Owl wings could be the answer to noise pollution

No, I’m not talking some kind of macabre insulation made up of owl feathers, as fabulously Disney villain as that might be. Rather, aerospace engineer and aeroacoustics expert (the noise associated with airflow, apparently) Anupam Sharma reckons that that owl wings provide valuable bio-inspiration for noise-reducing innovation in the aircraft and wind-turbine industries.

Owl wings could be the answer to noise pollution

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If, like me, you live under the flight path of a major international airport, or amidst a wind farm, the assistant professor of aerospace engineering at Iowa State might just be your saving grace. Sharma noticed that the owl “is almost completely silent in flight”, not only when gliding, but when flapping too, a feat he deemed “amazing”. Probably because aeroplanes don’t need to feed on rodents that would be put off by the loud hum of a General Electric GE90.

Sharma was able to detect a tripartite structure to the owl wing that is responsible for its hushed mode of aviation. The wing, he deciphered, comprised a leading edge with fine-toothed comb-like structure, trailing fringe feathers, and a downy coat encasing the wing.

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And while this isn’t a completely new concept – the US military has dabbled in owl-tech stealth-crafts – it’s the first time such a systematic computational approach has been taken. Sharma is working at one of the best supercomputing facilities in America – the Argonne National Library, Illinois – creating digital models and running multi-day simulations using more than 16,000 processors.

Sharma’s work is inspiring tangible results already. Collaborators at Virginia Tech have made like the owl and created model airfoils featuring a series of tiny ‘“finlets” and canopies, which ran parallel to the airflow, mimicking the bird’s downy coat. Flight performance was compared favourably with that of the conventional flat airfoil, reducing noise pollution up to five decibels over a wide frequency range.

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The research is so promising that Sharma and his team have been awarded a $500,000 (£386,000) CAREER grant by the National Science Foundation, in addition to a $100,000 (£77,000) endowment by the Iowa Space Grant Consortium. And deservedly so: “The results of this research could have an impact on the design of silent air vehicles with application in national defence, in commerce and in transportation,” said Sharma, of the study’s potential range.

Just don’t expect Heathrow to start looking like the ornithological section of your local wildlife trust. Boeing 747s won’t, alas, be adorned with downy feathers, says Sharma: “Our approach is bio-inspired as opposed to bio-mimicry […] Our designs won’t look like owl wings. We’re studying the physical mechanisms behind the owl wings and applying those to aircraft wings, rotor blades of jet engines and wind turbines.”

So there you go. We knew owls were wise, but shaking up the aeroacoustics industry with a view to tackling noise pollution? That we did not foresee.

Images: Christopher Gannon, Iowa State University

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