic force. The wetting front at that time is readily observed as flat and saturated. Under an initially wet condition, capillary rise occurs as a water film thickening process associated with the jump process. Trapped air behind the wetting front renders the wetting front irregular and unsaturated. The capillary rise into an initially wet porous medium can be higher than that into an initially dry profile. During the drying process, large surface areas associated with the gas-liquid interface develop, allowing the porous medium to retain more water than during the wetting process at the same pressure. That mechanism explains better the hysteresis phenomenon in porous media in contrast to other mechanisms that now prevail.

A Bézier-Spline-based Model for the Simulation of Hysteresis in Variably Saturated Soil

Science.gov (United States)

Cremer, Clemens; Peche, Aaron; Thiele, Luisa-Bianca; Graf, Thomas; Neuweiler, Insa

2017-04-01

Most transient variably saturated flow models neglect hysteresis in the p_c-S-relationship (Beven, 2012). Such models tend to inadequately represent matrix potential and saturation distribution. Thereby, when simulating flow and transport processes, fluid and solute fluxes might be overestimated (Russo et al., 1989). In this study, we present a simple, computationally efficient and easily applicable model that enables to adequately describe hysteresis in the p_c-S-relationship for variably saturated flow. This model can be seen as an extension to the existing play-type model (Beliaev and Hassanizadeh, 2001), where scanning curves are simplified as vertical lines between main imbibition and main drainage curve. In our model, we use continuous linear and Bézier-Spline-based functions. We show the successful validation of the model by numerically reproducing a physical experiment by Gillham, Klute and Heermann (1976) describing primary drainage and imbibition in a vertical soil column. With a deviation of 3%, the simple Bézier-Spline-based model performs significantly better that the play-type approach, which deviates by 30% from the experimental results. Finally, we discuss the realization of physical experiments in order to extend the model to secondary scanning curves and in order to determine scanning curve steepness. {Literature} Beven, K.J. (2012). Rainfall-Runoff-Modelling: The Primer. John Wiley and Sons. Russo, D., Jury, W. A., & Butters, G. L. (1989). Numerical analysis of solute transport during transient irrigation: 1. The effect of hysteresis and profile heterogeneity. Water Resources Research, 25(10), 2109-2118. https://doi.org/10.1029/WR025i010p02109. Beliaev, A.Y. & Hassanizadeh, S.M. (2001). A Theoretical Model of Hysteresis and Dynamic Effects in the Capillary Relation for Two-phase Flow in Porous Media. Transport in Porous Media 43: 487. doi:10.1023/A:1010736108256. Gillham, R., Klute, A., & Heermann, D. (1976). Hydraulic properties of a porous

Modeling solute transport in a heterogeneous unsaturated porous medium under dynamic boundary conditions on different spatial scales

Science.gov (United States)

Cremer, Clemens; Neuweiler, Insa; Bechtold, Michel

2013-04-01

Understanding transport of solutes/contaminants through unsaturated soil in the shallow subsurface is vital to assess groundwater quality, nutrient cycling or to plan remediation projects. Alternating precipitation and evaporation conditions causing upward and downward flux with differing flow paths, changes in saturation and related structural heterogeneity make the description of transport in the unsaturated zone near the soil-surface a complex problem. Preferential flow paths strongly depend, among other things, on the saturation of a medium. Recent studies (e.g. Bechtold et al., 2011) showed lateral flow and solute transport during evaporation conditions (upward flux) in vertically layered sand columns. Results revealed that during evaporation water and solute are redistributed laterally from coarse to fine media deeper in the soil, and towards zones of lowest hydraulic head near to the soil surface. These zones at the surface can be coarse or fine grained depending on saturation status and evaporation flux. However, if boundary conditions are reversed and precipitation is applied, the flow field is not reversed in the same manner, resulting in entirely different transport patterns for downward and upward flow. Therefore, considering net-flow rates alone is misleading when describing transport in the shallow unsaturated zone. In this contribution, we analyze transport of a solute in the shallow subsurface to assess effects resulting from the superposition of heterogeneous soil structures and dynamic flow conditions on various spatial scales. Two-dimensional numerical simulations of unsaturated flow and transport in heterogeneous porous media under changing boundary conditions are carried out using a finite-volume code coupled to a particle tracking algorithm to quantify solute transport and leaching rates. In order to validate numerical simulations, results are qualitatively compared to those of a physical experiment (Bechtold et al., 2011). Numerical

Fractal analysis of fracture increasing spontaneous imbibition in porous media with gas-saturated

KAUST Repository

Cai, Jianchao; Sun, Shuyu

2013-01-01

Spontaneous imbibition (SI) of wetting liquid into matrix blocks due to capillary pressure is regarded as an important recovery mechanism in low permeability fractured reservoir. In this paper, an analytical model is proposed for characterizing SI horizontally from a single plane fracture into gas-saturated matrix blocks. The presented model is based on the fractal character of pores in porous matrix, with gravity force included in the entire imbibition process. The accumulated mass of wetting liquid imbibed into matrix blocks is related to a number of factors such as contact area, pore fractal dimension, tortuosity, maximum pore size, porosity, liquid density and viscosity, surface tension, contact angle, as well as height and tilt angle of the fracture. The mechanism of fracture-enhanced SI is analyzed accordingly. Because of the effect of fracture, the gravity force is positive to imbibition process. Additionally, the farther away from the fracture top of the pore, the more influential the hydrostatic pressure is upon the imbibition action. The presented fractal analysis of horizontal spontaneous imbibition from a single fracture could also shed light on the scaling study of the mass transfer function between matrix and fracture system of fractured reservoirs. © 2013 World Scientific Publishing Company.

Enhanced transport of zerovalent iron nanoparticles in saturated porous media by guar gum

International Nuclear Information System (INIS)

Tiraferri, Alberto; Sethi, Rajandrea

2009-01-01

In order to ensure adequate mobility of zerovalent iron nanoparticles in natural aquifers, the use of a stabilizing agent is necessary. Polymers adsorbed on the nanoparticle surface will give rise to electrosteric stabilization and will decrease attachment to the surface soil grains. Water saturated sand-packed columns were used in this study to investigate the transport of iron nanoparticle suspensions, bare or modified with the green polymer guar gum. The suspensions were prepared at 154 mg/L particle concentration and 0.5 g/L polymer concentration. Transport experiments were conducted by varying the ionic strength, ionic composition, and approach velocity of the fluid. Nanoparticle deposition rates, attachment efficiencies, and travel distances were subsequently calculated based on the classical particle filtration theory. It was found that bare iron nanoparticles are basically immobile in sandy porous media. In contrast, guar gum is able to ensure significant nanoparticle transport at the tested conditions, regardless of the chemistry of the solution. Attachment efficiency values for guar gum-coated nanoparticles under the various conditions tested were smaller than 0.066. Although the calculated travel distances may not prove satisfactory for field application, the investigation attested the promising role of guar gum to ensure mobility of iron nanoparticles in the subsurface environment.

Fractal analysis of fracture increasing spontaneous imbibition in porous media with gas-saturated

KAUST Repository

Cai, Jianchao

2013-08-01

Spontaneous imbibition (SI) of wetting liquid into matrix blocks due to capillary pressure is regarded as an important recovery mechanism in low permeability fractured reservoir. In this paper, an analytical model is proposed for characterizing SI horizontally from a single plane fracture into gas-saturated matrix blocks. The presented model is based on the fractal character of pores in porous matrix, with gravity force included in the entire imbibition process. The accumulated mass of wetting liquid imbibed into matrix blocks is related to a number of factors such as contact area, pore fractal dimension, tortuosity, maximum pore size, porosity, liquid density and viscosity, surface tension, contact angle, as well as height and tilt angle of the fracture. The mechanism of fracture-enhanced SI is analyzed accordingly. Because of the effect of fracture, the gravity force is positive to imbibition process. Additionally, the farther away from the fracture top of the pore, the more influential the hydrostatic pressure is upon the imbibition action. The presented fractal analysis of horizontal spontaneous imbibition from a single fracture could also shed light on the scaling study of the mass transfer function between matrix and fracture system of fractured reservoirs. © 2013 World Scientific Publishing Company.

Experimental procedure for determination of dispersion coefficient in a column of porous medium using radiotracer; Procedimento experimental para determinacao do coeficiente de dispersao num meio poroso em coluna utilizando radiotracador

Energy Technology Data Exchange (ETDEWEB)

Souza, Roberto de [Universidade Federal, Rio de Janeiro, RJ (Brazil). Coordenacao dos Programas de Pos-graduacao de Engenharia; Heilbron Filho, Paulo Fernando Lavalle [Comissao Nacional de Energia Nuclear (CNEN), Rio de Janeiro, RJ (Brazil)

1997-12-31

The experimental procedures used for determination of parameters such as the molecular diffusion and the diffusion by mechanical convection, responsible for the dispersion in the porous medium, are presented. The experiments were conduct in a column, based on the theory of hydrodynamic dispersion. The radiotracer technique was employed to monitor the dispersion of the radioactive cloud through the porous medium. The radionuclide employed was the bromide 82 (Br{sup 82}), in the KBr chemical form 11 refs., 5 figs., 4 tabs.; e-mail: rs at serv.com.ufrj.br; paulo at cnen.gov.br

Map of fluid flow in fractal porous medium into fractal continuum flow.

Science.gov (United States)

Balankin, Alexander S; Elizarraraz, Benjamin Espinoza

2012-05-01

This paper is devoted to fractal continuum hydrodynamics and its application to model fluid flows in fractally permeable reservoirs. Hydrodynamics of fractal continuum flow is developed on the basis of a self-consistent model of fractal continuum employing vector local fractional differential operators allied with the Hausdorff derivative. The generalized forms of Green-Gauss and Kelvin-Stokes theorems for fractional calculus are proved. The Hausdorff material derivative is defined and the form of Reynolds transport theorem for fractal continuum flow is obtained. The fundamental conservation laws for a fractal continuum flow are established. The Stokes law and the analog of Darcy's law for fractal continuum flow are suggested. The pressure-transient equation accounting the fractal metric of fractal continuum flow is derived. The generalization of the pressure-transient equation accounting the fractal topology of fractal continuum flow is proposed. The mapping of fluid flow in a fractally permeable medium into a fractal continuum flow is discussed. It is stated that the spectral dimension of the fractal continuum flow d(s) is equal to its mass fractal dimension D, even when the spectral dimension of the fractally porous or fissured medium is less than D. A comparison of the fractal continuum flow approach with other models of fluid flow in fractally permeable media and the experimental field data for reservoir tests are provided.

Onset of convection in a porous medium with sidewall heat transfer

International Nuclear Information System (INIS)

Kassoy, D.R.; Wang, M.; Weidman, P.D.

1985-01-01

A linear stability analysis is developed for convection in a vertically oriented finite slab of saturated porous material. The large vertical sidewall surfaces admit heat transfer while the small endwalls are insulated. A vertical temperature difference is imposed between the upper and lower horizontal surfaces. Results are obtained from an asymptotic evaluation of the exact stability criteria for a rectangular parallelpiped in the limit of small gap width element of → 0, where element of = narrow horizontal dimension/height. The critical Rayleigh number R/sub c/ = 0(element of/sup -2/) when the heat transfer boundary condition is applied directly to the sidewall. The convection mode consists of tightly packed three-dimensional cells with a wave number α = 0(element of/sup -1/2/). Only when the effective Biot number is sufficiently small, 0(element of/sup 2/), are the classical results approached; R/sub c/ → 4π/sup 2/, α/sub c/ = 0(1). If the slab is sandwiched between two impermeable conducting blocks with horizontal extent similar to the slab height, then the small scale modes disappear and R/sub c/ = 0(element of/sup -1/). However, sufficiently thin conducting blocks are compatible with R/sub c/ = 0(element of/sup -2/) and α = 0(element of/sup -1/2/

Concurrent aggregation and transport of graphene oxide in saturated porous media: Roles of temperature, cation type, and electrolyte concentration.

Science.gov (United States)

Wang, Mei; Gao, Bin; Tang, Deshan; Yu, Congrong

2018-04-01

Simultaneous aggregation and retention of nanoparticles can occur during their transport in porous media. In this work, the concurrent aggregation and transport of GO in saturated porous media were investigated under the conditions of different combinations of temperature, cation type (valence), and electrolyte concentration. Increasing temperature (6-24 °C) at a relatively high electrolyte concentration (i.e., 50 mM for Na + , 1 mM for Ca 2+ , 1.75 mM for Mg 2+ , and 0.03 and 0.05 mM for Al 3+ ) resulted in enhanced GO retention in the porous media. For instance, when the temperature increased from 6 to 24 °C, GO recovery rate decreased from 31.08% to 6.53% for 0.03 mM Al 3+ and from 27.11% to 0 for 0.05 mM Al 3+ . At the same temperature, increasing cation valence and electrolyte concentration also promoted GO retention. Although GO aggregation occurred in the electrolytes during the transport, the deposition mechanisms of GO retention in the media depended on cation type (valence). For 50 mM Na + , surface deposition via secondary minima was the dominant GO retention mechanism. For multivalent cation electrolytes, GO aggregation was rapid and thus other mechanisms such as physical straining and sedimentation also played important roles in controlling GO retention in the media. After passing through the columns, the GO particles in the effluents showed better stability with lower initial aggregation rates. This was probably because less stable GO particles with lower surface charge densities in the porewater were filtered by the porous media, resulting in more stable GO particle with higher surface charge densities in the effluents. An advection-dispersion-reaction model was applied to simulate GO breakthrough curves and the simulations matched all the experimental data well. Copyright © 2017 Elsevier Ltd. All rights reserved.

Simulation of uncompressible fluid flow through a porous media

International Nuclear Information System (INIS)

Ramirez, A.; Gonzalez, J.L.; Carrillo, F.; Lopez, S.

2009-01-01

Recently, a great interest has been focused for investigations about transport phenomena in disordered systems. One of the most treated topics is fluid flow through anisotropic materials due to the importance in many industrial processes like fluid flow in filters, membranes, walls, oil reservoirs, etc. In this work is described the formulation of a 2D mathematical model to simulate the fluid flow behavior through a porous media (PM) based on the solution of the continuity equation as a function of the Darcy's law for a percolation system; which was reproduced using computational techniques reproduced using a random distribution of the porous media properties (porosity, permeability and saturation). The model displays the filling of a partially saturated porous media with a new injected fluid showing the non-defined advance front and dispersion of fluids phenomena.

METHOD OF IMPREGNATING A POROUS MATERIAL

Science.gov (United States)

Steele, G.N.

1960-06-01

A method of impregnating a porous body with an inorganic uranium- containing salt is outlined and comprises dissolving a water-soluble uranium- containing salt in water; saturating the intercommunicating pores of the porous body with the salt solution; infusing ammonia gas into the intercommunicating pores of the body, the ammonia gas in water chemically reacting with the water- soluble uranium-containing salt in the water solvent to form a nonwater-soluble uranium-containing precipitant; and evaporating the volatile unprecipitated products from the intercommunicating pores whereby the uranium-containing precipitate is uniformly distributed in the intercommunicating peres of the porous body.

Pore-Scale Hydrodynamics in a Progressively Bioclogged Three-Dimensional Porous Medium: 3-D Particle Tracking Experiments and Stochastic Transport Modeling

Science.gov (United States)

Carrel, M.; Morales, V. L.; Dentz, M.; Derlon, N.; Morgenroth, E.; Holzner, M.

2018-03-01

Biofilms are ubiquitous bacterial communities that grow in various porous media including soils, trickling, and sand filters. In these environments, they play a central role in services ranging from degradation of pollutants to water purification. Biofilms dynamically change the pore structure of the medium through selective clogging of pores, a process known as bioclogging. This affects how solutes are transported and spread through the porous matrix, but the temporal changes to transport behavior during bioclogging are not well understood. To address this uncertainty, we experimentally study the hydrodynamic changes of a transparent 3-D porous medium as it experiences progressive bioclogging. Statistical analyses of the system's hydrodynamics at four time points of bioclogging (0, 24, 36, and 48 h in the exponential growth phase) reveal exponential increases in both average and variance of the flow velocity, as well as its correlation length. Measurements for spreading, as mean-squared displacements, are found to be non-Fickian and more intensely superdiffusive with progressive bioclogging, indicating the formation of preferential flow pathways and stagnation zones. A gamma distribution describes well the Lagrangian velocity distributions and provides parameters that quantify changes to the flow, which evolves from a parallel pore arrangement under unclogged conditions, toward a more serial arrangement with increasing clogging. Exponentially evolving hydrodynamic metrics agree with an exponential bacterial growth phase and are used to parameterize a correlated continuous time random walk model with a stochastic velocity relaxation. The model accurately reproduces transport observations and can be used to resolve transport behavior at intermediate time points within the exponential growth phase considered.

Modeling Transport in Fractured Porous Media with the Random-Walk Particle Method: The Transient Activity Range and the Particle-Transfer Probability

International Nuclear Information System (INIS)

Lehua Pan; G.S. Bodvarsson

2001-01-01

Multiscale features of transport processes in fractured porous media make numerical modeling a difficult task, both in conceptualization and computation. Modeling the mass transfer through the fracture-matrix interface is one of the critical issues in the simulation of transport in a fractured porous medium. Because conventional dual-continuum-based numerical methods are unable to capture the transient features of the diffusion depth into the matrix (unless they assume a passive matrix medium), such methods will overestimate the transport of tracers through the fractures, especially for the cases with large fracture spacing, resulting in artificial early breakthroughs. We have developed a new method for calculating the particle-transfer probability that can capture the transient features of diffusion depth into the matrix within the framework of the dual-continuum random-walk particle method (RWPM) by introducing a new concept of activity range of a particle within the matrix. Unlike the multiple-continuum approach, the new dual-continuum RWPM does not require using additional grid blocks to represent the matrix. It does not assume a passive matrix medium and can be applied to the cases where global water flow exists in both continua. The new method has been verified against analytical solutions for transport in the fracture-matrix systems with various fracture spacing. The calculations of the breakthrough curves of radionuclides from a potential repository to the water table in Yucca Mountain demonstrate the effectiveness of the new method for simulating 3-D, mountain-scale transport in a heterogeneous, fractured porous medium under variably saturated conditions

An Iterative Implicit Scheme for Nanoparticles Transport with Two-Phase Flow in Porous Media

KAUST Repository

El-Amin, Mohamed

2016-06-01

In this paper, we introduce a mathematical model to describe the nanoparticles transport carried by a two-phase flow in a porous medium including gravity, capillary forces and Brownian diffusion. Nonlinear iterative IMPES scheme is used to solve the flow equation, and saturation and pressure are calculated at the current iteration step and then the transport equation is solved implicitly. Therefore, once the nanoparticles concentration is computed, the two equations of volume of the nanoparticles available on the pore surfaces and the volume of the nanoparticles entrapped in pore throats are solved implicitly. The porosity and the permeability variations are updated at each time step after each iteration loop. Numerical example for regular heterogenous permeability is considered. We monitor the changing of the fluid and solid properties due to adding the nanoparticles. Variation of water saturation, water pressure, nanoparticles concentration and porosity are presented graphically.

