Transient Response of a Plate-Liquid System Under an Aerial Detonation : Simulation and Experiments

International audienceThis paper presents a mixed numerical approach to model the blast waves generated by the detonation of a spherical stoichiometric mixture of propane and oxygen, impacting a plate-liquid system. The problem is split into two parts. The first calculation part relies on the modeling of the blast load and its propaga-tion. Over-pressure distribution, in this part, is presented and reveals a very good level of agreement with experimental results. The time and space scales of the blast load data must be compatible with the plate- liquid system. This compatibility is ensured by an appropriate spatio-temporal interpolation technique. This technique is presented and its effectiveness and accuracy are demonstrated. The second part consists in modeling the response of the coupled plate-liquid system under the numerical blast load model. Experiments at reduced scale are carried out in two configurations in order to assess the effectiveness of this mixed numerical approach. Convincing results are obtained and discussed

Étude de sensibilité d’une méthode d’interfaçage 1D-3D numérique

Pour gagner en faisabilité, plusieurs modèles de calculs, dont la simulation des explosions, combinent des méthodes uni et tridimensionnelles. La solution du calcul unidimensionnel est la condition initiale du calcul tridimensionnel. Pour être exploitée, cette solution doit être transférée de manière convenable au maillage tridimensionnel. Plusieurs techniquesd’interfaçage 1D-3D sont présentées et testées ici. Une étude de sensibilité est proposée pour déterminer la technique la plus appropriée. Précision, conservation des directions privilégiées et sensibilité au maillage sont plus particulièrement examinées

Efficient 3D numerical prediction of the pressure wave generated by high-speed trains entering tunnels

International audienceThe topic of this paper is to present a new methodology for the three-dimensional numerical simulation of the entrance of high-speed trains in a tunnel. The movement of the train is made thanks to a technique of sliding meshes and a conservative treatment of the faces between two domains. All parts of the development are thought with the aim to reduce the computational time. In particular, non reflecting boundary conditions for non-structured three-dimensional meshes are developed in order to limit the calculation domain. Validations of the methodology are presented on different test cases

Human mesenchymal stromal cell-secreted lactate induces M2-macrophage differentiation by metabolic reprogramming

Human mesenchymal stromal cells (MSC) have been shown to dampen immune response and promote tissue repair, but the underlying mechanisms are still under investigation. Herein, we demonstrate that umbilical cord-derived MSC (UC-MSC) alter the phenotype and function of monocyte-derived dendritic cells (DC) through lactate-mediated metabolic reprogramming. UC-MSC can secrete large quantities of lactate and, when present during monocyte-to-DC differentiation, induce instead the acquisition of M2-macrophage features in terms of morphology, surface markers, migratory properties and antigen presentation capacity. Microarray expression profiling indicates that UC-MSC modify the expression of metabolic-related genes and induce a M2-macrophage expression signature. Importantly, monocyte-derived DC obtained in presence of UC-MSC, polarize naïve allogeneic CD4+ T-cells into Th2 cells. Treatment of UC-MSC with an inhibitor of lactate dehydrogenase strongly decreases lactate concentration in culture supernatant and abrogates the effect on monocyte-to- DC differentiation. Metabolic analysis further revealed that UC-MSC decrease oxidative phosphorylation in differentiating monocytes while strongly increasing the spare respiratory capacity proportional to the amount of secreted lactate. Because both MSC and monocytes are recruited in vivo at the site of tissue damage and inflammation, we propose the local increase of lactate concentration induced by UC-MSC and the consequent enrichment in M2-macrophage generation as a mechanism to achieve immunomodulation

Socializing One Health: an innovative strategy to investigate social and behavioral risks of emerging viral threats

In an effort to strengthen global capacity to prevent, detect, and control infectious diseases in animals and people, the United States Agency for International Development’s (USAID) Emerging Pandemic Threats (EPT) PREDICT project funded development of regional, national, and local One Health capacities for early disease detection, rapid response, disease control, and risk reduction. From the outset, the EPT approach was inclusive of social science research methods designed to understand the contexts and behaviors of communities living and working at human-animal-environment interfaces considered high-risk for virus emergence. Using qualitative and quantitative approaches, PREDICT behavioral research aimed to identify and assess a range of socio-cultural behaviors that could be influential in zoonotic disease emergence, amplification, and transmission. This broad approach to behavioral risk characterization enabled us to identify and characterize human activities that could be linked to the transmission dynamics of new and emerging viruses. This paper provides a discussion of implementation of a social science approach within a zoonotic surveillance framework. We conducted in-depth ethnographic interviews and focus groups to better understand the individual- and community-level knowledge, attitudes, and practices that potentially put participants at risk for zoonotic disease transmission from the animals they live and work with, across 6 interface domains. When we asked highly-exposed individuals (ie. bushmeat hunters, wildlife or guano farmers) about the risk they perceived in their occupational activities, most did not perceive it to be risky, whether because it was normalized by years (or generations) of doing such an activity, or due to lack of information about potential risks. Integrating the social sciences allows investigations of the specific human activities that are hypothesized to drive disease emergence, amplification, and transmission, in order to better substantiate behavioral disease drivers, along with the social dimensions of infection and transmission dynamics. Understanding these dynamics is critical to achieving health security--the protection from threats to health-- which requires investments in both collective and individual health security. Involving behavioral sciences into zoonotic disease surveillance allowed us to push toward fuller community integration and engagement and toward dialogue and implementation of recommendations for disease prevention and improved health security

