Gas dispersion in granular porous media under air-dry and wet conditions

Naveed, Muhammad, Hamamoto, Shoichiro, Kawamoto, Ken, Sakaki, Toshihiro, Takahashi, Manabu, Komatsu, Toshiko, Wollesen de Jonge, Lis, Lamandé, Mathieu and Moldrup, Per (2012) Gas dispersion in granular porous media under air-dry and wet conditions. Soil Science Society of America Journal, 76 (3). p. 845. ISSN 0361-5995

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Abstract

Subsurface gaseous-phase transport is governed by three gas transport parameters: the air permeability coefficient (ka), gas diffusion coefficient (DP), and gas dispersion coefficient (DH). Among these, DH is the least understood due to hitherto limited research into the relationship between gas dispersion and soil physical characteristics. In this study, a series of advection–dispersion experiments was performed on granular porous media to identify the effects of soil column dimensions (length and diameter), particle size and shape, dry bulk density, and moisture content on the magnitude of gas dispersion. Glass beads and various sands of different shapes (angular and rounded) with mean particle diameters (d50) ranging from 0.19 to 1.51 mm at both air-dry and variable moisture contents were used as granular porous media. Gas dispersion coefficients and gas dispersivities (α = DH/v, where v is the pore-gas velocity) were determined by fitting the advection–dispersion equation to the measured breakthrough curves. For all test conditions, DH increased linearly with v. The test results showed that neither soil column length nor diameter had significant effect on gas dispersivity. Under air-dry conditions, higher gas dispersivities were observed for media with wider particle size distribution and higher dry bulk density. The minor effect of particle shape on gas dispersivity was found under both air-dry and wet conditions. Under wet conditions, the variations in gas dispersivity were mainly controlled by the air-filled porosity. An empirical model was also proposed for the prediction of gas dispersivity in granular, unsaturated porous media.

Item Type: Article
Subjects: Construction and engineering > Civil and environmental engineering
Construction and engineering
Depositing User: Muhammad Naveed
Date Deposited: 17 May 2018 15:03
Last Modified: 18 May 2018 06:57
URI: http://repository.uwl.ac.uk/id/eprint/5006

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