Research Article

African Journals Online (AJOL)

2016-06-09

Jun 9, 2016 ... Journal of Fundamental and Applied Sciences is licensed under a Creative ... and mass transfer from a vertical flat plate in a porous medium saturated with ... boundary layer with suction and mass transfer in a porous medium.

Capturing poromechanical coupling effects of the reactive fracturing process in porous rock via a DEM-network model

Science.gov (United States)

Ulven, Ole Ivar; Sun, WaiChing

2016-04-01

Fluid transport in a porous medium has important implications for understanding natural geological processes. At a sufficiently large scale, a fluid-saturated porous medium can be regarded as a two-phase continuum, with the fluid constituent flowing in the Darcian regime. Nevertheless, a fluid mediated chemical reaction can in some cases change the permeability of the rock locally: Mineral dissolution can cause increased permeability, whereas mineral precipitation can reduce the permeability. This might trigger a complicated hydro-chemo-mechanical coupling effect that causes channeling of fluids or clogging of the system. If the fluid is injected or produced at a sufficiently high rate, the pressure might increase enough to cause the onset and propagation of fractures. Fractures in return create preferential flow paths that enhance permeability, localize fluid flow and chemical reaction, prevent build-up of pore pressure and cause anisotropy of the hydro-mechanical responses of the effective medium. This leads to a complex coupled process of solid deformation, chemical reaction and fluid transport enhanced by the fracture formation. In this work, we develop a new coupled numerical model to study the complexities of feedback among fluid pressure evolution, fracture formation and permeability changes due to a chemical process in a 2D system. We combine a discrete element model (DEM) previously used to study a volume expanding process[1, 2] with a new fluid transport model based on poroelasticity[3] and a fluid-mediated chemical reaction that changes the permeability of the medium. This provides new insights into the hydro-chemo-mechanical process of a transforming porous medium. References [1] Ulven, O. I., Storheim, H., Austrheim, H., and Malthe-Sørenssen, A. "Fracture Initiation During Volume Increasing Reactions in Rocks and Applications for CO2 Sequestration", Earth Planet. Sc. Lett. 389C, 2014a, pp. 132 - 142, doi:10.1016/j.epsl.2013.12.039. [2] Ulven, O. I

Simulation of uncompressible fluid flow through a porous media

Energy Technology Data Exchange (ETDEWEB)

Ramirez, A. [Instituto Politecnico Nacional (SEPI-ESIQIE-IPN), Unidad Profesional Zacatenco, Laboratorio de Analisis Met. (Edif. ' Z' y Edif. ' 6' P.B.), Mexico City (Mexico)], E-mail: adaramil@yahoo.com.mx; Gonzalez, J.L. [Instituto Politecnico Nacional (SEPI-ESIQIE-IPN), Unidad Profesional Zacatenco, Laboratorio de Analisis Met. (Edif. ' Z' y Edif. ' 6' P.B.), Mexico City (Mexico); Carrillo, F. [Instituto Politecnico Nacional (SEPI-CICATA-IPN), Unidad Altamira Tamaulipas, Mexico (Mexico); Lopez, S. [Instituto Mexicano del Petroleo (I.M.P.-D.F.), Mexico (Mexico)

2009-02-28

Recently, a great interest has been focused for investigations about transport phenomena in disordered systems. One of the most treated topics is fluid flow through anisotropic materials due to the importance in many industrial processes like fluid flow in filters, membranes, walls, oil reservoirs, etc. In this work is described the formulation of a 2D mathematical model to simulate the fluid flow behavior through a porous media (PM) based on the solution of the continuity equation as a function of the Darcy's law for a percolation system; which was reproduced using computational techniques reproduced using a random distribution of the porous media properties (porosity, permeability and saturation). The model displays the filling of a partially saturated porous media with a new injected fluid showing the non-defined advance front and dispersion of fluids phenomena.

Distinguishing oil and water layers in a cracked porous medium using pulsed neutron logging data based on Hudson's crack theory

Science.gov (United States)

Zhang, Xueang; Yang, Zhichao; Tang, Bin; Wang, Renbo; Wei, Xiong

2018-05-01

During geophysical surveys, water layers may interfere with the detection of oil layers. In order to distinguish between oil and water layers in porous cracked media, research on the properties of the cracks, the oil and water layers, and their relation to pulsed neutron logging characteristics is essential. Using Hudson's crack theory, we simulated oil and water layers in a cracked porous medium with different crack parameters corresponding to the well log responses. We found that, in a cracked medium with medium-angle (40°-50°) cracks, the thermal neutron count peak value is higher and more sensitive than those in low-angle and high-angle crack environments; in addition, the thermal neutron density distribution shows more minimum values than in other cases. Further, the thermal neutron count and the rate of change for the oil layer are greater than those of the water layer, and the time spectrum count peak value for the water layer in middle-high-angle (40°-70°) cracked environments is higher than that of the oil layer. The thermal neutron density distribution sensitivity is higher in the water layer with a range of small crack angles (0°-30°) than in the oil layer with the same range of angles. In comparing the thermal neutron density distribution, thermal neutron count peak, thermal neutron density distribution sensitivity, and time spectrum maximum in the oil and water layers, we find that neutrons in medium-angle (40°-50°) cracked reservoirs are more sensitive to deceleration and absorption than those in water layers; neutrons in approximately horizontal (0°-30°) cracked water layers are more sensitive to deceleration than those in reservoirs. These results can guide future work in the cracked media neutron logging field.

Hydromagnetic thermosolutal instability of compressible walters' (model B' rotating fluid permeated with suspended particles in porous medium

Directory of Open Access Journals (Sweden)

G Rana

2016-09-01

Full Text Available The thermosolutal instability of compressible Walters' (model B' elastico-viscous rotating fluid permeated with suspended particles (fine dust in the presence of vertical magnetic field in porous medium is considered. By applying normal mode analysis method, the dispersion relation has been derived and solved analytically. It is observed that the rotation, magnetic field, suspended particles and viscoelasticity introduce oscillatory modes. For stationary convection the Walters' (model B' fluid behaves like an ordinary Newtonian fluid and it is observed that the rotation and stable solute gradient has stabilizing effects and suspended particles are found to have destabilizing effect on the system, whereas the medium permeability has stabilizing or destabilizing effect on the system under certain conditions. The magnetic field has destabilizing effect in the absence of rotation, whereas in the presence of rotation, magnetic field has stabilizing or destabilizing effect under certain conditions.

Application of artificial neural network for heat transfer in porous cone

Science.gov (United States)

Athani, Abdulgaphur; Ahamad, N. Ameer; Badruddin, Irfan Anjum

2018-05-01

Heat transfer in porous medium is one of the classical areas of research that has been active for many decades. The heat transfer in porous medium is generally studied by using numerical methods such as finite element method; finite difference method etc. that solves coupled partial differential equations by converting them into simpler forms. The current work utilizes an alternate method known as artificial neural network that mimics the learning characteristics of neurons. The heat transfer in porous medium fixed in a cone is predicted using backpropagation neural network. The artificial neural network is able to predict this behavior quite accurately.

Experimental study on cavity flow natural convection in porous medium, saturated with an Al(sub2)0(sub3) 60% EG-40% water nanofluid

CSIR Research Space (South Africa)

Grobler, Carla

2015-07-01

Full Text Available Natural convection is convection where the fluid motion is driven by buoyancy forces. Porous media and nanofluids have an impact on the heat transfer capabilities of thermal systems. The present experimental study is part of ongoing research...

Boiling in porous media

International Nuclear Information System (INIS)

1998-01-01

This conference day of the French society of thermal engineers was devoted to the analysis of heat transfers and fluid flows during boiling phenomena in porous media. This book of proceedings comprises 8 communications entitled: 'boiling in porous medium: effect of natural convection in the liquid zone'; 'numerical modeling of boiling in porous media using a 'dual-fluid' approach: asymmetrical characteristic of the phenomenon'; 'boiling during fluid flow in an induction heated porous column'; 'cooling of corium fragment beds during a severe accident. State of the art and the SILFIDE experimental project'; 'state of knowledge about the cooling of a particulates bed during a reactor accident'; 'mass transfer analysis inside a concrete slab during fire resistance tests'; 'heat transfers and boiling in porous media. Experimental analysis and modeling'; 'concrete in accidental situation - influence of boundary conditions (thermal, hydric) - case studies'. (J.S.)

Cation-Inhibited Transport of Graphene Oxide Nanomaterials in Saturated Porous Media: The Hofmeister Effects.

Science.gov (United States)

Xia, Tianjiao; Qi, Yu; Liu, Jing; Qi, Zhichong; Chen, Wei; Wiesner, Mark R

2017-01-17

Transport of negatively charged nanoparticles in porous media is largely affected by cations. To date, little is known about how cations of the same valence may affect nanoparticle transport differently. We observed that the effects of cations on the transport of graphene oxide (GO) and sulfide-reduced GO (RGO) in saturated quartz sand obeyed the Hofmeister series; that is, transport-inhibition effects of alkali metal ions followed the order of Na + cations having large ionic radii (and thus being weakly hydrated) interacted with quartz sand and GO and RGO more strongly than did cations of small ionic radii. In particular, the monovalent Cs + and divalent Ca 2+ and Ba 2+ , which can form inner-sphere complexes, resulted in very significant deposition of GO and RGO via cation bridging between quartz sand and GO and RGO, and possibly via enhanced straining, due to the enhanced aggregation of GO and RGO from cation bridging. The existence of the Hofmeister effects was further corroborated with the interesting observation that cation bridging was more significant for RGO, which contained greater amounts of carboxyl and phenolic groups (i.e., metal-complexing moieties) than did GO. The findings further demonstrate that transport of nanoparticles is controlled by the complex interplay between nanoparticle surface functionalities and solution chemistry constituents.

Rn3D: A finite element code for simulating gas flow and radon transport in variably saturated, nonisothermal porous media

International Nuclear Information System (INIS)

Holford, D.J.

1994-01-01

This document is a user's manual for the Rn3D finite element code. Rn3D was developed to simulate gas flow and radon transport in variably saturated, nonisothermal porous media. The Rn3D model is applicable to a wide range of problems involving radon transport in soil because it can simulate either steady-state or transient flow and transport in one-, two- or three-dimensions (including radially symmetric two-dimensional problems). The porous materials may be heterogeneous and anisotropic. This manual describes all pertinent mathematics related to the governing, boundary, and constitutive equations of the model, as well as the development of the finite element equations used in the code. Instructions are given for constructing Rn3D input files and executing the code, as well as a description of all output files generated by the code. Five verification problems are given that test various aspects of code operation, complete with example input files, FORTRAN programs for the respective analytical solutions, and plots of model results. An example simulation is presented to illustrate the type of problem Rn3D is designed to solve. Finally, instructions are given on how to convert Rn3D to simulate systems other than radon, air, and water

The effective thermal conductivity of porous media based on statistical self-similarity

International Nuclear Information System (INIS)

Kou Jianlong; Wu Fengmin; Lu Hangjun; Xu Yousheng; Song Fuquan

2009-01-01

A fractal model is presented based on the thermal-electrical analogy technique and statistical self-similarity of fractal saturated porous media. A dimensionless effective thermal conductivity of saturated fractal porous media is studied by the relationship between the dimensionless effective thermal conductivity and the geometrical parameters of porous media with no empirical constant. Through this study, it is shown that the dimensionless effective thermal conductivity decreases with the increase of porosity (φ) and pore area fractal dimension (D f ) when k s /k g >1. The opposite trends is observed when k s /k g t ). The model predictions are compared with existing experimental data and the results show that they are in good agreement with existing experimental data.

A New Appraoch to Modeling Immiscible Two-phase Flow in Porous Media

DEFF Research Database (Denmark)

Yuan, Hao; Shapiro, Alexander; Stenby, Erling Halfdan

In this work we present a systematic literature review regarding the macroscopic approaches to modeling immiscible two-phase flow in porous media, the formulation process of the incorporate PDE based on Film Model(viscous coupling), the calculation of saturation profile around the transition zone...... to modeling immiscible two-phase flow in porous media. The suggested approach to immiscible two-phase flow in porous media describes the dispersed mesoscopic fluids’ interfaces which are highly influenced by the injected interfacial energy and the local interfacial energy capacity. It reveals a new...... possibility of modeling two-phase flow through energy balance. The saturation profile generated through the suggested approach is different from those through other approaches....

A lattice Boltzmann investigation of steady-state fluid distribution, capillary pressure and relative permeability of a porous medium: Effects of fluid and geometrical properties

Science.gov (United States)

Li, Zi; Galindo-Torres, Sergio; Yan, Guanxi; Scheuermann, Alexander; Li, Ling

2018-06-01

Simulations of simultaneous steady-state two-phase flow in the capillary force-dominated regime were conducted using the state-of-the-art Shan-Chen multi-component lattice Boltzmann model (SCMC-LBM) based on two-dimensional porous media. We focused on analyzing the fluid distribution (i.e., WP fluid-solid, NP fluid-solid and fluid-fluid interfacial areas) as well as the capillary pressure versus saturation curve which was affected by fluid and geometrical properties (i.e., wettability, adhesive strength, pore size distribution and specific surface area). How these properties influenced the relative permeability versus saturation relation through apparent effective permeability and threshold pressure gradient was also explored. The SCMC-LBM simulations showed that, a thin WP fluid film formed around the solid surface due to the adhesive fluid-solid interaction, resulting in discrete WP fluid distributions and reduction of the WP fluid mobility. Also, the adhesive interaction provided another source of capillary pressure in addition to capillary force, which, however, did not affect the mobility of the NP fluid. The film fluid effect could be enhanced by large adhesive strength and fine pores in heterogeneous porous media. In the steady-state infiltration, not only the NP fluid but also the WP fluid were subjected to the capillary resistance. The capillary pressure effect could be alleviated by decreased wettability, large average pore radius and improved fluid connectivity in heterogeneous porous media. The present work based on the SCMC-LBM investigations elucidated the role of film fluid as well as capillary pressure in the two-phase flow system. The findings have implications for ways to improve the macroscopic flow equation based on balance of force for the steady-state infiltration.

Effect of rotation on peristaltic flow of a micropolar fluid through a porous medium with an external magnetic field

International Nuclear Information System (INIS)

Abd-Alla, A.M.; Abo-Dahab, S.M.; Al-Simery, R.D.

2013-01-01

In this paper, the effects of both rotation and magnetic field of a micropolar fluid through a porous medium induced by sinusoidal peristaltic waves traveling down the channel walls are studied analytically and computed numerically. Closed-form solutions under the consideration of long wavelength and low-Reynolds number is presented. The analytical expressions for axial velocity, pressure rise per wavelength, mechanical efficiency, spin velocity, stream function and pressure gradient are obtained in the physical domain. The effect of the rotation, density, Hartmann number, permeability, coupling number, micropolar parameter and the non-dimensional wave amplitude in the wave frame is analyzed theoretically and computed numerically. Numerical results are given and illustrated graphically in each case considered. Comparison was made with the results obtained in the presence and absence of rotation and magnetic field. The results indicate that the effect of rotation, density, Hartmann number, permeability, coupling number, micropolar parameter and the non-dimensional wave amplitude are very pronounced in the phenomena. - Highlights: • The effects of induced magnetic field and rotation in peristaltic motion of a two dimensional of a micropolar fluid through a porous medium • The exact and closed form solutions are presented • Different wave shapes are considered to observe the behavior of the axial velocity, pressure rise, mechanical efficiency, spin velocity, stream function and pressure gradient

Effect of rotation on peristaltic flow of a micropolar fluid through a porous medium with an external magnetic field

Energy Technology Data Exchange (ETDEWEB)

Abd-Alla, A.M., E-mail: mohmrr@yahoo.com [Maths Department, Faculty of Science, Taif University (Saudi Arabia); Abo-Dahab, S.M., E-mail: sdahb@yahoo.com [Maths Department, Faculty of Science, Taif University (Saudi Arabia); Maths Department, Faculty of Science, SVU, Qena 83523 (Egypt); Al-Simery, R.D. [Maths Department, Faculty of Science, Taif University (Saudi Arabia)

2013-12-15

In this paper, the effects of both rotation and magnetic field of a micropolar fluid through a porous medium induced by sinusoidal peristaltic waves traveling down the channel walls are studied analytically and computed numerically. Closed-form solutions under the consideration of long wavelength and low-Reynolds number is presented. The analytical expressions for axial velocity, pressure rise per wavelength, mechanical efficiency, spin velocity, stream function and pressure gradient are obtained in the physical domain. The effect of the rotation, density, Hartmann number, permeability, coupling number, micropolar parameter and the non-dimensional wave amplitude in the wave frame is analyzed theoretically and computed numerically. Numerical results are given and illustrated graphically in each case considered. Comparison was made with the results obtained in the presence and absence of rotation and magnetic field. The results indicate that the effect of rotation, density, Hartmann number, permeability, coupling number, micropolar parameter and the non-dimensional wave amplitude are very pronounced in the phenomena. - Highlights: • The effects of induced magnetic field and rotation in peristaltic motion of a two dimensional of a micropolar fluid through a porous medium • The exact and closed form solutions are presented • Different wave shapes are considered to observe the behavior of the axial velocity, pressure rise, mechanical efficiency, spin velocity, stream function and pressure gradient.

Study of the Effect of Turbulence and Large Obstacles on the Evaporation from Bare Soil Surface through Coupled Free-flow and Porous-medium Flow Model

Science.gov (United States)

Gao, B.; Smits, K. M.

