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Etude du tranport 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 3, 2005 - 3:00:30 PM
Last modification on : Friday, April 19, 2019 - 1:20:57 AM
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Fabien Cherblanc. Etude du tranport miscible en milieux poreux hétérogènes: Prise en compte du non-équilibre. Sciences de l'ingénieur [physics]. Université Sciences et Technologies - Bordeaux I, 1999. Français. ⟨tel-00010366⟩

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