Most sensible air travelers dread turbulence. A little atmospheric hiccup can shake airplanes, rattle nerves and spill beverages. A Cornell-led collaboration has found that birds don't mind at all.
By combining wind speed data with the measured accelerations of a golden eagle outfitted with GPS tracking instruments, the researchers suggest that, rather than hindering flight, turbulence is a source of energy that birds may use to their advantage.
This counterintuitive discovery could revise what we know about avian flight, and help the aerospace industry develop faster, more efficient ways to fly in turbulent environments.
[...] While the flight of birds may appear easy and graceful to earthbound spectators, winged animals are actually navigating air flow that is structured, textured and constantly in flux, according to Gregory Bewley, assistant professor in the Sibley School of Mechanical and Aerospace Engineering, who led the team.
[...] In order to take his experiments out of the lab and into the sky, Bewley's team partnered with two groups -- Conservation Science Global and Cellular Tracking Technologies. Scientists from these companies captured a female golden eagle in Alabama, rigged it with a solar GPS telemetry unit with an accelerometer weighing less than 3 ounces, then released the bird.
[...] They found a "highly irregular, fluctuating pattern" in the eagle's accelerations, which resembles the typical trajectories of particles in turbulent airflows. At timescales ranging from 0.5 to 10 seconds -- which translates to approximately 1 to 25 wingbeats -- the eagle's accelerations and atmospheric turbulence were completely in synch.
[...] "If you could find a path in which every vortex is pushing you the right way, then obviously you get there a little faster with a little less energy," Bewley said. "We're still working hard to understand turbulence by itself. I think it's fascinating that there might be some practical empirical knowledge embodied in wildlife that we don't appreciate yet."
Kasey M. Laurent, Bob Fogg, Tobias Ginsburg, et al. Turbulence explains the accelerations of an eagle in natural flight [$], Proceedings of the National Academy of Sciences (DOI: 10.1073/pnas.2102588118)