Inclusion Of Permeability Research Articles

Anti-plane analysis for elliptical inclusion in magnetoelectroelastic materials

This paper considers the multi-field coupling in magneroelectroelastic composite materials consisting of the inclusion and the matrix are magnetoelectroelastic materials. The mechanical, electric and magnetic fields around an elliptical cylinder inclusion are formulated by complex potentials. Inside the inclusion, the strain, electric and magnetic fields are found to be uniform and vary with the shape of the ellipse. When the inclusion is reduced to a crack, along the interface, the strain, electric field strength and magnetic field strength equal the corresponding remote ones, which can be used as the boundary condition. Special cases, such as a rigid and permeable inclusion, a soft and impermeable inclusion, a line inclusion and a crack problem are discussed in detail.

Infrared magnetic response in a random silicon carbide micropowder

We generalize the theoretical model of magnetic metamaterials made of dielectric particles to treat random particle sizes, shapes, and orientations. We demonstrate that the magnetic-dipole response of these randomly shaped subwavelength particles can be approximated with Mie theory as though they were spheres, while a quasistatic ellipsoidal approximation is used for the electric-dipole response. We verify our model with experimental measurement of a bulk magnetic response in a micropowder of milled SiC particles. Using such a crude powder could lead to immensely simplified negative permeability inclusions for negative index metamaterials.

Investigation of liquefaction and pore water pressure development in layered sands

This paper presents the results of shaking table model tests which were carried out to investigate the pore water pressure generation and related liquefaction mechanism in layered sand deposits. The experiments were performed on uniform sand columns, silt interlayered sand columns and two layered sand columns deposited at various relative densities and subjected to different input excitations. During the experiments excess pore water pressures were measured by pore pressure transducers installed at three different depths and, surface settlements and thickness of water film developed under less permeable inclusions were measured by a digital camera. The experimental results are discussed and compared to demonstrate the effects of relative density, input acceleration and presence of a silt seam on the generation of excess pore water pressure in sand deposits subjected to dynamic loading. The results showed that the presence of a less permeable silt interlayer within the sand deposit and existence of a loose sand layer underlying dense sand deposits can have significant effect on the pore water pressure generation mechanism.

Hillslope dynamics modeled with increasing complexity

Summary Few studies have investigated how much model complexity is needed to simulate both the hillslope outflow and the internal hillslope dynamics. We studied the influence of model complexity on simulations for the Panola Mountain trenched hillslope. We analyzed the influences of the inclusion of bedrock permeability, variable soil depth and preferential flow on modeled hillslope responses. We found that without the inclusion of bedrock leakage the long-term subsurface flow response measured at the trenchface and the threshold relation between total precipitation and total subsurface flow could not be simulated adequately. Individual events could still be represented acceptably, showing the importance of long time series for model calibration and validation. The use of spatially constant bedrock conductivity allowed us to simulate spatially variable bedrock leakage rates because of the spatially variable depths of saturation. Without variable soil depth the spatial variability of subsurface flow along the trenchface and its temporal dynamics during events could not be represented. In addition the spatial patterns of saturation at the soil-bedrock interface did not agree with the observed patterns and responses to smaller events were underestimated. Inclusion of preferential flow mainly influenced the distribution of the maximum saturation depths at the soil-bedrock interface and increased peak flows and recessions. Soil moisture measurements were less useful for model validation for the Panola hillslope than measurements of the spatial patterns of saturation and subsurface flow. We plea for a new blue print for the set-up of hillslope experiments such that their data is useful for studies on hillslope model complexity and for model validation and rejection.

