Owls' wings could hold the key to beating wind turbine noise

Credit: CC0 Public Domain

A new study has revealed how inspiration from owls' wings could allow aircraft and wind turbines to become quieter.

Researchers from Japan and China studied the serrations in the leading edge of owls' wings, gaining new insight into how they work to make the birds' flight silent.

Their results, published today in the journal Bioinspiration and Biomimetics, point towards potential mechanisms for suppression in , aircraft, multi-rotor drones and other machines.

Lead author Professor Hao Liu, from Chiba University, Japan, said: "Owls are known for silent flight, owing to their unique features, which are normally characterised by leading-edge serrations, trailing-edge fringes and velvet-like surfaces.

"We wanted to understand how these features affect aerodynamic force production and , and whether they could be applied elsewhere."

The researchers analysed owl-inspired feather wing models with and without leading edge serrations, by combining large-eddy simulations - a mathematical model for turbulence used in to simulate air flows - and Particle-Image Velocimetry (PIV) and force measurements in a low-speed wind tunnel.

They discovered leading-edge serrations can passively control the transition between laminar, or streamline air flow, and turbulent air flow over the upper wing surface, at angles of attack (AoA) between zero and 20 degrees. This means they play a crucial role in aerodynamic force and sound production.

Professor Liu said: "We found, however, that a trade-off exists between force production and sound suppression. Serrated leading-edges reduce at lower AoAs than 15° compared to clean leading-edges, but can achieve noise reduction and aerodynamic performance at AoAs above 15°, which owl wings often reach in flight.

"These owl-inspired leading edge serrations, if applied to wind turbine blades, aircraft wings or drone rotors, could provide a useful biomimetic design for flow control and noise reduction.

"At a time when issues of noise are one of the main barriers to the building of wind turbines, for example, a method for reducing the noise they generate is most welcome."

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More information: Chen Rao et al, Owl-inspired leading-edge serrations play a crucial role in aerodynamic force production and sound suppression, Bioinspiration & Biomimetics (2017). DOI: 10.1088/1748-3190/aa7013
Journal information: Bioinspiration and Biomimetics

Citation: Owls' wings could hold the key to beating wind turbine noise (2017, July 4) retrieved 14 October 2019 from https://techxplore.com/news/2017-07-owls-wings-key-turbine-noise.html
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User comments

Jul 04, 2017
"At a time when issues of noise are one of the main barriers to the building of wind turbines"

Really? From what I gather 'wind-turbine-syndrome' is an entirely fictional disease pushed by some fossil fuel funded activist groups. Funnily a study found that wind turbine syndrome is correlated with the media coverage of it - but not with the location of wind parks. Go figure.

That said: we have these wind turbines all over the place and
a) they aren't near enough houses to be heard (certainly not when compared to airports, train lines or highways)
b) they don't make much noise (particularly not when compared to the noise wind makes on its own...you know: because when they turn in the first place it tends to be somewhat windy?)
c) off-shore the problem is non-existent (and if there is some issue with noise that is transferred into the water then insulation of the underwater parts is probably a much easier fix.

Jul 05, 2017
I have been suggesting that the turbulent boundary layer on aircraft wings can be damped by streamers inside the layer, so as to reduce the local drag. But except for some marine applications nobody wants to know.

Jul 05, 2017
Funny how we spend so much effort to reduce the noise of "air around an airfoil" yet every year after winter we spend the rest of the year listening to the noisy Harley-Davidson motorcycles freed from their winter home, most of which have virtually no muffler and going with a "straight pipe" exhaust system. Getting after those noisy machines will create a far quieter environment than tweaking the wind turbine.

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