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Etude du transport miscible en milieux poreux hétérogènes: Prise en compte du non-équilibre

Abstract : The impact of heterogeneities on solute transport in the subsurface has been the focus of intensive
research in recent years. Anomalous dispersion at the field-scale is partly attributed to physical nonequilibrium
effects such as solute transfer between different regions with highly contrasted characteristics
(permeability, porosity, ...).
With large-scale non-equilibrium effects, macroscopic miscible flow cannot be described using the
classical advective-dispersive transport equation. An up-scaling method must be used in order to take into
account the heterogeneities, and give a macroscopic representation of solute transport. This change of
scale problem has been treated theoretically by different up-scaling techniques, such as the method of
large-scale volume averaging. This method calculates the transport equations and the effective properties
at a given scale by an averaging process over the equations corresponding to the lower scale. In this way,
the large-scale properties are given explicitly from a local representation of heterogeneities through a set
of three closure problems. The resulting model is an extension of dual-porosity models, with the
capability of dealing with fully "mobile-mobile" systems. Several one-equation models are derived and
compared (asymptotic behavior, local equilibrium assumption, non-equilibrium case).
A numerical procedure is proposed to solve the closure problems for any geometry, and therefore
calculate the macroscopic transport coefficients. In order to test the two-equation model, theoretical
results are compared to numerical experiments in the case of stratified and nodular systems. Then, we
explore the possibility of using this two-medium treatment in connection with a geo-statistical
representation of the heterogeneities. Random stratified systems and bi-dimensionnal random media are
studied, the results show a reasonable agreement between theory and experiment.
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Contributor : Fabien Cherblanc <>
Submitted on : Monday, October 16, 2006 - 6:30:11 PM
Last modification on : Wednesday, May 29, 2019 - 10:04:01 AM
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Fabien Cherblanc. Etude du transport miscible en milieux poreux hétérogènes: Prise en compte du non-équilibre. Hydrologie. Université Sciences et Technologies - Bordeaux I, 1999. Français. ⟨tel-00106971⟩

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