Analytical effective coefficient and a first-order approximation for linear flow through block permeability inclusions

We present a closed form solution for the upscaled diffusion coefficient and derive a first-order homogenized approximation to linear flow equations with periodic and rapidly oscillating coefficients. The coefficients are defined as step functions describing inclusions of various shapes in a main matrix. This constitutes the n -dimensional upscaled version of Darcy’s law for linear flow in such systems. We consider the two-scale asymptotic expansion of the solution of the flow equation, and develop a corrector to an analytical approximation for the solution of the periodic cell-problem. We demonstrate that the proposed analytical form for the effective coefficient satisfies the generalized Voigt–Reiss’ inequality and is in agreement with other known theoretical results, including the geometric average for the checkerboard geometry, and with some published numerical results. The zeroth-order approximation in H 1 ( Ω ) is readily obtained and the first-order approximation in L 2 ( Ω ) is derived from the proposed analytical approximation to the basis functions. The analytical basis functions are also used to define a correction function that incorporates the heterogeneous features into the zeroth-order approximation to the gradient and flux, which considerably improves the convergence results. We illustrate the procedure with coefficients describing square inclusions with contrast ratios between the inclusion and the matrix as 10:1, 100:1, 1000:1 and 1:10, respectively. We demonstrate numerically that the convergence properties of the proposed approximations agree with the classical theoretical results in homogenization theory.

A radio-wave method for detecting and identifying permeable inclusions in stratified inhomogeneous media

The problems associated with the efficiency of practical application of a numerical algorithm for detecting, locating, and identifying inhomogeneous dielectric inclusions in plane-layered media are considered. The results of computational experiments on the determination of both physical and geometric parameters of inhomogeneities and the effect of the measurement error on the quality of the inspection procedure are presented. This method can be used in the nondestructive testing of the quality of industrial dielectric articles.

Quantification of cerebral perfusion using arterial spin labeling: Two‐compartment models

One of the advantages of arterial spin labeling (ASL) techniques over other techniques for measuring cerebral perfusion is that with ASL it is possible to achieve accurate quantification. This is particularly useful in the field of functional imaging, where accurate measurements of perfusion change can help untangle the complex physiological changes that occur following neuronal activation. However, the linearity of the perfusion estimate over a wide range of perfusion values may be more important than absolute values. For several years, single-compartment models have dominated the literature, and it has been assumed that the labeled water diffuses freely throughout the tissue voxel. However, recent work, as summarized in this review, has shown that this assumption is inaccurate and leads to an overestimation of perfusion at low perfusion rates, and an underestimation at high rates. The inclusion of restricted permeability of the capillary wall to water in a two-compartment model offers improved quantification.

Modelling of unsaturated water flow in soils with highly permeable inclusions

In this paper the mathematical macroscopic modeling of unsaturated water flow in a porous medium (soil) with highly permeable porous inclusions is presented. It is supposed that water flow in each sub domain can be described by the strongly non-linear Richards' equation. Gravity effects are considered. The upscaling process of this stiff problem is performed using the homogenization method of periodic structures with asymptotic expansions. The resulting non-linear macroscopic description is a one equation model, revealing the local equilibrium of the capillary pressure head. The effective water retention capacity was found to be the volume average of the water retention capacities of the two porous sub-domains. The effective conductivity tensor is obtained from a linear and non-stiff boundary value problem at the heterogeneity scale. To cite this article: J. Lewandowska, J.-L. Auriault, C. R. Mecanique 332 (2004).

Time‐dependent transport in heterogeneous formations of bimodal structures: 2. Results

The theoretical results of part 1 [Dagan and Fiori, 2003] for modeling time‐dependent, advective transport of a conservative solute in porous formations of bimodal structure are applied to illustrate the behavior of a few trajectory statistical moments as function of time, of the permeability contrast κ, and of the inclusions volume density n. The computations are carried out for circular (2D) and spherical (3D) inclusions to represent isotropic media. Advective transport is solved by studying the distortion of a thin plume, linear (2D) or planar (3D), normal to the mean velocity U and moving through a single inclusion. The deformation of the plume is determined from the residual trajectories of solute particles that are derived numerically by a quadrature. The longitudinal macrodispersivity is defined by αL(t; n, κ) = (2U)−1dX11/dt, where X11 is the trajectories second moment in the mean flow direction. The general behavior of the time‐dependent longitudinal dispersivity αL(t; n, κ) and, in particular, its constant, large time limit are examined. The tendency of αL to the “Fickian” limit with time depends strongly on the conductivity contrast; in particular, for low permeable inclusions (κ ≪ 1) it may be extremely slow. It is shown that the first‐order approximation in the conductivity contrast κ is of limited validity (0.3 < κ < 2). The transverse moment X22 tends asymptotically to a constant value. The analysis of the trajectory high order moments shows that the probability density function (pdf) of the solute trajectories tends to normality at large time. Similar to the “Fickian” limit the normal distribution may be reached at very large time in presence of low conductivity inclusions, with the pdf characterized by significant tailing for the trailing part of the pdf.

