Journal ArticleDOI
Tortuosity in Porous Media: A Critical Review
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TLDR
The concept of tortuosity is used to characterize the structure of porous media, to estimate their electrical and hydraulic conductivity, and to study the travel time and length for tracer dispersion as mentioned in this paper.Abstract:
The concept of tortuosity is used to characterize the structure of porous media, to estimate their electrical and hydraulic conductivity, and to study the travel time and length for tracer dispersion, but different types of tortuosity—geometric, hydraulic, electrical, and diffusive—have been used essentially interchangeably in the literature. Here, we critically review the tortuosity models developed empirically, analytically, and numerically for flow in both saturated and unsaturated porous media. We emphasize that the proposed tortuosity models are distinct and thus may not be used interchangeably. Given the variety of models that have been developed, and the sharp differences between some of them, no consensus has emerged unifying the models in a coherent way. Related treatments of tortuosity are found in the literature on porous catalysts. In such materials, nonlinear reactions ordinarily accompany transport, and the effective diffusivity within the pore space in the presence of the reactions is distinct from the one in their absence. Thus, because tortuosity may be defined as the ratio of the effective diffusivities in the bulk material and within the pore space, a careful treatment of tortuosity may need to distinguish between transport with and without reactions. This complication is ultimately relevant to soils as well, because bioremediation and biodegradation in soils are always accompanied by nonlinear reactions. Common models of tortuosity include both logarithmic functions and power laws. In many cases, the differences between the logarithmic and power-law phenomenologies are not great, but power laws can usually be reconciled with percolation concepts. Invoking percolation theory provides both insight into the origin of the power functions and a framework for understanding differences between tortuosity models.read more
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References
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Journal ArticleDOI
A closed-form equation for predicting the hydraulic conductivity of unsaturated soils
van Genuchten,M. Th. +1 more
TL;DR: Van Genuchten et al. as mentioned in this paper proposed a closed-form analytical expression for predicting the hydraulic conductivity of unsaturated soils based on the Mualem theory, which can be used to predict the unsaturated hydraulic flow and mass transport in unsaturated zone.
Journal ArticleDOI
Über die von der molekularkinetischen Theorie der Wärme geforderte Bewegung von in ruhenden Flüssigkeiten suspendierten Teilchen
TL;DR: In el marco del Proyecto subvencionado by the Fundación Antorchas (FAN) as discussed by the authors, el material was digitalizado, e.g., en la Biblioteca del Departamento de Fisica de la Facultad de Ciencias Exactas de la Universidad Nacional de La Plata.
Journal ArticleDOI
A new model for predicting the hydraulic conductivity of unsaturated porous media
TL;DR: In this article, a simple analytic model is proposed which predicts the unsaturated hydraulic conductivity curves by using the moisture content-capillary head curve and the measured value of the hydraulic conductivities at saturation.
Journal ArticleDOI
The electrical resistivity log as an aid in determining some reservoir characteristics
TL;DR: The usefulness of the electrical resistivity log in determining reservoir characteristics is governed largely by: (1) the accuracy with which the true resistivity of the formation can be determined; (2) the scope of detailed data concerning the relation of resistivity measurements to formation characteristics; (3) the available information concerning the conductivity of connate or formation waters; and (4) the extent of geologic knowledge regarding probable changes in facies within given horizons, both vertically and laterally, particularly in relation to the resultant effect on the electrical properties of the reservoir as mentioned in this paper.
Journal ArticleDOI
Percolation and Conduction
TL;DR: In this article, an extension of percolation theory to treat transport is described, and a general expression for the conductance of such networks is derived, which relates to the spin-stiffness coefficient of dilute ferromagnet.