Layer Of Porous Medium Research Articles

Asymptotic study of premixed flames in inert porous media layers of finite width: Parametric analysis of heat recirculation phenomena

In this paper, we present an investigation on super-adiabatic premixed flames in an inert porous medium layer of finite length. The combustion process is modeled by a one-step Arrhenius kinetics in which density variations are taken into account. The asymptotic case of large ratio of thermal conductivities of solid to gas phases and the high activation energy limit are explored. The results obtained for these limiting cases are compared to those for finite values of these parameters. The use of the flame sheet model allows us to obtain steady-state solutions in an analytical form thus facilitating the parametric analysis.The investigation focuses on the phenomenon of multiplicity of steady-state solutions. It is shown that two or three (nontrivial) steady-state solutions are possible, depending on the flow rate intensity. The critical values of the parameters for the existence of multiple solutions are also determined. The stability of the obtained solutions is finally investigated by means of time-dependent simulations.

Near miscible relative permeability curves in layered porous media- investigations via diffuse interface Lattice Boltzmann method

The relative permeability of immiscible multi-phase flow in Layered 2D porous media is investigated employing the diffuse interface Lattice Boltzmann model. The interfacial tension is set to small value to mimic the near miscible condition of the fluids. The model is validated with static and dynamic analytical solutions. Three classes of porous media are examined: A high permeable porous media, a low permeable porous media, and layered dual permeable porous media. For the later case, parallel and serie conditions were considered. For each condition, three proportion of layers were studied; I– 25% of the high permeable layer, II– 50% of the high permeable layer, and III– 75% of high permeable layer. For each condition, the viscous coupling effects due to viscosity ratio, the capillary number and the effect of the fluid patterns on the relative permeability curves were investigated. The simulation results showed very small errors compare with the analytical permeability solutions of layered porous media. The findings showed that despite the dual permeable serie system, the relative permeability curve of dual permeable parallel geometry is closely matched with the analytical solution.

Flow in a channel with porous insert

Filtration of an incompressible liquid (gas) in a non-deformable porou s medium is investigated. The results of numerical simulation of the hydrodynamic features of the flow arising after the passage of the liquid through a layer of an immobile porous medium are presented. An interpenetrating model of multiphase media is used to describe such flows. The porosity and permeability of the porous medium, as well as the force of interfacial interaction, are considered in the framework of compliance with the Kozeny-Karman ratio. The influence of the geometrical shape of the bulk layer on the nature and magnitude of the inhomogeneity of the flow velocity behind the obstacle is shown. Considering the shape of the porous medium significantly affects the flow parameters. Numerical simulation results are compared with experimental data. The effects of the non-uniformity of the fluid velocity field arising from the curvature of the layer surface and the influence of the arising inhomogeneity on the velocity are investigated by the methods of a computational experiment. A qualitative comparison is made of velocity inhomogeneities when a fluid flows through a porous obstacle. For the numerical implementation of the filtration equation of the interpenetrating model, a SIMPLElike algorithm was used.

Double diffusive convective motion in a reactive porous medium layer saturated by a non-Newtonian Kuvshiniski fluid

The impact of chemical reactions on the double-diffusive convective motion in a non-Newtonian viscoelastic fluid (Kuvshiniski type) saturated porous layer is examined applying both linear and nonlinear stability techniques. The Darcy model that includes the Kuvshiniski type viscoelastic effect of viscoelastic fluid and the Boussinesq estimation is employed as the momentum equation. The conditions for the occurrence of the stationary and oscillatory style of convective motions are determined by applying linear stability theory in terms of a critical thermal Rayleigh–Darcy number. Using the weakly nonlinear stability analysis, the convective heat and mass transfers are calculated. It is observed that the occurrence of oscillatory convection is possible only if the value of the solute Rayleigh–Darcy number is negative and also depends on other involved physical parameters. With rising values of the Kuvshiniski parameter and the heat capacity ratio, the range of the solute Rayleigh–Darcy number in which oscillatory convection is privileged diminishes, whereas it grows with the chemical reacting parameter and the Lewis number. The critical thermal Rayleigh–Darcy number at which the convective motion occurs increased nearly 3% with a 15% increase in the value of the Kuvshiniski parameter. Furthermore, the convective heat and mass transfers are reduced by growing the Kuvshiniski parameter and the heat capacity ratio, while both are enhanced by increasing the thermal Rayleigh–Darcy number and the solute Rayleigh–Darcy number.

