Modèles bas-Reynolds appliqués à une couche limite compressible

Dans ce rapport, nous comparons plusieurs modèles à bas Reynolds pour une plaque plane supersonique dont les résultats expérimentaux ont été établie par Mabey \cite{mab}. On présentera les différentes modifications imposées durant cette étude afin de prendre en compte la compressibilité de l'écoulement et d'accélérer la vitesse de convergence vers l'état stationnaire. Ce travail a pour but de sélectionner le modèle présentant les meilleurs avantages numériques

Résolution de l'équation de Poisson sur des maillages étirés par une méthode multigrille

Dans ce papier, nous étudions une méthode multigrille adaptée pour la résolution des EDP du second ordre sur des maillages étirés. Nous utilisons l'approche multigrille de type volumes finis agglomérés développée pour la résolution des équations d'Euler. Tout d'abord, on présente une méthode de génération automatique des grilles grossières, basée sur l'équation de Poisson. Les dérivées secondes sont approchées sur chaque niveau en introduissant un facteur de correction. Ensuite, on applique cette méthode pour résoudre l'équation de Poisson et les équations de Navier-Stokes

A Semi-Coarsening Strategy for Unstructured MG with Agglomeration

The extension of the ideas of multigrid to complex compressible flow calculation is generally not straight-forward, especially when non-embedded grids or volume agglomerations are used in order to work with unstructured grids. In this report, we study a multigrid method for solving second order PDE's on stretched unstructured triangulations. We use the finite volume agglomeration multigrid approach developed for solving the Euler equations. First, we present a method to generate coarse grids by volume agglomeration, allowing a directional semi-coarsening based on the Poisson's equation coefficients. The second order derivatives are approximated at each level by introducing a correction factor adapted to semi-coarsening. Then, we apply this method to solve the Poisson equation and extend it to the 2D turbulent Navier-Stokes equations with a low-Reynolds boundary heatment

Simulations of corrosion product transfer with the OSCAR v1.2 code

International audienceActivated Corrosion Products (ACPs) generate a radiation field in PWRs, which is the major contributor to the dose absorbed by nuclear power plant staff working during shutdown operations and maintenance. Therefore, a thorough understanding of the mechanisms that control the corrosion product transfer is of the highest importance. Since the 1970's, the R&D strategy in France has been based on experiments in test loops representative of PWR conditions, on in-situ gamma spectrometry measurements of the PWR primary system contamination and on simulation code development. The simulation of corrosion product transfers in PWR primary circuits is a major challenge since it involves many physical and chemical phenomena including: corrosion, dissolution, precipitation, erosion, deposition, convection, activation… In addition to the intrinsic difficulty of multi-physics modelling, the primary systems present severe operating conditions (300 °C, 150 bar, neutron flux, fluid velocity up to 15 m.s-1 and very low corrosion product concentrations). The purpose of the OSCAR code, developed by the CEA in cooperation with EDF and AREVA NP, is to predict the PWR primary system contamination by corrosion and fission products. The OSCAR code is considered to be not only a tool for numerical simulations and predictions (operational practices improvements and new-built PWRs design) but also one that might combine and organise all new knowledge useful to progress on contamination. The OSCAR code for Products of Corrosion, OSCAR PC, allows researchers to analyse the corrosion product behaviour and to calculate the ACP volume and surface activities of the primary and auxiliary systems. In the new version, OSCAR PC V1.2, the corrosion product transfer in the particulate form is enhanced and a new feature is the possibility to simulate cold shutdowns. In order to validate this version, the contamination transfer has been simulated in 5 French PWRs with different operating and design characteristics. After a description of the models of the main transfer mechanisms, the paper presents the calculated ACP surface and volume activities, the calculated concentrations of metallic elements and their comparisons with on-site measurements for one of the 5 validation cases. The simulations of a steam generator replacement and a cold shutdown are also presented. There is a good agreement between the OSCAR PC V1.2 results and the measured values during power operation and cold shutdown as well. Furthermore, the variations with operating cycle of the surface activities are correctly reproduced. Compared to the previous versions, these improvements are mainly due to the improvement of the thermodynamic database of the OSCAR chemistry module, PHREEQCEA, and to the enhancement of the corrosion product transfer in the particulate form

Description Osteo-Oto-Hepato-Enteric (O2HE) syndrome, a new recessive autosomal syndrome secondary to loss of function mutations in the UNC45A gene

51st Conference of the European-Society-of-Human-Genetics (ESHG) in conjunction with the European Meeting on Psychosocial Aspects of Genetics (EMPAG), Milan, ITALY, JUN 16-19, 2018International audienc

Description Osteo-Oto-Hepato-Enteric (O2HE) syndrome, a new recessive autosomal syndrome secondary to loss of function mutations in the UNC45A gene

51st Conference of the European-Society-of-Human-Genetics (ESHG) in conjunction with the European Meeting on Psychosocial Aspects of Genetics (EMPAG), Milan, ITALY, JUN 16-19, 2018International audienc