Obi, the Parrotlet, Laser Goggles, and Air Vortices

         A parrotlet named Obi has his own set of custom-made safety goggles (made from human-sized ones) to protect his eyes when he flies through a laser sheet, as he has been trained to do. Researchers at Stanford University are studying how air moves in the wake of Obi's flight.

  

     This 46-second video of Obi's flight shows the vortices swirling around the bird's flightpath, thanks to the lasers he is flying through.

        Researchers at Stanford University are studying how the air moves in the wake of a bird's flight. Thank to Obi, along with graduate students Eric Gutierrez and Diana Chin, and mechanical engineer David Letink, we now know that there may be some faults in many flight models.

       "The goal of our study was to compare very commonly used models in the literature to figure out how much lift a bird, or other flying animal, generates based off its wake," Chin said. "What we found was that all three models we tried out were very inaccurate because they make assumptions that aren't necessarily true."

     To test the models, the team trained Obi, a parrotlet or pocket parrot, to wear the goggles and fly from one perch to another. Then a laser sheet was seeded with non-toxic, aerosol-sized particles. As Obi flew through this laser sheet, the disturbed particles swirled into vortices left in his wake.

     The tests showed something unexpected. Computer models predicted that once the whirling air patterns or vortices were created by a bird's wings, they would remain relatively stable in the air. But the patterns Obi traced began to disintegrate after the bird flapped its wings just a few times.

      "We were surprised to find the vortices that are usually drawn in papers and text books as beautiful doughnut rings turned out to break up dramatically after two to three wing beats," Lentink said. He explained that this meant the models, which are widely used in animal flight studies to calculate an animal's lift based on the wake it produced, were likely inaccurate.


      "Whereas vortex breakup happens far away behind the aircraft (more than a thousand meters) in birds, it can happen very close to the bird, within two or three wingbeats , and it is much more violent," said Letink.

      The team also found that the models they tested did not accurately predict the lift generated by Obi's wings. This research joins other studies conducted by the lab on many different animals, including different bird species, bats, and insects. The team hopes the findings can be used to help develop flying robots or drones that flap wings, rather than rely on rotors.

Wonder if Obi knows Obi-wan Kenobi,
Steph