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Fluid Dynamics Colloquium

Monday, Sep 12th, 2005, 4:00 pm
Cullimore Lecture Hall, Room 611
New Jersey Institute of Technology

Unidirectional Flight of a Flapping Wing

Jun Zhang

Assistant Professor

Courant Institute and Department of Physics, NYU

Abstract

The locomotion of most fish and birds is realized by flapping wings or fins transverse to the direction of travel. Here, we study experimentally the dynamics of a wing that is "flapped" up and down but is free to move in the horizontal direction. We show that flapping flight occurs abruptly at a critical flapping frequency as a symmetry-breaking bifurcation. We then investigate the separate effects of flapping frequency, wing thickness and flexibility. We further seek the optimal parameters of the flapping locomotion. In particular, we study at what flapping amplitude the forward flight speed is highest (minimum Strouhal number) and at what amplitude the flapping wing has the lowest threshold to forward flight. Overall, we emphasize the robustness of the thrust-generating mechanisms determining the forward flight speed of a flapping wing, as observed in our experiments.