Composite Porous Media Research Articles

Novel wet combustion chamber concept CFD studies with triple water inlet

Presented wet combustion chamber concept contains several integrated elements, which altogether form a prototype able to reduce extremely high oxy-combustion temperatures (up to 2800 °C) in an elevated pressure above 10 bars. To enable such capability, liquid water is supplied directly into the combustor flame zone. This is obtained with the front spray injection and water permeation through the two separate liner segments, which are made of the ceramic matrix composite (CMC) porous medium. This material was developed by the aerospace industry to take advantage of the heat resistance and low density of ceramics while reducing the brittleness of its monolithic form. Taking various interactions into account, analysed model couples rapid oxy-combustion process with the instant water evaporation. Particularly important phenomena occur at the surfaces of water droplets penetrating the flame with the axial velocity of 100 m/s. Rapid evaporation of each of them induces significant mixing force driven by the local thermal gradients. For the nominal case, 3D results were validated against the 0D calculations. While the nominal water mass split is 14% at the front plus 86% at the liner, other supply ratios were taken into account and are reported in the results section. Combustion process was modelled with GRI-Mech 3.0 mechanism.

Removal of Hexavalent Chromium in Aqueous Solution by Cellulose Filter Paper Loaded with Nano-Zero-Valent Iron: Performance Investigation and Numerical Modeling.

Cr(VI) pollution in water bodies is very harmful to human health and the environment. Therefore, it is necessary to remove Cr(VI) from water. In this study, the composite (FP-nZVI) was prepared by loading nano-zero-valent iron (nZVI) onto cellulose filter paper (FP) using a liquid-phase reduction method to improve the dispersibility and oxidation resistance of nZVI. In batch experiments, the effects of iron loading of FP-nZVI, initial concentration of Cr(VI), temperature, and pH on Cr(VI) removal were particularly investigated. The maximum removal rate of 98.6% was achieved at 25 °C, pH = 5, initial concentration of Cr(VI) of 20 mg/L, and FeCl3·6H2O solution concentration of 0.8 mol/L. The removal of Cr(VI) by FP-nZVI conformed to a pseudo-second-order kinetic model and Langmuir isotherm model. The mechanism of Cr(VI) removal was a multi-step removal mechanism, involving adsorption, reduction, and coprecipitation. Column experiments investigated the effect of flow rate (1 mL/min, 3 mL/min, and 5 mL/min) on Cr(VI) removal. We found that increasing flow rate slightly decreased the removal rate of Cr(VI). The transport of Cr(VI) in composite porous media was simulated using HYDRUS-1D, and the results show that the two-site model can well simulate the reactive transport of Cr(VI). This study may provide a useful reference for the remediation of groundwater contaminated with Cr(VI) or other similar heavy metals using FP-nZVI.

Unsaturated Hydraulic Conductivity in Composite Porous Media

Determining the constitutive properties that describe the incipient hydraulic behavior of the materials, including the matrix domains and the distribution of macro and micropores, is crucial to analyzing the preferential water flow in saturated soils, ks, and unsaturated, ku. This study focused on determining the hydraulic conductivity in porous media under total and partial saturation conditions. The infiltration characteristics of three reconstituted soils were evaluated using five suction ranges employing conventional permeameters, an automated dual system, and mini-disk infiltrometers. The experimental cycles were carried out in granular soils with mixtures of diatomaceous soils, iron oxide (Fe2O3), and calcium carbonate (CaCO3) in 5–40% proportions. The differences between the granular microstructures of each material and the different hydraulic interaction mechanisms (suctione levels) significantly affected the values of ks and ku and the coupling between the pore domains and the defined water regime. Additionally, a lower impact was observed in the data set exposed to higher percentages of Fe2O3 and CaCO3 in different suction ranges, mainly due to a tension effect (meniscus) generated by suction in the granular skeleton. Since both parameters are mutually correlated and have a similar impact between methods and soil cores, ks and ku must be optimized simultaneously in each mechanism analyzed. The main findings of this work result in the confirmation that the unsaturated permeability decreases as suction is imposed on the sample. As well as the addition of different materials with Particle Size Distribution finer than the base sample, it also reveals a reduction in hydraulic conductivity, both saturated and unsaturated.

