A pendulum in a flowing soap film

We consider the dynamics of a pendulum made of a rigid ring attached to an elastic filament immersed in a flowing soap film. The system shows an oscillatory instability whose onset is a function of the flow speed, length of the supporting string, the ring mass, and ring radius. We characterize this...

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Bibliographic Details
Published inPhysics of fluids (1994) Vol. 25; no. 4
Main Authors Bandi, M. M., Concha, A., Wood, R., Mahadevan, L.
Format Journal Article
LanguageEnglish
Published 01.04.2013
Subjects
Dynamical systems
Dynamics
Filaments
Imaging
Instability
Pendulums
Soap films
Vorticity
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Summary:We consider the dynamics of a pendulum made of a rigid ring attached to an elastic filament immersed in a flowing soap film. The system shows an oscillatory instability whose onset is a function of the flow speed, length of the supporting string, the ring mass, and ring radius. We characterize this system and show that there are different regimes where the frequency is dependent or independent of the pendulum length depending on the relative magnitude of the added-mass. Although the system is an infinite-dimensional, we can explain many of our results in terms of a one degree-of-freedom system corresponding to a forced pendulum. Indeed, using the vorticity measured via particle imaging velocimetry allows us to make the model quantitative, and a comparison with our experimental results shows we can capture the basic phenomenology of this system.
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ISSN:1070-6631
1089-7666
DOI:10.1063/1.4800057