M³: a multiphase, multiconstituant and multiprocess code to model contaminated

70% of the contaminated sites in France are with organic compounds (hydrocarbons, chlorinated solvents,…). Modeling such contamination can be difficult as it is governed by numerous and highly coupled mechanisms (multiphase flow, dissolution and volatilization of Non Aqueous Phase Liquids(NAPL), sorption and biodegradation). Whereas many numerical codes include some of these mechanisms, none of them, to our knowledge, allows the modeling of the full set of mechanisms. A new code, called M3 for Multiphase, Multicomponent, Multiprocess, is then being developed to address this kind of modeling. The originality of the code stands both in the diversity of the mechanisms and in original formalisms such as non-local equilibrium dissolution of NAPL or biodegradation formalism dedicated to chlorinated solvents. After a short description of the numerical code, test cases will be presented to highlight the capacity of the code to model many situations that might be accoutered when dealing with contaminated sites (prediction of an accidental spill, temporal evolution of a source zone and its impact on aquifers, assessment of biodegradation…)

CubicM, un code de calcul pour simuler le devenir de polluants organiques dans le milieu souterrain

Le logiciel CubicM est dédié à la modélisation du devenir des polluants organiques dans le milieu souterrain. L'originalité du code tien dans le fait que i)il intègre l'ensemble des mécanismes qui régissent le comportement de ce type de polluants (écoulements triphasiques / transport / dissolution / biodégradation ...); ii) des formalismes mathématiques originaux ont été inclus afin de gagner en précision. Cet outil permet ainsi de modéliser un grand nombre de situations rencontrées sur des sites pollués

Multiphase multicomponent modelling of the NAPL transfer in the subsurface using Method of Lines

This paper presents the three dimensional multicomponent multi-phase simulator CUBICM (M3 ) combining reactive transport and mass transfer modules. The main purpose of this tool is to evaluate and quantify Non-Aqueous Phase Liquid (NAPL) plume attenuation by soil microorganisms and kinetic mass transfer processes such as dissolution, volatilization, sorption. Physical, biological and numerical concepts are given here in a fully embedded method of lines scheme using control volume finite element. The aim of the developed numerical code is to allow a flexible selection of physical formalisms via a dedicated Graphical User Interface in order to study the fate of pollutants in time and space. Various test cases are then illustrated with 2D and 3D semi-realistic heterogeneous configurations

Comparative genomics reveal novel heat shock regulatory mechanisms in Staphylococcus aureus and other Gram-positive bacteria

International audienceMultiple regulatory mechanisms for coping with stress co-exist in low G+C Gram-positive bacteria. Among these, the HrcA and CtsR repressors control distinct regulons in the model organism, Bacillus subtilis. We recently identified an orthologue of the CtsR regulator of stress response in the major pathogen, Staphylococcus aureus. Sequence analysis of the S. aureus genome revealed the presence of potential CtsR operator sites not only upstream from genes encoding subunits of the Clp ATP-dependent protease, as in B. subtilis, but also, unexpectedly, within the promoter regions of the dnaK and groESL operons known to be specifically controlled by HrcA. The tandem arrangement of the CtsR and HrcA operators suggests a novel mode of dual heat shock regulation by these two repressors. The S. aureus ctsR and hrcA genes were cloned under the control of the PxylA xylose-inducible promoter and used to demonstrate dual regulation of the dnaK and groESL operons by both CtsR and HrcA, using B. subtilis as a heterologous host. Direct binding by both repressors was shown in vitro by gel mobility shift and DNase I footprinting experiments using purified S. aureus CtsR and HrcA proteins. DeltactsR, DeltahrcA and DeltactsRDeltahrcA mutants of S. aureus were constructed, indicating that the two repressors are not redundant but, instead, act together synergistically to maintain low basal levels of expression of the dnaK and groESL operons in the absence of stress. This novel regulatory mode appears to be specific to Staphylococci

Filtration d’un gaz à faible pression en milieux poreux. Quasi-statique et acoustique

National audienc

Gas flow with low gas pressure in porous media. Quasi-statics and acoustics

International audienc

Effet Klinkenberg en milieu à double porosité

National audienc

Modélisation des écoulements de gaz dans les milieux poreux et poreux fracturés (effet Klinkenberg et effets d'échelles)

Cette étude traite de la modélisation des écoulements de gaz dans les milieux poreux. Lorsque la pression du gaz est faible ou dans les milieux poreux étroits, l'effet Klinkenberg intervient et modifie l'écoulement. L'objectif ici est d'étudier l'influence de cet effet dans diverses situations. L'application d'une méthode d'homogénéisation permet d'abord d'établir des modèles théroriques macroscopiques. Ceux-ci sont alors intégrés dans un code éléments finis afin de préciser le comportement du gaz. Les transferts en milieux à simple porosité sont d'abord envisagés : lorsque des variations thermiques apparaissent, en régime dynamique et dans les composites poreux. Dans ces trois cas, l'effet Klinkenberg agit sur la perméabilité. En double porosité, l'étude des écoulements conduit à des modèles complexes faisant apparaître des effets d'échelles. L'effet klinkenberg peut alors agir sur la perméabilité, le terme de couplage des échelles et sur le domaine de validité des modèles.GRENOBLE1-BU Sciences (384212103) / SudocSudocFranceF

Effet Klinkenberg en milieu à double porosité

National audienc