RT Journal Article
SR Electronic
T1 The Wake of a Kestrel (<em>Falco Tinnunculus</em>) in Flapping Flight
JF Journal of Experimental Biology
JO J. Exp. Biol.
FD The Company of Biologists Ltd
SP 59
OP 78
VO 127
IS 1
A1 SPEDDING, G. R.
YR 1987
UL http://jeb.biologists.org/content/127/1/59.abstract
AB The structure of the wake behind a kestrel in medium-speed flight down a 36 m length of corridor was analysed qualitatively and quantitatively by stereophotogrammetry of multiple flash photographs of the motion of small soap-covered helium bubbles. The wake consists of a pair of continuous, undulating trailing vortices. The upstroke is therefore aerodynamically active and the circulation appears to remain constant along the wing whose geometry is altered during the course of the wingstroke. It is argued that the flight kinematics, and so the wake structure, of the kestrel may be typical of flapping flight at medium speeds and a flight model based on this wake geometry is presented. Rough estimates of the rate of momentum generated in the wake balance the weight almost exactly and a direct estimate of the induced power requirement from the wake measurements is obtained. The significance of these results for the various alternative aerodynamic descriptions and energetic predictions of models of flapping animal flight is briefly assessed