Silent Flyers
Ambience: Owl hoots
An owl’s wings are designed for stealth flying. But just how the design works is still a bit of a mystery. I’m Jim Metzner and this is the Pulse of the Planet.
Devenport: It’s been known for over 80 years that owls are very silent flyers and also that an owl’s wings have unique features that appear to be related to the silent flight. There are three features; one is little feathers that go forward at the front of the wing; another one is the kind of fringe that is formed by the feathers at the back of the wing; and the third one is the little hairs that grow out of the wing surface.
William Devenport is a professor of engineering at Virginia Tech. He’s been taking a close look at why an owl’s wing is so silent.
Devenport: The focus of our work has really been to look at the possible effects of these little hairs. And these previously haven’t been understood at any great depth in terms of what they can do to the sound made in flight.
Our original thought came from the fact that the owl has little hairs growing out of its feathers, and we thought that the owl used these to quieten the sound made by the air rushing over the rough surface of the owl’s wings. But in the course of our experimentation, we decided that actually the owl more likely uses these to quieten the sound made by the trailing edge of its wing, which is much louder than the rough surfaces.
Devenport and his colleagues are aiming to design a silent wind turbine blade inspired by the fine structure of an owl’s wing.
Devenport: Our intent was to take the inspiration that came from the owl’s hair, and the results that we had seen in our first wind tunnel tests and use them to come up with structures that we could put on the back of a wind turbine blade or on a wing that would quieten that wind turbine blade or wing.
We’ll hear more in future programs. I’m Jim Metzner and this is the Pulse of the Planet.