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A bird in laser goggles has helped scientists discover a new phenomenon in the physics of flight.
Swirling vortices appear in the flow of air that follows a bird’s wingbeat. But for slowly flying birds, these vortices were unexpectedly short-lived, researchers from Stanford University report December 6 in Bioinspiration and Biomimetics. The results could help scientists better understand how animals fly, and could be important for designing flying robots (SN: 2/7/15, p. 1.
To study the complex air currents produced by birds’ flapping wings,
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, the researchers trained a Pacific parrotlet, a small species of parrot, to fly through laser light — with the appropriate eye protection,
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, of course. Study coauthor Eric Gutierrez, who recently graduated from Stanford, built tiny,
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, 3-D?printed laser goggles for the bird,
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, named Obi.
Gutierrez and colleagues tracked the air currents left in Obi’s wake by spraying a fine liquid mist in the air, and illuminating it with a laser spread out into a two-dimensional sheet. High-speed cameras recorded the action at 1,000 frames per second.
The vortex produced by the bird “explosively breaks up,
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,” says mechanical engineer David Lentink, a coauthor of the study. “The flow becomes very complex,
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, much more turbulent.” Comparing three standard methods for calculating the lift produced by flapping wings showed that predictions didn’t match reality, thanks to the unexpected vortex breakup.








BIRD FLIGHT?Using a high-speed camera, scientists captured the swirling vortices produced by a slowly flying bird. Surprisingly, they found that the vortices rapidly dissipated. The unexpected effect suggests that scientists need to rethink methods for calculating the lift produced under such conditions. E,
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. Gutierrez/Lentink Lab/Stanford Univ,
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.





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