What is it about?
The leading edge/trailing edge switching mode of flapping wing flight is advantageous because it allows airfoils to have camber. In this paper, the effect of camber was investigated in a series of two dimensional, unsteady, laminar computations with dynamic mesh for plunging and pitching airfoils operating at Reynolds numbers from 100 to 2,500 and reduced frequencies of 0.5 to 2. Vortices are identified shedding from the edges. Lift is created by a downward directed wake and by rotational circulation. Camber was found to increase lift at every Reynolds number and reduced frequency in this study.
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Why is it important?
Several important flow features have been identified. These include vortices shed from the two edges, circulation caused by the rotation of the airfoil, and the downward directed wake. This circulation and downward directed wake both create lift. Cambered airfoils create more lift than non-cambered airfoils at every Reynolds number and reduced frequency studied here, but camber is most beneficial at low reduced frequencies and large Reynolds numbers in this range. Reduced frequency has a much more profound effect than Reynolds number.
Perspectives
Dynamic mesh CFD is more complicated than fixed mesh and is an important method for studying flapping wing flight of insects, birds, and unmanned air vehicles (UAVs). This paper reports simulations of various leading edge trailing edge switching mode dynamics and shows how they generate lift and may be advantageous for flight in the low Reynolds number flow regime.
Dr. Taylor Swanson
Read the Original
This page is a summary of: Effect of Camber on Force Generation in Leading Edge/Trailing Edge Switching Hovering Mode, June 2009, American Institute of Aeronautics and Astronautics (AIAA),
DOI: 10.2514/6.2009-4103.
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