Transport and Relaxation Phenomena in Porous Media

Hilfer, R.

doi:10.1002/9780470141519.ch3

Cited by 96 publications

(66 citation statements)

References 283 publications

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“…In general, the detailed reconstruction of the structural properties for the porous material can be performed by the methods of the percolation theory [15], deterministic or stochastic geometry [16]. 6.…”

Section: The Function Of Distribution Of the Pore Sizes According To mentioning

confidence: 99%

Investigation of the structural properties of porous material according to the sorption isotherms and drainage curves

Holubets¹

2016

Math. Model. Comput.

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Section: The Function Of Distribution Of the Pore Sizes According To mentioning

confidence: 99%

Investigation of the structural properties of porous material according to the sorption isotherms and drainage curves

Holubets¹

2016

Math. Model. Comput.

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“…Determining local density distributions is a very general way to characterize the nanostructure of composite materials 45 . It is conceivable that the structural resonances correspond to local regions with different volume fractions of Ni nanoparticles in the sample.…”

Section: Spectral Density Functionsmentioning

confidence: 99%

Spectral density analysis of the optical properties of Ni-Al 2 O 3 nano-composite films

2011

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Thin films consisting of transition metal nanoparticles in an insulating oxide exhibit a high solar absorptance together with a low thermal emittance and are used as coatings on solar collector panels. In order to optimise the nanocomposites for this application a more detailed understanding of their optical properties is needed. Here we use a highly efficient recently developed numerical method to extract the spectral density function of nickel-aluminum oxide (Ni-Al 2 O 3 ) composites from experimental data on the dielectric permittivity in the visible and near-infrared wavelength ranges. Thin layers of Ni-Al 2 O 3 were produced by a sol-gel technique. Reflectance and transmittance spectra were measured by spectrophotometry in the wavelength range 300 to 2500 nm for films with thicknesses in the range 50 to 100 nm. Transmission electron microscopy showed crystalline Ni particles with sizes in the 3 to 10 nm range. The spectral density function shows a multi-peak structure with three or four peaks clearly visible. The peak positions are influenced by particle shape, local volume fraction distributions and particle-particle interactions giving rise to structural resonances in the response of the composite to an electromagnetic field.

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“…Numerical and experimental investigations of fluid flow in porous and granular media are of crucial importance in many research areas, such as the recovery of hydrocarbons from oil reservoirs [4,5], ground water flow [6] or gas diffusion in fuel cells [7]. In spite of extensive scientific research, there are still many open questions namely which and how macroscopic transport factors other than porosity affect the fluid flow in a porous medium with a given microstructure [7][8][9][10][11].…”

Section: Introductionmentioning

confidence: 99%

“…In spite of extensive scientific research, there are still many open questions namely which and how macroscopic transport factors other than porosity affect the fluid flow in a porous medium with a given microstructure [7][8][9][10][11]. An experimentally and numerically determinable parameter of porous materials is the intrinsic permeability which is highly sensitive to the underlying microstructure.…”

Section: Introductionmentioning

confidence: 99%

Hydraulic properties of porous sintered glass bead systems

et al. 2017

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In this paper, porous sintered glass bead packings are studied, using X-ray Computed Tomography (XRCT) images at 16 µm voxel resolution, to obtain not only the porosity field, but also other properties like particle sizes, pore throats and the permeability. The influence of the sintering procedure and the original particle size distributions on the microstructure, and thus on the hydraulic properties, is analyzed in detail. The XRCT data are visualized and studied by advanced image filtering and analysis algorithms on to the extracted sub-systems (cubes of different sizes) to determine the correlations between the microstruc- Institute of Applied Mechanics (CE), University of Stuttgart, Pfaffenwaldring 7, 70569 Stuttgart, Germany ture and the measured macroscopic hydraulic parameters. Since accurate permeability measurements are not simple, special focus lies on the experimental set up and procedure, for which a new innovative multi-purpose cell based on a modular concept is presented. Furthermore, segmented voxel-based images (defining the microstructure) are used for 3D (three-dimensional) lattice Boltzmann simulations to directly compute some of the properties in the creeping flow regime. A very good agreement between experimental and numerical porosity and permeability could be achieved, in most cases, validating the numerical model and results. Porosity and permeability gradients along the sample height could be related to gravity acting during sintering. Furthermore, porosity increases in the outer zones of the samples due to the different contact geometry between the beads and the confining cylinder wall during sintering (which is replaced by a membrane during permeability testing to close these pores at the surface of the sample). The influence of different filters on the gray scale distributions and the impact of the segmentation procedure on porosity and permeability is systematically studied. The complex relationships and dependencies between numerically determined permeabilities and hydraulic influence parameters are investigated carefully. In accordance to the well-known Kozeny-Carman model, a similar trend for local permeability values in dependence on porosity and particle diameter is obtained. Other than statistical models, which estimate the pore throat distribution on the basis of the particle size distribution, in this study XRCT scans are used to determine the pore throats in sintered granular systems, which are finally linked to the intrinsic permeability through the lattice Boltzmann simulations. From the μXRCT analysis two distinct peaks in pore throat distributions could be identified, which can be clearly assigned to typical pore throat areas occurring in polydisperse granular systems. Moreover, a linear dependency between average pore throat diameter and porosity as well as between permeability and pore throat diameter is reported. Furthermore, almost identical mean values for porosity and permeability are found from sub-system and full-system REV analysis. For sintered granular...

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Transport and Relaxation Phenomena in Porous Media

Cited by 96 publications

References 283 publications

Investigation of the structural properties of porous material according to the sorption isotherms and drainage curves

Investigation of the structural properties of porous material according to the sorption isotherms and drainage curves

Spectral density analysis of the optical properties of Ni-Al 2 O 3 nano-composite films

Hydraulic properties of porous sintered glass bead systems

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