Etude numérique et expérimentale du processus de recompression le long d'un éjecteur supersonique

Un éjecteur est un assemblage de 2 tuyères coaxiales, soumis à un processus complexe de recompression par chocs obliques. Ce processus est analysé en suivant la pression statique le long de l'axe de l'éjecteur. Le système de mesure développé consiste en un tube capillaire, doté d'un orifice permettant la prise de la pression, pouvant se translater le long de l'éjecteur. Des simulations numériques sont par ailleurs réalisées utilisant des modèles de turbulence RANS. La comparaison expérimental-numérique montre une bonne cohérence malgré un léger décalage dans le nombre et l'amplitude des chocs

Caractérisation numérique et expérimentale en phase transitoire d'une sonde de température dans une enceinte close sous vide et à la pression atmosphérique

Ce travail présente les résultats numériques et expérimentaux concernant une sonde de température pour les mesures en écoulements gazeux instationnaires. La sonde de température, développée au laboratoire, est constituée d'un microthermocouple en couche mince intégré dans une gaine céramique introduite dans une vis. Les applications concernent les transferts de chaleur pariétaux rencontrés dans les écoulements oscillants de gaz chauds tels que ceux rencontrés dans les moteurs à combustion interne

Software-Based Burst Mode Reception Implementation for Time-domain Wavelength Interleaved Networks

International audienceWe demonstrate burst mode functionality on a continuous commercial receiver piloted by real-time control plane in an end-to-end sub-wavelength switching test-bed. The results show the receiver can maintain its continuous performance with marginal penalty regardless of data burst absence duration. Introduction Switching sub-wavelength entities inside the big pipes channels appears as a promising solution for the operator that has to build a network with an efficient filling and different services. Access to the sub-wavelength granularity directly at the optical layer is an alternative to electrical solution to reduce cost and power consumption by saving on electrical transit and electrical-to-optical and optical-to-electrical conversions. Amongst the various Sub-Lambda Photonically Switched Network (SLPSN) solutions, Time-domain Wavelength Interleaved Networking (TWIN) is an interesting solution since it provides optically transparent sub-wavelength grooming at intermediate/core nodes, while the intelligence and processing power remains at control plane and the edge node

First experimental demonstration of real-time orchestration in a Multi-head metro network

International audienceWe present for the first time the experimental demonstration of a Real-Time control-plane on the Multi-hEad sub-wavElength swiTching (MEET), Metro architecture. The key control assets are calculated and provided to the edge nodes in a form of grant files. These grant files eliminate the contention possibility at source nodes and destinations, thus they offer a lossless passive optical grooming and multiplexing/demultiplexing at the intermediate nodes. The experimental results validate the control plane structure designed based on a deterministic operating system well scalable for a regional metro network

De l'usage des logiques modales pour la gestion de l'incertitude des données : application en archéologie

International audienceArchaeological information systems offer methods and tools for representing collected data and performing analyses with which taking into account imperfect data is often hard to please. Our contribution describes the use of several modal logics to model and verify the effects of the consideration of uncertain data, but also to check the quality of a corpus in an in-terdisciplinary collaborative environment. The modelling and the reasoning based on uncertain data, which are studied in this article, are integrated open and extensible platform allowing to manage archaeological data. From the computing point of view, the reasoner used, based on the first order logic, provides the archaeologists with ways to validate or not their hypotheses. Some examples of reasoning are proposed for data describing an ecclesiastical person.Les systèmes d'information archéologiques offrent des méthodes et des outils pour re-présenter les données collectées et effectuer des analyses avec lesquels la prise en compte de données imparfaites est souvent délicate. Notre contribution porte sur l'utilisation de plusieurs logiques modales pour modéliser et tester les effets de la prise en compte de données incer-taines, mais aussi pour vérifier la qualité d'un corpus tout en travaillant dans un environnement collaboratif interdisciplinaire. La modélisation et le raisonnement sur des données incertaines, proposés dans cet article, s'intègrent dans une plateforme ouverte et extensible permettant de gérer les données archéologiques. Sur le plan informatique, le raisonneur utilisé, basé sur la logique du premier ordre, fournit aux archéologues, les moyens de valider ou non leurs hy-pothèses. Quelques exemples de raisonnement sont propposés pour des données décrivant un personnage ecclésiastique. ABSTRACT. Archaeological information systems offer methods and tools for representing collected data and performing analyses with which taking into account imperfect data is often hard to please. Our contribution describes the use of several modal logics to model and verify the effects of the consideration of uncertain data, but also to check the quality of a corpus in an in-terdisciplinary collaborative environment. The modelling and the reasoning based on uncertain data, which are studied in this article, are integrated open and extensible platform allowing to manage archaeological data. From the computing point of view, the reasoner used, based on the first order logic, provides the archaeologists with ways to validate or not their hypotheses. Some examples of reasoning are proposed for data describing an ecclesiastical person

Instrumentation thermique en écoulement microfluidique

National audienc

Dynamic operation of a micro-thermocouple sensor as a vacuum gauge

International audienceWe present an experimental characterization of a new vacuum gauge based on a K type micro thermocouple with 25.4 μm diameter. This sensor is intended for the simultaneous measurement of the temperature and pressure in the ranges extending from 293 K to 400 K and 10−1 Pa to 105 Pa respectively. The paper gives an investigation of the micro-thermocouple vacuum gauge signal for the oscillating heating and cooling processes. The operation of the sensor is based on the analysis of the frequency of the oscillating signal obtained from an electric Joule heating of fixed duration and a cooling of variable duration depending on gas pressure in the vacuum chamber volume. The frequency of the signal oscillation is a function of the gas pressure in the system. Due to its low thermal inertia (time constant of 30 ms), this gauge gives two pieces of information simultaneously: the temperature and the pressure of the gas. Experiments are conducted with dry air

Visualization of flow instabilities in supersonic ejectors using Large Eddy Simulation

International audienc

Development and testing of a pressure probe for centerline static pressure measurement in supersonic nozzles and ejectors

International audienceThis work describes the development and testing of a system for measuring static pressure along the axis of supersonic flow devices such as convergent–divergent nozzles or ejectors. The pressure probe consists of a capillary tube positioned at the ejector centerline. A hole is perforated perpendicularly on the wall of the thin tube to capture and deport the static pressure measurement to a piezoelectric sensor located at one extremity of the tube outside the ejector. The measurements obtained are compared with numerical results from computational fluid dynamics simulations and wall pressure measurements. The first tests demonstrate the good capability of the pressure probe to detect shocks occurring in the flow and to provide continuous axial distributions of the static pressure