Bird in Protective Goggles Creates Vortex to Aid Flight Research

Researchers from Stanford University have found a way to help explain how animals generate enough lift to fly and what this could mean for the way flying robots and drones are designed.

"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," stated Diana Chin. A graduate student in the Lentink Lab, Chin is one of the authors of the study. "What we found was that all three models we tried out were very inaccurate because they make assumptions that aren't necessarily true."

Parrotlets, the second smallest parrot species, were trained as a means to precisely measure the vortices it produced during flight. The study published in Bioinspiration and Biomimetics could be referenced when designing flying robots and drones so they could be guided by the biology of animals since Lentink specializes in bio-inspired robots.

Eric Gutierrez, the study's lead author, fitted the parrotlets with protective goggles and prompted them to fly through aerosol particles that were primed to scatter and track at the slightest disruption. A graduate student working with Stanford mechanical engineer David Lentink, Gutierrez trained the bird to fly through a seeded laser sheet. The bird's wing motion disturbed the particles to generate a detailed record of the vortices created by the flight. The particles swirling off the parrotlet's wingtips created the clearest picture to date of the wake left by a flying animal.

"Now, whereas vortex breakup happens far away behind the aircraft, like 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," explained Lentink, the study's senior author.

Lentink believes that their findings could be combined with detailed flow measurements to better understand and model the aerodynamic phenomena involved in animal flight.

"Many people look at the results in the animal flight literature for understanding how robotic wings could be designed better," shared Lentink. "Now, we've shown that the equations that people have used are not as reliable as the community hoped they were. We need new studies, new methods to really inform this design process much more reliably."