Flapping dynamics of an inverted flag
نویسندگان
چکیده
منابع مشابه
Oblique waves lift the flapping flag.
The flapping of the flag is a classical model problem for the understanding of fluid-structure interaction: How does the flat state lose stability? Why do the nonlinear effects induce hysteretic behavior? We show in this Letter that, in contrast with the commonly studied model, the full three-dimensional flag with gravity has no stationary state whose stability can be formally studied: The wave...
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We reconsider the classical problem of the instability of a flapping flag in an inviscid background flow with a vortex sheet wake, and reformulate it as a nonlinear eigenvalue problem. We solve the problem numerically for the 20 lowest wave number modes. We find that the lowest wave number mode is the first to become unstable, and has the fastest growth rate within 3.5 decades of the stability ...
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We investigate the "flapping flag" instability through a model for an inextensible flexible sheet in an inviscid 2D flow with a free vortex sheet. We solve the fully-nonlinear dynamics numerically and find a transition from a power spectrum dominated by discrete frequencies to an apparently continuous spectrum of frequencies. We compute the linear stability domain which agrees with previous app...
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over a wide range of speeds (Westneat, 1996; Walker and Westneat, 2000, 2002a,b). Swimming performance (determined in speed endurance tests for fishes) shows that pectoral propulsors in some species are capable of generating thrusts that can power speeds up to 10 body lengths s–1 (Walker and Westneat, 2002a,b). In addition, these species are highly maneuverable in complex three-dimensional reef...
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A recent experiment has shown “inverted drafting” in flags: the drag force on one flag is increased by excitation from the wake of another. Here we use vortex sheet simulations to show that inverted drafting occurs when the flag wakes add coherently to form strong vortices. By contrast, normal drafting occurs for higher-frequency oscillations, when the vortex wake becomes more complex and mixed...
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ژورنال
عنوان ژورنال: Journal of Fluid Mechanics
سال: 2013
ISSN: 0022-1120,1469-7645
DOI: 10.1017/jfm.2013.555