Scientists from the University of Bristol and the Royal Veterinary College have figured out how birds can fly in gusty conditions in the wind. The new discovery, detailed in the journal Proceedings of the Royal Society B, could serve as the basis for the development of small-scale aircraft inspired by the structure of birds and their flight mechanics.
“We know that birds are surprisingly good at handling the conditions that challenge created aircraft of similar size, but until now we did not understand the mechanisms behind this process”, said Dr. Shane Windsor of the University of Bristol’s Department of Aerospace Engineering.
New research shows that birds’ wings act as a suspension system to cope with changing wind conditions. The scientists used an innovative combination of high-speed 3D surface reconstruction based on the video, computed tomography (CT), and computational fluid dynamics (CFD). So they wanted to understand how the morphing of their wings helps birds to “throw off” gusts of wind, that is, their changing shape and position.
In an experiment conducted at the Royal Veterinary College’s Structure and Motion Laboratory, the team filmed Lily’s vulture sliding through a series of fan-generated vertical gusts of wind. Lily is a falconry trained bird, a veteran of many nature documentaries, so “she was not at all embarrassed by the light and cameras,” scientists from Bristol assure.
“We started with very gentle gusts of wind in case Lily had any difficulties. But it was soon discovered that even at the highest gust speeds, Lily was unperturbed. She calmly flew straight ahead to receive the award for the food that her trainer Lloyd Buck was holding”, commented Professor Richard Bomfrey of the Royal Veterinary College.
“Lily flew through bumpy gusts of wind and consistently kept her head and torso on a surprisingly stable trajectory as if she were flying with a suspension system. When we analyzed the data, we were surprised that the “suspension system effect” did not just happen. Its aerodynamics were also influenced by the mass of Lily’s wings. In comparison, each of our upper limbs makes up about 5% of our body weight; for a bird, it is about twice as much. They use this mass to effectively absorb gusts of wind”, explained study author Dr. Jorn Cheney of the Royal Veterinary College.
Perhaps most exciting is the discovery that the very part of the suspension ‘effect’, which is responsible for speed, is built into the wing mechanics. This is why the birds don’t need to actively do anything for the system to work. The mechanics are very elegant, ”concludes Dr. Jonathan Stevenson of the University of Bristol.
The next step in the research will be the development of suspension systems based on the unique mechanics of bird flight.