Effect of electric field on the onset of Jeffery fluid convection in a heat-generating porous medium layer

Effect of electric field on the onset of Jeffery fluid convection in a heat-generating porous medium layer

An Analytical Model for Thermal Taylor Dispersion in Layered Porous Media

An Analytical Model for Thermal Taylor Dispersion in Layered Porous Media

Influence of the Form of Porous Insert in the Flow of a Viscous Liquid in a Plane Pipe

Filtration of an incompressible liquid (gas) in a non-deformable porous medium is investigated. The results of numerical simulation of the hydrodynamic features of the flow arising after the passage of the liquid through a layer of an immobile porous medium are presented. An interpenetrating model of multiphase media is used to describe such flows. Kozeny-Karman relations are used as the interaction force. The influence of the geometrical shape of the bulk layer on the nature and magnitude of the inhomogeneity of the flow velocity around the obstacle is shown. The shape of the porous medium significantly affects the flow parameters. Numerical simulation results are compared with experimental data. The shape of the porous medium significantly affects the flow parameters. Numerical simulation results are compared with experimental data. The effects of non-uniformity of the fluid velocity field arising due to the shape of the layer surface are investigated by the methods of a computational experiment. A qualitative comparison is made of velocity inhomogeneities when a fluid flows through a porous obstacle. For the numerical implementation of the filtration equation of the interpenetrating model, a SIMPLE-like algorithm was used.

Technique of numerical simulation of wave processes in a heterogeneous hydrate-containing porous medium

A technique for numerical simulation of wave propagation in a hydrate-containing porous medium consisting of layers with different properties is proposed. The method is based on a mathematical model previously developed by the authors, which considers the difference between the velocities and pressures of the skeleton and fluid, and the McCormack finite difference method. A computer implementation of the model was performed, and preliminary calculations were carried out, which showed the efficiency of the proposed methodology. The possibility of applying this approach to the numerical solution of the problem of propagation and reflection of pressure waves in a layered hydrate-containing porous medium is shown.

COMBINED EFFECT OF INTERNAL HEATING AND THROUGH-FLOW IN A NANOFLUID SATURATED POROUS MEDIUM UNDER LOCAL THERMAL NONEQUILIBRIUM

In this paper the combined effect of internal heating and through-flow in a porous medium layer saturated by nanofluid is studied under local thermal nonequilibrium. Free-free isothermal boundaries have been considered for the analysis. The Brinkman model is used for the porous medium. The nanofluid is assumed to be incorporated with the effect of thermophoresis and Brownian motion. The particles, fluid, and solid-matrix are at different temperatures, i.e., a three temperature model has been used for local thermal nonequilibrium (LTNE). To investigate the onset of convection and heat/mass transfer both linear and nonlinear stability analysis have been featured. We conclude that the effects of internal heating and through-flow play a vital role in the heat and mass transfer inside the system.

Quantitative analysis of dominant mechanisms in improving fluid sweeping uniformity in a layered heterogeneous system via xanthan gum addition.

Although it has been proven that the addition of shear-thinning polymers can lead to an improvement in the sweeping efficiency of the remedial agent in heterogeneous aquifers, the related mechanisms require further investigation. This study revealed the mechanisms associated with the improvement of fluid sweeping uniformity. Under the assumption of no transverse flow existed between layers, the variation patterns of the fluid sweeping uniformity in strip layered heterogeneous media (RP/RK) with the change of the fluid hydraulic conductivity were investigated. The outcomes showed that, for the hydraulic conductivity dominated fluid sweeping uniformity control, the performance was satisfactory only when the ratio of the hydraulic conductivities of viscous fluid in porous media (PM) layers (K1P/K2P) is less than 2.5 times that of pure oxidant solution (K1K/K2K), and PM combinations with higher permeability contrast usually present a wider applicability and better performance. In addition, transverse fluid movement was more likely to occur in layers with low permeability contrasts (2.3-5) than in those with relatively higher permeability contrasts (> 11). The observed transverse pressure difference directly confirmed the hypothesis of the dynamics of the cross-flow mechanism that existed during viscous fluid flow, and the relationships between the fluid fronts and the pressure head difference at each point (Px) were proposed. Our study exemplifies an effective strategy for determining the most economically effective co-injection concentration of xanthan to achieve highly efficient delivery of remedial agents.

Direct discrete complex image method for sound field evaluation above a non-locally reacting layer.

