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Discretizing the fracture-matrix interface to simulate solute transport |
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| Authors: | Weatherill Douglas Graf Thomas Simmons Craig T Cook Peter G Therrien Rene Reynolds David A |
| Institution: | Département de Géologie et Génie Géologique, UniversitéLaval, Quebec, Canada G1K 7P4;and; Currently at Centre of Geosciences, Goldschmidtstrasse 3, Georg-August-University Göttingen, 37077 Göttingen, Germany.; School of Chemistry, Physics and Earth Sciences, Flinders University, South Australia, Australia;; CSIRO Land and Water, Private Bag 2, Glen Osmond, South Australia 5064, Australia;; Département de Géologie et Génie Géologique, UniversitéLaval, Quebec, Canada;; School of Environmental Systems Engineering, University of Western Australia, M015, 35 Stirling Highway, Crawley, Western Australia 6009, Australia; |
| Abstract: | This article examines the required spatial discretization perpendicular to the fracture-matrix interface (FMI) for numerical simulation of solute transport in discretely fractured porous media. The discrete-fracture, finite-element model HydroGeoSphere ( Therrien et al. 2005 ) and a discrete-fracture implementation of MT3DMS ( Zheng 1990 ) were used to model solute transport in a single fracture, and the results were compared to the analytical solution of Tang et al. (1981) . To match analytical results on the relatively short timescales simulated in this study, very fine grid spacing perpendicular to the FMI of the scale of the fracture aperture is necessary if advection and/or dispersion in the fracture is high compared to diffusion in the matrix. The requirement of such extremely fine spatial discretization has not been previously reported in the literature. In cases of high matrix diffusion, matching the analytical results is achieved with larger grid spacing at the FMI. Cases where matrix diffusion is lower can employ a larger grid multiplier moving away from the FMI. The very fine spatial discretization identified in this study for cases of low matrix diffusion may limit the applicability of numerical discrete-fracture models in such cases. |
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