Can the maintenance of overpressured fluids in large strike-slip fault zones explain their apparent weakness?

Research Article| June 01, 2001 Can the maintenance of overpressured fluids in large strike-slip fault zones explain their apparent weakness? Daniel R. Faulkner; Daniel R. Faulkner 1Department of Earth Sciences, University of Manchester, Manchester M13 9PL, UK Search for other works by this author on: GSW Google Scholar Ernest H. Rutter Ernest H. Rutter 1Department of Earth Sciences, University of Manchester, Manchester M13 9PL, UK Search for other works by this author on: GSW Google Scholar Geology (2001) 29 (6): 503–506. https://doi.org/10.1130/0091-7613(2001)029<0503:CTMOOF>2.0.CO;2 Article history received: 06 Sep 2000 rev-recd: 31 Jan 2001 accepted: 19 Feb 2001 first online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Daniel R. Faulkner, Ernest H. Rutter; Can the maintenance of overpressured fluids in large strike-slip fault zones explain their apparent weakness?. Geology 2001;; 29 (6): 503–506. doi: https://doi.org/10.1130/0091-7613(2001)029<0503:CTMOOF>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract The nucleation of earthquakes on weak faults is still poorly understood. Favored models for weakening have invoked the presence of high-pressure fluids contained within the fault. Here, from detailed field mapping, permeability measurements, and modeling, we assess how pressurized fluids may be impounded by layers of low-permeability phyllosilicate- rich fault gouge. Constraints are made on the permeability anisotropy, fluid-flow pathways, and fluid-loss rates from a large transcurrent fault zone. It is concluded that phyllosilicate-rich fault gouges having permeabilities ranging from 10−17 to 10−21 m2 and cumulative layer thicknesses of ∼50–200 m (from field observations) need fluid fluxes at the base of the brittle part of a large transcurrent fault (assumed to extend from 0 to 15 km depth) of ∼0.1 m3·m−2·yr−1. Furthermore, permeability anisotropy must exceed three orders of magnitude for overpressures to develop. This finding implies that vertical permeability must be enhanced by relatively permeable inclusions of fractured protolith within the fault zone, enclosed by walls of low-permeability gouge. For cross-zone flow, the lateral continuity of the phyllosilicate-rich fault-gouge layers provides effective barriers to fluid flow both into and out of the fault zone. This geometry restricts the origin of fluids in large fault zones as it favors fluids derived from deep sources. However, the fluid flux over time of mantle-derived CO2 and water produced from dehydration reactions has been estimated and appears inadequate. Given the frictional characteristics of phyllosilicate-rich fault gouge, small earthquakes and fault creep are the most likely modes of failure, facilitated by the buildup of high-pressure fluids in cells, producing spatial weakening of the fault. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Slow advection and diffusion through low permeability inclusions