2017-12-01

Evaporation is a strongly coupled exchange process of mass, momentum and energy between the atmosphere and the soil. Several mechanisms influence evaporation, such as the atmospheric conditions, the structure of the soil surface, and the physical properties of the soil. Among the previous studies associated with evaporation modeling, most efforts use uncoupled models which simplify the influences of the atmosphere and soil through the use of resistance terms. Those that do consider the coupling between the free flow and porous media flow mainly consider flat terrain with grain-scale roughness. However, larger obstacles, which may form drags or ridges allowing normal convective air flow through the soil, are common in nature and may affect the evaporation significantly. Therefore, the goal of this work is to study the influence of large obstacles such as wavy surfaces on the flow behavior within the soil and exchange processes to the atmosphere under turbulent free-flow conditions. For simplicity, the soil surface with large obstacles are represented by a simple wavy surface. To do this, we modified a previously developed theory for two-phase two-component porous-medium flow, coupling it to single-phase two-component turbulent flow to simulate and analyze the evaporation from wavy soil surfaces. Detailed laboratory scale experiments using a wind tunnel interfaced with a porous media tank were carried out to test the modeling results. The characteristics of turbulent flow across a permeable wavy surface are discussed. Results demonstrate that there is an obvious recirculation zone formed at the surface, which is special because of the accumulation of water vapor and the thicker boundary layer in this area. In addition, the influences of both the free flow and porous medium on the evaporation are also analyzed. The porous medium affects the evaporation through the amount of water it can provide to the soil surface; while the atmosphere influences the evaporation

Numerical study for enhancing the thermal conductivity of phase change material (PCM) storage using high thermal conductivity porous matrix

International Nuclear Information System (INIS)

Mesalhy, Osama; Lafdi, Khalid; Elgafy, Ahmed; Bowman, Keith

2005-01-01

In this paper, the melting process inside an irregular geometry filled with high thermal conductivity porous matrix saturated with phase change material PCM is investigated numerically. The numerical model is resting on solving the volume averaged conservation equations for mass, momentum and energy with phase change (melting) in the porous medium. The convection motion of the liquid phase inside the porous matrix is solved considering the Darcy, Brinkman and Forchiemer effects. A local thermal non-equilibrium assumption is considered due to the large difference in thermal properties between the solid matrix and PCM by applying a two energy equation model. The numerical code shows good agreement for pure PCM melting with another published numerical work. Through this study it is found that the presence of the porous matrix has a great effect on the heat transfer and melting rate of the PCM energy storage. Decreasing the porosity of the matrix increases the melting rate, but it also damps the convection motion. It is also found that the best technique to enhance the response of the PCM storage is to use a solid matrix with high porosity and high thermal conductivity

The Effect of Wettability Heterogeneity on Relative Permeability of Two-Phase Flow in Porous Media: A Lattice Boltzmann Study

Science.gov (United States)

Zhao, Jianlin; Kang, Qinjun; Yao, Jun; Viswanathan, Hari; Pawar, Rajesh; Zhang, Lei; Sun, Hai

2018-02-01

Relative permeability is a critical parameter characterizing multiphase flow in porous media and it is strongly dependent on the wettability. In many situations, the porous media are nonuniformly wet. To investigate the effect of wettability heterogeneity on relative permeability of two-phase flow in porous media, a multi-relaxation-time color-gradient lattice Boltzmann model is adopted to simulate oil/water two-phase flow in porous media with different oil-wet solid fractions. For the water phase, when the water saturation is high, the relative permeability of water increases with the increase of oil-wet solid fraction under a constant water saturation. However, as the water saturation decreases to an intermediate value (about 0.4-0.7), the relative permeability of water in fractionally wet porous media could be lower than that in purely water-wet porous media, meaning additional flow resistance exists in the fractionally wet porous media. For the oil phase, similar phenomenon is observed. This phenomenon is mainly caused by the wettability-related microscale fluid distribution. According to both our simulation results and theoretical analysis, it is found that the relative permeability of two-phase flow in porous media is strongly related to three parameters: the fluid saturation, the specific interfacial length of fluid, and the fluid tortuosity in the flow direction. The relationship between the relative permeability and these parameters under different capillary numbers is explored in this paper.

Use of Invasion Percolation Models To Study the Secondary Migration of Oil and Related Problems

Energy Technology Data Exchange (ETDEWEB)

Wagner, G.

1997-09-01

In oil reservoir engineering, multi-phase displacement processes are important. This doctoral thesis describes simulations of the slow displacement of a wetting fluid by a non-wetting fluid in a complex, random porous medium and in a single fracture. The study is restricted to two-phase flow in the quasi-static limit in which viscous forces can be neglected. The secondary migration of oil takes place in this regime, however, the discussion is broader in scope. The thesis connects the problem of slow two-phase flow to percolation theory and discusses the mechanisms that control immiscible displacements. A new, modified version of the invasion percolation model is used to simulate an imbibition process in a porous medium and the migration of a cluster of non-wetting fluid through a porous medium saturated with a wetting fluid. The simulations include the secondary migration of oil through porous homogeneous rock. Fluid migration through heterogeneous porous media is simulated qualitatively. Slow displacement of a wetting fluid by a non-wetting fluid in a single rock fracture is simulated by using the standard invasion percolation model. Experiments and simulations are performed to study the fragmentation of invasion percolation-like structures of non-wetting fluid in a porous medium saturated with a wetting fluid. A scenario is studied in which a cluster of non-wettable fluid migrates through a porous medium that is saturated with a wetting fluid, the migration being driven by continuously increasing buoyancy forces. There is a simulation of the secondary migration of oil in both two- and three-dimensional media. 361 refs., 115 figs.

A new theoretical interpretation of Archie's saturation exponent

Directory of Open Access Journals (Sweden)

P. W. J. Glover

2017-07-01

Full Text Available This paper describes the extension of the concepts of connectedness and conservation of connectedness that underlie the generalized Archie's law for n phases to the interpretation of the saturation exponent. It is shown that the saturation exponent as defined originally by Archie arises naturally from the generalized Archie's law. In the generalized Archie's law the saturation exponent of any given phase can be thought of as formally the same as the phase (i.e. cementation exponent, but with respect to a reference subset of phases in a larger n-phase medium. Furthermore, the connectedness of each of the phases occupying a reference subset of an n-phase medium can be related to the connectedness of the subset itself by Gi = GrefSini. This leads naturally to the idea of the term Sini for each phase i being a fractional connectedness, where the fractional connectednesses of any given reference subset sum to unity in the same way that the connectednesses sum to unity for the whole medium. One of the implications of this theory is that the saturation exponent of any phase can be now be interpreted as the rate of change of the fractional connectedness with saturation and connectivity within the reference subset.

Journal of Earth System Science | Indian Academy of Sciences

Indian Academy of Sciences (India)

The propagation of elastic waves along a cylindrical borehole filled with/without liquid and embedded in an infinite porous medium saturated by two immiscible fluids has been studied. The theory of porous media saturated by two immiscible fluids developed by Tuncay and Corapcioglu (1997) is employed. Frequency ...

Effects of chemical reaction in thermal and mass diffusion of micropolar fluid saturated in porous regime with radiation and ohmic heating

Directory of Open Access Journals (Sweden)

Kumar Hitesh

2016-01-01

Full Text Available The present paper analyzes the chemically reacting free convection MHD micropolar flow, heat and mass transfer in porous medium past an infinite vertical plate with radiation and viscous dissipation. The non-linear coupled partial differential equations are solved numerically using an implicit finite difference scheme known as Keller-box method. The results for concentration, transverse velocity, angular velocity and temperature are obtained and effects of various parameters on these functions are presented graphically. The numerical discussion with physical interpretations for the influence of various parameters also presented.

Law of nonlinear flow in saturated clays and radial consolidation

Institute of Scientific and Technical Information of China (English)

无

2007-01-01

It was derived that micro-scale amount level of average pore radius of clay changed from 0.01 to 0.1 micron by an equivalent concept of flow in porous media. There is good agreement between the derived results and test ones. Results of experiments show that flow in micro-scale pore of saturated clays follows law of nonlinear flow. Theoretical analyses demonstrate that an interaction of solid-liquid interfaces varies inversely with permeability or porous radius. The interaction is an important reason why nonlinear flow in saturated clays occurs. An exact mathematical model was presented for nonlinear flow in micro-scale pore of saturated clays. Dimension and physical meanings of parameters of it are definite. A new law of nonlinear flow in saturated clays was established. It can describe characteristics of flow curve of the whole process of the nonlinear flow from low hydraulic gradient to high one. Darcy law is a special case of the new law. A mathematical model was presented for consolidation of nonlinear flow in radius direction in saturated clays with constant rate based on the new law of nonlinear flow. Equations of average mass conservation and moving boundary, and formula of excess pore pressure distribution and average degree of consolidation for nonlinear flow in saturated clay were derived by using an idea of viscous boundary layer, a method of steady state in stead of transient state and a method of integral of an equation. Laws of excess pore pressure distribution and changes of average degree of consolidation with time were obtained. Results show that velocity of moving boundary decreases because of the nonlinear flow in saturated clay. The results can provide geology engineering and geotechnical engineering of saturated clay with new scientific bases. Calculations of average degree of consolidation of the Darcy flow are a special case of that of the nonlinear flow.

Free Convection over a Permeable Horizontal Flat Plate Embedded in a Porous Medium with Radiation Effects and Mixed Thermal Boundary Conditions

OpenAIRE

Najiyah S. Khasi'ie; Roziena Khairuddin; Najihah Mohamed; Mohd Zuki Salleh; Roslinda Nazar; Ioan Pop

2012-01-01

Problem statement: In this study, the mathematical modeling of free convection boundary layer flow over a permeable horizontal flat plate embedded in a porous medium under mixed thermal boundary conditions and radiation effects is considered. Approach: The transformed boundary layer equations are solved numerically using the shooting method. Results: Numerical solutions are obtained for the wall temperature, the heat transfer coefficient, as well as the velocity and temperature profiles. The ...

Influence of gas law on ultrasonic behaviour of porous media under pressure.

Science.gov (United States)

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. 2010 Elsevier B.V. All rights reserved.

Effect of the hydrophilic and hydrophobic characteristics of the gas diffusion medium on polymer electrolyte fuel cell performance under non-humidification condition

International Nuclear Information System (INIS)

Park, Heesung

2014-01-01

Highlights: • GDM played significant role in the PEFC performance under dry condition. • Hydrophobicity of GDM affect the water condensation at the surface. • Optimum water saturation in the porous layer was between 0.1 and 0.3. - Abstract: Water is a significant component of polymer electrolyte fuel cells, affecting the proton conductivity in the membrane electrolyte. Therefore, polymer electrolyte fuel cells are generally operated with a humidifier to maintain a high relative humidity of the supplied gases; however, the humidifier contributes additional weight and cost. Although many studies have attempted to develop polymer electrolyte fuel cells without a humidifier, the studies have been mainly focused on the self-humidified membrane electrolyte and catalyst layer. In this paper, the author investigates the effect of polytetrafluoroethylene coated gas diffusion medium on the water content in the membrane electrolyte. The water condensation on the surfaces of the gas diffusion medium is visualised when the polymer electrolyte fuel cell is operated under non-humidification conditions. Numerical simulation suggests that the optimum water saturation is between 0.1 and 0.3 at the gas diffusion medium to hydrate the membrane electrolyte sufficiently without significantly blocking the diffused species under non-humidification conditions

Free convective flow of a stratified fluid through a porous medium bounded by a vertical plane

Directory of Open Access Journals (Sweden)

H. K. Mondal

1994-01-01

Full Text Available Steady two-dimensional free convection flow of a thermally stratified viscous fluid through a highly porous medium bounded by a vertical plane surface of varying temperature, is considered. Analytical expressions for the velocity, temperature and the rate of heat transfer are obtained by perturbation method. Velocity distribution and rate of heat transfer for different values of parameters are shown in graphs. Velocity distribution is also obtained for certain values of the parameters by integrating the coupled differential equations by Runge-Kutta method and compared with the analytical solution. The chief concern of the paper is to study the effect of equilibrium temperature gradient on the velocity and the rate of heat transfer.

Hall effects on MHD flow of heat generating/absorbing fluid through porous medium in a rotating parallel plate channel

Science.gov (United States)

Swarnalathamma, B. V.; Krishna, M. Veera

2017-07-01

We studied heat transfer on MHD convective flow of viscous electrically conducting heat generating/absorbing fluid through porous medium in a rotating channel under uniform transverse magnetic field normal to the channel and taking Hall current. The flow is governed by the Brinkman's model. The diagnostic solutions for the velocity and temperature are obtained by perturbation technique and computationally discussed with respect to flow parameters through the graphs. The skin friction and Nusselt number are also evaluated and computationally discussed with reference to pertinent parameters in detail.

Elastoplastic model for unsaturated, quasi-saturated and fully saturated fine soils

Directory of Open Access Journals (Sweden)

Lai Ba Tien

2016-01-01

Full Text Available In unsaturated soils, the gaseous phase is commonly assumed to be continuous. This assumption is no more valid at high saturation ratio. In that case, air bubbles and pockets can be trapped in the porous network by the liquid phase and the gas phase becomes discontinuous. This trapped air reduces the apparent compressibility of the pore fluid and affect the mechanical behavior of the soil. Although it is trapped in the pores, its dissolution can take place. Dissolved air can migrate through the pore space, either by following the flow of the fluid or by diffusion. In this context, this paper present a hydro mechanical model that separately considers the kinematics and the mechanical behavior of each fluid species (eg liquid water, dissolved air, gaseous air and the solid matrix. This new model was implemented in a C++ code. Some numerical simulations are performed to demonstrate the ability of this model to reproduce a continuous transition of unsaturated to saturated states.

Dynamic seismic signatures of saturated porous rocks containing two orthogonal sets of fractures: theory versus numerical simulations

Science.gov (United States)

Guo, Junxin; Rubino, J. Germán; Glubokovskikh, Stanislav; Gurevich, Boris

2018-05-01

The dispersion and attenuation of seismic waves are potentially important attributes for the non-invasive detection and characterization of fracture networks. A primary mechanism for these phenomena is wave-induced fluid flow (WIFF), which can take place between fractures and their embedding background (FB-WIFF), as well as within connected fractures (FF-WIFF). In this work, we propose a theoretical approach to quantify seismic dispersion and attenuation related to these two manifestations of WIFF in saturated porous rocks permeated by two orthogonal sets of fractures. The methodology is based on existing theoretical models for rocks with aligned fractures, and we consider three types of fracture geometries, namely, periodic planar fractures, randomly spaced planar fractures and penny-shaped cracks. Synthetic 2-D rock samples with different degrees of fracture intersections are then explored by considering both the proposed theoretical approach and a numerical upscaling procedure that provides the effective seismic properties of generic heterogeneous porous media. The results show that the theoretical predictions are in overall good agreement with the numerical simulations, in terms of both the stiffness coefficients and the anisotropic properties. For the seismic dispersion and attenuation caused by FB-WIFF, the theoretical model for penny-shaped cracks matches the numerical simulations best, whereas for representing the effects due to FF-WIFF the periodic planar fractures model turns out to be the most suitable one. The proposed theoretical approach is easy to apply and is applicable not only to 2-D but also to 3-D fracture systems. Hence, it has the potential to constitute a useful framework for the seismic characterization of fractured reservoirs, especially in the presence of intersecting fractures.

Experimental study and modeling of gas diffusion through partially water saturated porous media. Application to Vycor glasses, geo-polymers and CEM V cement pastes

International Nuclear Information System (INIS)

Boher, C.

2012-01-01

This work documents the relationship that exists between the transfer properties of a material (pore size distribution, total porosity accessible to water, water saturation degree), and its diffusion coefficient. For this sake, materials having a quasi mono modal porosity are used: Vycor glasses and geo-polymers. We also use materials having a complex porosity: CEM V cement pastes. The use of Vycor glasses and geo-polymers allows quantifying the gas diffusion coefficient through materials having known pores size, as a function of their water saturation degree. The use of cement pastes allows checking if it is possible to decompose the diffusion coefficient of a complex porosity material, in an assembling of diffusion coefficients of quasi mono modal porosity materials. For this sake, the impact of pore network arrangement on the diffusion coefficient is studied in great details. This study is divided into three parts:1)Measurement of the geometric characteristics of materials porous network by means of the mercury intrusion porosimetry, water porosimetry, isotherms of nitrogen sorption / desorption, and water desorption tests. 2) Measurement of the materials diffusion coefficient, as a function of their relative humidity storage, and their water saturation degree. 3) Modeling the diffusion coefficient of the materials, and study the impact of the pore network (tortuosity, pores connection). (author) [fr

Application of X-ray CT investigation of CO{sub 2}-brine flow in porous media

Energy Technology Data Exchange (ETDEWEB)

Jiang, Lanlan; Liu, Yu; Song, Yongchen; Yang, Mingjun; Zhao, Yuechao; Zhao, Jiafei; Zhang, Yi; Shen, Zijian [Dalian University of Technology, Key Laboratory of Ocean Energy Utilization and Energy Conservation of Ministry of Education, Dalian (China); Xue, Ziqiu [Research Institute of Innovative Technology for the Earth, Kizugawa City, Kyoto (Japan); Suekane, Tetsuya [Tokyo Institute Technology, Department of Energy Sciences, Nagatsuta, Yokohama (Japan)

2015-05-15

A clear understanding of two-phase flows in porous media is important for investigating CO{sub 2} geological storage. In this study, we conducted an experiment of CO{sub 2}/brine flow process in porous media under sequestration conditions using X-ray CT technique. The flow properties of relative permeability, porosity heterogeneity, and CO{sub 2} 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 CO{sub 2} saturation and porosity distribution, which changes with different flow rates and fractional flows. The heterogeneity of the porous media influences the distribution of CO{sub 2}; moreover, gravity, fractional flows, and flow rates influence CO{sub 2} 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. (orig.)

Humic acid transport in saturated porous media: influence of flow velocity and influent concentration.

Science.gov (United States)

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. Copyright © 2014. Published by Elsevier B.V.

Hydromagnetic boundary layer micropolar fluid flow over a stretching surface embedded in a non-darcian porous medium with radiation

Directory of Open Access Journals (Sweden)

Mostafa A. A. Mahmoud

2006-01-01

Full Text Available We have studied the effects of radiation on the boundary layer flow and heat transfer of an electrically conducting micropolar fluid over a continuously moving stretching surface embedded in a non-Darcian porous medium with a uniform magnetic field. The transformed coupled nonlinear ordinary differential equations are solved numerically. The velocity, the angular velocity, and the temperature are shown graphically. The numerical values of the skin friction coefficient, the wall couple stress, and the wall heat transfer rate are computed and discussed for various values of parameters.