Advective Trapping in the Flow Through Composite Heterogeneous Porous Media

We study the mechanisms of advective trapping in composite porous media that consist of circular inclusions of distributed hydraulic conductivity embedded in a high conductivity matrix. Advective trapping occurs when solute enters low velocity regions in the media. Transport is analyzed in terms of breakthrough curves measured at the outlet of the system. The curve’s peak behavior depends on the volume fraction occupied by the inclusions, while the tail behavior depends on the distribution of hydraulic conductivity values. In order to quantify the observed behaviors, we derive two equivalent upscaled transport models. First, we derive a Lagrangian trapping model using the continuous-time random walk framework that is parameterized in terms of volume fraction and the distribution of conductivities in the inclusions. Second, we establish a non-local partial differential equation for the mobile solute concentration by volume averaging of the microscale transport equation. We show the equivalence between the two models as well as (first-order) multirate mass transfer models. The upscaled approach parameterized by medium and flow properties captures all features of the observed solute breakthrough curves and sheds new light on the modeling of advective trapping in heterogeneous media.

Brown and Korringa’s expression for the saturated bulk modulus at high frequencies: Modification of Mavko and Jizba’s squirt flow model

The squirt flow model developed by Mavko and Jizba has been widely applied to quantify elastic moduli/velocities of fluid-saturated rocks at ultrasonic frequencies and the related modulus/velocity dispersion between ultrasonic and seismic frequencies. In the model, the high-frequency saturated bulk modulus is obtained by taking the unrelaxed frame bulk modulus as the drained/dry one as the input to Biot’s or Gassmann’s formula. However, when using Gassmann’s formula, the “new” rock matrix contains rock mineral matrix and fluid-saturated soft pores, which is heterogeneous at the microscopic scale and thus breaks the fundamental assumption of microhomogeneity for Gassmann’s formula. Therefore, the high-frequency saturated bulk modulus computed by Gassmann’s formula is inaccurate, especially when the soft-pore fraction (SPF) (the ratio of soft porosity to total porosity) or crack density is large. To this end, we have derived the Brown and Korringa’s expression (Mavko-Jizba-Gurevich [MJG]-BK model) for the high-frequency saturated bulk modulus in Mavko and Jizba’s model based on Berryman and Milton’s generalized Gassmann’s equations for the composite porous media, which correctly characterizes the microheterogeneity of new rock matrix. The parameters in the MJG-BK model are totally determined by measured quantities in the laboratory. Numerical example indicates that the MJG model is consistent with the MJG-BK model at small SPFs or crack densities. When the SPF/crack density becomes large, the difference between them becomes large, the MJG model loses its accuracy, and the MJG-BK model is preferred. Furthermore, experiment data from the laboratory validate the effectiveness of the proposed MJG-BK model. In summary, the model develops Brown and Korringa’s expression for Mavko and Jizba’s squirt flow model and can be used to calculate the high-frequency saturated bulk modulus at different SPFs or crack densities more accurately.

Analytical solution of cloaking in creeping flow inside composite porous media with simultaneous heat transfer

ABSTRACT This paper presents a theoretical analysis of steady-state creeping flow in a composite porous domain with coupling heat transfer. The problem arises in thermal cloaking studies in which it is desirable to hide an obstacle from the surrounding hydrodynamic and thermal fields, by suitably covering the obstacle with a cloak having specific material properties. The particular system under investigation consists of a porous composite region, with a thermal-hydro field driven by imposed temperature and pressure difference in the surrounding. Both two dimensional circular and three-dimensional axisymmetric spherical annuli are considered. Under the validity of Darcy law for a porous medium, an exact solution satisfying the continuity, momentum and energy equations at any Péclet number is derived. The analytical results have been numerically verified using the commercial code COMSOL.

Multidimensional computational models of gas combustion in heterogeneous porous medium

The processes of filtration gas combustion in heterogeneous porous medium is studying. The presence of two opposite modes of front propagation made it possible to stabilize the combustion front in a composite porous medium with piecewise constant porosity. A feature of this study is the presentation of the original model not in the traditional form of a system of parabolic equations, but in the form of integral conservation laws in terms of the temperature of the porous medium, the total gas enthalpy, and the mass of gas mixture, and the fluxes corresponding to these functions.

