Plans for go-faster wind turbine blades get a lift from the wings of an owl

barn owl

Close-up of an owl wing showing the 'comb-edge'
Close-up of an owl wing showing the ‘comb-edge’







                   By DARA BUTTERFIELD

Researchers at Cambridge University have developed a modification for wind turbine blades that could make them quieter and able to run faster.

The researches have said that currently many wind turbines are heavily ‘braked’ to limit their speed so that they do not exceed noise limits. With this new coating it would be possible to run the turbines at a faster rate and increase generation while still making less noise.

The new modification has been inspired by the wings of owls, which are famous for their stealthy flight.

Professor Nigel Peake, lead researcher, University of Cambridge, said: “Many owls – primarily large owls like barn owls or great grey owls – can hunt by stealth, swooping down and capturing their prey undetected. While we’ve known this for centuries, what hasn’t been known is how or why owls are able to fly in silence.

“No other bird has this sort of intricate wing structure. Much of the noise caused by a wing – whether it’s attached to a bird, a plane or a fan – originates at the trailing edge where the air passing over the wing surface is turbulent.

“The structure of an owl’s wing serves to reduce noise by smoothing the passage of air as it passes over the wing – scattering the sound so their prey can’t hear them coming.”

The most unique aspect of owl feathers is the comb-like or fimbriate (fringe-like) leading edge of the primary wing feathers referred to as “flutings or “fimbriae”. With a normal bird in flight, air rushes over the surface of the wing, creating turbulence, which makes a gushing noise. With an owl wing, the comb-like feather edge breaks down the turbulence into little groups called micro-turbulences. This effectively muffles the sound of the air rushing over the wing surface and allows the owl to fly silently.

The researchers sought to mimic the noise-scattering effect and carried out successful trials using material similar to that used on wedding veils. They then developed a prototype material using 3D-printed plastic and tested it in a wind tunnel. The turbine blade they tested showed that the material cut noise by up to 10 decibels, without having any noticeable effect on its aerodynamics.

The researchers now plan to test the material on a full-size functioning wind turbine.

Last November Ministers launched a review into disturbance from turbine noise led by the Institute of Acoustics; the results have yet to be published.

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