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Drag reduction of a blunt body by unsteady shear layer forcing and Coanda blowing

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URI: http://hdl.handle.net/2042/57588
Title: Drag reduction of a blunt body by unsteady shear layer forcing and Coanda blowing
Author: Barros, Diogo; Borée, Jacques; R. Noack, Bernd; Spohn, Andreas; Ruiz, Tony
Abstract: Nous étudions les effets d'un forçage périodique du sillage sur la traînée d'un corps non-profilé au culot droit. Avec la combinaison des jets pulsés et d'une surface courbée, le contrôle augmente de 30% la pression au culot grâce à l'effet Coanda et à la periodicité des jets. La fréquence d'actuation est un ordre de grandeur plus élevé que les instabilités du sillage. Avec la vélocimétrie par image de particules, nous observons que l'actuation diminue la section verticale du sillage et modifie l'evolution de la vorticité des couches cisaillées. Toutefois, la dynamique du sillage proche ne semble pas être modifiée qualitativement. We analyze the effects of periodic forcing on the wake and drag of a square back bluff body. In combination with a Coanda effect, shear-layer forcing by periodic blowing allows to recover over 30% of the base pressure. The actuation frequency is an order of magnitude higher than the natural shear-layer instabilities. Velocity measurements indicate that the forced wake is thinner and that the vorticity along the shear layer development is modified. However, the wake dynamics further downstream remains very similar to the unforced vortex shedding mode.We analyze the effects of periodic forcing on the wake and drag of a square back bluff body. In combination with a Coanda effect, shear-layer forcing by periodic blowing allows to recover over 30% of the base pressure. The actuation frequency is an order of magnitude higher than the natural shear-layer instabilities. Velocity measurements indicate that the forced wake is thinner and that the vorticity along the shear layer development is modified. However, the wake dynamics further downstream remains very similar to the unforced vortex shedding mode.
Subject: drag reduction; wakes; flow control
Publisher: AFM, Association Française de Mécanique
Date: 2015

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