Science

Owl feathers pass their wisdom on to wind turbines

Owl feathers pass their wisdom...
The secret to owls' quiet flight lies in a layer of down on their wings
The secret to owls' quiet flight lies in a layer of down on their wings
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The secret to owls' quiet flight lies in a layer of down on their wings
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The secret to owls' quiet flight lies in a layer of down on their wings

Owls are known for their near-silent flight, which allows them to swoop down on prey unheard. Wind turbines, on the other hand, are often accused of being too noisy. A team of British and American scientists is currently addressing the one situation with the other, by copying the structure of owl feathers to make turbine blades more quiet.

The researchers – from Lehigh University, Virginia Tech, Florida Atlantic University and the University of Cambridge – started by analyzing the wing feathers of large owls. More specifically, they were interested in the layer of down that covers the upper surface of the wings.

That down is made up of a forest of tiny hairs, which each stick up almost perpendicular to the main feather before bending back in the direction of the air flow. Each hair also has a barb at the end, which interlocks with barbs on surrounding hairs. The result is that the down is topped with a soft canopy of linked hair tips, which the air flows over instead of the rougher feather surface beneath.

Using a 3D printer, the scientists partially replicated that structure in the form of a series of "finlets" that could be attached to the trailing edge of wind turbine blades. Although those finlets do feature a unidirectional layer of "hairs" like the down, they don't have the interlocking barbs at their ends. According to the researchers, this makes the material even more aerodynamic than the owl down, as air is channeled straight through it instead of being deflected off of it.

In wind tunnel tests, it was found that when attached to an airfoil such as a turbine blade, the finlets could lower wind noise by as much as 10 decibels without affecting aerodynamic performance. The technology could conceivably also be applied to things like car door seals and windows, where wind noise can likewise be a problem.

This isn't the first time that we've seen wind turbine blades copying animals' body structure. Previously, the bumps on humpback whales' flippers have been replicated in order to improve the blades' performance.

Source: Lehigh University

11 comments
IX
Some photos/diagrams would have been nice...
Imran Sheikh
The problem is not the wing dear. You are taking aerodynamics all wrong . When you start pumping air in a medium where the air is steady the fast moving air and the motionless air collide its like a "air clap" that noise we here. Its technically a speaker the wind tunnel. To make the wind tunnel silent you need to pull the equal amount of air outside of the tunnel to make it less noisy. Better use gigantic noise cancellation speakers after the fan.
Rumata
The secret of the silence of the owl's flight is not a special structure of the owl's feather, but the lower specific (weight per area) load of the owl's wing, relative to other birds. Attaching sound-supressing or vortex-supressing structures to the trailing edge of a turbine blade might help decreasing noise, but it has nothing to do with the owl's feathers.
JanHolland
There is some prior art here .... And this is already a Commercial Off the Shelf (COTS) item. In 2009 Stefan Oerlemans wrote a thesis on this titled Detection of aeroacoustic sound sources on aircraft and wind turbines. He later went on to do more research on this at the Netherlands Aerospace Center. Since he moved to Siemens they have now incorporated this feature in their windturbines, see https://www.siemens.com/press/PR2016090418WPEN
CraigAllenCorson
Has it occurred to anyone yet that this technique could be applied to airplane and boat propellers, wings, that sort of thing? If not, I take full credit. (-:
Island Architect
It stuns me that you would post stuff on wind engines and never once require the data on % efficiency.
N E V E R O N C E !!!!
You must not be real engineers but play toy versions who are simply hackers!
Bill Dickens
ljaques
I'm more familiar with smaller wind turbines, but the vast majority of the noise created by wind turbines is in the -power train-, not the blades. Sure, quieter blades help, but let's lower the noise from the noisemaker, not the whup-whups.
Ralf Biernacki
@Imran: nothing is "pumping air" here. These are wind turbines; the entire air mass is moving past them, there is no shear layer "where the moving air and motionless air collide". The shear layer is at the surface of the blade, and directly downstream of it where the upper and lower streams recombine. And those places are exactly where they place the finlets, to smooth out air vibrations due to the shear.
Paul Smith
Island Architect, I am sorry to hear that you are stunned, but this article concerns the noise of turbines, not the performance, and the performance is not affected at any rate as the noise was reduced by as "much as 10 decibels without affecting aerodynamic performance."
Craig Jennings
I've only seen a couple of wind turbines. From what I've seen the loudest noise they make is when their blades pass the tower with the classic low frequency "whumph" that travels for miles. Changing that interaction would be better if efforts were to be expended in just one place. A more aerodynamic shape for the tower/movable cowling would go a ways to reducing the air pressures at that point.