Projet ANR H2MNO4

Welcome to H2MNO4

Overview

This website is dedicated to the ANR H2MNO4

Proposal

Abstract

The project H2MNO4 (ANR funded project) will develop numerical models for reactive transport in heterogeneous media. It defines six mathematical and computational challenges and three applications for environmental problems with societal impact. This basic research project matches perfectly well with the first topic of the ANR program and concerns also the fifth topic. The project relies on a consortium of six partners, involving four public research laboratories (INRIA, Geosciences Rennes, ICJ, Pprime), one public institution (ANDRA) and one SME (ITASCA). The consortium has strong interactions with the H+ observatory and two international research laboratories. Numerical models and simulations are essential for studying the fate of contaminants in aquifers. The three applications concern freshwater supply, remediation of mine drainage, waste geological disposal. Chemical reactions must be coupled with advection and dispersion when modeling the contamination of aquifers. The objective is to design both Eulerian and Lagrangian models to deal with challenging modeling issues. Indeed: • the two scales of chemistry and transport must be coupled; • chemical reactivity is conditioned by physical processes, among which diffusion, hydrodynamic dispersion and mixing; • chemical reactions involve many species, interacting with each other and with the aquifer; thresholds govern the precipitation or dissolution of minerals; • dispersion coefficients can vary from one species to another; • waste storage means an evolution of the repository during thousands of years; • reactions are highly nonlinear and lead to dynamic sharp fronts. These complex models give rise to numerical difficulties that require adaptive discrete schemes and advanced computational tools. An original Lagrangian model, dealing with interacting particles and heterogeneity, will be designed by the project and will rely on a sound mathematical study. Chemistry will include kinetic and equilibrium reactions, with mobile and fixed species produced by sorption or precipitation. The coupled model is then a set of nonlinear Partial Differential Algebraic Equations. So far, simulations using Lagrangian methods do not take into account such complex systems thus a breakthrough of the project will be to overcome this limit. If Eulerian methods are able to deal with complex chemistry, the transport process, the nonlinearities and the size of the problems require advanced computational tools. Numerical artifacts such as artificial diffusion or oscillations can appear, mainly when advection dominates. Global methods are more robust than sequential ones, at the price of solving large sparse linear systems (the size is the number of cells times the number of primary species). The target is to run 3D models with 10 millions of cells and 30 species. In such models, memory and CPU requirements are large, because of the spatial and temporal scales. The project aims at using high performance computing and scalable solvers in order to provide efficient methods. Target computers are composed of up to 500 cores in clusters of Grid’5000 and up to 2000 cores of multiprocessors at Genci (Idris and Cines). Software development and simulations on multicore architectures is a major task in the project. Emphasis will be put on adaptive discrete schemes and on optimized parallel algorithms. Another strong point of the project is related to benchmarking. Test cases will help in validating the numerical models and software. They will contribute to choosing the best method for the problem at hand and to solving industrial problems that arise in water resources management, mine drainage and waste disposal.

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