Simulation numérique de l'entrée en tunnel d'un train à grande vitesse

Ce travail porte sur le développement d'un code numérique tridimensionnel pour la simulation d'entrées en tunnels de trains à grande vitesse en vue de proposer des solutions afin de réduire les nuisances occasionnées. L'écoulement de l'air est modélisé par les équations d'Euler instationnaires. Ces équations sont discrétisées à l'aide d'une formulation en volumes finis et résolues grâce à un schéma solveur de Riemann approché, d'ordre supérieur, particulièrement adapté à la propagation d'ondes. Pour gérer le mouvement relatif du train par rapport au tunnel, une méthode de maillage glissant est utilisée avec un traitement conservatif des faces aux niveaux des jonctions de maillages. Le domaine est ainsi décomposé en plusieurs sous-domaines, maillés indépendamment avec un mailleur cartésien automatique basé sur un maillage surfacique triangulaire. Pour réduire le domaine, et donc le temps de calcul, et accélérer la stabilisation de l'écoulement avant l'entrée du train, des conditions aux limites non réflectives sont implémentées. La méthodologie est validée sur plusieurs cas tests. Une étude paramétrique de l'influence d'un auvent à l'entrée du tunnel sur le gradient de l'onde de compression pression initiale est effectuée. Les paramètres de cette étude sont la forme, la longueur et la section de l'auvent. Enfin, l'effet d'ouvertures dans l'auvent est simulé.This work aims at the development of a three-dimensional numerical code for the simulation of high-speed trains entering tunnels in order to propose solutions to reduce nuisances caused. The airflow is modeled by the unsteady Euler equations. These equations are discretized using a finite volume formulation and solved with a higher order approximate Riemann solver scheme, particularly suitable for waves propagations. In order to manage the relative motion of the train from the tunnel, a sliding grid method is used with a conservative treatment of the faces located at domains junctions. The overall domain is thus decomposed into several sub-domains, meshed independently with an automatic Cartesian grid generator based on a triangular surfacic mesh. In order to reduce the calculation domain and to accelerate the flow stabilization around the train, a non-reflecting boundary condition is implemented. The methodology is validated on several test cases. A parametric study of a hood effect on the initial compression wave gradient is done. Pararneters of this study are the section, the length, and the hood shape. Then, opened hood effect was simulated.VALENCIENNES-BU Sciences Lettres (596062101) / SudocSudocFranceF

Numerical and reduced-scale experimental investigation of blast wave shape in underground transportation infrastructure

International audienceWhen an explosion occurs in a tunnel, the study of the blast wave quickly becomes complicated, owing to the multiple propagation patterns of the blast wave (Incident wave, regular and Mach reections) and to the geometrical conditions. Considering this problem, two patterns can be revealed. Near the explosive, the well known free-eld pressure wave can be observed. After multiple reections on the tunnel's walls, this overpressure behaves like a one-dimensional (1D) wave. One aim of this paper is to determine the position of this transition spherical-to-planar wave propagation in a tunnel using both numerical and reduced-scale experiments, and thereby validate the dedicated law established in a previous work. For this purpose, a detonation of TNT in a tunnel with a cross-section of up to 55 m 2 is considered. Results show good agreement between the numerical simulations and experiments. The transition zone between the three-dimensional (3D) and the 1D wave is well detected. An application to a simplied subway station is also investigated which shows that signicant planar waves can be transmitted to the neighboring stations via the junction tunnels

Étude de l'écoulement turbulent transitoire dans une conduite

Ce travail a pour objectif l'étude du frottement pariétal dans un écoulement turbulent transitoire en conduite. C'est dans ce cadre qu'un dispositif expérimental a été conçu pour étudier l'évolution des profils de vitesse dans un écoulement transitoire. Dans cette étude, l'application réussie de la vélocimétrie ultrasonore Doppler et de la méthode polarographique pour un écoulement turbulent transitoire est présentée. Après une brève présentation de leurs principes, quelques résultats sont présentés