Owls are well known for their ability to hunt their prey without making too much noise. This unique trait is what inspired scientists to develop an experimental coating technology that will allow wind turbines and other fan blades such as those used for airplanes and computers to operate silently.
Researchers from the University of Cambridge in the United Kingdom and from three other institutions in the United States have designed a coating that allows surfaces to mimic the characteristics of the wings of an owl.
The new material helps reduce the noise wind turbines make during operation, allowing it to run at higher speeds and produce more energy. This improvement could deliver more megawatts of valuable electricity even in areas with average-sized wind farms.
Nigel Peake, a professor at Cambridge's applied mathematics and theoretical physics department and lead researcher of the study, explained that while it has long been known that large owls, such as the great grey owl or barn owl, often hunt their prey by stealth, it remained unclear how or why the animals are able to do so.
Peake worked with fellow researchers at the Florida Atlantic University (FAU), Lehigh University and Virginia Tech (VT) in examining the feathers of owls in high detail through high resolution microscopy.
They found that the flight feathers on the wings of an owl have a downy covering that resembles a forest canopy especially when viewed from above. Aside from this fluffy covering, the bird's wings also have a comb of bristles that are spaced evenly along the leading edge as well as elastic and porous fringe located on the trailing edge.
In order to recreate the owl's wing structure, Peake and his team created a covering that is capable of scattering the noise produced by the blades of a turbine in a similar way.
At first, the researchers tried covering the blades with a material similar to the one used to make wedding veils.
While it was able to reduce the surface noise by as much as 30 decibels, the material was deemed unsuitable to use on an airplane or a wind turbine.
The scientists then created an experimental material using the same design principles as the wedding veil but made of three-dimensional plastic.
When they applied the material on a full-sized segment of a wind turbine blade, it was able to bring down the noise in the wind tunnel by as much as 10 decibels without any significant impact on the aerodynamics.
The new coating technology still needs to be optimized and tested on an airplane before it could be approved for other complicated purposes, but it is already being viewed as a potential material for various types of blades and wings.
The researchers plan to test the material on a wind turbine next.
The findings of the University of Cambridge-led study were presented at the American Institute of Aeronautics and Astronautics (AIAA) Aeroacoustics Conference in Dallas, Texas.
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