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Bat stuff

Some might be interested in this, as it connects to
the ecospace discussion:

Science 11 May 2007:
Vol. 316. no. 5826, pp. 894 - 897
DOI: 10.1126/science.1142281

Bat Flight Generates Complex Aerodynamic Tracks
A. Hedenström,1* L. C. Johansson,1 M. Wolf,1 R. von
Busse,2 Y. Winter,2,3 G. R. Spedding4 

The flapping flight of animals generates an
aerodynamic footprint as a time-varying vortex wake in
which the rate of momentum change represents the
aerodynamic force. We showed that the wakes of a small
bat species differ from those of birds in some
important respects. In our bats, each wing generated
its own vortex loop. Also, at moderate and high flight
speeds, the circulation on the outer (hand) wing and
the arm wing differed in sign during the upstroke,
resulting in negative lift on the hand wing and
positive lift on the arm wing. Our interpretations of
the unsteady aerodynamic performance and function of
membranous-winged, flapping flight should change
modeling strategies for the study of equivalent
natural and engineered flying devices.

You know there's someting up when it's "should" and
not "might" ;-)



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