Meeting Abstract

P3.151  Monday, Jan. 6 15:30  Aerodynamics of Morphing Wings in Flapping and Gliding Flight MISTICK, E.A.*; KLAASSENVANOORSCHOT, B; TOBALSKE, B.W.; Harvard University; University of Montana; University of Montana emilymistick@college.harvard.edu

Birds are capable of continuously altering the size and shape of their wings. This changing morphology is hypothesized to alter aerodynamic performance (i.e. maximum force production and/or efficiency, defined as lift:drag ratio) across flight modes such as steady flapping, gliding, and takeoff. We examined the differences between swept and extended wings in flapping and gliding flight for ten different raptor species in the orders Accipitriformes, Strigiformes, and Falconiformes. Wings were dried in swept and extended configurations, then held fixed in a wind tunnel at 14.1 m/s to simulate gliding flight and spun on a propeller at in vivo angular velocities to simulate mid-downstroke flapping flight during takeoff. Vertical and horizontal force production was measured for each wing through a range of angles of attack. We found that (1) extended wings produce more vertical and less horizontal force per unit area (higher L:D) than swept wings in flapping takeoff flight, and (2) swept wings outperform extended wings in gliding flight at attack angles above ~20 degrees. These results suggest the presence of leading edge vortex (LEV) formation on the swept wings in gliding flight, and also bring into question current thoughts regarding the importance of emarginated primary feathers in breaking up costly wing-tip vortices. This material is based upon work supported by the National Science Foundation Graduate Research Fellowship under Grant No. DGE-0809127 and DGE-1313190 and by the Herchel Smith Harvard Undergraduate Science Research Program.