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Mono- and multi-frequency vortex-induced vibrations of a long tensioned beam in shear flow

Bourguet, Rémi and Lucor, Didier and Triantafyllou, Michael S. Mono- and multi-frequency vortex-induced vibrations of a long tensioned beam in shear flow. (2012) Journal of Fluids and Structures, 32. 52-64. ISSN 0889-9746

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Official URL: http://dx.doi.org/10.1016/j.jfluidstructs.2011.05.008

Abstract

The mono-frequency as well as multi-frequency vortex-induced vibrations of a tensioned beam of aspect ratio 200, immersed in a linear shear flow at Reynolds number 330 and free to move in both the in-line and cross-flow directions, are studied by means of direct numerical simulation. The structural responses are composed of mixed standing traveling wave patterns. We observe a switch between mono-and multi-frequency vibrations when the mass ratio changes from a value of 3 to 6, while keeping constant the non dimensional cable and beam phase velocities. This switch is attributed to the accompanying change in the time-averaged in-line curvature of the beam, which alters the oncoming flow velocity component normal to the structure configuration. It is shown, in general, that the mono- or multi-frequency nature of the response is controlled by the form of the profile of the normal component of the oncoming flow. Mono- and multi-frequency vibrations may occur in both the in-line and cross-flow directions, with a frequency ratio close to 2. Each excited frequency is associated with a single structural wavenumber. The local synchronization between the vortex shedding and the cross-flow oscillation, i.e. the lock-in condition, occurs in the high velocity zone and covers a similar spanwise extent in both the mono- and multi-frequency cases. Counter-clockwise figure-eight trajectories are very likely to occur within the lock-in region. In both the mono- and multi-frequency types of response, the flow excites the structural vibrations within the lock-in region and damps the structural motions in the non-lock-in region. The multi-frequency character of the response impacts both the lock-in phenomenon and the fluid–structure energy transfer.

Item Type:Article
Additional Information:Thanks to Elsevier editor. The original PDF can be found at http://www.sciencedirect.com/science/article/pii/S0889974611000946
Audience (journal):International peer-reviewed journal
Uncontrolled Keywords:
Institution:Other partners > Massachusetts Institute of Technology - MIT (USA)
Other partners > Université Pierre et Marie Curie, Paris 6 - UPMC (FRANCE)
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Deposited By: Remi BOURGUET
Deposited On:14 Nov 2013 11:00

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