Heavy Flags Undergo Spontaneous Oscillations in Flowing Water

Michael Shelley, Nicolas Vandenberghe, and Jun Zhang

Phys. Rev. Lett. 94, 094302 – Published 9 March 2005

Abstract

By immersing a compliant yet self-supporting sheet into flowing water, we study a heavy, streamlined, and elastic body interacting with a fluid. We find that above a critical flow velocity a sheet aligned with the flow begins to flap with a Strouhal frequency consistent with animal locomotion. This transition is subcritical. Our results agree qualitatively with a simple fluid dynamical model that predicts linear instability at a critical flow speed. Both experiment and theory emphasize the importance of body inertia in overcoming the stabilizing effects of finite rigidity and fluid drag.

Received 26 February 2004

DOI:https://doi.org/10.1103/PhysRevLett.94.094302

Authors & Affiliations

Michael Shelley¹, Nicolas Vandenberghe^1,*, and Jun Zhang^1,2

¹Applied Mathematics Laboratory, Courant Institute of Mathematical Sciences, New York University, 251 Mercer Street, New York, New York 10012, USA
²Department of Physics, New York University, 4 Washington Place, New York, New York 10003, USA

^*Current address: IRPHE, 49 rue F. Joliot-Curie, BP 146 13384 Marseille Cedex 13, France.

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Issue

Vol. 94, Iss. 9 — 11 March 2005

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