Wings that waggle could cut emissions by 20%

Wings which force air to waggle sideways could cut airline fuel bills by 20% according to research funded by the UK’s Engineering and Physical Sciences Research Council (EPSRC) and Airbus.

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The new approach, which promises to dramatically reduce mid-flight drag, uses tiny air powered jets which redirect the air, making it flow sideways back and forth over the wing.

The jets work by the Helmholtz resonance principle - when air is forced into a cavity the pressure increases, which forces air out and sucks it back in again causing an oscillation – the same phenomenon that happen when blowing over a bottle.

Dr Duncan Lockerby, from the University of Warwick, who is leading the project, said: “This has come as a bit of a surprise to all of us in the aerodynamics community. It was discovered, essentially, by waggling a piece of wing from side to side in a wind tunnel.”

“The truth is we’re not exactly sure why this technology reduces drag but with the pressure of climate change we can’t afford to wait around to find out. So we are pushing ahead with prototypes and have a separate three-year project to look more carefully at the physics behind it.”

Engineers have known for some time that tiny ridges known as ‘riblets’ – like those found on sharks bodies – can reduce skin-friction drag, (a major contorbiutor to mid-flight drag), by around 5%. But the new micro-jet system being developed by Dr Lockerby and his colleagues could, they claim, reduce skin friction drag by up to 40%.

The research, being carried out with scientists at Cardiff, Imperial, Sheffield, and Queen’s University Belfast, is still at concept stage although it is hoped the new wings could be ready for trials as early as 2012.

Dr Lockerby tells Future Proof: “The wings/aircraft surface make the airflow “waggle” rather than the wings waggle structurally… which would be quite disconcerting to the passengers I sense.

“We envision many thousands of small cavities sunk within the surface of the aircraft. Each cavity would have one or a series of outlets that air would flow in and out of; directed perpendicular to the direction of travel.

“This creates an oscillation in the airflow very near to the surface – the boundary layer – which, via a physical mechanism we are working to fully understand, reduces the frictional drag.”



 

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