Simulation multi-domaines et calcul parallèle pour l'aéroacoustique en écoulement confiné

Un outil numérique de simulations aéroacoustiques est présenté pour des applications à des géométries complexes. Le solveur est basé sur des schémas à différences finies d'ordre élevé, ce qui impose l'utilisation de maillages structurés. Pour traiter des géométries complexes, le domaine de calcul est subdivisé en maillages partiellement recouvrants. La communication entre les différents maillages est réalisée par interpolations. L'utilisation de polynômes de Lagrange d'ordre elevé permet de maintenir l'ordre global de la solution. Le code est entièrement parallélisé à l'aide de la librairie MPI. La diffraction d'un pulse acoustique par un cylindre ainsi que l'écoulement transsonique dans un tube circulaire en 3-D sont présentés. Les deux simulations se comparent très bien avec les solutions analytiques

Applications of a high-order algorithm for LES and CAA in complex geometries

In confined flows, non-linear interactions between acoustics and aerodynamics produce high pressure levels. To tackle these couplings, a numerical tool is developed: Code_Safari. It is based on optimized high-order finite-difference schemes in conjunction with optimized filters on a multi-domain approach. A shock-capturing filter is also applied. Code_Safari is validated on classical test problems and used for realistic applications (ducted cavity, sudden enlargement, rod-airfoil interaction)

Des chiffres et des lettres

Les historiens ont de tout temps utilisé les textes. Mais leur approche a longtemps été purement empirique. Au fond, l’objectif primordial de l’historien était de disposer d’un texte sûr, d’où l’accent sur la critique des sources d’une part, et sur l’établissement du contenu de l’autre : une fois le texte solidement établi, on pouvait l’utiliser avec le statut de source autorisée et sous la forme de citations. Le découpage sélectif produit par le choix des citations tenait lieu d’interprétati..

Modélisation de sols irréguliers par une impédance effective dans des codes de propagation acoustique

L’impact acoustique d’installations industrielles ou de transport sur l’environnement est fréquemment évalué en utilisant des méthodes d’ingénierie simplifiées. Afin de valider ces méthodes, il est nécessaire de disposer de résultats numériques de référence pour des situations réalistes de propagation en milieu extérieur. Ces situations incluent une variabilité géométrique des frontières du milieu (topographie, discontinuités dues à des obstacles, rugosité du sol), qui est souvent mal caractérisée (incertitudes de mesure) et connue uniquement de manière statistique. L’objectif de ce travail est d’implémenter des modèles d’impédance effective tenant compte de la rugosité du sol dans des codes de référence de propagation acoustique, notamment dans le domaine temporel. L’utilisation de ces modèles d’impédance effective permet de ne pas avoir à mailler les irrégularités du sol et ainsi de réduire le coût des calculs. On s’intéresse aux modèles d’impédance effective proposés par Attenborough, dans lesquels la rugosité est considérée à travers des petits diffuseurs de géométrique simple (demi-cylindres, demi-ellipses, triangles isocèles) disposés de manière régulière ou aléatoire le long du chemin de propagation. Des modèles d’impédance effective définis à partir de spectres de rugosité sont également étudiés. Des résultats de calculs utilisant ces modèles d'impédance dans des codes de calculs temporels de référence (TLM et FDTD) sont présentés

Fast And Accurate Co2 Properties Calculation Algorithm For Massive Numerical Simulations Of Supersonic Two-phase Ejectors

This work presents a look-up table method to compute the thermodynamic properties of CO2. It is motivated by the massive employment of this fluid in the industrial domain, especially in the ejector-expansion cycle. Computational Fluid Dynamics (CFD) simulations have been used in the past to investigate two-phase ejector flows. CO2 exhibits then large property variations due to phase transition. As a result, it cannot be accurately modelled by a general analytical Equation of State (EoS), such as Peng-Robinson EoS and Perfect gas EoS, etc. Hence, a tabulated EoS is developed here based on the Span-Wagner (EoS), covering the temperature range from 217 to 800 K and pressures up to 50 MPa. Supercritical, liquid, vapor and liquid-vapor states are all included in this tabulated EoS. Besides, the density and the internal energy are chosen as two independent inputs to compute the other properties. The method is designed to be coupled with the system of equations in its conservative form which is a usual formulation for compressible solvers. Through two validation cases, the proposed tabulated EoS shows good performances in terms of accuracy and efficiency, making it suitable for future massive CFD simulations

Spatially broad opening of the blood-brain barrier with an unfocused ultrasound transducer in rabbits

International audienceThe aim of this work was to study the opening of the blood-brain barrier (BBB) over a large volume using an unfocused ultrasound device in the presence of ultrasound contrast agents in rabbits. A mono-element planar 1MHz ultrasound transducer was used to perform burst sonications in 24 healthy New-Zealand white rabbits after craniectomy and during intravenous injection of Sonovue®. The transducer was operated with a pulse repetition frequency of 1Hz, and a range of pulses lengths and in situ acoustic pressures (10-35ms and 0.3-1MPa respectively). Opening of the BBB was observed in contrast-enhanced images in a 4.7T MRI, through blue dye extravasation and with confocal microscopy. Adverse effects were analyzed on histology. A significant BBB opening limited spatially to the extent of the ultrasound field was observed. BBB opening appeared during the sonication and lasted for several hours. Monitoring was possible on MRI sequences as a significant gadolinium contrast enhancement (p<0.0001). BBB opening was associated with perivascular blood red cell extravasation and transient vascular spasm. In conclusion, the BBB can be opened in large areas of the brain with low power unfocused ultrasound, with limited tissue damage, and could permit safe drug delivery in the brain. Work supported by CarThera and Région Ile-de-France

D3.8 Final version of the personalization and positioning software tool with documentation. PIPER EU Project

The aim of this report is to provide an overview of the final version of the PIPER framework and application. The software, along with its documentation, and not the report, constitutes the main part of the deliverable. The software and documentation were already distributed at the Final Workshop and online (under the Open Source license GPLv2 or later for the software, and the GNU FDL 1.3 license for the documentation). The documentation includes detailed descriptions of the framework principles, user interface, metadata, along with the modules and their parameters. It also includes application scenarios (called workflows). Information about the use of the modules is complemented by Tutorials that were developed as part of WP1 (online on the wiki) and explanatory videos were developed as part of WP4 (videos of the final workshop, now available on YouTube). The headers in the source code files (also available online) list the main contributors to the software. The report will therefore not provide details about information that is already available elsewhere but will only provide a very brief summary of the functionalities available. Some of the descriptions are excerpts of the manual

Implications of the polymorphism of HLA-G on its function, regulation, evolution and disease association

The HLA-G gene displays several peculiarities that are distinct from those of classical HLA class I genes. The unique structure of the HLA-G molecule permits a restricted peptide presentation and allows the modulation of the cells of the immune system. Although polymorphic sites may potentially influence all biological functions of HLA-G, those present at the promoter and 3′ untranslated regions have been particularly studied in experimental and pathological conditions. The relatively low polymorphism observed in the MHC-G coding region both in humans and apes may represent a strong selective pressure for invariance, whereas, in regulatory regions several lines of evidence support the role of balancing selection. Since HLA-G has immunomodulatory properties, the understanding of gene regulation and the role of polymorphic sites on gene function may permit an individualized approach for the future use of HLA-G for therapeutic purposes

Directorium divini cultus ad Cathedralis Ecclesiae Minoriccensis : eiusque Dioecesis usum

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