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Spanwise gradients in flow speed help stabilize leading-edge vortices on revolving wings

Jardin, Thierry and David, Laurent Spanwise gradients in flow speed help stabilize leading-edge vortices on revolving wings. (2014) Physical Review E, 90 (1). ISSN 1539-3755

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Official URL: http://dx.doi.org/10.1103/PhysRevE.90.013011

Abstract

While a leading-edge vortex on an infinite translating wing is shed after a short distance of travel, its counterpart on a finite span revolving insect wing or maple seed membrane exhibits robust attachment. The latter explains the aerodynamic lift generated by such biological species. Here we analyze the mechanisms responsible for leading-edge vortex attachment. We compute the Navier-Stokes solution of the flow past a finite span wing (i) embedded in a uniform oncoming flow, (ii) embedded in a spanwise varying oncoming flow, and (iii) revolving about its root. We show that over flapping amplitudes typical of insect flight (ϕ=120∘), the spanwise gradient of the local wing speed may suffice in maintaining leading-edge vortex attachment. We correlate this result with the development of spanwise flow, driven by the spanwise gradient of pressure, and we evaluate the sensitivity of such a mechanism to the Reynolds number. It is noted, however, that leading-edge vortex attachment through the spanwise gradient of the local wing speed does not promote large lift, which ultimately arises from centrifugal and Coriolis effects.

Item Type:Article
Additional Information:Thanks to Physical Review E editor. The original PDF of the article can be found at Physical Review E website : http://journals.aps.org/pre/abstract/10.1103/PhysRevE.90.013011
Audience (journal):International peer-reviewed journal
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Institution:Université de Toulouse > Institut Supérieur de l'Aéronautique et de l'Espace - ISAE-SUPAERO (FRANCE)
Other partners > Université de Poitiers (FRANCE)
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Deposited By: Thierry Jardin
Deposited On:21 Jul 2014 15:25

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