Semi-Analysis for the Pseudo-Colloid Migration of Multi-member Decay Chains in the Fractured Porous Medium with the Flux Boundary

International Nuclear Information System (INIS)

Jeong, Mi Seon; Hwang, Yong Soo; Kang, Chul Hyung

2010-01-01

Far-field modeling of radionuclide transport is an important component of general safety assessment studies carried out within the framework of storage of high-level radioactive waste in underground repositories. After a canister failure, radionuclides are leached from the backfilling and penetrate the surrounding bedrock, the final barrier between pollutant and Man's environment. Migration by pure diffusion through a hard tock or clay barrier is a rather slow process. In Fractured porous media, all of the groundwater flow occur within the fractures because fractures have permeabilities of several orders of magnitude larger than those of the rock matrix, if the geological layers are fully saturated with water. So radionuclides dissolved in groundwater will be transported along a fracture with molecular diffusion from the fracture to the rock matrix. Molecular diffusion from the fractures into the porous matrix constitutes an attenuation mechanism that can be highly order to prepare for extreme cases, it is assumed that the pollutants arrive rapidly in a fractured zone where transport takes place at much higher velocities. The specific problem of radionuclide transport through a fractured medium has been tackled by many scientists.According to the electromagnetic interaction between the solute and the colloid, solutes are absorbed by the colloid, and then we are called the pseudo-colloid. The natural colloid can exist inside a fracture with a density of 105 particles per one liter of a liquid. When the radionuclide migrates through a fractured rock, solutes sorb on natural colloids as well as the stationary fracture wall solid surface. Due to natural colloids, whose particle size is larger than that of solutes, colloids can migrate faster than solutes. Therefore, these pseudo-colloids, which are the sorbed solute molecules on the natural colloids, can also migrate faster than the solute. Both the solute and the pseudocolloid are sorbed onto and desorbed from

Natural convection in a composite fluid-porous cavity by the boundary element method

International Nuclear Information System (INIS)

Jecl, R.; Skerget, L.

2005-01-01

The main purpose of this work is to present the use of the boundary element method (BEM) for analyzing the convective fluid flow and heat transfer in composite fluid-porous media domain when the fluid is compressible. In our case the flow is modeled by utilizing the Brinkman extended Darcy momentum equation (Brinkman model) which is commonly used when it is important to satisfy the no-slip boundary condition and when one wishes to compare flows in porous medium with those in pure fluids. The Brinkman equation reduce to the classical Navier Stokes equation for clear fluid when the permeability tends to infinity (porosity is equal to unity), i.e. when the solid matrix in the porous medium disappears and, when the permeability is finite the equation is valid for porous medium. Therefore it is possible to handle porous medium free fluid interface problems by changing the properties of the medium in the computational domain appropriately. Our goal is to widen the applicability of the computational model based on the boundary domain integral method (BDIM) which is an extension of the classical BEM. The governing equations are transformed by using the velocity-vorticity variables formulation and therefore the computation scheme is partitioned into kinematic and kinetic part. (authors)

Notes on HP1 a software package for simulating variably-saturated water flow, heat transport, solute transport, and biogeochemistry in porous media. HP1 Version 2.2

Energy Technology Data Exchange (ETDEWEB)

Jacques, D.; Simunek, J.

2010-01-15

HP1 is a comprehensive modeling tool in terms of processes and reactions for simulating reactive transport and biogeochemical processes in variably-saturated porous media. HP1 results from coupling the water and solute transport model HYDRUS-1D (Simunek et al., 2009a) and PHREEQC-2 (Parkhurst and Appelo, 1999). This note provides an overview of how to set up and execute a HP1 project using version 2.2.002 of HP1 and version 4.13 of the graphical user interface (GUI) of HYDRUS-1D. A large part of this note are step-by-step instructions for selected examples involving mineral dissolution and precipitation, cation exchange, surface complexation and kinetic degradation networks. The implementation of variably-saturated flow conditions, changing boundary conditions, a layered soil profile or immobile water is also illustrated.

Notes on HP1 a software package for simulating variably-saturated water flow, heat transport, solute transport, and biogeochemistry in porous media. HP1 Version 2.2

International Nuclear Information System (INIS)

Jacques, D.; Simunek, J.

2010-01-01

HP1 is a comprehensive modeling tool in terms of processes and reactions for simulating reactive transport and biogeochemical processes in variably-saturated porous media. HP1 results from coupling the water and solute transport model HYDRUS-1D (Simunek et al., 2009a) and PHREEQC-2 (Parkhurst and Appelo, 1999). This note provides an overview of how to set up and execute a HP1 project using version 2.2.002 of HP1 and version 4.13 of the graphical user interface (GUI) of HYDRUS-1D. A large part of this note are step-by-step instructions for selected examples involving mineral dissolution and precipitation, cation exchange, surface complexation and kinetic degradation networks. The implementation of variably-saturated flow conditions, changing boundary conditions, a layered soil profile or immobile water is also illustrated.

Microfluidic systems for the analysis of viscoelastic fluid flow phenomena in porous media

NARCIS (Netherlands)

Galindo-Rosales, F.J.; Campo-Deano, L.; Pinho, F.T.; Van Bokhorst, E.; Hamersma, P.J.; Oliveira, M.S.N.; Alves, M.A.

2011-01-01

In this study, two microfluidic devices are proposed as simplified 1-D microfluidic analogues of a porous medium. The objectives are twofold: firstly to assess the usefulness of the microchannels to mimic the porous medium in a controlled and simplified manner, and secondly to obtain a better

Development of flow and heat transfer in the vicinity of a vertical plate embedded in a porous medium with viscous dissipation effects

KAUST Repository

El-Amin, Mohamed; Salama, Amgad; Sun, Shuyu; Reddy Gorla, Rama Subba

2012-01-01

In this paper, the effects of viscous dissipation on unsteady free convection from an isothermal vertical flat plate in a fluidsaturated porous medium are investigated. The Darcy-Brinkman model is employed to describe the flow field. A new model of viscous dissipation is used for the Darcy-Brinkman model of porous media. The simultaneous development of the momentum and thermal boundary layers is obtained by using a finite-difference method. Boundary layer and Boussinesq approximation have been incorporated. Numerical calculations are carried out for various parameters entering into the problem. Velocity and temperature profiles as well as the local friction factor and local Nusselt number are displayed graphically. It is found that as time approaches infinity, the values of the friction factor and heat transfer coefficient approach steady state. © 2012 by Begell House, Inc.

Chemical reaction effect on MHD free convective surface over a moving vertical plate through porous medium

Directory of Open Access Journals (Sweden)

R.S. Tripathy

2015-09-01

Full Text Available An attempt has been made to study the heat and mass transfer effect in a boundary layer flow of an electrically conducting viscous fluid subject to transverse magnetic field past over a moving vertical plate through porous medium in the presence of heat source and chemical reaction. The governing non-linear partial differential equations have been transformed into a two-point boundary value problem using similarity variables and then solved numerically by fourth order Runge–Kutta fourth order method with shooting technique. Graphical results are discussed for non-dimensional velocity, temperature and concentration profiles while numerical values of the skin friction, Nusselt number and Sherwood number are presented in tabular form for various values of parameters controlling the flow system.

Erbium doped stain etched porous silicon

International Nuclear Information System (INIS)

Gonzalez-Diaz, B.; Diaz-Herrera, B.; Guerrero-Lemus, R.; Mendez-Ramos, J.; Rodriguez, V.D.; Hernandez-Rodriguez, C.; Martinez-Duart, J.M.

2008-01-01

In this work a simple erbium doping process applied to stain etched porous silicon layers (PSLs) is proposed. This doping process has been developed for application in porous silicon solar cells, where conventional erbium doping processes are not affordable because of the high processing cost and technical difficulties. The PSLs were formed by immersion in a HF/HNO 3 solution to properly adjust the porosity and pore thickness to an optimal doping of the porous structure. After the formation of the porous structure, the PSLs were analyzed by means of nitrogen BET (Brunauer, Emmett and Teller) area measurements and scanning electron microscopy. Subsequently, the PSLs were immersed in a saturated erbium nitrate solution in order to cover the porous surface. Then, the samples were subjected to a thermal process to activate the Er 3+ ions. Different temperatures and annealing times were used in this process. The photoluminescence of the PSLs was evaluated before and after the doping processes and the composition was analyzed by Fourier transform IR spectroscopy

Acoustic emission in a fluid saturated heterogeneous porous layer with application to hydraulic fracture

Energy Technology Data Exchange (ETDEWEB)

Nelson, J.T. (California Univ., Berkeley, CA (USA). Dept. of Mechanical Engineering Lawrence Berkeley Lab., CA (USA))

1988-11-01

A theoretical model for acoustic emission in a vertically heterogeneous porous layer bounded by semi-infinite solid regions is developed using linearized equations of motion for a fluid/solid mixture and a reflectivity method. Green's functions are derived for both point loads and moments. Numerically integrated propagators represent solutions for intermediate heterogeneous layers in the porous region. These are substituted into a global matrix for solution by Gaussian elimination and back-substitution. Fluid partial stress and seismic responses to dislocations associated with fracturing of a layer of rock with a hydraulically conductive fracture network are computed with the model. A constitutive model is developed for representing the fractured rock layer as a porous material, using commonly accepted relationships for moduli. Derivations of density, tortuosity, and sinuosity are provided. The main results of the model application are the prediction of a substantial fluid partial stress response related to a second mode wave for the porous material. The response is observable for relatively large distances, on the order of several tens of meters. The visco-dynamic transition frequency associated with parabolic versus planar fluid velocity distributions across micro-crack apertures is in the low audio or seismic range, in contrast to materials with small pore size, such as porous rocks, for which the transition frequency is ultrasonic. Seismic responses are predicted for receiver locations both in the layer and in the outlying solid regions. In the porous region, the seismic response includes both shear and dilatational wave arrivals and a second-mode arrival. The second-mode arrival is not observable outside of the layer because of its low velocity relative to the dilatational and shear wave propagation velocities of the solid region.

Numerical simulation of porous burners and hole plate surface burners

Directory of Open Access Journals (Sweden)

Nemoda Stevan

2004-01-01

Full Text Available In comparison to the free flame burners the porous medium burners, especially those with flame stabilization within the porous material, are characterized by a reduction of the combustion zone temperatures and high combustion efficiency, so that emissions of pollutants are minimized. In the paper the finite-volume numerical tool for calculations of the non-isothermal laminar steady-state flow, with chemical reactions in laminar gas flow as well as within porous media is presented. For the porous regions the momentum and energy equations have appropriate corrections. In the momentum equations for the porous region an additional pressure drop has to be considered, which depends on the properties of the porous medium. For the heat transfer within the porous matrix description a heterogeneous model is considered. It treats the solid and gas phase separately, but the phases are coupled via a convective heat exchange term. For the modeling of the reaction of the methane laminar combustion the chemical reaction scheme with 164 reactions and 20 chemical species was used. The proposed numerical tool is applied for the analyses of the combustion and heat transfer processes which take place in porous and surface burners. The numerical experiments are accomplished for different powers of the porous and surface burners, as well as for different heat conductivity character is tics of the porous regions.

The kinetics of ice-lens growth in porous media

KAUST Repository

Style, Robert W.

2012-01-09

Abstract We analyse the growth rate of segregated ice (ice lenses) in freezing porous media. For typical colloidal materials such as soils we show that the commonly employed Clapeyron equation is not valid macroscopically at the interface between the ice lens and the surrounding porous medium owing to the viscous dynamics of flow in premelted films. The flow in these films gives rise to an \\'interfacial resistance\\' to flow towards the growing ice which causes a significant drop in predicted ice-growth (heave) rates. This explains why many previous models predict ice-growth rates that are much larger than those seen in experiments. We derive an explicit formula for the ice-growth rate in a given porous medium, and show that this only depends on temperature and on the external pressures imposed on the freezing system. This growth-rate formula contains a material-specific function which can be calculated (with knowledge of the geometry and material of the porous medium), but which is also readily experimentally measurable. We apply the formula to plate-like particles, and show that the results can be matched with previous experimental data. Finally we show how the interfacial resistance explains the observation that the maximum heave rate in soils occurs in medium-grained particles such as silts, while heave rates are smaller for fine-and coarse-grained particles. © 2012 Cambridge University Press.

Mixed convective thermally radiative micro nanofluid flow in a stretchable channel with porous medium and magnetic field

Energy Technology Data Exchange (ETDEWEB)

Rauf, A., E-mail: raufamar@ciitsahiwal.edu.pk; Shahzad, S. A.; Meraj, M. A. [Department of Mathematics, Comsats Institute of Information Technology, Sahiwal 57000 (Pakistan); Siddiq, M. K. [Department of CASPAM, Bahauddin Zakariya University, Multan 63000 (Pakistan); Raza, J. [School of Quantitative Sciences, Universiti Utara Malaysia, 06010, Sintok, Kedah (Malaysia)

2016-03-15

A numerical study is carried out for two dimensional steady incompressible mixed convective flow of electrically conductive micro nanofluid in a stretchable channel. The flow is generated due to the stretching walls of the channel immersed in a porous medium. The magnetic field is applied perpendicular to the walls. The impact of radiation, viscous dissipation, thermophoretic and Brownian motion of nanoparticles appear in the energy equation. A numerical technique based on Runge-Kutta-Fehlberg fourth-fifth order (RFK45) method is used to express the solutions of velocity, microrotation, temperature and concentration fields. The dimensionless physical parameters are discussed both in tabular and graphical forms. The results are also found in a good agreement with previously published literature work.

Mass Transfer and Porous Media (MTPM)

Energy Technology Data Exchange (ETDEWEB)

Rotenberg, B.; Marry, V.; Malikova, N.; Vuilleumier, R.; Giffaut, E.; Turq, P.; Robinet, J.C.; Diaz, N.; Sardini, P.; Goutelard, F.; Menut, D.; Parneix, J.C.; Sammartino, S.; Pret, D.; Coelho, D.; Jougnot, D.; Revil, A.; Boulin, P.F.; Angulo-Jaramillo, R.; Daian, J.F.; Talandier, J.; Berne, P.; Cochepin, B.; Trotignon, L.; Bildstein, O.; Steefel, C.; Lagneau, V.; Van der Lee, J.; Birchall, D.J.; Harrington, J.F.; Noy, D.J.; Sellin, P.; Bildstein, O.; Piault, E.; Trotignon, L.; Montarnal, P.; Deville, E.; Genty, A.; Le Potier, C.; Imbert, C.; Semete, P.; Desgree, P.; Fevrier, B.; Courtois, A.; Touze, G.; Sboui, A.; Roberts, J.E.; Jaffre, J.; Glaus, M.A.; Rosse, R.; Van Loon, L.R.; Matray, J.M.; Parneix, J.C.; Tinseau, E.; Pret, D.; Mayor, J.C.; Ohkubo, T.; Kikuchi, H.; Yamaguchi, M.; Alonso, U.; Missana, T.; Garcia-Gutierrez, M.; Patelli, A.; Siitari-Kauppi, M.; Leskinen, A.; Rigato, V.; Samper, J.; Dewonck, S.; Zheng, L.; Yang, Q.; Naves, A.; Dai, Z.; Samper, J.; Wolfsberg, A.; Levitt, D.; Cormenzana, J.L.; Missana, T.; Mingarro, M.; Schampera, B.; Dultz, S.; Riebe, B.; Samper, J.; Yang, Q.; Genty, A.; Perraud, D.; Poller, A.; Mayer, G.; Croise, J.; Marschall, P.; Krooss, B.; Matray, J.M.; Tanaka, T.; Vogel, P.; Lavanchy, J.M.; Enssle, C.P.; Cruchaudet, M.; Dewonck, S.; Descostes, M.; Blin, V.; Radwan, J.; Poinssot, C.; Mibus, J.; Sachs, S.; Devol-Brown, I.; Motellier, S.; Tinseau, E.; Thoby, D.; Marsal, F.; DeWindt, L.; Tinseau, E.; Pellegrini, D.; Bauer, A.; Fiehn, B.; Marquardt, Ch.; Romer, J.; Gortzen, A.; Kienzler, B

2007-07-01

This session gathers 48 articles (posters) dealing with: interlayer / micro-pore exchange of water and ions in clays: a molecular dynamics study; the multi-scale characterisation of mineral and textural spatial heterogeneities in Callovo-Oxfordian argilite and its consequence on solute species diffusion modelling; the diffusion of ions in unsaturated clay rocks: Theory and application to the Callovo- Oxfordian argillite; the porous media characterization with respect to gas transfer in Callovo Oxfordian argillite; the predictions on a 2-D cementation experiment in porous medium: intercomparison on the Comedie project; the large-scale gas injection test (LASGIT) at the Aespoe hard rock laboratory in Sweden; simulating the geochemical coupling between vitrified waste, canister and near-field on the alliances platform; toward radionuclide transport calculations on whole radioactive waste disposal with CAST3M platform; the experimental study of the water permeability of a partially saturated argillite; a mixed hexahedral finite elements for Darcy flow calculation in clay porous media; the diffusive properties of stainless steel filter discs before and after use in diffusion experiments with compacted clays; the structural organization of porosity in the Opalinus clay at the Mont Terri Rock Laboratory under saturated and unsaturated conditions; the evaluation of pore structure in compacted saturated Bentonite using NMR relaxometry; diffusion coefficients measurement in consolidated clays: a combination of micro-scale profiling and solid pore structure analyses; the numerical interpretation of in-situ DIR diffusion experiments on the Callovo- Oxfordian clay at the Meuse/Haute-Marne URL the identification of relative conductivity models for water flow and solute transport in unsaturated compacted Bentonite; diffusion experiments in Callovo- Oxfordian clay from the Meuse/Haute-Marne URL, France: experimental setup and data analyses; the transport in organo

Finite element computation of multi-physical micropolar transport phenomena from an inclined moving plate in porous media

Science.gov (United States)

Shamshuddin, MD.; Anwar Bég, O.; Sunder Ram, M.; Kadir, A.

2018-02-01

Non-Newtonian flows arise in numerous industrial transport processes including materials fabrication systems. Micropolar theory offers an excellent mechanism for exploring the fluid dynamics of new non-Newtonian materials which possess internal microstructure. Magnetic fields may also be used for controlling electrically-conducting polymeric flows. To explore numerical simulation of transport in rheological materials processing, in the current paper, a finite element computational solution is presented for magnetohydrodynamic, incompressible, dissipative, radiative and chemically-reacting micropolar fluid flow, heat and mass transfer adjacent to an inclined porous plate embedded in a saturated homogenous porous medium. Heat generation/absorption effects are included. Rosseland's diffusion approximation is used to describe the radiative heat flux in the energy equation. A Darcy model is employed to simulate drag effects in the porous medium. The governing transport equations are rendered into non-dimensional form under the assumption of low Reynolds number and also low magnetic Reynolds number. Using a Galerkin formulation with a weighted residual scheme, finite element solutions are presented to the boundary value problem. The influence of plate inclination, Eringen coupling number, radiation-conduction number, heat absorption/generation parameter, chemical reaction parameter, plate moving velocity parameter, magnetic parameter, thermal Grashof number, species (solutal) Grashof number, permeability parameter, Eckert number on linear velocity, micro-rotation, temperature and concentration profiles. Furthermore, the influence of selected thermo-physical parameters on friction factor, surface heat transfer and mass transfer rate is also tabulated. The finite element solutions are verified with solutions from several limiting cases in the literature. Interesting features in the flow are identified and interpreted.

Reactive transport modeling in variably saturated porous media with OGS-IPhreeqc

Science.gov (United States)

He, W.; Beyer, C.; Fleckenstein, J. H.; Jang, E.; Kalbacher, T.; Shao, H.; Wang, W.; Kolditz, O.