Thin layers of porous media are widely adopted in sound absorption and noise control applications due to their compact arrangement. Particularly, porous media with low flow resistivity exhibit complex, non-local reaction behavior. Therefore, sound field prediction above these media is computationally challenging. This is due to singularities and branch points in the expression for the reflection coefficient. This paper introduces a framework based on the direct discrete complex image method to analyze the sound field above a rigid-backed, non-locally reacting porous sample. In contrast to traditional complex image applications, the proposed framework avoids the extraction of the quasi-static term and the poles from the reflection coefficient. Instead, the reflection coefficient-including its singularities-is directly approximated in terms of a series of complex exponentials, whose coefficients are determined with the matrix pencil method. This study analyzes the sound field above two test samples made of melamine and rockwool. The sound field computation is efficient and accurate in the near- and in the far-field. Moreover, predicted specific impedances agree well with experimental in situ impedance measurements. The proposed framework serves for more applications including object detection in multilayered porous grounds or sound propagation prediction in layered atmosphere.

Heat transfer and entropy generation analysis of water-Fe3O4/CNT hybrid magnetic nanofluid flow in a trapezoidal wavy enclosure containing porous media with the Galerkin finite element method

The present study addresses theoretically and computationally the performance of electrically conducting water-Fe3O4/CNT hybrid nanofluid in three-dimensional free convection and entropy generation in a wavy-walled trapezoidal enclosure. The enclosure has two layers—a hybrid nanoliquid layer and a permeable medium layer. A transverse magnetic field is acting in the upward direction. Newtonian flow is considered, and the modified Navier–Stokes equations are employed with Lorentz hydromagnetic body force, Darcian and Forchheimer drag force terms. The wavy side walls are heated while the top and vertical walls are adiabatic. An elliptic cylindrical cooled fin is positioned at the center of the cavity, and several different tilting angles of the fin are considered. The transformed, non-dimensional systems of coupled nonlinear partial differential equations with their corresponding boundary conditions are solved numerically with the Galerkin Finite Element Method (FEM) using the COMSOL Multiphysics software platform. The impact of Darcy number, Hartmann number, volume fraction, undulation number of the wavy wall and Rayleigh number (thermal buoyancy parameter) on the streamlines, isotherms and Bejan number contours are investigated. Extensive visualization of the thermal flow characteristics is included. With increasing Hartmann and Rayleigh numbers, the average Bejan number is reduced strongly whereas the average Nusselt number is only depleted significantly at very high values of Rayleigh and high Hartmann numbers. With increasing undulation number, a slight elevation in average Bejan number at intermediate Rayleigh numbers is noticed, whereas the average Nusselt number is substantially boosted, and the effect is maximized at a very high Rayleigh number where the average Nusselt number was increased by 35%. An increment in Darcy number (i.e., reduction in permeability of the porous medium layer) is observed to considerably elevate the average Nusselt number at high values of the Rayleigh number up to 20%, whereas the contrary response is computed in average Bejan number, where it showed a reduction by 10 times. The simulations apply to hybrid magnetic nanofluid fuel cells and electromagnetic nanomaterials processing in cavities.

Influence of Grain Size Transition on Flow and Solute Transport through 3D Layered Porous Media

Abstract Soils and other geologic porous media often have contrasting grain size layers associated with a grain size transition zone between layers. However, this transition zone is generally simplified to a plane of zero thickness for modeling assumption, and its influence has always been neglected in previous studies. In this study, an approach combining a deposition process and a random packing process was developed to generate 3D porous media without and with consideration of the transition zone. The direct numerical models for solving the flow and concentration fields were implemented to investigate the influence of the grain size transition on flow and solute transport. Our results showed that although the transition zone occupied 13.6% of the entire layered porous medium, it had little influence on the distribution of flow velocity at the scale of the entire layered porous medium. However, the transition zone had a significant influence on the local flow field, which was associated with the increased spatial variability of velocity and the varied distribution of flow velocity. This varied local flow field could increase the solute residence time and delay the breakthrough time for solute transport. Although using both the advection-dispersion equation (ADE) and the mobile and immobile (MIM) models to fit the breakthrough curves (BTCs) for solute transport through layered porous media resulted in trivial errors, the ADE model failed to capture the influence induced by the local flow field, especially the influence of the transition zone. In contrast, the MIM model was shown to be able to capture the influence of the transition on solute transport. It was found that the mass transfer rate α, a parameter of the MIM model, was significantly improved by the presence of the transition zone, while it decreased as the transition zone fraction increased. Our study emphasized that the transition zone can vary the local flow field at the pore scale, while it has little influence on the hydraulic properties (e.g., hydraulic conductivity) of the macroscale flow field. However, the local flow field varied by the transition zone has a significant influence on solute transport.

