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Flapping dynamics of an inverted flag

Kim, Daegyoum and Cossé, Julia and Cerdeira, Cecilia Huertas and Gharib, Morteza (2013) Flapping dynamics of an inverted flag. Journal of Fluid Mechanics, 736 . R1-R12. ISSN 0022-1120.

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The dynamics of an inverted flag are investigated experimentally in order to find the conditions under which self-excited flapping can occur. In contrast to a typical flag with a fixed leading edge and a free trailing edge, the inverted flag of our study has a free leading edge and a fixed trailing edge. The behaviour of the inverted flag can be classified into three regimes based on its non-dimensional bending stiffness scaled by flow velocity and flag length. Two quasi-steady regimes, straight mode and fully deflected mode, are observed, and a limit-cycle flapping mode with large amplitude appears between the two quasi-steady regimes. Bistable states are found in both straight to flapping mode transition and flapping to deflected mode transition. The effect of mass ratio, relative magnitude of flag inertia and fluid inertia, on the non-dimensional bending stiffness range for flapping is negligible, unlike the instability of the typical flag. Because of the unsteady fluid force, a flapping sheet can produce elastic strain energy several times larger than a sheet of the deformed mode, improving the conversion of fluid kinetic energy to elastic strain energy. According to the analysis of the leading-edge vortex formation process, the time scale of optimal vortex formation correlates with efficient conversion to elastic strain energy during bending.

Item Type:Article
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URLURL TypeDescription DOIArticle
Gharib, Morteza0000-0002-2204-9302
Additional Information:© 2013 Cambridge University Press. Received 6 September 2013; revised 8 October 2013; accepted 16 October 2013; first published online 4 November 2013. This research was supported by a grant of the Gordon and Betty Moore Foundation.
Funding AgencyGrant Number
Gordon and Betty Moore FoundationUNSPECIFIED
Subject Keywords:aerodynamics, flow–structure interactions
Record Number:CaltechAUTHORS:20131216-092317508
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Official Citation: Daegyoum Kim, Julia Cossé, Cecilia Huertas Cerdeira and Morteza Gharib (2013). Flapping dynamics of an inverted flag. Journal of Fluid Mechanics, 736, R1 doi:10.1017/jfm.2013.555
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:43014
Deposited By: Ruth Sustaita
Deposited On:16 Dec 2013 18:07
Last Modified:03 Oct 2019 06:03

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