2014-12-01

Worldwide, sustainable water resource management becomes an increasingly challenging task due to the growth of population and extensive applications of fertilizer in agriculture. Moreover, climate change causes further stresses to both water quantity and quality. Reactive transport modeling in the coupled soil-aquifer system is a viable approach to assess the impacts of different land use and groundwater exploitation scenarios on the water resources. However, the application of this approach is usually limited in spatial scale and to simplified geochemical systems due to the huge computational expense involved. Such computational expense is not only caused by solving the high non-linearity of the initial boundary value problems of water flow in the unsaturated zone numerically with rather fine spatial and temporal discretization for the correct mass balance and numerical stability, but also by the intensive computational task of quantifying geochemical reactions. In the present study, a flexible and efficient tool for large scale reactive transport modeling in variably saturated porous media and its applications are presented. The open source scientific software OpenGeoSys (OGS) is coupled with the IPhreeqc module of the geochemical solver PHREEQC. The new coupling approach makes full use of advantages from both codes: OGS provides a flexible choice of different numerical approaches for simulation of water flow in the vadose zone such as the pressure-based or mixed forms of Richards equation; whereas the IPhreeqc module leads to a simplification of data storage and its communication with OGS, which greatly facilitates the coupling and code updating. Moreover, a parallelization scheme with MPI (Message Passing Interface) is applied, in which the computational task of water flow and mass transport is partitioned through domain decomposition, whereas the efficient parallelization of geochemical reactions is achieved by smart allocation of computational workload over

Solute transport through porous media using asymptotic dispersivity

Indian Academy of Sciences (India)

ber of processes and porous media properties including convective transport .... existence of regions within the porous medium in which there is minimum advective flow. .... concentration at x = L. The initial and the exit boundary conditions can be .... rial was cleaned, washed and dried to ensure that the material free from ...

Investigation of the Klinkenberg effect in a micro/nanoporous medium by direct simulation Monte Carlo method

Science.gov (United States)

Yang, Guang; Weigand, Bernhard

2018-04-01

The pressure-driven gas transport characteristics through a porous medium consisting of arrays of discrete elements is investigated by using the direct simulation Monte Carlo (DSMC) method. Different porous structures are considered, accounting for both two- and three-dimensional arrangements of basic microscale and nanoscale elements. The pore scale flow patterns in the porous medium are obtained, and the Knudsen diffusion in the pores is studied in detail for slip and transition flow regimes. A new effective pore size of the porous medium is defined, which is a function of the porosity, the tortuosity, the contraction factor, and the intrinsic permeability of the porous medium. It is found that the Klinkenberg effect in different porous structures can be fully described by the Knudsen number characterized by the effective pore size. The accuracies of some widely used Klinkenberg correlations are evaluated by the present DSMC results. It is also found that the available correlations for apparent permeability, most of which are derived from simple pipe or channel flows, can still be applicative for more complex porous media flows, by using the effective pore size defined in this study.

Thermophysical properties of a fluid-saturated sandstone

International Nuclear Information System (INIS)

Abid, Muhammad; Hammerschmidt, Ulf; Koehler, Juergen

2014-01-01

Thermophysical properties of a fluid-saturated stone are presented that are obtained by using the transient hot-bridge technique (THB) at ambient conditions. Measurements are succeedingly done each after having filled the porous stone structure first with six different fluids of distinct thermal conductivities and next with six different gases also having different thermal conductivities. Variations in thermal conductivity, thermal diffusivity and volumetric specific heat due to liquid or gas saturations are discussed. Internal pore structure of the stone is studied by using Scanning Electron Microscopy (SEM), Mercury Intrusion Porosimetry (MIP) and other standardized density methods at ambient conditions. Effect of interstitial pore pressure on thermophysical properties are also discussed in the context of Knudsen effect. (authors)

Magnetic Resonance Imaging in degenerative disease of the lumbar spine: Fat Saturation technique and contrast medium.

Science.gov (United States)

D'Aprile, Paola; Nasuto, Michelangelo; Tarantino, Alfredo; Cornacchia, Samantha; Guglielmi, Giuseppe; Jinkins, J Randy

2018-01-19

To examine both anterior and posterior elements of the lumbar spine in patients with low back pain using MRI T2-weighted sequences with Fat Saturation (FS) and contrast enhanced T1-weighted sequences with FS. Two thousand eight hundred and twenty (2820) patients (1628 male, 1192 female, mean age 54) presenting low back pain underwent MRI standard examination (Sagittal T1w TSE and T2w TSE, axial T1 SE) with the addition of sagittal and axial T2w Fat Sat (FS) sequences. Among all the patients, 987 (35%) have been studied adding Contrast Enhanced (CE) T1w FS sequences after administration of contrast medium. Among 987 patients studied with contrast medium, we found: active-inflammatory intervertebral osteochondrosis in 646 (65%) patients; degenerative-inflammatory changes in facet joints (facet joint effusion, synovitis, synovial cysts) in 462 (47%); spondylolysis in 69 (7%); degenerative-inflammatory changes of the flava, interspinous and supraspinous ligaments in 245 (25%); inflammatory changes of posterior perispinal muscles in 84 (8%) patients. In patients with suspected no-disc-related low back pain, the implementation of T2w FS and CE T1w FS sequences to the standard MR protocol could allow a better identification of degenerative-inflammatory changes more likely associated to the pain.

A Three-Dimensional Model of Two-Phase Flows in a Porous Medium Accounting for Motion of the Liquid–Liquid Interface

DEFF Research Database (Denmark)

Shapiro, Alexander A.

2018-01-01

A new three-dimensional hydrodynamic model for unsteady two-phase flows in a porous medium, accounting for the motion of the interface between the flowing liquids, is developed. In a minimum number of interpretable geometrical assumptions, a complete system of macroscale flow equations is derived......, their expansion or contraction is also described, while rotation has been proven negligible. A detailed comparison with the previous studies for the two-phase flows accounting for propagation of the interface on micro- and macroscale has been carried out. A numerical algorithm has been developed allowing...

Hall effects on unsteady MHD reactive flow of second grade fluid through porous medium in a rotating parallel plate channel

Science.gov (United States)

Krishna, M. Veera; Swarnalathamma, B. V.

2017-07-01

We considered the transient MHD flow of a reactive second grade fluid through porous medium between two infinitely long horizontal parallel plates when one of the plate is set into uniform accelerated motion in the presence of a uniform transverse magnetic field under Arrhenius reaction rate. The governing equations are solved by Laplace transform technique. The effects of the pertinent parameters on the velocity, temperature are discussed in detail. The shear stress and Nusselt number at the plates are also obtained analytically and computationally discussed with reference to governing parameters.

Tritium transport in lithium ceramics porous media

International Nuclear Information System (INIS)

Tam, S.W.; Ambrose, V.

1991-01-01

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 relative contribution of diffusion and convective flow to tritium transport in porous lithium ceramics. 15 refs., 4 figs

Self-consistency of a heterogeneous continuum porous medium representation of a fractured medium

International Nuclear Information System (INIS)

Hoch, A.R.; Jackson, C.P.; Todman, S.

1998-01-01

For many of the rocks that are, or have been, under investigation as potential host rocks for a radioactive waste repository, groundwater flow is considered to take place predominantly through discontinuities such as fractures. Although models of networks of discrete features (DFN models) would be the most realistic models for such rocks, calculations on large length scales would not be computationally practicable. A possible approach would be to use heterogeneous continuum porous-medium (CPM) models in which each block has an effective permeability appropriate to represent the network of features within the block. In order to build confidence in this approach, it is necessary to demonstrate that the approach is self-consistent, in the sense that if the effective permeability on a large length scale is derived using the CPM model, the result is close to the value derived directly from the underlying network model. It is also desirable to demonstrate self-consistency for the use of stochastic heterogeneous CPM models that are built as follows. The correlation structure of the effective permeability on the scale of the blocks is inferred by analysis of the effective permeabilities obtained from the underlying DFN model. Then realizations of the effective permeability within the domain of interest are generated on the basis of the correlation structure, rather than being obtained directly from the underlying DFN model. A study of self-consistency is presented for two very different underlying DFN models: one based on the properties of the Borrowdale Volcanic Group at Sellafield, and one based on the properties of the granite at Aespoe in Sweden. It is shown that, in both cases, the use of heterogeneous CPM models based directly on the DFN model is self-consistent, provided that care is taken in the evaluation of the effective permeability for the DFN models. It is also shown that the use of stochastic heterogeneous CPM models based on the correlation structure of the

Equilibrium and transfer in porous media 2 transfer laws

CERN Document Server

Daïan, Jean-François

2014-01-01

A porous medium is composed of a solid matrix and its geometrical complement: the pore space. This pore space can be occupied by one or more fluids. The understanding of transport phenomena in porous media is a challenging intellectual task.  This book provides a detailed analysis of the aspects required for the understanding of many experimental techniques in the field of porous media transport phenomena. It is aimed at studentsor engineers who may not be looking specifically to become theoreticians in porous media, but wish to integrate knowledge of porous media with their previous scientif

Unexpected large room-temperature ferromagnetism in porous Cu{sub 2}O thin films

Energy Technology Data Exchange (ETDEWEB)

Hou, Xue [College of Physics Science & Information Engineering, Hebei Normal University, Shijiazhuang 050024 (China); Key Laboratory of Advanced Films of Hebei Province, Shijiazhuang 050024 (China); Sun, Huiyuan, E-mail: huiyuansun@126.com [College of Physics Science & Information Engineering, Hebei Normal University, Shijiazhuang 050024 (China); Key Laboratory of Advanced Films of Hebei Province, Shijiazhuang 050024 (China); Liu, Lihu; Jia, Xiaoxuan; Liu, Huiyuan [College of Physics Science & Information Engineering, Hebei Normal University, Shijiazhuang 050024 (China); Key Laboratory of Advanced Films of Hebei Province, Shijiazhuang 050024 (China)

2015-05-15

Porous Cu{sub 2}O films have been fabricated on porous anodic alumina substrates using DC-reactive magnetron sputtering with pure Cu targets, and unexpectedly large room temperature ferromagnetism has been observed in the films. The maximum saturation magnetic moment along the out-of-plane direction was as high as 94 emu/cm{sup 3}. Photoluminescence spectra show that the ferromagnetism originates with oxygen vacancies. The ferromagnetism could be adjusted by changing the concentration of oxygen vacancies through annealing in an oxygen atmosphere. These observations suggest that the origin of the ferromagnetism is due to coupling between oxygen vacancies with local magnetic moments in the porous Cu{sub 2}O films, which can occur either directly through exchange interactions between oxygen vacancies, or through the mediation of conduction electrons. Such a ferromagnet without the presence of any ferromagnetic dopant may find applications in spintronic devices. - Highlights: • Porous Cu{sub 2}O films were deposited on porous anodic alumina (PAA) substrates. • Significant room-temperature ferromagnetism has been observed in porous Cu{sub 2}O films. • Ferromagnetism of Cu{sub 2}O films exhibited different magnetic signals with the field. • The saturation magnetization is 94 emu/cm{sup 3} with an out-of-plane.

Seismic response analysis of the deep saturated soil deposits in Shanghai

Science.gov (United States)

Huang, Yu; Ye, Weimin; Chen, Zhuchang

2009-01-01

The quaternary deposits in Shanghai are horizontal soil layers of thickness up to about 280 m in the urban area with an annual groundwater table between 0.5 and 0.7 m from the surface. The characteristics of deep saturated deposits may have important influences upon seismic response of the ground in Shanghai. Based on the Biot theory for porous media, the water-saturated soil deposits are modeled as a two-phase porous system consisting of solid and fluid phases, in this paper. A nonlinear constitutive model for predicting the seismic response of the ground is developed to describe the dynamic characters of the deep-saturated soil deposits in Shanghai. Subsequently, the seismic response of a typical site with 280 m deep soil layers, which is subjected to four base excitations (El Centro, Taft, Sunan, and Tangshan earthquakes), is analyzed in terms of an effective stress-based finite element method with the proposed constitutive model. Special emphasis is given to the computed results of accelerations, excess pore-water pressures, and settlements during the seismic excitations. It has been found that the analysis can capture fundamental aspects of the ground response and produce preliminary results for seismic assessment.

Transport Modeling of Modified Magnetite Nanoparticles with Sodium Dodecyl Sulfate in a Saturated Sandy Soil

Directory of Open Access Journals (Sweden)

Ahmad Farrokhian Firouzi

2017-02-01

Full Text Available Introduction: Nanoparticles due to their large specific area and reactivity recently have been used in several environmental remediation applications such as degradation of organic compounds and pesticides and adsorption of heavy metals and inorganic anions. Because of concern over potential threats of nanoparticle releases into the soil–water environment, a number of studies have been carried out to investigate the transport, retention and deposition of nanoparticles in saturated porous media. Many of these studies are based on measurements of transport in columns packed with idealized porous media consisting of spherical glass beads or sand. The nanoparticles are usually introduced into the column and breakthrough curve concentrations are measured at the column outlet. To examine the effect of various parameters on the transport of nanoparticles in porous medium, for convenience, all the parameters considered the same in the experiments, and only one parameter in the experiments is changed and investigated. Materials and Methods: The objective of this research is quantitative study of modified magnetite nanoparticles transport in saturated sand-repacked columns. The modified magnetite nanoparticles with Sodium dodecyl sulfate were synthesized following the protocol described by Si et al. (2004. The experimental setup included a suspension reservoir, Teflon tubing, a HPLC pump, and a glass column (2.5 cm i.d. and 20 cm height. Therefore, breakthrough curves of modified magnetite nanoparticles with Sodium dodecyl sulfate and chloride were determined under saturated conditions and influence of nanoparticles concentration (0.1 and 0.5 g.L-1 and pore velocity (pressure head of 2 and 10 cm on nanoparticles transport were investigated. For each medium bed, the background solution were first pumped through the column in the up-flow mode to obtain a steady flow state. Then, a tracer test was conducted by introducing CaCl2 solution into the column

Understanding the evolution of channeling and fracturing in porous medium due to fluid flow.

Science.gov (United States)

Turkaya, Semih; Toussaint, Renaud; Kvalheim Eriksen, Fredrik; Daniel, Guillaume; Langliné, Olivier; Grude Flekkøy, Eirik; Jørgen Måløy, Knut

2017-04-01

Fluid induced brittle deformation of porous medium is a phenomenon commonly present in everyday life. From an espresso machine to volcanoes, from food industry to construction, it is possible to see traces of this phenomenon. In this work, analogue models are developed in a linear geometry, with confinement and at low porosity to study the instabilities that occur during fast motion of fluid in dense porous materials: fracturing, fingering, and channeling. We study these complex fluid/solid mechanical systems - in a rectangular Hele-Shaw cell with three closed boundaries and one semi-permeable boundary - using two monitoring techniques: optical imaging using a high speed camera (1000 fps), high frequency resolution accelerometers and piezoelectrical sensors. Additionally, we develop physical models rendering for the fluid mechanics in the channels and the propagation of microseismic waves around the fracture. We then compare a numerical resolution of this physical system with the observed experimental system. In the analysis phase, we compute the power spectrum of the acoustic signal in time windows of 5 ms, recorded by shock accelerometers Brüel & Kjaer 4374 (Frq. Range 1 Hz - 26 kHz) with 1 MHz sampling rate. The evolution of the power spectrum is compared with the optical recordings. These peaks on the spectrum are strongly influenced by the size and branching of the channels, compaction of the medium, vibration of air in the pores and the fundamental frequency of the plate. Furthermore, the number of these stick-slip events, similar to the data obtained in hydraulic fracturing operations, follows a Modified Omori Law decay with an exponent p value around 0.5. An analytical model of overpressure diffusion predicting p = 0.5 and two other free parameters of the Omori Law (prefactor and origin time) is developed. The spatial density of the seismic events, and the time of end of formation of the channels can also be predicted using this developed model. Different

Throughflow and non-uniform heating effects on double diffusive oscillatory convection in a porous medium

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Palle Kiran

2016-03-01

Full Text Available A weak nonlinear oscillatory mode of thermal instability is investigated while deriving a non autonomous complex Ginzburg–Landau equation. Darcy porous medium is considered in the presence of vertical throughflow and time periodic thermal boundaries. Only infinitesimal disturbances are considered. The disturbances in velocity, temperature and solutal fields are treated by a perturbation expansion in powers of amplitude of applied temperature field. The effect of throughflow has either to stabilize or to destabilize the system for stress free and isothermal boundary conditions. Nusselt and Sherwood numbers are obtained numerically and presented the results on heat and mass transfer. It is found that, throughflow and thermal modulation can be used alternatively to control the heat and mass transfer. Further, it is also found that oscillatory flow enhances the heat and mass transfer than stationary flow. Effect of modulation frequency and phase angle on mean Nusselt number is also discussed.

Evaluation of a combined drug-delivery system for proteins assembled with polymeric nanoparticles and porous microspheres; characterization and protein integrity studies.

Science.gov (United States)

Alcalá-Alcalá, Sergio; Benítez-Cardoza, Claudia G; Lima-Muñoz, Enrique J; Piñón-Segundo, Elizabeth; Quintanar-Guerrero, David

2015-07-15

This work presents an evaluation of the adsorption/infiltration process in relation to the loading of a model protein, α-amylase, into an assembled biodegradable polymeric system, free of organic solvents and made up of poly(D,L-lactide-co-glycolide) acid (PLGA). Systems were assembled in a friendly aqueous medium by adsorbing and infiltrating polymeric nanoparticles into porous microspheres. These assembled systems are able to load therapeutic amounts of the drug through adsorption of the protein onto the large surface area characteristic of polymeric nanoparticles. The subsequent infiltration of nanoparticles adsorbed with the protein into porous microspheres enabled the controlled release of the protein as a function of the amount of infiltrated nanoparticles, since the surface area available on the porous structure is saturated at different levels, thus modifying the protein release rate. Findings were confirmed by both the BET technique (N2 isotherms) and in vitro release studies. During the adsorption process, the pH of the medium plays an important role by creating an environment that favors adsorption between the surfaces of the micro- and nano-structures and the protein. Finally, assays of α-amylase activity using 2-chloro-4-nitrophenyl-α-D-maltotrioside (CNP-G3) as the substrate and the circular dichroism technique confirmed that when this new approach was used no conformational changes were observed in the protein after release. Copyright © 2015 Elsevier B.V. All rights reserved.

