Vortex Lift Contributions in the Spanwise Plane in Flapping Wings

Document Type

Conference Paper

Publication Date

5-2006

Publication Source

24th AIAA Applied Aerodynamics Conference

Abstract

Vortices in the vicinity of the wingtip generate lift force in the spanwise plane of flapping wings. In previous studies by the authors to determine the contribution of pure spanwise flow (flow parallel to the wing surface) to the overall lift force in flapping wings, vortex-like structures were identified in the spanwise plane. In classical fixed wing aerodynamics, the presence of wingtip vortices has been shown to increase the lift locally near the tip. Additionally, the impingement of large vortices on the upper surface of delta wings is considered to contribute largely to the lift force at higher angles of attack. It is thus proposed that vortices in the spanwise plane (streamwise vorticity) generate lift in a similar manner in flapping wings.

Using a mechanical ornithopter with wings fabricated in-house, vortices were identified at several different locations along the span of the wing, and at numerous different points throughout the flapping cycle under a variety of operating conditions. The lift generated by these spanwise planar oriented vortices was quantified experimentally using Digital Particle Image Velocimetry. After subtracting inertial effects from the total measured lift force via force transducer the vortex lift force was found to be significant.

ISBN/ISSN

978-1-62410-028-4

Comments

Permission documentation is on file.

Publisher

American Institute of Aeronautics and Astronautics

Place of Publication

San Francisco, CA

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