Positivity problem and reactive transport simulation ...

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XVI International Conference on Computational Methods in Water Resources (CMWR-XVI) Ingeniørhuset

Positivity problem and reactive transport simulation in porous media
Author:Christophe Le Potier <clepotier@cea.fr> (Commissariat à l'energie atomique)
Alain Genty <alain.genty@cea.fr> (Commissariat à l'energie atomique)
Presenter:Christophe Le Potier <clepotier@cea.fr> (Commissariat à l'energie atomique)
Date: 2006-06-18     Track: Special Sessions     Session: Multi-Disciplinary Approaches To Reactive Transport Simulation In Aquifer Systems

During the last decade, a large amount of work has been done in reactive transport modeling in porous media leading today to geochemical transport codes based on the coupling of transport models and geochemistry modules. In the framework of high-level nuclear waste repository safety calculations, we developed such a code with the numerical platform ALLIANCES allowing the coupling of several classical transport codes (Porflow, MT3D, Traces, Cast3m) and geochemistry modules (PhreeqC, Chess). In order to avoid negative concentration calculation stemming from the transport model that may induce mass non-conservation, non consistent concentration field or geochemistry module fail, one generally use for reactive transport simulations orthogonal meshes oriented with the main velocity direction in spite of the fact that orthogonal meshes are not well adapted to the description of the repository near field including cylindrical shapes (like wastes canisters, repository vaults, galleries) and lead to coarse problem description and/or time consuming calculations. In this paper, we investigate with our ALLIANCES platform, on unstructured 2D mesh of cylindrical shape, the impact of using different spatial schemes (Mixed Hydrid Finite Elements, Finite Volumes (MPFA)) for the transport model including anisotropic heterogeneous dispersive tensor on negative concentration calculation and on global impact on reactive transport model in term of concentration field and mass conservation errors.