A numerical study of the additive Schwarz preconditioned exact Newton method (ASPEN) as a nonlinear preconditioner for immiscible and compositional porous media flow

Domain decomposition methods are widely used as preconditioners for Krylov subspace linear solvers. In the simulation of porous media flow there has recently been a growing interest in nonlinear preconditioning methods for Newton’s method. In this work, we perform a numerical study of a spatial additive Schwarz preconditioned exact Newton (ASPEN) method as a nonlinear preconditioner for Newton’s method applied to both fully implicit or sequential implicit schemes for simulating immiscible and compositional multiphase flow. We first review the ASPEN method and discuss how the resulting linearized global equations can be recast so that one can use standard preconditioners developed for the underlying model equations. We observe that the local fully implicit or sequential implicit updates efficiently handle the local nonlinearities, whereas long-range interactions are resolved by the global ASPEN update. The combination of the two updates leads to a very competitive algorithm. We illustrate the behavior of the algorithm for conceptual one and two-dimensional cases, as well as realistic three dimensional models. A complexity analysis demonstrates that Newton’s method with a fully implicit scheme preconditioned by ASPEN is a very robust and scalable alternative to the well-established Newton’s method for fully implicit schemes.

Using Complex Probability Amplitudes to Simulate Solute Transport in Composite Porous Media

AbstractProbability amplitudes are fundamental to quantum mechanics and offer robust descriptions of complicated systems, which have allowed physicists to explain behaviors inaccessible to classical physics. This article ponders how some of the same conceptual underpinnings of the mathematics used for modeling quantum systems might be applied to subsurface water resources problems and speculates how these tools could facilitate applications on quantum computers. A probability amplitude‐based model for describing advective‐dispersive transport in porous media using linear operators is investigated. The proposed complex valued model decomposes spreading into two “sub‐continuum partial dispersion” coefficients, and this recovers classical spreading when the sum of these coefficients is the Fickian dispersion coefficient. However, the probability amplitudes have a many‐to‐one relationship to a probability distribution, so it embeds a level of heterogeneity into seemingly equivalent functions. Two propagators with different sub‐continuum coefficients may have the same macroscopic behavior when either is considered in isolation, but when they act on the other the system’s behavior changes. Differences in the amplitudes cause a reduction in spreading as velocity correlations are disrupted, despite both propagators having identical dispersion coefficients, and this cannot be achieved using classical methods without changing the dispersion coefficient. The main point is that these amplitude‐based models offer a way to embed information about the system into the propagators, instead of just “averaging it out” when making an upscaled model.

Effects of percolation on the effective conductivity of irregular composite porous media

We develop a phenomenological model for the effective conductivity of porous media that consist of two distinct materials characterized by different values of hydraulic conductivity. Our focus is two-fold: first, to relate the terms and parameters of macroscale conductivity to the spatial variability of local flow and conductivity observed in computational experiments, and second to develop a reduced order model for effective conductivity based on those observations. Darcys law is assumed to hold at local (mesoscopic) and large (macroscopic) scales. At the mesoscale a composite medium is a configuration of irregular subdomains consisting of two different materials. The resulting heterogeneities force fluid to flow along irregular paths, and this produces spatial variability in the magnitude and the orientation of the Darcy flux. This variability, along with the macroscopic effective conductivity, depends on the proportion of the total volume allocated to each material, the ratio of the two conductivity values, and the spatial connectivity of material subvolumes. Computational experiments indicate that the effects of heterogeneity are most pronounced when the two conductivity values are very different, and when the volume fraction of the more conductive material is near a percolation threshold. The percolation threshold is the critical volume fraction of the more conductive material at which the medium is no longer traversed by connected paths through that material. The percolation threshold determines the existence of three regimes in effective conductivity, two where the effective conductivity obeys power laws and is dominated by one of the materials, and a third intermediate regime that interpolates between the power laws.

Removal of Food Carmoisine Dye E-112 From Waste Water Using Different Manufactured Media

The industrial and agricultural waste water contains many contaminants; one of them is the food carmoisine dye E112, which causes a series problems for the environment. Adsorption using porous media is one of the solutions to this problem. In the present work, activated silica sand (ASS), activated carbon (AC), porcelanite, silt and composite porous media, were prepared and used to remove the E112 from waste water using adsorption technique. It was predicted that the removal efficiency was affected by many factors such as time, pH, dose and ozonation of media. These factors were studied and analyzed to investigate the best media which is the activated carbon with the highest removal efficiency than the other porous medias. The results showed that:• The best removal efficiency of carmoisine dye E-112 was by activated carbon (AC) that reaching to 76% under specific conditions (7 of pH, 20g of AC and 10 mg/l initial concentration of dye) which were selected after several attempts until reaching the best results of removal efficiency.• Ozonation (ozon pumping to the porous media) was the effective reason of removal efficiency increasing.• The best one of porous medias according to the removal efficiency was: AC> ASS> composite> porcilanite> silt.

