Direct simulation of heterogeneous diffusion and inversion procedure applied to an out-diffusion experiment. Test case of Palmottu granite.
J Contam Hydrol
; 93(1-4): 21-37, 2007 Aug 15.
Article
en En
| MEDLINE
| ID: mdl-17346849
ABSTRACT
An out-diffusion laboratory experiment using a non-reactive tracer was fitted using the Time Domain Diffusion (TDD) method. This rapid particle tracking method allows simulation of the heterogeneous diffusion based on pore-scale images and local values of diffusivities. The superimposed porosity and mineral 2D maps act as computation grids to condition diffusion pathways. We focused on a Palmottu granite sample, in which the connected pore space has a composite microstructure with cracks linking microporous minerals and is above the percolation threshold. Three main results were achieved (i) When compared to the fitting obtained with one coefficient (best mean square residual R = 1.6 x 10(-2)), diffusion is shown to be suitably characterised with two coefficients related to cracks and microporous minerals (best R = 6.5 x 10(-4)), (ii) rather than imposing a local apparent diffusion coefficient D(a) independent of the local porosity Phi, a best fit is obtained by applying Archie's relationship D(a) = D(0) x G with G = Phi(m) to each pixel of the calculation grids (G is the geometry factor, D(0) is the diffusion coefficient in free fluid, and m is Archie's exponent), and (iii) the order of magnitude of the fitted diffusion coefficient or Archie's exponents (m=0 for microcracks and m=1.82 for microporous minerals) is physically realistic.
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Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Contaminación Radiactiva del Agua
/
Purificación del Agua
Tipo de estudio:
Prognostic_studies
/
Risk_factors_studies
País/Región como asunto:
Europa
Idioma:
En
Revista:
J Contam Hydrol
Asunto de la revista:
TOXICOLOGIA
Año:
2007
Tipo del documento:
Article
País de afiliación:
Francia