Heterogeneous porous media with low permeability lenses can produce contaminant plumes with extended tails. Highly asymmetric breakthrough curves cannot be described well by an advection–dispersion equation (ADE) with a uniform velocity and dispersion coefficient. The character of such a solute plume depends on many factors, including plume size, the geometry and arrangement of the low permeability inclusions, and the transport through such regions. We develop an inclusion Peclet number that effectively characterizes the relative importance of advection and diffusion for transport within a low permeability lens. This inclusion Peclet number is a function of the far-field velocity, the effective diffusion coefficient, the length scale of the inclusion, and the ratio of the permeability of the lens to that of the surrounding matrix. We investigate the effects of a single, elliptical inclusion on the arrival of a solute at a downgradient control plane with numerical particle tracking. Effects specific to advection or diffusion dominance within the inclusion are subtle: diffusion gives rise to more distributed tailing whereas advection produces behavior that is more abrupt. These slight differences are not enough to allow one to determine the dominant process within the inclusion by observing the first three temporal moments alone. The time scale for the dominant transport process within the inclusion is the primary factor affecting the contaminant tailing. For high inclusion Peclet numbers (when advection dominates), the characteristic time varies with the permeability contrast, the far-field velocity, and the size and geometry of the inclusion. For low inclusion Peclet numbers (when diffusion dominates), the characteristic time varies with the size of the inclusion and the effective diffusion coefficient.

Response of Inhomogeneous Seabed around Buried Pipeline under Ocean Waves

Recently, considerable efforts have been devoted to the phenomenon of wave-seabed-pipeline interaction. However, conventional investigations for this problem have been concerned with a uniform seabed, despite the strong evidences of variable permeability and shear modulus. In this paper, a finite-element model is proposed to investigate the wave-induced pore pressure, effective stresses, and soil displacements in the vicinity of a buried pipeline in a porous seabed with variable permeability and shear modulus. The numerical results indicate that the inclusion of variable permeability and shear modulus significantly affects the wave-induced soil response around the pipeline. The influence of the variable permeability and shear modulus and geometry of the pipe on the wave-induced soil response around a buried pipeline are also detailed.

Wall material properties of yeast cells. Part II. Analysis

In the preceding paper (Part I) force–deformation data were measured with the compression experiment in conjunction with the initial radial stretch ratio and the initial wall-thickness to cell-radius ratio for baker's yeast ( Saccharomyces cerevisiae). In this paper, these data have been analysed with the mechanical model of Smith et al. ( Smith, Moxham & Middelberg (1998) Chemical Engineering Science, 53, 3913–3922) with the wall constitutive behaviour defined a priori as incompressible and linear-elastic. This analysis determined the mean Young's modulus ( E ̄ ), mean maximum von Mises stress-at-failure ( σ ̄ VM,f ) and mean maximum von Mises strain-at failure ( ε ̄ VM,f ) to be E ̄ =150±15 MPa, σ ̄ VM,f =70±4 MPa and ε ̄ VM,f =0.75±0.08, respectively. The mean Young's modulus was not dependent ( P⩾0.05) on external osmotic pressure (0–0.8 MPa) nor compression rate (1.03–7.68 μm/s) suggesting the incompressible linear-elastic relationship is representative of the actual cell-wall constitutive behaviour. Hydraulic conductivities were also determined and were comparable to other similar cell types (0–2.5 μm/MPa s). The hydraulic conductivity distribution was not dependent on external osmotic pressure (0–0.8 MPa) nor compression rate (1.03–7.68 μm/s) suggesting inclusion of cell-wall permeability in the mechanical model is justified. ε ̄ VM,f was independent of cell diameter and to a first-approximation unaffected ( P⩾0.01) by external osmotic pressure and compression rate, thus providing a reasonable failure criterion. This criterion states that the cell-wall material will break when the strain exceeds ε ̄ VM,f =0.75±0.08. Variability in overall cell strength during compression was shown to be primarily due to biological variability in the maximum von Mises strain-at-failure. These data represent the first estimates of cell-wall material properties for yeast and the first fundamental analysis of cell-compression data. They are essential for describing cell-disruption at the fundamental level of fluid–cell interactions in general bioprocesses. They also provide valuable new measurements for yeast-cell physiologists.