The Role of Surface Infiltration in Hydromechanical Coupling Effects in an Unsaturated Porous Medium of Semi-Infinite Extent

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L. Z. Wu

2017-01-01

Full Text Available Rainfall infiltration into an unsaturated region of the earth’s surface is a pervasive natural phenomenon. During the rainfall-induced seepage process, the soil skeleton can deform and the permeability can change with the water content in the unsaturated porous medium. A coupled water infiltration and deformation formulation is used to examine a problem related to the mechanics of a two-dimensional region of semi-infinite extent. The van Genuchten model is used to represent the soil-water characteristic curve. The model, incorporating coupled infiltration and deformation, was developed to resolve the coupled problem in a semi-infinite domain based on numerical methods. The numerical solution is verified by the analytical solution when the coupled effects in an unsaturated medium of semi-infinite extent are considered. The computational results show that a numerical procedure can be employed to examine the semi-infinite unsaturated seepage incorporating coupled water infiltration and deformation. The analysis indicates that the coupling effect is significantly influenced by the boundary conditions of the problem and varies with the duration of water infiltration.

Review of enhanced vapor diffusion in porous media

International Nuclear Information System (INIS)

Webb, S.W.; Ho, C.K.

1998-01-01

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

A cellular automaton simulation of contaminant transport in porous media

International Nuclear Information System (INIS)

Freed, D.M.; Simonson, S.A.

1995-01-01

A simulation tool to investigate radionuclide transport in porous groundwater flow is described. The flow systems of interest are those important in determining the fate of radionuclides emplaced in an underground repository, such as saturated matrix flow, matrix and fracture flow in the unsaturated zone, and viscous fingering in porous fractures. The work discussed here is confined to consideration of saturated flow in porous media carrying a dilute, sorptive species. The simulation technique is based on a special class of cellular automata known as lattice gas automata (LGA) which are capable of predicting hydrodynamic behavior. The original two-dimensional scheme (that of Frisch et. al. known as the FHP model) used particles of unit mass traveling on a triangular lattice with unit velocity and undergoing simple collisions which conserve mass and momentum at each node. These microscopic rules go over to the incompressible Navier-Stokes equations in the macroscopic limit. One of the strengths of this technique is the natural way that heterogeneities, such as boundaries, are accommodated. Complex geometries such as those associated with porous microstructures can be modeled effectively. Several constructions based on the FHP model have been devised, including techniques to eliminate statistical noise, extension to three dimensions, and the addition of surface tension which leads to multiphase flow

Opposing flow in square porous annulus: Influence of Dufour effect

International Nuclear Information System (INIS)

Athani, Abdulgaphur; Al-Rashed, Abdullah A. A. A.; Khaleed, H. M. T.

2016-01-01

Heat and mass transfer in porous medium is very important area of research which is also termed as double diffusive convection or thermo-solutal convection. The buoyancy ratio which is the ratio of thermal to concentration buoyancy can have negative values thus leading to opposing flow. This article is aimed to study the influence of Dufour effect on the opposing flow in a square porous annulus. The partial differential equations that govern the heat and mass transfer behavior inside porous medium are solved using finite element method. A three node triangular element is used to divide the porous domain into smaller elements. Results are presented with respect to geometric and physical parameters such as duct diameter ratio, Rayleigh number, radiation parameter etc. It is found that the heat transfer increase with increase in Rayleigh number and radiation parameter. It is observed that Dufour coefficient has more influence on velocity profile.

Opposing flow in square porous annulus: Influence of Dufour effect

Energy Technology Data Exchange (ETDEWEB)

Athani, Abdulgaphur, E-mail: abbu.bec@gmail.com [Dept. of Mechanical Engineering, Anjuman Institute of Technology & Management, Bhatkal (India); Al-Rashed, Abdullah A. A. A., E-mail: aa.alrashed@paaet.edu.kw [Dept. of Automotive and Marine Engineering Technology, College of Technological Studies, The Public Authority for Applied Education and Training (Kuwait); Khaleed, H. M. T., E-mail: khalid-tan@yahoo.com [Dept of Mechanical Engineering, Faculty of Engineering, Islamic University, Madinah Munawwarra (Saudi Arabia)

2016-06-21

Heat and mass transfer in porous medium is very important area of research which is also termed as double diffusive convection or thermo-solutal convection. The buoyancy ratio which is the ratio of thermal to concentration buoyancy can have negative values thus leading to opposing flow. This article is aimed to study the influence of Dufour effect on the opposing flow in a square porous annulus. The partial differential equations that govern the heat and mass transfer behavior inside porous medium are solved using finite element method. A three node triangular element is used to divide the porous domain into smaller elements. Results are presented with respect to geometric and physical parameters such as duct diameter ratio, Rayleigh number, radiation parameter etc. It is found that the heat transfer increase with increase in Rayleigh number and radiation parameter. It is observed that Dufour coefficient has more influence on velocity profile.

Methane accumulation and forming high saturations of methane hydrate in sandy sediments

Energy Technology Data Exchange (ETDEWEB)

Uchida, T.; Waseda, A. [JAPEX Research Center, Chiba (Japan); Fujii, T. [Japan Oil, Gas and Metals National Corp., Chiba (Japan). Upstream Technology Unit

2008-07-01

Methane supplies for marine gas hydrates are commonly attributed to the microbial conversion of organic materials. This study hypothesized that methane supplies were related to pore water flow behaviours and microscopic migration in intergranular pore systems. Sedimentology and geochemistry analyses were performed on sandy core samples taken from the Nankai trough and the Mallik gas hydrate test site in the Mackenzie Delta. The aim of the study was to determine the influence of geologic and sedimentolic controls on the formation and preservation of natural gas hydrates. Grain size distribution curves indicated that gas hydrate saturations of up to 80 per cent in pore volume occurred throughout the hydrate-dominant sand layers in the Nankai trough and Mallik areas. Water permeability measurements showed that the highly gas hydrate-saturated sands have a permeability of a few millidarcies. Pore-space gas hydrates occurred primarily in fine and medium-grained sands. Core temperature depression, core observations, and laboratory analyses of the hydrates confirmed the pore-spaces as intergranular pore fillings. Results of the study suggested that concentrations of gas hydrates may require a pore space large enough to occur within a host sediments, and that the distribution of porous and coarser-grained sandy sediments is an important factor in controlling the occurrence of gas hydrates. 11 refs., 4 figs.

Osmosis, filtration and fracture of porous media

International Nuclear Information System (INIS)

Suarez Antola, R.

2001-01-01

Filtration was produced in a small scale physical model of a granular porous medium of cylindrical shape.The same volume flow was obtained either applying a difference in hydrostatic pressure or in osmotic pressure.In the first case a process of sustained erosion ending in an hydraulic short circuit was observed,while in the second case the material remained stable.This paradoxical strength behaviour is explained using some results from differential geometry,classical field theory and thermo-kinetic theory.The fracture process of a continuous matrix in a porous medium under the combined effect of filtration and external mechanical loads in then considered.The obtained results can be applied to the textural and compressive strength of wet concrete

MHD flow of a micropolar fluid over a stretchable disk in a porous medium with heat and mass transfer

Directory of Open Access Journals (Sweden)

A. Rauf

2015-07-01

Full Text Available This article studies the simultaneous impacts of heat and mass transfer of an incompressible electrically conducting micropolar fluid generated by the stretchable disk in presence of porous medium. The thermal radiation effect is accounted via Rosseland’s approximation. The governing boundary layer equations are reduced into dimensionless form by employing the suitable similarity transformations. A finite difference base algorithm is utilized to obtain the solution expressions. The impacts of physical parameters on dimensionless axial velocity, radial velocity, micro-rotation, temperature and concentrations profiles are presented and examined carefully. Numerical computation is performed to compute shear stress, couple stress, heat and mass rate at the disk.

MHD flow of a micropolar fluid over a stretchable disk in a porous medium with heat and mass transfer

Energy Technology Data Exchange (ETDEWEB)

Rauf, A., E-mail: raufamar@ciitsahiwal.edu.pk; Meraj, M. A. [Department of Mathematics, CIIT Sahiwal 57000 (Pakistan); Ashraf, M.; Batool, K. [Department of CASPAM, Bahauddin Zakariya University, Multan 63000 (Pakistan); Hussain, M. [Department of Sciences & Humanities, National University of computer & Emerging Sciences, Islamabad 44000 (Pakistan)

2015-07-15

This article studies the simultaneous impacts of heat and mass transfer of an incompressible electrically conducting micropolar fluid generated by the stretchable disk in presence of porous medium. The thermal radiation effect is accounted via Rosseland’s approximation. The governing boundary layer equations are reduced into dimensionless form by employing the suitable similarity transformations. A finite difference base algorithm is utilized to obtain the solution expressions. The impacts of physical parameters on dimensionless axial velocity, radial velocity, micro-rotation, temperature and concentrations profiles are presented and examined carefully. Numerical computation is performed to compute shear stress, couple stress, heat and mass rate at the disk.

Effect of Carreau-Yasuda rheological parameters on subcritical Lapwood convection in horizontal porous cavity saturated by shear-thinning fluid

Science.gov (United States)

Khechiba, Khaled; Mamou, Mahmoud; Hachemi, Madjid; Delenda, Nassim; Rebhi, Redha

2017-06-01

The present study is focused on Lapwood convection in isotropic porous media saturated with non-Newtonian shear thinning fluid. The non-Newtonian rheological behavior of the fluid is modeled using the general viscosity model of Carreau-Yasuda. The convection configuration consists of a shallow porous cavity with a finite aspect ratio and subject to a vertical constant heat flux, whereas the vertical walls are maintained impermeable and adiabatic. An approximate analytical solution is developed on the basis of the parallel flow assumption, and numerical solutions are obtained by solving the full governing equations. The Darcy model with the Boussinesq approximation and energy transport equations are solved numerically using a finite difference method. The results are obtained in terms of the Nusselt number and the flow fields as functions of the governing parameters. A good agreement is obtained between the analytical approximation and the numerical solution of the full governing equations. The effects of the rheological parameters of the Carreau-Yasuda fluid and Rayleigh number on the onset of subcritical convection thresholds are demonstrated. Regardless of the aspect ratio of the enclosure and thermal boundary condition type, the subcritical convective flows are seen to occur below the onset of stationary convection. Correlations are proposed to estimate the subcritical Rayleigh number for the onset of finite amplitude convection as a function of the fluid rheological parameters. Linear stability of the convective motion, predicted by the parallel flow approximation, is studied, and the onset of Hopf bifurcation, from steady convective flow to oscillatory behavior, is found to depend strongly on the rheological parameters. In general, Hopf bifurcation is triggered earlier as the fluid becomes more and more shear-thinning.

Method for obtaining silver nanoparticle concentrations within a porous medium via synchrotron X-ray computed microtomography.

Science.gov (United States)

Molnar, Ian L; Willson, Clinton S; O'Carroll, Denis M; Rivers, Mark L; Gerhard, Jason I

2014-01-21

Attempts at understanding nanoparticle fate and transport in the subsurface environment are currently hindered by an inability to quantify nanoparticle behavior at the pore scale (within and between pores) within realistic pore networks. This paper is the first to present a method for high resolution quantification of silver nanoparticle (nAg) concentrations within porous media under controlled experimental conditions. This method makes it possible to extract silver nanoparticle concentrations within individual pores in static and quasi-dynamic (i.e., transport) systems. Quantification is achieved by employing absorption-edge synchrotron X-ray computed microtomography (SXCMT) and an extension of the Beer-Lambert law. Three-dimensional maps of X-ray mass linear attenuation are converted to SXCMT-determined nAg concentration and are found to closely match the concentrations determined by ICP analysis. In addition, factors affecting the quality of the SXCMT-determined results are investigated: 1) The acquisition of an additional above-edge data set reduced the standard deviation of SXCMT-determined concentrations; 2) X-ray refraction at the grain/water interface artificially depresses the SXCMT-determined concentrations within 18.1 μm of a grain surface; 3) By treating the approximately 20 × 10(6) voxels within each data set statistically (i.e., averaging), a high level of confidence in the SXCMT-determined mean concentrations can be obtained. This novel method provides the means to examine a wide range of properties related to nanoparticle transport in controlled laboratory porous medium experiments.

Study of numerical schemes for two-phase flow in porous media for any meshes: application to storage of nuclear waste

International Nuclear Information System (INIS)

Angelini, O.

2010-01-01

The two-phase flow in porous media is a complex phenomenon and which relate to many industrial problems. EDF works on the feasibility and the safety of a storage in deep geologic layer of nuclear waste. In this domain the simulation of the two-phase flow in porous media is particularly important in at least three domains: first of all during the phase of ventilation of the galleries of the storage which could de-saturate the rock and so modify its properties, but also during the phase of re-saturation of the materials and finally during the arrival of the water on the metal parts contained in the storage which will then involve phenomena of corrosion and a hydrogen release. In this context, EDF wishes to obtain robust numerical methods without restrictive condition on the mesh. This work is dedicated at first to the development of the finite volume scheme SUSHI (Scheme Using Stabilization and Hybrid Interfaces) in the code of mechanics of EDF, Code Aster in order to simulate the two-phase flow in porous media. This scheme was developed in 2D and in 3D. At the same time a new formulation which allows to simulate in a uniform way the flows in saturated and unsaturated porous media for miscible and immiscible problems is proposed. Various studies simulating difficulties related to the problems of the storage of nuclear waste in deep geological layers were study. We can quote the study of a bi-material which advances the capillary re-balancing of a material by an other one possessing properties and initial very heterogeneous conditions in saturation. We will also quote the study of the injection of hydrogen in an porous media initially saturated in pure water which is proposed by the benchmark 'two-phase Flow' proposed by the GNR MOMAS. This study had for objective to bring to light the good treatment of the appearance of a phase in a saturated porous media and thus the relevance of our new formulation to study with a way unified a problem of saturated flow and a

Multiphase flow simulation with gravity effect in anisotropic porous media using multipoint flux approximation

KAUST Repository

Negara, Ardiansyah; Salama, Amgad; Sun, Shuyu

2015-01-01

Numerical investigations of two-phase flows in anisotropic porous media have been conducted. In the flow model, the permeability has been considered as a full tensor and is implemented in the numerical scheme using the multipoint flux approximation within the framework of finite difference method. In addition, the experimenting pressure field approach is used to obtain the solution of the pressure field, which makes the matrix of coefficient of the global system easily constructed. A number of numerical experiments on the flow of two-phase system in two-dimensional porous medium domain are presented. In this work, the gravity is included in the model to capture the possible buoyancy-driven effects due to density differences between the two phases. Different anisotropy scenarios have been considered. From the numerical results, interesting patterns of the flow, pressure, and saturation fields emerge, which are significantly influenced by the anisotropy of the absolute permeability field. It is found that the two-phase system moves along the principal direction of anisotropy. Furthermore, the effects of anisotropy orientation on the flow rates and the cross flow index are also discussed in the paper.

Multiphase flow simulation with gravity effect in anisotropic porous media using multipoint flux approximation

KAUST Repository

Negara, Ardiansyah

2015-03-04

Numerical investigations of two-phase flows in anisotropic porous media have been conducted. In the flow model, the permeability has been considered as a full tensor and is implemented in the numerical scheme using the multipoint flux approximation within the framework of finite difference method. In addition, the experimenting pressure field approach is used to obtain the solution of the pressure field, which makes the matrix of coefficient of the global system easily constructed. A number of numerical experiments on the flow of two-phase system in two-dimensional porous medium domain are presented. In this work, the gravity is included in the model to capture the possible buoyancy-driven effects due to density differences between the two phases. Different anisotropy scenarios have been considered. From the numerical results, interesting patterns of the flow, pressure, and saturation fields emerge, which are significantly influenced by the anisotropy of the absolute permeability field. It is found that the two-phase system moves along the principal direction of anisotropy. Furthermore, the effects of anisotropy orientation on the flow rates and the cross flow index are also discussed in the paper.

Lattice Boltzmann simulation for temperature-sensitive magnetic fluids in a porous square cavity

International Nuclear Information System (INIS)

Jin Licong; Zhang Xinrong; Niu Xiaodong

2012-01-01

A lattice Boltzmann method is developed to simulate temperature-sensitive magnetic fluids in a porous cavity. In the simulation, the magnetic force, efficient gravity, viscous loss term and geometric loss term in porous medium are imported to the momentum equation. To test the reliability of the method, a validation with water in porous cavity is carried out. Good agreements with the previous results verify that the present lattice Boltzmann method is promising for simulation of magnetic fluids in porous medium. In this study, we investigate the change of magnetization with external magnetic field, and we present numerical results for the streamlines, isotherms, and magnetization at vertical or horizontal mid-profiles for different values of Ram. In addition, Nusselt numbers changing with magnetic Rayleigh numbers are also investigated. - Highlights: → Developed a lattice Boltzmann method for magnetic nano-fluids in porous cavity. → Clarified flow and heat transfer for different values of (magnetic) Rayleigh numbers. → Heat transfer enhancement for magnetic fluid in porous cavity.

Heat and mass transfer on a MHD third grade fluid with partial slip flow past an infinite vertical insulated porous plate in a porous medium

International Nuclear Information System (INIS)

Baoku, I.G.; Olajuwon, B.I.; Mustapha, A.O.

2013-01-01

Highlights: ► We model the flow of a MHD third grade fluid, heat and mass transfer in a porous medium with partial slip flow regime. ► We examine the effects of pertinent parameters on the velocity, temperature and species concentration distributions. ► The values momentum and thermal boundary layers increase with increasing third grade parameter β. ► The consequences of increasing the permeability parameter m and partial slip parameter λ give rise to fluid velocity. ► The magnetic field parameter H decreases the momentum boundary layer and increases the concentration boundary layer. -- Abstract: The influence of third grade, partial slip and other thermophysical parameters on the steady flow, heat and mass transfer of viscoelastic third grade fluid past an infinite vertical insulated plate subject to suction across the boundary layer has been investigated. The space occupying the fluid is porous. The momentum equation is characterized by a highly nonlinear boundary value problem in which the order of the differential equation exceeds the number of available boundary conditions. An efficient numerical scheme of midpoint technique with Richardson’s extrapolation is employed to solve the governing system of coupled nonlinear equations of momentum, energy and concentration. Numerical calculations were carried out for different values of various interesting non-dimensional quantities in the slip flow regime with heat and mass transfer and were shown with the aid of figures. The values of the wall shear stress, the local rate of heat and mass transfers were obtained and tabulated. The analysis shows that as the fluid becomes more shear thickening, the momentum boundary layer decreases but the thermal boundary layer increases; the magnetic field strength is found to decrease with an increasing temperature distribution when the porous plate is insulated. The consequences of increasing the permeability parameter and Schmidt number decrease both the momentum

A linear analytical study of Soret-driven ferrothermohaline convection in an anisotropic porous medium

International Nuclear Information System (INIS)

Sekar, R.; Raju, K.; Vasanthakumari, R.