Rayleigh wave at composite porous half space saturated by two immiscible fluids

• Rayleigh wave on composite porous medium containing immiscible fluids is investigated. • Phase speed of Rayleigh wave increases in unsaturated medium. • Increase in porosity increases the phase speed of Rayleigh wave. • Viscosity of the fluids causes energy loss and results in higher attenuation of Rayleigh wave. The propagation of Rayleigh wave along the free surface of a composite porous half-space saturated by two immiscible fluids is studied. A complex valued dispersion equation is obtained and solved numerically to examine phase speed and attenuation of Rayleigh wave propagating in the medium. Comparative study of the behavior of Rayleigh wave in saturated and unsaturated media is conducted by considering a porous rock composed of shaley sandstone and clay content with pores containing water-oil and water-gas, respectively. Variations in phase speed and attenuation of Rayleigh wave are presented with variations in porosity of medium, fluid saturation in pores and frequency parameter. Results of numerical simulation demonstrate the applicability of study of Rayleigh waves in estimating the porosity of the medium, properties of fluids and their relative saturation present in the pores.

Flow and heat transfer of composite porous medium saturated with nanofluid

The present article is concerned with the heat transfer of nanofluid saturated with porous medium sandwiched between clear viscous fluid filled in a vertical channel. The model is developed to analyze the behavior of nanofluids taking into account the solid volume fraction. The governing equations are obtained based on the Darcy׳s law for the porous medium and Tiwari and Das model to define the nanofluid. The viscous and Darcy dissipation terms are included in the energy equation. The transformed dimensionless governing equations are solved analytically using regular perturbation. Investigations are carried out on the flow characteristics for different values of Grashof number, Brinkman number, solid volume fraction and porous parameter using water as base fluid and copper as nanoparticle. Flow and heat transfer are also observed using five different types of nanoparticles. It is found that the maximum value of Nusselt number is obtained for silver nanoparticle.

Effect of pore connectivity on reflection amplitudes of an inhomogeneous wave in a composite porous solid saturated by two immiscible fluids

Present paper aims to study the phenomenon of reflection and transmission when an inhomogeneous wave strikes some discontinuity in a composite porous medium saturated by two immiscible viscous fluids. The incident wave splits into six reflected and six transmitted waves at the interface. All reflected and transmitted waves are inhomogeneous in nature with different directions of propagation vector and attenuation vector. A dimensionless parameter \(\varsigma \in [0, 1]\) is introduced to represent the extent of connection among the pores at the interface. Expression of Umov–Poynting vector is derived to obtain energy flux vector. Continuity of energy flux vector at the interface gives the required boundary conditions for the system. Connecting parameter \(\varsigma \) is also employed in boundary conditions to model the partial connection of pores at the interstices of two media. For numerical discussion we consider a porous medium composed of sandstone and ice, saturated with oil and water. The effect of parameter \(\varsigma \) and angle of incidence is determined numerically on the amplitude and the energy ratios of reflected and transmitted waves.

Effect of homogeneous and heterogeneous reactions on the solute dispersion in composite porous medium

The Taylor dispersion of a solute for composite porous medium between two parallel plates with first-order chemical reaction is studied analytically. The fluids in both the regions are incompressible and the transport properties are assumed to be constant. The results are shown graphically for various values of viscosity ratio, pressure gradient and porous parameter on the effective dispersion coefficient and volumetric flow rate. It is found that for both homogeneous and heterogeneous chemical reactions, the effective dispersion coefficient decreases as porous parameter increases. The validity of the results obtained for composite porous media is verified by comparison with the available porous medium results for one fluid model and good agreement is found. Also two fluid model in the absence of porous matrix is compared with the available one fluid model results and the values tally very well.Keywords: Taylor dispersion, immiscible fluids, horizontal channel, porous medium, chemical reaction.

Drying of a tape-cast layer: Numerical investigation of influencing parameters

In this study, the evaporation of water from a ceramic-water mixture is investigated numerically with the purpose of understanding the drying process of the thin sheets produced by the tape casting process. In the scope of this work, a Representative Elementary Volume (REV) scale model concept for coupling non-isothermal multi-phase compositional porous-media flow and single-phase compositional laminar free-flow developed by Jabbari et al. (2016), is used for a thorough analysis of the influential parameters. Specifically, we investigate the influence of ventilation speed magnitude, vmax, the equivalent diameter of particles of the porous medium, dp, the porosity of the porous medium, ϕ, the initial temperature in the free-flow region, Tff, and the initial temperature in the porous-medium region, Tpm, on the characteristic drying curves of a thin ceramic layer. We, moreover, conduct a statistical analysis based on numerical experiments in combination with a fractional factorial design of the aforementioned parameters. The analysis accounts for the effects of parameters on the characteristic drying curves of a thin ceramic layer. The effects of varying each of the parameters as well as their mutual interaction are shown with particular attention to the maximal drying rate as well as the final time for the drying process.

