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Diffusive Transport of Gases in Wet Porous Media. Application to Radon
Author(s) -
Meslin Pierre-Yves,
Adler Pierre M.,
Sabroux Jean-Christophe
Publication year - 2010
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj2009.0474
Subject(s) - porous medium , saturation (graph theory) , porosity , soil water , diffusion , mineralogy , materials science , soil science , thermodynamics , chemistry , geology , geotechnical engineering , physics , mathematics , combinatorics
The prediction of macroscopic diffusion coefficients in dry and wet porous media still strongly relies on measurements, and numerous semi‐empirical correlations have been proposed over the years to replace burdensome experimentations, but the range of validity of these correlations can be limited and is not even well‐defined. Here, we present ab initio numerical calculations of the diffusion coefficient of two classes of porous media, namely consolidated and unconsolidated soils, where the water phase distribution is obtained by a lattice Boltzmann technique incorporating interfacial tension and wetting. We show that these reconstructed media can well represent two categories of soils generally encountered, namely undisturbed and repacked soils, whose diffusivities, to first order, exhibit two distinct dependencies on porosity under dry conditions, but a similar dependence on the water saturation level. We provide a theoretical support to the popular Buckingham law for dry undisturbed soils in the 0.2 to 0.45 porosity range investigated here. This semi‐empirical correlation also compares well with our results on wet consolidated soils, although the dependence of the diffusion coefficient on the water saturation level does not seem to be a simple power law. These results, supported by available experiments on gases such as oxygen, hydrogen, or carbon dioxide, appear to be representative of large classes of porous media. The data and their correlations relative to radon are discussed. Finally, some discrepancy with experimental data regarding the value of the percolation threshold remains, which should be investigated further in the future.