Onset of solutal convection in layered sorbing porous media with clogging

The effect of pore clogging on the onset of solute-driven convection in a layered sorbing porous medium consisting of two sublayers with distinct permeabilities is investigated. Solute transport in the medium is described by the nonlinear MIM model involving the Langmuir equation. The solute is divided into two phases. The first one is a mobile phase that drifts with flow and the second one is an immobile phase captured by porous matrix and reducing the total pore space. The model takes into account the saturation concentration, which is a maximal possible amount of solute adsorbed by a unit volume of porous medium. The degree of pore clogging is determined through a clogging coefficient proportional to the saturation concentration. Another coefficient is a sorption parameter including the ratio of adsorption and desorption rates. By varying these coefficients, we obtain the threshold solutal Rayleigh–Darcy number for the onset of convection in the following three types of layered sorbing systems: (1) system with the upper thin highly permeable sublayer, (2) system with the lower thin highly permeable sublayer, and (3) system with equal thick sublayers. The results show that convection onset delays due to the enhancement of clogging effect in all of the three systems. It is more difficult to induce convection here because the pore plugging together with an increase in adsorption rate as compared to desorption rate reduces the mean porosity and permeability of porous matrix. Forward and reverse transitions between the critical convective rolls with different wavelengths are found to occur in the systems 1 and 2 containing the upper or lower thin highly permeable sublayers as the sorption parameter increases. A sequence of “local convection – large-scale convection – local convection” transitions is observed in system 1. There is an opposite sequence of “large-scale convection – local convection – large-scale convection” transitions in system 2. The preferred convective roll width at the onset of convection changes by almost fifth times at the described forward and reverse transitions. It roughly corresponds to the ratio of the total thickness of porous system to that of the thin highly permeable sublayer where local convection generates.

Investigating temperature-driven water transport in cathode gas diffusion media of PEMFC with a non-isothermal, two-phase model

Temperature distribution affects water transport in the porous medium layer of proton exchange membrane fuel cell (PEMFC) by phase-change-induced (PCI) flow. Thus, it is meaningful to reveal the role of PCI flow in removing water. In the present work, a 1-D, non-isothermal, two-phase model is employed to investigate the water transport in cathode gas diffusion layer (GDL) and micro porous layer (MPL). A dimensionless parameter Ts is also proposed to characterize the relation between PCI flow and capillary-driven (CD) flow. It is found that elevating the operating temperature (from 323.15 K to 363.15 K) can facilitate the PCI flow. The high anode and low cathode relative humidity (RHa90%/RHc50%) case contributes to the optimal output performance, corresponding to the largest Ts number and thermal strain. The thermal strain is insignificant compared with the swelling strain and the hygrothermal strain is influenced by the combination of output performance, water distribution and operating conditions. Furthermore, reducing water saturation (sc) at the GDL/gas channel (GC) interface (from 0.12 to 0.0) is conducive to enhancing the proportion of PCI flow in GDL and MPL. By adjusting the operating temperature, inlet RH and removing water at the GDL/GC interface in time enable enhancement of PCI flow and better performance. This work aims to provide a valuable reference for understanding the water transport process and optimizing water management.

Effects of a magnetic field on double-diffusive convection of a nanofluid in a cavity saturated by wavy layers of porous media: ISPH analysis

PurposeThe purpose of this study is to use the incompressible smoothed particle hydrodynamics method to examine the influences of a magnetic field on the double-diffusive convection caused by a rotating circular cylinder with paddles within a square cavity filled by a nanofluid.Design/methodology/approachThe cavity is saturated by two wavy layers of non-Darcy porous media with a variable amplitude parameter. The embedded circular cylinder with paddles carrying T_h and C_h is rotating around the cavity center by a uniform circular velocity.FindingsThe lineaments of nanofluid velocity and convective flow, as well as the mean of Nusselt and Sherwood numbers, are represented below the variations on the frequency parameter, amplitude parameter of the wavy porous layers, Darcy parameter, nanoparticles parameter, Hartmann number and Ryleigh number. The performed simulations showed the role of paddles mounted on circular cylinders for enhancing the transmission of heat and mass within a cavity. The wavy porous layers at the lower Darcy parameter are playing as a blockage for the nanofluid flow within the porous area. Increasing the concentration of the nanoparticles to 6% reduces the maximum flow speed by 8.97% and maximum streamlines |ψ|max by 10.76%. Increasing Hartmann number to 100 reduces the maximum flow speed by 65.83% and |ψ|max by 75.54%.Originality/valueThe novelty of this work is to examine the effects of an inclined magnetic field and rotating novel shape of a circular cylinder with paddles on the transmission of heat/mass in the interior of a nanofluid-filled cavity saturated by undulating porous medium layers.

