A prototype coating for wind turbine blades, based on the structure of the wings of owls, could significantly reduce the amount of noise they make.
Early tests of the material shows it cuts down the noise from wind turbines and other types of fan blades including aircraft.
The new surface would allow wind turbines to be run at higher speeds to produce more energy while making less noise. Currently, the turbines are heavily braked to help keep the noise down.
The surface was developed by researchers at the University of Cambridge in collaboration with researchers at three institutions in the USA. Their results will be presented this week at the American Institute of Aeronautics and Astronautics Aeroacoustics Conference in Dallas.
“Many owls – primarily large owls like barn owls or great grey owls – can hunt by stealth, swooping down and capturing their prey undetected,” saysProfessor Nigel Peake of Cambridge’s Department of Applied Mathematics and Theoretical Physics, who led the research.
“While we’ve known this for centuries, what hasn’t been known is how or why owls are able to fly in silence.”
Peake and his collaborators at Virginia Tech, Lehigh and Florida Atlantic Universities used high resolution microscopy to examine owl feathers in fine detail.
The flight feathers on an owl’s wing have a downy covering, which resembles a forest canopy when viewed from above.
The owl wings also have a flexible comb of evenly-spaced bristles along their leading edge, and a porous and elastic fringe on the trailing edge.
“No other bird has this sort of intricate wing structure,” says Peake. “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 researchers then developed a prototype material made of 3D-printed plastic and tested it on a full-sized segment of a wind turbine blade.
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