Bat wing airfoil and planform structures relating to aerodynamic cleanliness
R. D. Bullen A C and N. L. McKenzie BA 43 Murray Drive, Hillarys, WA 6025, Australia.
B Department of Environment and Conservation, PO Box 51, Wanneroo, WA 6065, Australia.
C Corresponding author. Email: bullen2@bigpond.com
Australian Journal of Zoology 55(4) 237-247 https://doi.org/10.1071/ZO07010
Submitted: 11 February 2007 Accepted: 21 June 2007 Published: 24 September 2007
Abstract
In this paper we examine 12 species of Western Australian bat for anatomical and morphometric attributes related to wing lift and drag characteristics. We present values for bat wing camber (typically 6.5–9%) and its location, measurements of wing planform and tip shape (typically elliptical but with two different tip designs), dimensions of wing leading-edge flaps (typically 8–10.5% of hand wing chord but with some species having much larger flaps up to 18%) and then discuss several features related to airflow separation control.
All species assessed had thin, low-camber airfoil sections, an optimisation appropriate to the range of Reynolds Numbers in which bats fly. Wing relative cleanliness was consistent with, and functionally appropriate to, species foraging strategy. The interceptors had the point of maximum camber well forward and no trailing edge wing fences, optimisations for minimum drag generation. The air-superiority bats had leading-edge fences optimised for maximum lift generation while maintaining low drag. Surface bats were characterised by their low-aspect-ratio wingtips and the absence of optimisations for either low section drag or high lift. The frugivore and the carnivore appear to be discrete optimisations while the emballinurid had a long and broad leading edge flap in combination with a high-aspect-ratio tip.
We propose a range of lift and drag coefficient values for use in models of metabolic power output.
Acknowledgements
We thank C. L. Bullen and M. H. McKenzie for field assistance. The Western Australian Department of Environment and Conservation contributed to the cost of the project. J. McRae prepared the artwork of Fig. 4. We also thank three referees who provided critical reviews of an early version of this manuscript.
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