Prediction of Cerebral Aneurysm Hemodynamics With Porous-Medium Models of Flow-Diverting Stents via Deep Learning

The interventional treatment of cerebral aneurysm requires hemodynamics to provide proper guidance. Computational fluid dynamics (CFD) is gradually used in calculating cerebral aneurysm hemodynamics before and after flow-diverting (FD) stent placement. However, the complex operation (such as the construction and placement simulation of fully resolved or porous-medium FD stent) and high computational cost of CFD hinder its application. To solve these problems, we applied aneurysm hemodynamics point cloud data sets and a deep learning network with double input and sampling channels. The flexible point cloud format can represent the geometry and flow distribution of different aneurysms before and after FD stent (represented by porous medium layer) placement with high resolution. The proposed network can directly analyze the relationship between aneurysm geometry and internal hemodynamics, to further realize the flow field prediction and avoid the complex operation of CFD. Statistical analysis shows that the prediction results of hemodynamics by our deep learning method are consistent with the CFD method (error function <13%), but the calculation time is significantly reduced 1,800 times. This study develops a novel deep learning method that can accurately predict the hemodynamics of different cerebral aneurysms before and after FD stent placement with low computational cost and simple operation processes.

Asymptotic Analysis of Unsteady Ideal Gas Flow Through Layered Porous Media

Asymptotic Analysis of Unsteady Ideal Gas Flow Through Layered Porous Media

Exploration of anisotropy on nonlinear stability of thermohaline viscoelastic porous convection

The nonlinear stability of thermohaline convection in a horizontal layer of an anisotropic porous medium saturated with an Oldroyd-B fluid is studied using a modified perturbation method. Anisotropy in permeability, thermal and solute diffusivities is modelled as second-rank tensors. The cubic Landau equations for steady and oscillatory bifurcating solutions are derived. It is apparent that subcritical instability is possible depending on the choices of governing parameters indicating the linear stability theory is not sufficient to capture the onset of convection. The effect of strain retardation parameter, solute Darcy-Rayleigh number, thermal anisotropy parameter as well as solute anisotropy parameter is to delay, while the effect of stress relaxation parameter, Lewis number and the mechanical anisotropy parameter is to hasten the onset of oscillatory convection. It is found that the stationary bifurcating solution is subcritical while that of oscillatory is supercritical at higher values of solute Darcy-Rayleigh number. The results of Maxwell fluid are obtained as a limiting case. Heat and mass transports are estimated using Nusselt number and Sherwood number, respectively and by tuning the anisotropy parameters it is possible to control the same.

Simulation of the onset of convection in a porous medium layer saturated by a couple-stress nanofluid

Linear and nonlinear stability analyses for the onset of time-dependent convection in a horizontal layer of a porous medium saturated by a couple-stress non-Newtonian nanofluid, intercalated between two thermally insulated plates, are presented. Brinkman and Maxwell–Garnett formulations are adopted for nanoscale effects. A modified Darcy formulation that includes the time derivative term is used for the momentum equation. The nanofluid is assumed to be dilute and this enables the porous medium to be treated as a weakly heterogeneous medium with variation of thermal conductivity and viscosity, in the vertical direction. The general transport equations are solved with a Galerkin-type weighted residuals method. A perturbation method is deployed for the linear stability analysis and a Runge–Kutta–Gill quadrature scheme for the nonlinear analysis. The critical Rayleigh number, wave numbers for the stationary and oscillatory modes, and frequency of oscillations are obtained analytically using linear theory, and the nonlinear analysis is executed with minimal representation of the truncated Fourier series involving only two terms. The effect of various parameters on the stationary and oscillatory convection behavior is visualized. The effect of couple-stress parameter on the stationary and oscillatory convections is also shown graphically. It is found that the couple-stress parameter has a stabilizing effect on both the stationary and oscillatory convections. Transient Nusselt number and Sherwood number exhibit an oscillatory nature when time is small. However, at very large values of time, both Nusselt number and Sherwood number values approach their steady-state values. The study is relevant to the dynamics of biopolymers in solution in microfluidic devices and rheological nanoparticle methods in petroleum recovery.