Capillary effects on phase behavior of liquid and gaseous propane and dynamics of hydrate formation and dissociation in porous media

Using a precision adiabatic calorimetry method the phase behavior of liquid and gaseous propane with water in bulk as well as in dry and water saturated porous media have been studied in the temperature range from 240 to 350 K and the pressure range from 0.1 to 12 MPa. Quartz powder with a grain size from 25 to 38 mk as a porous medium was used. Water saturation of the porous medium was about 0.247 ± 0.001 of porous volume. From thermodynamic point of view such water saturation of the porous volume is sufficient to consider the pore water phase practically as a bulk phase. A composite porous medium is formed from the quartz powder grains covered by a water film. In fact, the water film is a mechanical continuation of the quartz powder grains. The water film forms a configuration (a curvature) of the porous space as well predetermines a surface wettability of the composite porous medium. We study capillary effect in composite porous media due to capillary condensation and capillary evaporation of propane, both on a lyophilic surface and on a lyophobic surface of water film. Based on the experimental data of specific heat and temperature derivative of pressure at constant volume, the phase diagrams of propane in bulk and in water saturated and dry quartz powder have been constructed (including the gas hydrate field of phase diagram).

Drying of a tape-cast layer: Numerical modelling of the evaporation process in a graded/layered material

Evaporation of water from a ceramic layer is a key phenomenon in the drying process for the manufacturing of water-based tape cast ceramics. In this paper we present a coupled free-flow-porous-media model on the Representative Elementary Volume (REV) scale for coupling non-isothermal multi-phase compositional porous-media flow — for the ceramic layer — and single-phase compositional laminar free flow — for the air above it. The preliminary results show the typical expected evaporation behaviour from a porous medium initially saturated with water, and water–vapour transport to the free-flow region in accordance with the available results from the literature. We elaborate on and discuss the characteristic drying-rate curve for a single layer ceramic, and compare it with that of a graded/layered ceramic. We, moreover, show the influence of the mean diameter of particles of the porous medium (dp) — which directly affects the intrinsic permeability (K) based on the well-known Ergun’s equation — of each single ceramic layer on the drying behaviour of a graded/layered ceramic.

Wave-Induced Flow of Pore Fluid in a Double-Porosity Solid Under Liquid Layer

This study considers the incidence of an acoustic wave through a liquid at its boundary with a double-porosity solid, which is saturated with a viscous fluid. This incident wave refracts to the continuing double-porosity medium as four attenuating waves. Of these four waves, three are longitudinal waves, which induce a flow of pore fluid across the dual-porosity network in the porous aggregate. The amount of this fluid flow is expressed in terms of the dilatations of various constituents in composite porous medium. This wave-induced flow in double-porosity solid is separated into the contributions from each of the three longitudinal waves. For the propagation of harmonic waves, each contribution becomes the function of wave frequency. A numerical example is solved to calculate the contributions of three refracted longitudinal waves to the induced fluid flow in double-porosity ocean bed. Due to the normal incidence of acoustic waves, fluid flow is induced mainly by the fastest longitudinal wave. However, for oblique incidence of acoustic wave, it is the slowest longitudinal wave, which induces much of the fluid flow, particularly near critical incidence. To induce a larger flow of pore fluid, the longitudinal waves prefer the pervious ocean bottom. Effects of incident direction, wave frequency, pore fluid viscosity, permeability, radius of spherical inclusions and sealing of boundary pores are analysed on the wave-induced flow of pore fluid.

放射性物質吸着除去を目的としたゼオライト／HA 複合体の作製と吸着特性評価

Zeolite/HA composite porous medium was prepared by the Gelation Freezing Method. Montmorillonite was used as a bonding material. Composite porous medium was prepared by freeze-drying a slurry which was added to aqueous gelatin solution to powder mixture of zeolite, HA and montmorillonite. Prepared the complex was heated at 500 ℃ and 800 ℃. The crystallinity was evaluated using X-ray diffractometer (XRD). The surface was observed with a scanning electron microscope (SEM). Flexural strength was calculated by destructive testing. In SEM analysis, it was observed that there is a pore in the all samples. The lower freezing temperature, the smaller pore size becomes.