Two-dimensional scattering of electromagnetic waves from a permeable inclusion in an anisotropic medium

Integrodifferential equations for the cross section of the scatterer and a collocation method are used to obtain a numerical solution of the problem of scattering of an H-polarized wave by an anisotropic layer of a three-layer dielectric structure.

Calculating unsteady seepage in a pressure gradient in the presence of thin weakly permeable inclusions

A new mathematical model is developed for unsteady seepage in a pressure gradient through a compressible foundation of a gravity dam with an antiseepage curtain. High-accuracy discretization algorithms are developed for the corresponding initial boundary-value problem with a discontinuous solution.

Reinforced Soil Structures with Poorly Draining Backfills. Part I: Reinforcement Interactions and Functions

In this and a companion paper (Mitchell and Zornberg 1994), the use and performance of reinforced soil structures constructed with poorly draining and/or cohesive backfills is evaluated. This evaluation shows that proper design and construction can result in stable, durable, and economical earth structures. Permeable reinforcements may be especially useful for soil structures with poorly draining backfills because the drainage capabilities of the geosynthetic can dissipate excess pore water pressures, thus enhancing stability. Consequently, the design of a safe and economical structure should address two aspects specific to poorly draining backfills: the cohesive soil-reinforcement interaction and the reinforcement drainage characteristics. The present paper focuses on experimental and analytical studies undertaken to evaluate these issues. Tensile strength, durability, and creep response of geosynthetics embedded in marginal soils are also addressed. There is strong experimental evidence that permeable inclusions can effectively reinforce clay structures.

Solution of the nonlinear seepage problem with weakly permeable inclusions

An algorithm for numerical solution of the problem is proposed. Calculations performed by the corresponding programs are reported. The effect of inclusions on seepage characteristics is analyzed.

An Experimental Investigation of the Effect of Idealized Heterogeneity on the Dispersion of Miscible Fluids

Laboratory experiments on dispersion of miscible fluids in a porous medium have been performed. Dimensionally scaled two‐dimensional models were packed with both homogeneous and idealized heterogeneous permeability distributions. Longitudinal dispersion coefficients were calculated by mapping the flow into the streamline‐equipotential coordinate system. The results of these experiments indicate that the dispersion coefficient is not a function of the spatial scale of the system provided that the permeability distribution is preserved as the system dimension is increased. Also, it was found that an inclusion of permeability differing from the surrounding medium could result in both Gaussian and non‐Gaussian tracer distributions depending upon the location of the inclusion, and systems with heterogeneous permeability distributions sometimes resulted in dispersion similar to that for homogeneous media. In some instances, the dispersion everywhere within the system appeared to be Fickian, but when the dispersion was monitored at the withdrawal point from the system, the dispersion appeared to be non‐Fickian.

Macroscopic dispersion in porous media: The controlling factors

One of the most important limitations to the application of modeling techniques for the analysis of mass transfer in groundwater systems is the difficulty in characterizing the dispersive character of natural systems. Although large quantities of experimental data exist for laboratory scale experiments, the handful of measurements which have been obtained from regional systems suggest that dispersion produced by large‐scale porous medium nonidealities is considerably more important. In this paper the effects of macroscopic dispersion are simulated for uniform heterogeneous porous media under conditions of one‐ dimensional flow. The idealized media considered for detailed analysis consist of low permeability inclusions within a higher‐permeability medium. When the inclusions are not arranged rather homogeneously within the region, a unique dispersivity value for the medium cannot be defined, and dispersivity changes as a function of space. The magnitude of dispersion is controlled by the contrast in hydraulic conductivity between the inclusions and the remainder of the medium, the number of inclusions, and the mode of aggregation. Generally, dispersivity is found to decrease as the conductivity contrast decreases and the structure of the medium is regularized. It will be possible to estimate the dispersivity of a medium by using stochastic analysis. Hypothetical porous media with characteristics similar to those of some actual medium will yield a range of dispersivity values. The basic data for this technique will be detailed statistical analysis of the mode of porous medium aggregation and the conductivity contrasts within the medium.