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Lieu : Amphithéâtre Becquerel, 14h

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Lieu : amphithéâtre Grégory, 14h00

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Lieu : Amphithéâtre Langevin, ESPCI, 14h30

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Lieu : Centre Intermondes, La Rochelle

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http://www.centre-intermondes.com/centre-intermondes.com/Accueil.html

Lieu : Grand Hall, École polytechnique

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Le LadHyX participe à la Fête de la Science, avec notamment un stand sur la physique du sport. https://www.polytechnique.edu/fr/content/la-science-en-fete-lx

Lieu : Amphithéâtre Carnot, 14h

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Lieu : Inscription http://www.aiv.asso.fr

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L'Association de l'Ingénierie du Vent (AIV, Belgique-France-Suisse) organise ses journées 2016 à l'Ecole Polytechnique en partenariat avec le LadHyX. Le 18 avril une journée de formation, destinée aux ingénieurs, architectes, étudiants sera dispensée par un panel de spécialistes sur le thème "Les effets sur du vent sur les structures dans l'Eurocode". La seconde journée du 19 sera consacrée à l'Assemblée Générale de l'AIV avec notamment la remise du prix INNO-VENT 2016. Inscriptions (date limite 4 avril) et renseignements sur http://www.aiv.asso.fr

Lieu : http://www.academie-sciences.fr/fr/350

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Pour célébrer ses 350 ans, l'Académie des sciences vous propose un an d'événements et de créations pour tous les publics.

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What is fluid-solid interactions ? It is what happens when the motions of a fluid and of a solid are somehow coupled. This happens all the time, around you when leaves flutter in the wind, inside you when your heart beats, above you when wings of a plane vibrate, under the sea... The idea behind this MOOC is to give you the basic tools to be able to predict and eventually mitigate things called flutter, galloping, sloshing, vortex-induced vibrations, added mass, to cite a few. We are going to consider any possible domains of applications such as civil engineering, aerospace engineering, nuclear engineering, ocean engineering, biomechanics and even food processing ! This is why we called the course “Fundamentals of Fluid Solid Interactions ”. There are so many phenomena and so many models that we need to work together on the basic mechanisms . If you want to see how fluid-solid interactions work, and be able to use that knowledge, join us before January 11th 2016 ! It happens here : https://www.coursera.org/course/fsi

Lieu : Amphi Becquerel - 14h

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Local and global eigendynamics of free plumes are analyzed in this dissertation, with a particular focus on the possibility of self-sustained global oscillations. Such behavior in plumes is examined from the perspective of hydrodynamic stability. In this investigation, local absolute instability as well as linear global instability are found in the plumes, suggesting that plumes may indeed display self-sustained oscillator behavior. The frequency of the most unstable global mode matches closely with the self-excited axisymmetric puffing reported from experiments and direct numerical simulations of plumes and buoyant jets. A low Mach number approximation is employed for the global instability analysis, which captures the non-Boussinesq effects in flows with arbitrarily large density variations. The Boussinesq setting represents a special case of the low Mach number formulation, reached in the limit of small density variations. In this limit, a local analysis indicates the presence of an absolute instability of very low frequency for helical perturbations. However, this absolute instability does not appear to provoke a global instability, possibly due to its small absolute growth rate. The dynamics of plumes are contrasted with that of buoyant jets; these two regimes of the vertical flow of hot fluid are characterized by the Richardson number Ri. An endogeneity analysis demonstrates that global instability in jets (low Ri) is mostly driven by base flow shear, whereas the global destabilization of plumes (high Ri) is dominantly caused by buoyancy. The local instability modes in Boussinesq plumes are interpreted by means of the perturbation kinetic energy equation.

Lieu : Amphi Becquerel - 14h

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Lieu : Amphi Poisson - 14h

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In the oceans and atmosphere, the dynamics of vortices is affected by stable density stratification along the vertical and the Coriolis force due to the Earth’s rotation. To better characterize the dynamics of such vortices, the stability of an isolated vortex in stratified-rotating fluids is investigated numerically and analytically. When the ambient fluid is strongly stratified and rapidly rotating, some columnar vortices are unstable to an instability that bends and slices the vortex into pancake-shaped vortices. The mechanism of this instability is explained and an instability condition is derived. Secondly, the stability of vortices with a pancake shape is studied. Several instabilities are found depending on the intensities of the stratification and rotation and on the aspect ratio of the vortex. The main effect of the pancake shape is to confine the instabilities of columnar vortices and to trigger different instabilities due to the density distortions within the vortex core.

Lieu : Amphi Monge - 14h

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Foams are ubiquitous in numerous products of our daily life. The tiny bubbles making them up strongly modify the properties of the material in which they are embedded. They render cosmetics smoother, ice-creams more unctuous, and construction materials lightweight and insulating. However, a foam is not stable and quickly looses its structure. It is known that an armor of icroscopic particles enclosing the bubbles is able to stabilize a foam, but the physical mechanisms at play remain largely unknown. We demonstrate a novel method to probe the mechanics of a single 0.1 mm armored bubble. We can thus finely observe the way the bubble deforms, which yields unprecedented comprehension of the stabilization. This thesis then tackles the problem in its globality, by showing the emergence and propagation of disorder within an initially very ordered foam.