Meeting Abstract
89.5 Thursday, Jan. 7 PIV-based study of the near wake of a white-throated sparrow KIRCHHEFER, AJ*; GURKA, R; KOPP, G; GUGLIELMO, C; The University of Western Ontario; Ben-Gurion University; The University of Western Ontario; The University of Western Ontario akirchhe@uwo.ca
Flight has many advantages; however, it suffers due to its relatively high energy cost. One may expect that natural selection will cause birds to have physical characteristics and behaviors which are well suited for flight and reduce this energy cost. Since well before the first flying machines, birds have been studied in hopes of learning first how to create flying machines and subsequently how to improve them. To date, the majority of attention has been given to the far wake, where the vorticity shed from the wing has amalgamated into more or less coherent structures. Knowledge of these coherent structures has facilitated measurement of momentum in the wake, leading to the solution of the “momentum paradox.” While this represents a cornerstone in our knowledge of bird flight, our knowledge of the near wake remains limited. Investigation is required to elucidate the role of the body and the role of the different feather types. Particle image velocimetry (PIV) measurements have been performed in the near wake region of taxidermically mounted white throated sparrow models in the Boundary Layer Wind Tunnel Laboratory at the University of Western Ontario. Measurements have been taken at various locations along the wing span to ensure a complete survey of flows characteristic to each feather type. Each white throated sparrow corresponds to a different wing flexion, phase-locked at the mid down stroke. Wake characteristics, including mean velocity profiles and turbulence profiles, are presented over the typical range of speeds and over a typical range of angles of attack. Significant findings include the onset of an asymmetry in turbulence intensity at medium to high speed. The role of this phenomenon in the formation of actual flapping flight is discussed.