2013-01-01

The Soret-driven ferrothermoconvective instability of multi- component fluid in an anisotropic porous medium heated from below and salted from above has been analyzed using Brinkman model for various values of anisotropic parameter. The salinity effect is contained in magnetization and density of the ferrofluid and the system is assumed to have anisotropy in the vertical direction and isotropy in the horizontal direction. A small perturbation imparted on the basic state and a linear stability analysis is used for this model for which the normal mode technique is applied. The present analysis has been carried out through both stationary as well as oscillatory modes. The vertical anisotropy tends to destabilize the system. -- Highlights: ► We examine the effect of anisotropy and magnetization of convection in Soret effect. ► The system loses its stability for critical Rayleigh number for various parameters like R s and K 1 . ► The larger temperature difference is needed to guarantee the occurring of convection. ► The Soret effect plays a dominant role for the stability of the system

Response of skirted suction caissons to monotonic lateral loading in saturated medium sand

Science.gov (United States)

Li, Da-yong; Zhang, Yu-kun; Feng, Ling-yun; Guo, Yan-xue

2014-08-01

Monotonic lateral load model tests were carried out on steel skirted suction caissons embedded in the saturated medium sand to study the bearing capacity. A three-dimensional continuum finite element model was developed with Z_SOIL software. The numerical model was calibrated against experimental results. Soil deformation and earth pressures on skirted caissons were investigated by using the finite element model to extend the model tests. It shows that the "skirted" structure can significantly increase the lateral capacity and limit the deflection, especially suitable for offshore wind turbines, compared with regular suction caissons without the "skirted" at the same load level. In addition, appropriate determination of rotation centers plays a crucial role in calculating the lateral capacity by using the analytical method. It was also found that the rotation center is related to dimensions of skirted suction caissons and loading process, i.e. the rotation center moves upwards with the increase of the "skirted" width and length; moreover, the rotation center moves downwards with the increase of loading and keeps constant when all the sand along the caisson's wall yields. It is so complex that we cannot simply determine its position like the regular suction caisson commonly with a specified position to the length ratio of the caisson.

Transport and Retention of Carboxymethylcellulose-Modified Carbon Nanotube-Magnetite Nanohybrids in Water-Saturated Porous Media

Science.gov (United States)

Wang, D.; Su, C.

2017-12-01

Carbon-metal oxide nanohybrids (NHs) are increasingly recognized as the next-generation, promising group of nanomaterials for solving emerging environmental issues and challenges. This research, for the first time, systematically explored the transport and retention of the multifunctional carbon nanotube-magnetite (CNT-Fe3O4) NHs in water-saturated porous media under environmentally relevant physicochemical conditions. An environment-benign macromolecule, carboxymethylcellulose (CMC), was employed to stabilize the NHs. Classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory and colloid transport model were used to describe the transport and retention of the NHs. Our results showed that transport of the magnetic CNT-Fe3O4 NHs was lower than that of the parent CNT due to greater aggregation (induced by magnetic attraction) during transport. The DLVO theory well-interpreted the NHs' transport; and secondary minimum played dominant roles in NHs' retention. A novel transport feature, an initial low and following sharp peaks occurred frequently in the NHs' breakthrough curves; and the magnitude and location of both transport peaks varied with different experimental conditions due to the interplay between variability of the fluid viscosity and aggregation-dispersion nature of the NHs. Very promisingly, the estimated maximum transport distance of NHs using the Tufenkji-Elimelech equation ranged between 0.38-46 m, supporting the feasibility of employing the magnetically recyclable CNT-Fe3O4 NHs for in-situ nanoremediation of contaminated soils, sediment aquifers, and groundwater.

Analytical method for steady state heat transfer in two-dimensional porous media

Energy Technology Data Exchange (ETDEWEB)

Siegal, R.; Goldstein, M.E.

1970-07-01

A general technique has been devised for obtaining exact solutions for the heat transfer behavior of a 2- dimensional porous cooled medium. Fluid flows through the porous medium from a reservoir at constant pressure and temperature to a second reservoir at a lower pressure. For the type of flow involved, the surfaces of the porous region that are each at constant pressure are boundaries of constant velocity potential. This fact is used to map the porous region into a strip bounded by parallel potential lines in a complex potential plane. The energy equation, derived by assuming the local matrix and fluid temperatures are equal, is transformed into a separable equation when its independent variables are changed to the coordinates of the potential plane. This allows the general solution for the temperature distribution to be found in the potential plane. The solution is then mapped into the physical plane to yield the heat transfer characteristics of the porous region. An example problem of a porous wall having a step in thickness and a specified surface temperature or heat flux is worked out in detail.

Subsurface Transport Over Reactive Multiphases (STORM): A general, coupled, nonisothermal multiphase flow, reactive transport, and porous medium alteration simulator, Version 2 user's guide

International Nuclear Information System (INIS)

Bacon, D.H.; White, M.D.; McGrail, B.P.

2000-01-01

The Hanford Site, in southeastern Washington State, has been used extensively to produce nuclear materials for the US strategic defense arsenal by the Department of Energy (DOE) and its predecessors, the US Atomic Energy Commission and the US Energy Research and Development Administration. A large inventory of radioactive and mixed waste has accumulated in 177 buried single- and double shell tanks. Liquid waste recovered from the tanks will be pretreated to separate the low-activity fraction from the high-level and transuranic wastes. Vitrification is the leading option for immobilization of these wastes, expected to produce approximately 550,000 metric tons of Low Activity Waste (LAW) glass. This total tonnage, based on nominal Na 2 O oxide loading of 20% by weight, is destined for disposal in a near-surface facility. Before disposal of the immobilized waste can proceed, the DOE must approve a performance assessment, a document that described the impacts, if any, of the disposal facility on public health and environmental resources. Studies have shown that release rates of radionuclides from the glass waste form by reaction with water determine the impacts of the disposal action more than any other independent parameter. This report describes the latest accomplishments in the development of a computational tool, Subsurface Transport Over Reactive Multiphases (STORM), Version 2, a general, coupled non-isothermal multiphase flow and reactive transport simulator. The underlying mathematics in STORM describe the rate of change of the solute concentrations of pore water in a variably saturated, non-isothermal porous medium, and the alteration of waste forms, packaging materials, backfill, and host rocks

Accumulation of medium-chain, saturated fatty acyl moieties in seed oils of transgenic Camelina sativa.

Directory of Open Access Journals (Sweden)

Zhaohui Hu

Full Text Available With its high seed oil content, the mustard family plant Camelina sativa has gained attention as a potential biofuel source. As a bioenergy crop, camelina has many advantages. It grows on marginal land with low demand for water and fertilizer, has a relatively short life cycle, and is stress tolerant. As most other crop seed oils, camelina seed triacylglycerols (TAGs consist of mostly long, unsaturated fatty acyl moieties, which is not desirable for biofuel processing. In our efforts to produce shorter, saturated chain fatty acyl moieties in camelina seed oil for conversion to jet fuel, a 12:0-acyl-carrier thioesterase gene, UcFATB1, from California bay (Umbellularia californica Nutt. was expressed in camelina seeds. Up to 40% of short chain laurate (C12:0 and myristate (C14:0 were present in TAGs of the seed oil of the transgenics. The total oil content and germination rate of the transgenic seeds were not affected. Analysis of positions of these two fatty acyl moieties in TAGs indicated that they were present at the sn-1 and sn-3 positions, but not sn-2, on the TAGs. Suppression of the camelina KASII genes by RNAi constructs led to higher accumulation of palmitate (C16:0, from 7.5% up to 28.5%, and further reduction of longer, unsaturated fatty acids in seed TAGs. Co-transformation of camelina with both constructs resulted in enhanced accumulation of all three medium-chain, saturated fatty acids in camelina seed oils. Our results show that a California bay gene can be successfully used to modify the oil composition in camelina seed and present a new biological alternative for jet fuel production.

Experimental validation of a numerical model of two-phase displacement in porous medium

International Nuclear Information System (INIS)

Genty, A.

1996-01-01

Burial in geological layers appears to be an interesting solution to dispose of radioactive wastes. This thesis analyzes and simulates the behaviour of gas produced by waste barrels corrosion. The released contaminated gas drains the water initially present in the host rock and yields a water-gas two phase flow. A literature survey of two phase flow shows that fluid interfaces may display instabilities for definite flow characteristics. When the displacement is stable a smooth interface proceeds through the porous medium. When the interface shows fingering, the displacement is said to be 'viscous-unstable', and when the front is jagged the displacement is called 'capillary' displacement. A dimensional analysis of classical equations governing two phase flow in porous media is combined with a classification of dominant forces to define an original map of flow regimes that includes gravitational forces. The map is based on three dimensionless numbers and predicts a priori the flow type. For typical data describing a radioactive waste repository a 'viscous-unstable' displacement is predicted by the map. We simulate water-gas displacement with a numerical model previously developed; this code, based on the Muskat model, uses the mixed-hybrid finite elements technique and is therefore well adapted for tracking moving interfaces. Fluxes are well conserved, however instabilities cannot be simulated. We assume that there is always a scale to be found where instabilities can be averaged and we try to validate the model with experimental two phase flows. We performed laboratory water-gas flow experiments for a variety of flow conditions. The observed displacement types are consistent with the map of flow regimes. Good agreement with numerical simulations is obtained when precise parameters of the displacements are available, in particular relative permeability curves. We conclude that our model allows a first approach of migration of gas near a radioactive waste repository

Ensemble distribution for immiscible two-phase flow in porous media.

Science.gov (United States)

Savani, Isha; Bedeaux, Dick; Kjelstrup, Signe; Vassvik, Morten; Sinha, Santanu; Hansen, Alex

2017-02-01

We construct an ensemble distribution to describe steady immiscible two-phase flow of two incompressible fluids in a porous medium. The system is found to be ergodic. The distribution is used to compute macroscopic flow parameters. In particular, we find an expression for the overall mobility of the system from the ensemble distribution. The entropy production at the scale of the porous medium is shown to give the expected product of the average flow and its driving force, obtained from a black-box description. We test numerically some of the central theoretical results.

Numerical Modelling Of Humid Air Flow Around A Porous Body

Directory of Open Access Journals (Sweden)

Bohojło-Wiśniewska Aneta

2015-09-01

Full Text Available This paper presents an example of humid air flow around a single head of Chinese cabbage under conditions of complex heat transfer. This kind of numerical simulation allows us to create a heat and humidity transfer model between the Chinese cabbage and the flowing humid air. The calculations utilize the heat transfer model in porous medium, which includes the temperature difference between the solid (vegetable tissue and fluid (air phases of the porous medium. Modelling and calculations were performed in ANSYS Fluent 14.5 software.

Enhanced CAH dechlorination in a low permeability, variably-saturated medium

Science.gov (United States)

Martin, J.P.; Sorenson, K.S.; Peterson, L.N.; Brennan, R.A.; Werth, C.J.; Sanford, R.A.; Bures, G.H.; Taylor, C.J.; ,

2002-01-01

An innovative pilot-scale field test was performed to enhance the anaerobic reductive dechlorination (ARD) of chlorinated aliphatic hydrocarbons (CAHs) in a low permeability, variably-saturated formation. The selected technology combines the use of a hydraulic fracturing (fracking) technique with enhanced bioremediation through the creation of highly-permeable sand- and electron donor-filled fractures in the low permeability matrix. Chitin was selected as the electron donor because of its unique properties as a polymeric organic material and based on the results of lab studies that indicated its ability to support ARD. The distribution and impact of chitin- and sand-filled fractures to the system was evaluated using hydrologic, geophysical, and geochemical parameters. The results indicate that, where distributed, chitin favorably impacted redox conditions and supported enhanced ARD of CAHs. These results indicate that this technology may be a viable and cost-effective approach for remediation of low-permeability, variably saturated systems.

Nuclear magnetic resonance characterization of the stationary dynamics of partially saturated media during steady-state infiltration flow

Science.gov (United States)

Rassi, Erik M.; Codd, Sarah L.; Seymour, Joseph D.

2011-01-01

Flow in porous media and the resultant hydrodynamics are important in fields including but not limited to the hydrology, chemical, medical and petroleum industries. The observation and understanding of the hydrodynamics in porous media are critical to the design and optimal utilization of porous media, such as those seen in trickle-bed reactors, medical filters, subsurface flows and carbon sequestration. Magnetic resonance (MR) provides for a non-invasive technique that can probe the hydrodynamics on pore and bulk scale lengths; many previous works have characterized fully saturated porous media, while rapid MR imaging (MRI) methods in particular have previously been applied to partially saturated flows. We present time- and ensemble-averaged MR measurements to observe the effects on a bead pack partially saturated with air under flowing water conditions. The 10 mm internal diameter bead pack was filled with 100 μm borosilicate glass beads. Air was injected into the bead pack as water flowed simultaneously through the sample at 25 ml h-1. The initial partially saturated state was characterized with MRI density maps, free induction decay (FID) experiments, propagators and velocity maps before the water flow rate was increased incrementally from 25 to 500 ml h-1. After the maximum flow rate of 500 ml h-1, the MRI density maps, FID experiments, propagators and velocity maps were repeated and compared to the data taken before the maximum flow rate. This work shows that a partially saturated single-phase flow has global flow dynamics that return to characteristic flow statistics once a steady-state high flow rate has been reached. This high flow rate pushed out a significant amount of the air in the bead pack and caused the return of a preferential flow pattern. Velocity maps indicated that local flow statistics were not the same for the before and after blow out conditions. It has been suggested and shown previously that a flow pattern can return to

Nuclear magnetic resonance characterization of the stationary dynamics of partially saturated media during steady-state infiltration flow

International Nuclear Information System (INIS)

Rassi, Erik M; Codd, Sarah L; Seymour, Joseph D

2011-01-01

Flow in porous media and the resultant hydrodynamics are important in fields including but not limited to the hydrology, chemical, medical and petroleum industries. The observation and understanding of the hydrodynamics in porous media are critical to the design and optimal utilization of porous media, such as those seen in trickle-bed reactors, medical filters, subsurface flows and carbon sequestration. Magnetic resonance (MR) provides for a non-invasive technique that can probe the hydrodynamics on pore and bulk scale lengths; many previous works have characterized fully saturated porous media, while rapid MR imaging (MRI) methods in particular have previously been applied to partially saturated flows. We present time- and ensemble-averaged MR measurements to observe the effects on a bead pack partially saturated with air under flowing water conditions. The 10 mm internal diameter bead pack was filled with 100 μm borosilicate glass beads. Air was injected into the bead pack as water flowed simultaneously through the sample at 25 ml h -1 . The initial partially saturated state was characterized with MRI density maps, free induction decay (FID) experiments, propagators and velocity maps before the water flow rate was increased incrementally from 25 to 500 ml h -1 . After the maximum flow rate of 500 ml h -1 , the MRI density maps, FID experiments, propagators and velocity maps were repeated and compared to the data taken before the maximum flow rate. This work shows that a partially saturated single-phase flow has global flow dynamics that return to characteristic flow statistics once a steady-state high flow rate has been reached. This high flow rate pushed out a significant amount of the air in the bead pack and caused the return of a preferential flow pattern. Velocity maps indicated that local flow statistics were not the same for the before and after blow out conditions. It has been suggested and shown previously that a flow pattern can return to similar

Micro-poromechanics model of fluid-saturated chemically active fibrous media.

Science.gov (United States)

Misra, Anil; Parthasarathy, Ranganathan; Singh, Viraj; Spencer, Paulette

2015-02-01

We have developed a micromechanics based model for chemically active saturated fibrous media that incorporates fiber network microstructure, chemical potential driven fluid flow, and micro-poromechanics. The stress-strain relationship of the dry fibrous media is first obtained by considering the fiber behavior. The constitutive relationships applicable to saturated media are then derived in the poromechanics framework using Hill's volume averaging. The advantage of this approach is that the resultant continuum model accounts for the discrete nature of the individual fibers while retaining a form suitable for porous materials. As a result, the model is able to predict the influence of micro-scale phenomena, such as the fiber pre-strain caused by osmotic effects and evolution of fiber network structure with loading, on the overall behavior and in particular, on the poromechanics parameters. Additionally, the model can describe fluid-flow related rate-dependent behavior under confined and unconfined conditions and varying chemical environments. The significance of the approach is demonstrated by simulating unconfined drained monotonic uniaxial compression under different surrounding fluid bath molarity, and fluid-flow related creep and relaxation at different loading-levels and different surrounding fluid bath molarity. The model predictions conform to the experimental observations for saturated soft fibrous materials. The method can potentially be extended to other porous materials such as bone, clays, foams and concrete.

Evaporation Limited Radial Capillary Penetration in Porous Media.

Science.gov (United States)

Liu, Mingchao; Wu, Jian; Gan, Yixiang; Hanaor, Dorian A H; Chen, C Q

2016-09-27

The capillary penetration of fluids in thin porous layers is of fundamental interest in nature and various industrial applications. When capillary flows occur in porous media, the extent of penetration is known to increase with the square root of time following the Lucas-Washburn law. In practice, volatile liquid evaporates at the surface of porous media, which restricts penetration to a limited region. In this work, on the basis of Darcy's law and mass conservation, a general theoretical model is developed for the evaporation-limited radial capillary penetration in porous media. The presented model predicts that evaporation decreases the rate of fluid penetration and limits it to a critical radius. Furthermore, we construct a unified phase diagram that describes the limited penetration in an annular porous medium, in which the boundaries of outward and inward liquid are predicted quantitatively. It is expected that the proposed theoretical model will advance the understanding of penetration dynamics in porous media and facilitate the design of engineered porous architectures.

Fully-developed conjugate heat transfer in porous media with uniform heating

NARCIS (Netherlands)

Lopez Penha, D.J.; Stolz, S.; Kuerten, Johannes G.M.; Nordlund, M.; Kuczaj, Arkadiusz K.; Geurts, Bernardus J.

2012-01-01

We propose a computational method for approximating the heat transfer coefficient of fully-developed flow in porous media. For a representative elementary volume of the porous medium we develop a transport model subject to periodic boundary conditions that describes incompressible fluid flow through

Effect of thermal radiation and Hall current on heat and mass transfer of unsteady MHD flow of a viscoelastic micropolar fluid through a porous medium

Directory of Open Access Journals (Sweden)

B.I. Olajuwon

2014-12-01

Full Text Available Heat and mass transfer effects on unsteady flow of a viscoelastic micropolar fluid over an infinite moving permeable plate in a saturated porous medium in the presence of a transverse magnetic field with Hall effect and thermal radiation are studied. The governing system of partial differential equations is transformed to dimensionless equations using dimensionless variables. The dimensionless equations are then solved analytically using perturbation technique to obtain the expressions for velocity, microrotation, temperature and concentration. With the help of graphs, the effects of magnetic field parameter M, thermal radiation parameter Nr, Hall current parameter m, K, viscoelastic parameter a, and slip parameter h on the velocity, microrotation, temperature and concentration fields within the boundary layer are discussed. The result showed that increase in Nr and m increases translational velocity across the boundary layer while (a decreases translational velocity in the vicinity of the plate but the reverse happens when away from the plate. As h increases the translational velocity across the boundary layer increases. The higher the values of Nr, the higher the micro-rotational velocity effect while m lowers it. Also the effects n, a, m, Nr, Pr and Sc on the skin friction coefficient, Nusselt number and Sherwood numbers are presented numerically in tabular form. The result also revealed that increase in n reduces the skin friction coefficient. Pr enhances the rate of heat transfer while Sc enhances the rate of mass transfer.

