Coupling Linear Sloshing with Six Degrees of Freedom Rigid Body Dynamics

Fluid motion in tanks is usually described in space industry with the so-called Lomen hypothesis which assumes the vorticity is null in the moving frame. We establish in this contribution that this hypothesis is valid only for uniform rotational motions. We give a more general formulation of this coupling problem, with a compact formulation. We consider the mechanical modeling of a rigid body with a motion of small amplitude, containing an incompressible fluid in the linearized regime. We first establish that the fluid motion remains irrotational in a Galilean referential if it is true at the initial time. When continuity of normal velocity and pressure are prescribed on the free surface, we establish that the global coupled problem conserves an energy functional composed by three terms. We introduce the Stokes - Zhukovsky vector fields, solving Neumann problems for the Laplace operator in the fluid in order to represent the rotational rigid motion with irrotational vector fields. Then we have a good framework to consider the coupled problem between the fluid and the rigid motion. The coupling between the free surface and the ad hoc component of the velocity potential introduces a "Neumann to Dirichlet" operator that allows to write the coupled system in a very compact form. The final expression of a Lagrangian for the coupled system is derived and the Euler-Lagrange equations of the coupled motion are presented.Comment: 23 page

Boundary Element and Finite Element Coupling for Aeroacoustics Simulations

We consider the scattering of acoustic perturbations in a presence of a flow. We suppose that the space can be split into a zone where the flow is uniform and a zone where the flow is potential. In the first zone, we apply a Prandtl-Glauert transformation to recover the Helmholtz equation. The well-known setting of boundary element method for the Helmholtz equation is available. In the second zone, the flow quantities are space dependent, we have to consider a local resolution, namely the finite element method. Herein, we carry out the coupling of these two methods and present various applications and validation test cases. The source term is given through the decomposition of an incident acoustic field on a section of the computational domain's boundary.Comment: 25 page

Vers la certification du compilateur v5 d'Esterel dans Coq

Le compilateur v5 d'Esterel est basé sur un raffinement sémantique de la causalité correspondant aux «circuits constructifs» dans le domaine du matériel. La sémantique est présentée par un ensemble de règles d'inférence dans le style de la sémantique naturelle. Nous avons prouvé formellement la correction de la traduction d'une partie significative du langage en circuits au moyen du système de preuves Coq et de son interface utilisateur disponible dans Centaur. La nouvelle sémantique constructive d'Esterel a d'abord été écrite en Typol, donnant d'une part un interprète en Prolog et d'autre part une spécification en Coq. La traduction en circuit à la base du compilateur Esterel v5 a été directement spécifiée en Coq en utilisant l'ordre supérieur. Le principal travail a consisté à certifier le compilateur v5 en Coq en raisonnant sur ces spécifications

Les contrôleurs de nouvelle génération

Ce document a pour objectif de faire un tour d’horizon sur les interfaces hommemachine d’ancienne et de nouvelle génération et plus spécifiquement sur les contrôleurs utilisés par ces interfaces. Le document est séparé en trois parties principales. La première partie tente de retracer l’histoire des principaux contrôleurs dit « classiques », comme le clavier et la souris, ainsi que de ceux qui les ont précédés. La deuxième partie concerne les contrôleurs de nouvelle génération ainsi que leurs technologies. La dernière partie est un dossier sur l’application de démonstration développée pour le contrôleur de nouvelle génération Kinect

Valorization of agroforestry trees compartments into biobased materials and bioproducts: the case of wood branches

In many tropical countries, agroforestry systems provide both services for agriculture and for non-food economic sectors (housing and energy). Since six decades, European countries, including France, have massively excluded trees from the fields and crops in order to intensify mechanized agriculture. But the current agro ecological transition reverse the trend through the design of new agroforestry systems. Nevertheless, French farmers are still to be convinced about the economic reliability of such systems, building their agricultural models on an annual income, which is not so easy with trees that cost annually making economic returns only every few years. Different ways exist to reduce these misgivings, among them the integration of trees products into conventional wood market or to some niche markets. In parallel, wood or chemistry industries are to be convinced of the interest to harvest such woods. Aim Trees growing conditions are very different in agroforestry and in forests and so have a large influence on wood qualities that we currently assess making comparative measurements of mechanical, physical and biochemical properties between agroforestry and forestry woods for some given wood species. Agrpforestry farmers having to prune trees in order to control the light flux to the crops, they harvest every year a quite large volume of branches, valorizing them making mulching or energy. But, according to literature, wood of branches shows higher rates of polyphenols than wood of trunks and can open some new markets for branches. Materials and methods In the framework of the project “Agrobranche” financed by the French national agency for environment (Ademe), we screen biochemical contents of branches of different sizes from four species collected in two types of agroforestry systems: interplot systems (oak and chestnut); alleycropped system (poplar and walnut). We make first NIRS qualification on branches and tests of natural resistance to decay. Then we chipped the branches before processing chemical extractions and their qualification using UPLC-ESI-DAD-MS and CG-MS analysis in LERMAB, Nancy. For oak and chestnut, we have make comparison of extractives composition and rates between branches and wood of the trunk of the same trees. Major results and conclusion The comparison of extractives composition show a higher biochemical variability in wood of branches than in trunks. NIRS measurements make very effective prediction of the extractive composition determined by direct measurements; it seems possible to develop a NIRS-based rapid and non-destructive method to assess branches biochemical value directly on trees into the crops. Woods with more extractives resist more to decay than woods from trunks. These results are promising for new valorisation of branches coming from pruning of agroforestry trees

Lorentz Transform and Staggered Finite Differences for Advective Acoustics

38 pagesWe study acoustic wave propagation in a uniform stationary flow. We develop a method founded on the Lorentz transform and a hypothesis of irrotationality of the acoustic perturbation. After a transformation of the space-time and of the unknown fields, we derive a system of partial differential equations that eliminates the external flow and deals with the classical case of non advective acoustics. A sequel of the analysis is a new set of perfectly matched layers equations in the spirit of the work of Berenger and Collino. The numerical implementation of the previous ideas is presented with the finite differences method HaWAY on cartesian staggered grids. Relevant numerical tests are proposed

Détection automatique de réseaux enterrés par imagerie géoradar

National audienceAfin d’améliorer la connaissance de l’existant et d’éviter l’endommagement d’ouvrages tiers au cours de travaux de voirie, la localisation des canalisations de gaz de manière non destructive est devenue un important domaine de recherche ces dernières années. Pour répondre à cette problématique, nous utilisons un géoradar. La forme de l’ensemble des réflexions ainsi que leurs intensités donnent une indication sur la nature de l’objet. Une forme hyperbolique indique la présence d’un objet "ponctuel" situé au niveau de son aplomb. Ainsi la détection d’hyperbolesdans le radargramme permet de localiser des canalisations. Dans ces travaux, nous proposons une méthode pour détecter automatiquement les hyperboles des données géoradar à partir d'un dictionnaire de formes théoriques et de deux modèles obtenus par apprentissage supervisé.Cette méthode montre des résultats quantitatifs intéressants et a été testée sur des données réelles