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Waggling Air Flow Sideways Over Wings Could Cut Aircraft Fuel Consumption And Emissions by 20%

25 May 2009

Aircraft wings which redirect air to waggle sideways over their surfaces could significantly reduce drag and thus cut fuel consumption and emissions by 20%, according to researchers at the University of Warwick (UK). The new approach, which promises to dramatically reduce mid-flight drag, exploits Helmholtz resonance—the same phenomenon that happens when blowing over a bottle—to produce micro-scale jet flows in response to turbulent noise.

The main contributor to aerodynamic drag, and thus fuel consumption and emissions, is fine-scale turbulence that exists very near to the aircraft’s surface during cruise. The Turbulence Flow Control group at the University of Warwick has been studying non-powered (passive) flow control actuators as a means of reducing drag for some time, with the goal of developing flow-control technologies capable of major drag reductions on passenger jet aircraft.

Warwick is focusing on passive actuators because if an actuator is to be used on an aircraft, it must save more energy (in reduced drag) than it requires for its operation. Unfortunately, the researchers at Warwick note, many powered devices that have been developed for the drag-reduction application are unlikely to satisfy this fundamental net-saving requirement.

In a project funded jointly by the Engineering and Physical Sciences Research Council (EPSRC) and Airbus, Warwick and other universities are investigating the potential of using new types of passive devices for turbulent drag reduction. One of the ideas under investigation was the use of Helmholtz resonance.

Warwick is also investigating means by which the drag-reducing capabilities of riblets (surface ridges, such as on shark skin) can be amplified using these Helmholtz resonators.

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.

—Dr. Duncan Lockerby, University of Warwick, project leader

Engineers have known for some time that riblets can reduce skin-friction drag by around 5%. But the new micro-jet system being developed by Dr. Lockerby and his colleagues could reduce skin friction drag by up to 40%.

The research, part of a three-year £1.1-million (US$1.75-million) project 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.

If successful this technology could also have a major impact on the aerodynamic design and fuel consumptions of cars, boats and trains.

The UK aviation industry has announced targets to reduce emissions per passenger km by 50% by 2020.

The Engineering and Physical Sciences Research Council (EPSRC) is the UK’s main agency for funding research in engineering and the physical sciences. The EPSRC invests more than £740 million a year in research and postgraduate training, to help the nation handle the next generation of technological change.

Resources

  • University of Warwick Turbulence Flow Control Group

  • Duncan A. Lockerby, Peter W. Carpenter and Christopher Davies (2007) Is Helmholtz Resonance a Problem for Micro-jet Actuators? Flow, Turbulence and Combustion, Volume 78, Numbers 3-4 doi: 10.1007/s10494-006-9056-0

  • Duncan Lockerby, Peter Carpenter, Christopher Davies (2005) Control of Sublayer Streaks Using Microjet Actuators. AIAA Journal vol.43 no.9 (1878-1886) doi: 10.2514/1.14443

May 25, 2009 in Aviation, Fuel Efficiency | Permalink | Comments (10) | TrackBack (0)

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Comments

I suppose this principle can be applied to windturbines also.

Reducing fluid friction has significant beneficial application. E.G. ICE intake and exhaust flow.

Dr. Lockerby has the right idea, get the technology out there and find out why it works later.

Nonetheless, when understanding comes other benefits will be engineering tradeoffs such as cost/performance or sub-optimal retrofits to existing drag prone surfaces.

Someone give this guy more money and do both.

Nature is good to study for designs. One story was the reptile that could burrow under sand with no problems due to friction. That led to examining the skin and finding ridges that helped.

Nature has had millions of years to create good designs. There is no reason why we can not learn from all of this to make more progress more quickly.

Science learned from mother nature - like the fine foot hairs that allow geckos to cling to glass.
Except I am not aware of any Helmholtz resonance or waggling air effect in animals.
At first I thought this was akin to vortex shedding, but I guess not.
This sounds like it will lead to significant advances.
And it does not at all smell like a hoax or scam.
Time will tell –

yes we still have a lot to learn from nature in that regards, fishes and dolphin an go fast in water with little energy because they actively control the turbulences they generate. When you realize that salmons can swim thousands of miles agaisnt the stream of fast rivers without eating any food, it is just mind blowing. Nature has solved these energy problems long time ago, we are still in the infancy of learning how to manage energy in a ultra efficient way, and we have to do it for our own survival. Nature tweaked efficiency because it was the only way to survive, and there is no alternative.

I am not aware of any Helmholtz resonance or waggling air effect in animals.

I should say that I am not aware of any Helmholtz resonance or waggling air effect in animals that serves to reduce wind drag.
Some of those sounds at night in the jungle might well be from Helmholtz resonators.

Trehugger:

We survived by buying energy and many other products very cheaply from others who did not do so well.

Oil at $3 to $10 /barrel was so cheap that we did not need efficient vehicles. The same could be said for coffee, bananas, sugar, wood products etc etc.

Waggling airflow improvements have not been discovered soon enough. Nature has been mimicked in many forms from the design of boats, submarines, aircraft, shelters, and even escavators. Bio-mimicry will continue to be part of engineering design in the future.

If they ever create half of THE efficiency that is claimed with turbulence flow control, say around 20%, savings in direct fuel costs will be huge. All airliners that take on this technology stand to make a windfall profit in a very short time. If Warwick University was to ask for funding now they would return the investors their money in a few years. Why wait until 2012 for a prototype?

Maybe there is other vested interests in the fuel business. I never fly myself very much, but I say we should make these heavy chunks of metal that make thousands of flights a week around the world in very turbulent and dangerous conditions, fly as efficiently as they can. For safety sake. We only have so much cheap and easy fuel left, and then we will have to sit and watch the cost of flying go through the roof. I say we need aerodynamic development like this for our planets sake; yesterday.

Waggling airflow improvements have not been discovered soon enough. Nature has been mimicked in many forms from the design of boats, submarines, aircraft, shelters, and even escavators. Bio-mimicry will continue to be part of engineering design in the future.

If they ever create half of THE efficiency that is claimed with turbulence flow control, say around 20%, savings in direct fuel costs will be huge. All airliners that take on this technology stand to make a windfall profit in a very short time. If Warwick University was to ask for funding now they would return the investors their money in a few years. Why wait until 2012 for a prototype?

Maybe there is other vested interests in the fuel business. I never fly myself very much, but I say we should make these heavy chunks of metal that make thousands of flights a week around the world in very turbulent and dangerous conditions, fly as efficiently as they can. For safety sake. We only have so much cheap and easy fuel left, and then we will have to sit and watch the cost of flying go through the roof. I say we need aerodynamic development like this for our planets sake; yesterday.

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