Unsteady free surface flow in porous media: One-dimensional model equations including vertical effects and seepage face

Science.gov (United States)

Di Nucci, Carmine

2018-05-01

This note examines the two-dimensional unsteady isothermal free surface flow of an incompressible fluid in a non-deformable, homogeneous, isotropic, and saturated porous medium (with zero recharge and neglecting capillary effects). Coupling a Boussinesq-type model for nonlinear water waves with Darcy's law, the two-dimensional flow problem is solved using one-dimensional model equations including vertical effects and seepage face. In order to take into account the seepage face development, the system equations (given by the continuity and momentum equations) are completed by an integral relation (deduced from the Cauchy theorem). After testing the model against data sets available in the literature, some numerical simulations, concerning the unsteady flow through a rectangular dam (with an impermeable horizontal bottom), are presented and discussed.

Effective behavior of a free fluid in contact with a flow in a curved porous medium

DEFF Research Database (Denmark)

Dobberschütz, Sören

2015-01-01

The appropriate boundary condition between an unconfined incompressible viscous fluid and a porous medium is given by the law of Beavers and Joseph. The latter has been justified both experimentally and mathematically, using the method of periodic homogenization. However, all results so far deal...... only with the case of a planar boundary. In this work, we consider the case of a curved, macroscopically periodic boundary. By using a coordinate transformation, we obtain a description of the flow in a domain with a planar boundary, for which we derive the effective behavior: The effective velocity...... is continuous in normal direction. Tangential to the interface, a slip occurs. Additionally, a pressure jump occurs. The magnitude of the slip velocity as well as the jump in pressure can be determined with the help of a generalized boundary layer function. The results indicate the validity of a generalized...

Factors affecting storage of compressed air in porous-rock reservoirs

Energy Technology Data Exchange (ETDEWEB)

Allen, R.D.; Doherty, T.J.; Erikson, R.L.; Wiles, L.E.

1983-05-01

This report documents a review and evaluation of the geotechnical aspects of porous medium (aquifer) storage. These aspects include geologic, petrologic, geophysical, hydrologic, and geochemical characteristics of porous rock masses and their interactions with compressed air energy storage (CAES) operations. The primary objective is to present criteria categories for the design and stability of CAES in porous media (aquifers). The document will also describe analytical, laboratory, and field-scale investigations that have been conducted.

Travelling waves above the canopy of aquatic vegetation

Science.gov (United States)

Lyubimov, D.; Lyubimova, T.; Baidina, D.

2012-04-01

When fluid moves over a saturated porous medium with high permeability and porosity, the flow partially involves the fluid in porous medium, however, because of the great resistance force there arises sharp drop of tangential velocity. This leads to the development of instability similar to the Kelvin-Helmholtz instability on discontinuity surface of the tangential velocities of homogeneous fluids. Analogy becomes even more complete if we take into account the deformability of porous medium under the influence of pressure changes. Intensive vortices above the canopy of aquatic vegetation can lead to the coherent oscillations of vegetation, such traveling waves are called monami [1]. In the present paper we investigate stability of steady flow over a saturated porous medium. The importance of this problem is related to the applications to the dynamics of pollutants in the bottom layer of vegetation: the accumulation at low flow and salvo emissions with increasing velocity. We consider a two-layer system consisting of a layer of a viscous incompressible fluid and porous layer saturated with the same fluid located underneath. The lower boundary of the system is assumed to be rigid, the upper boundary - free and non-deformable. Weak slope of the river is taken into account. The problem is solved within the framework of single approach in which a two-layer system is described by a single system of equations for saturated porous medium and the presence of two layers is modeled by introducing variable permeability and porosity, depending on vertical coordinate. The flow in a saturated porous medium is described by the Brinkman model. Solution of the problem for steady flow shows that the velocity profile has two inflection points, which leads to the instability. The neutral curves are obtained for different values of the ratio d of porous layer thickness to full thickness. It is found that the dependence of critical Reynolds number on d is non-monotonic and the wave

Boiling phenomenon and heat transfer in bead-packed porous structure

International Nuclear Information System (INIS)

Zhang Xiaojie; ZHu Yanlei; Bai Bofeng; Yan Xiao; Xiao Zejun

2009-01-01

A visual study on pool boiling behavior and phase distribution was conducted on the porous structures made of staggered glass beads at atmospheric pressure. The bead-packed structure was heated on the bottom. The investigations were carried out respectively at different glass bead diameters which were 4 mm, 6 mm and 8 mm. The results show that during subcooled boiling, small isolated bubbles are formed on the heated surface and combine into main-bubbles, the dispersion frequency of the main-bubbles is low and the small bubbles scatter in the bead-packed porous structures. At the initial stage of saturated boiling, the bubble growth rate, the volume of main-bubbles and the range of continuous vapor phase increase. The dispersion frequency of main-bubbles increases with the increasing of heat flux. During film boiling, the heated surface is absolutely covered with vapor film and the porous structure is full of liquid. The larger the diameter of beads is, the higher heat flux is needed for the same phenomenon, and the higher maximum value of heat transfer coefficient will be. During the whole saturated boiling, and the heat transfer enhanced firstly and then weakened. Being opposite to that of the diameters of 4 mm and 8 mm, the heat transfer coefficient in the 6 mm-bead-packed porous structure decreases with the increasing of the heat flux. (authors)

Effect of pore structure on capillary condensation in a porous medium.

Science.gov (United States)

Deinert, M R; Parlange, J-Y

2009-02-01

The Kelvin equation relates the equilibrium vapor pressure of a fluid to the curvature of the fluid-vapor interface and predicts that vapor condensation will occur in pores or irregularities that are sufficiently small. Past analyses of capillary condensation in porous systems with fractal structure have related the phenomenon to the fractal dimension of the pore volume distribution. Recent work, however, suggests that porous systems can exhibit distinct fractal dimensions that are characteristic of both their pore volume and the surfaces of the pores themselves. We show that both fractal dimensions have an effect on the thermodynamics that governs capillary condensation and that previous analyses can be obtained as limiting cases of a more general formulation.

Effects of pH on nano-bubble stability and transport in saturated porous media

Science.gov (United States)

Hamamoto, Shoichiro; Takemura, Takato; Suzuki, Kenichiro; Nishimura, Taku

2018-01-01

An understanding of nano-scale bubble (NB) transport in porous media is important for potential application of NBs in soil/groundwater remediation. It is expected that the solution chemistry of NB water highly influences the surface characteristics of NBs and porous media and the interaction between them, thus affecting the stability and transport characteristics of NB. In this study, in addition to stability experiments, one-dimensional column transport experiments using glass beads were conducted to investigate the effects of pH on the NB transport behavior. The results showed that the NBs were more stable under higher pH. Column transport experiments revealed that entrapment of NBs, especially larger ones, was enhanced in lower-pH water, likely suggesting pH-dependent NB attachment and physical straining, both of which are also probably influenced by bubble size. Although relatively smaller NBs were released after switching the eluting fluid to one with lower ionic strength, most of the NBs in lower-pH water were still retained in the porous media even altering the chemical condition.

Heat and mass transfer effects on MHD viscoelastic fluid over a stretching sheet through porous medium in presence of chemical reaction

Directory of Open Access Journals (Sweden)

Manoj Kumar Nayak

2016-03-01

Full Text Available An attempt has been made to study the heat and mass transfer effects in a boundary layer flow through porous medium of an electrically conducting viscoelastic fluid subject to transverse magnetic field in the presence of heat source/sink and chemical reaction. It has been considered the effects of radiation, viscous and Joule dissipations and internal heat generation/absorption. Closed form solutions for the boundary layer equations of viscoelastic, second-grade and Walters׳ B′ fluid models are obtained. The method of solution involves similarity transformation. The transformed equations of thermal and mass transport are solved by applying Kummer׳s function. The solutions of temperature field for both prescribed surface temperature (PST as well as prescribed surface heat flux (PHF are obtained. It is important to remark that the interaction of magnetic field is found to be counterproductive in enhancing velocity and concentration distribution whereas the presence of chemical reaction as well as porous matrix with moderate values of magnetic parameter reduces the temperature and concentration fields at all points of flow domain.

Radial Fingering in a Porous Medium Digitation radiale dans un milieu poreux

Directory of Open Access Journals (Sweden)

Ni W.

2006-11-01

Full Text Available The theory of immiscible radial displacement in a Hele-Shaw cell is extended to the case of a porous medium contained between two closely-spaced parallel plates, and experiments are described for the displacement of glycerine by paraffin oil in such a system. Data are presented for the number of fingers, the breakthrough time, and the glycerine recovery, for a range of flowrates varying through three orders of magnitude. Good agreement between theory and experiment is observed. La théorie s'appliquant aux déplacements radiaux dans les cellules Hele-Shaw a été étendue à un système qui consiste en une couche mince de milieux poreux encapsulée entre deux plaques en verre. Dans cet article, on examine les déplacements de la glycérine par de l'huile de paraffine. En faisant varier le débit de l'huile de paraffine dans un intervalle de trois ordres de grandeur, on a étudié les variables telles que le nombre de digitations, le temps de percée et le taux de récupération de la glycérine. On a observé un bon accord entre la théorie et les résultats expérimentaux.

Influence of wall couple stress in MHD flow of a micropolar fluid in a porous medium with energy and concentration transfer

Science.gov (United States)

Khalid, Asma; Khan, Ilyas; Khan, Arshad; Shafie, Sharidan

2018-06-01

The intention here is to investigate the effects of wall couple stress with energy and concentration transfer in magnetohydrodynamic (MHD) flow of a micropolar fluid embedded in a porous medium. The mathematical model contains the set of linear conservation forms of partial differential equations. Laplace transforms and convolution technique are used for computation of exact solutions of velocity, microrotations, temperature and concentration equations. Numerical values of skin friction, couple wall stress, Nusselt and Sherwood numbers are also computed. Characteristics for the significant variables on the physical quantities are graphically discussed. Comparison with previously published work in limiting sense shows an excellent agreement.

Influence of Biochar on Deposition and Release of Clay Colloids in Saturated Porous Media.

Science.gov (United States)

Haque, Muhammad Emdadul; Shen, Chongyang; Li, Tiantian; Chu, Haoxue; Wang, Hong; Li, Zhen; Huang, Yuanfang

2017-11-01

Although the potential application of biochar in soil remediation has been recognized, the effect of biochar on the transport of clay colloids, and accordingly the fate of colloid-associated contaminants, is unclear to date. This study conducted saturated column experiments to systematically examine transport of clay colloids in biochar-amended sand porous media in different electrolytes at different ionic strengths. The obtained breakthrough curves were simulated by the convection-diffusion equation, which included a first-order deposition and release terms. The deposition mechanisms were interpreted by calculating Derjaguin-Landau-Verwey-Overbeek interaction energies. A linear relationship between the simulated deposition rate or the attachment efficiency and the fraction of biochar was observed ( ≥ 0.91), indicating more favorable deposition in biochar than in sand. The interaction energy calculations show that the greater deposition in biochar occurs because the half-tube-like cavities on the biochar surfaces favor deposition in secondary minima and the nanoscale physical and chemical heterogeneities on the biochar surfaces increase deposition in primary minima. The deposited clay colloids in NaCl can be released by reduction of ionic strength, whereas the presence of a bivalent cation (Ca) results in irreversible deposition due to the formation of cation bridging between the colloids and biochar surfaces. The deposition and release of clay colloids on or from biochar surfaces not only change their mobilizations in the soil but also influence the efficiency of the biochar for removal of pollutants. Therefore, the influence of biochar on clay colloid transport must be considered before application of the biochar in soil remediation. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Pollutant transport in clayey sands: reactive flows in saturated porous media and unsaturated flows

International Nuclear Information System (INIS)

Cadalen, Sebastien

2008-01-01

In the context of nuclear risk control associated to nuclear waste storage, the french nuclear agency plays an increasing role in terms of research and development in the area of subsurface contamination. This study focuses on an homogeneous porous media constituted of Fontainebleau sand and clay grains (illite) presenting sorption capacities. The modeling of the complex geometry and physical phenomena at different scales enables us to describe the average transport at Darcy's scale. The two main axes developed are the impact of an heterogeneous sorption on transport phenomena and the dispersivity of an unsaturated porous media. (author) [fr

Modeling of Flow, Transport and Controlled Sedimentation Phenomena during Mixing of Salt Solutions in Complex Porous Formations

Science.gov (United States)

Skouras, Eugene D.; Jaho, Sofia; Pavlakou, Efstathia I.; Sygouni, Varvara; Petsi, Anastasia; Paraskeva, Christakis A.

2015-04-01

-dimensional pore network, the dependence of the mass balance in all major directions is taken into account, either as a three-dimensional network of pores with specific geometry (cylinders, sinusoidal cells), or as a homogeneous random medium (Darcy description). The distribution of the crystals along the porous medium was calculated in the case of selective crystallization on the walls, which is the predominant effect to date in the experiments. The crystals distribution was also examined in the case where crystallization was carried out in the bulk solution. Salts sedimentation experiments were simulated both in an unsaturated porous medium and in a medium saturated with an oil phase. A comparison of the simulation results with corresponding experimental results was performed in order to design improved selective sedimentation of salts systems in porous formations. ACKNOWLEDGMENTS This research was partially funded by the European Union (European Social Fund-ESF) and Greek National Funds through the Operational program "Education and Lifelong Learning" under the action Aristeia II (Code No 4420).

Polarisations of quasi-waves in a general anisotropic porous solid ...

Indian Academy of Sciences (India)

in fluid-saturated porous media was developed by. Biot (1956). ... anisotropic permeability controlling the flow of vis- cous fluid in its pores. ..... solid: III reflection of plane waves at a free plane boundary (general case); Bull. Seism. Soc. Am. 52.

Combined natural convection and mass transfer effects on unsteady flow past an infinite vertical porous plate embedded in a porous medium with heat source

Energy Technology Data Exchange (ETDEWEB)

Das, S.S. [Department of Physics, K B D A V College, Nirakarpur, Khurda-752 019 (Orissa) (India); Tripathy, R.K. [Department of Physics, D R Nayapalli College, Bhubaneswar-751 012 (Orissa) (India); Padhy, R.K. [Department of Physics, D A V Public School, Chandrasekharpur, Bhubaneswar-751 021 (Orissa) (India); Sahu, M. [Department of Physics, Jupiter +2 Women’s Science College, IRC Village, Bhubaneswar-751 015 (Orissa) (India)

2012-07-01

This paper theoretically investigates the combined natural convection and mass transfer effects on unsteady flow of a viscous incompressible fluid past an infinite vertical porous plate embedded in a porous medium with heat source. The governing equations of the flow field are solved analytically for velocity, temperature, concentration distribution, skin friction and the rate of heat transfer using multi parameter perturbation technique and the effects of the flow parameters such as permeability parameter Kp, Grashof number for heat and mass transfer Gr, Gc; heat source parameter S, Schmidt number Sc, Prandtl number Pr etc. on the flow field are analyzed and discussed with the help of figures and tables. The permeability parameter Kp is reported to accelerate the transient velocity of the flow field at all points for small values of Kp (£1) and for higher values the effect reverses. The effect of increasing Grashof numbers for heat and mass transfer or heat source parameter is to enhance the transient velocity of the flow field at all points while a growing Schmidt number retards its effect at all points. A growing permeability parameter or heat source parameter increases the transient temperature of the flow field at all points, while a growing Prandtl number shows reverse effect. The effect of increasing Schmidt number is to decrease the concentration boundary layer thickness of the flow field at all points. Further, a growing permeability parameter enhances the skin friction at the wall and a growing Prandtl number shows reverse effect. The effect of increasing Prandtl number or permeability parameter leads to increase the magnitude of the rate of heat transfer at the wall.

The movement of groundwater flow in unsaturated fractured porous medium

International Nuclear Information System (INIS)

Li Jinxuan

1995-01-01

The author analyses the fundamental processes governing infiltration in fractured porous rock. Asymptotic solutions for the front movement are given for each flow period and comparisons with numerical solutions are made. The result of the study is relevant to nuclear waste storage, hazardous waste disposal and petroleum recovery

The effect of a microscale fracture on dynamic capillary pressure of two-phase flow in porous media

Science.gov (United States)

Tang, Mingming; Lu, Shuangfang; Zhan, Hongbin; Wenqjie, Guo; Ma, Huifang

2018-03-01

Dynamic capillary pressure (DCP) effects, which is vital for predicting multiphase flow behavior in porous media, refers to the injection rate dependence capillary pressure observed during non-equilibrium displacement experiments. However, a clear picture of the effects of microscale fractures on DCP remains elusive. This study quantified the effects of microscale fractures on DCP and simulated pore-scale force and saturation change in fractured porous media using the multiphase lattice Boltzmann method (LBM). Eighteen simulation cases were carried out to calculate DCP as a function of wetting phase saturation. The effects of viscosity ratio and fracture orientation, aperture and length on DCP and DCP coefficient τ were investigated, where τ refers to the ratio of the difference of DCP and static capillary pressure (SCP) over the rate of wetting-phase saturation change versus time. Significant differences in τ values were observed between unfractured and fractured porous media. The τ values of fractured porous media were 1.1  × 104 Pa ms to 5.68 × 105 Pa ms, which were one or two orders of magnitude lower than those of unfractured porous media with a value of 4 × 106 Pa. ms. A horizontal fracture had greater effects on DCP and τ than a vertical fracture, given the same fracture aperture and length. This study suggested that a microscale fracture might result in large magnitude changes in DCP for two-phase flow.

Prediction of the saturated hydraulic conductivity from Brooks and Corey’s water retention parameters

NARCIS (Netherlands)

Nasta, P.; Vrugt, J.A.; Romano, N.

2013-01-01

Prediction of flow through variably saturated porous media requires accurate knowledge of the soil hydraulic properties, namely the water retention function (WRF) and the hydraulic conductivity function (HCF). Unfortunately, direct measurement of the HCF is time consuming and expensive. In this

The unsaturated flow in porous media with dynamic capillary pressure

Science.gov (United States)

Milišić, Josipa-Pina