30 janvier 2020

Séminaire Jacques Borée

Jacques Borée est professeur à l' ENSMA (Poitiers) et directeur adjoint du laboratoire PPRIME
Turbulent near wakes and bluff body drag reduction

Drag reduction of ground vehicles has become a major challenge for the transport industry due to increasing need for reducing fuel consumption and carbon pollution.Flows around such bluff bodies correspond to locally or massively separated flows and our aim is both to develop techniques for bluff body wake manipulation (actuation methods, Active Flow Control – AFC – approaches) and to understand the origins of wake and drag changes. Drag reduction and driving stability are key problems for terrestrial transportation in order to cope with design, functionality and aerodynamics. Even for Aeronautics, helicopter or airplane transport may have large, flat loading ramps and poor aerodynamics of the aft body. Fuselage drag reduction and unsteady load alleviation are then key challenges. A fascinating aspect of these turbulent aerodynamics at significant Reynolds number (≈106) is the wide range of length and time scales. At the scale of the body, vortex shedding, an absolute instability, is responsible for self-sustained oscillations. Reflexional Symmetry Breaking, leading to random switching with a long time dynamic, is also observed. Specific flow structures, namely turbulent shear layers surrounding the near wake and 3D conical vortices of trailing type for slanted geometries, are interacting and have very important contributions. Two model situations will be discussed in the talk. Experimental models, accompanying metrologies, actuation strategies and physical mechanisms will be presented. For a square back wake, aligned with the flow or having a moderate yaw angle, our goal is to obtain a robust AFC strategy by driving the wake toward an unsteady symmetric state and by preventing the slow organization dynamic of the asymmetric state. For a slanted and smoothed aft geometry, one has to deal with introduction of longitudinal vorticity in the near wake and to address interactions of flow structures and near wake properties.

Résumé

30 janvier 2020, 09h0010h00
Building M6 Avenue Paul Langevin Villeneuve d'Asq

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01 décembre 2022

Wébinaire Esteban Ferrer

New avenues in high order fluid dynamics

Esteban Ferrer est professeur de mathématiques appliquées à l'école d'aéronautique (ETSIAE-UPM). Il a obtenu son doctorat à l'université d'Oxford (Royaume-Uni) et possède 20 ans d'expérience industrielle et universitaire dans le développement de techniques numériques pour les problèmes de fluides. Il travaille activement avec l'industrie et coordonne deux projets Européens. Ses principaux intérêts sont les méthodes d'ordre élevé pour la dynamique des fluides, la modélisation de la turbulence, l'apprentissage automatique, l'aéroacoustique pour l'aéronautique et l'énergie éolienne. Il a rédigé plus de 90 articles de journaux et de conférences sur ces sujets.