New Blade (Wing?) Design

[FlyingWolf]

http://www.whalepower.com/drupal/?q=node/2

Thought you pilot-engineers would find this interesting. This company is looking mostly at applications for turbines, but if what they claim is true (less drag, greater lift, drastically increased stall angle) it could have some pretty interesting application to aircraft.

Thursday, March 06, 2008

Whale-Inspired Wind Turbines

Mimicking the bumps on humpback-whale fins could lead to more efficient wind turbines.

By Tyler Hamilton

Marine scientists have long suspected that humpback whales' incredible agility comes from the bumps on the leading edges of their flippers. Now Harvard University researchers have come up with a mathematical model that helps explain this hydrodynamic edge. The work gives theoretical weight to a growing body of empirical evidence that similar bumps could lead to more-stable airplane designs, submarines with greater agility, and turbine blades that can capture more energy from the wind and water.

"We were surprised that we were able to replicate a lot of the findings coming out of wind tunnels and water tunnels using relatively simple theory," says Ernst van Nierop, a PhD candidate at the School of Engineering and Applied Sciences at Harvard. He coauthored the study with mathematics professor Michael Brenner and researcher Silas Alben.

The advantage of the humpback-whale flipper seems to be the angle of attack it's capable of--the angle between the flow of water and the face of the flipper. When the angle of attack of a whale flipper--or an airplane wing--becomes too steep, the result is something called stall. In aviation, stall means that there isn't enough air flowing over the top surface of the wing. This causes a combination of increased drag and lost lift, a potentially dangerous situation that can result in a sudden loss of altitude. Previous experiments have shown, however, that the angle of attack of a humpback-whale flipper can be up to 40 percent steeper than that of a smooth flipper before stall occurs.

In a paper recently published in Physical Review Letters and highlighted in the journal Nature, the Harvard research team showed that the bumps on the humpback flipper, known as tubercles, change the distribution of pressure on the flipper so that some parts of it stall before others. Since different parts of the flipper stall at different angles of attack, abrupt stalling is easier to avoid. This effect also gives the whale more freedom to attack at higher angles and the ability to better predict its hydrodynamic limitations.

The researchers also found that the amplitude of the bumps plays a greater role than the number of bumps along a flipper's leading edge. "The idea is, you could make an aircraft that's much harder to stall and easier to control," says van Nierop. For example, fighter jets could be designed to be more acrobatic without risk of stall-induced crashes. In the water, naval submarines could be made more nimble.

The Harvard research validates the first controlled wind-tunnel tests of model flippers, conducted five years ago at the U.S. Naval Academy, in Annapolis, MD, where it was shown that stall typically occurring at a 12-degree angle of attack is delayed until the angle reaches 18 degrees. In these tests, drag was reduced by 32 percent and lift improved by 8 percent.

That research was detailed in a 2004 study in collaboration with West Chester University and Duke University. "This [Harvard work] basically shows that theory and empirical measurements are close, and adds greater weight to our original assertion on the function of the tubercles," says Frank Fish, a biology professor at West Chester and a lead author of the original study.

(http://www.technologyreview.com/energy/20379/?a=f)

[StoleIt]

Weird. I am definitly no aero-engineer.

Wonder if this works on the same principle as vortex generators...Also interesting that they are using hydrodynamics as the base theory. We all now water doesn't flow like air. Look at the difference between a ships prop vs an airplanes for a reminder.

[SVFR]

For a minute this article changed my opinion of Harvard, and then I got to the end of the article and realized they just leached the idea from the Naval Academy.

[Seriously]

I don't ever see this being used on a fighter, at least not one that goes past Mach 1.

Weird. I am definitly no aero-engineer.

Wonder if this works on the same principle as vortex generators...Also interesting that they are using hydrodynamics as the base theory. We all now water doesn't flow like air. Look at the difference between a ships prop vs an airplanes for a reminder.

Water does flow like air, except with a much higher Reynolds number and less compressibility. The principles are the same though.

Edited November 14, 2008 by Seriously

[BQZip01]

I don't ever see this being used on a fighter, at least not one that goes past Mach 1.

Water does flow like air, except with a much higher Reynolds number and less compressibility. The principles are the same though.

WE also KNOW how to spell "know" (not "now")...

...Oh yeah...I went there...

:-)

[hindsight2020]

I don't ever see this being used on a fighter, at least not one that goes past Mach 1.

Water does flow like air, except with a much higher Reynolds number and less compressibility. The principles are the same though.

Bingo. That leading edge is a disaster for transonic flight. The concept is very much an extension of vortex generation applications. Great in theory for extending the usable AOA range, but rather limited in its ability to optimize, or even make possible, supersonic flight. Wave drag issues and a highly dynamic set of mach critical sections on a leading edge of that shape is counter-productive for a dedicated fighter. I can see the utility for marine applications where sonar considerations lend themselves to organic architecture, rather than internal moving parts, to affect a shape, but for flight, not even a halfway decent choice. Of course the 20,000 man hours some underpaid dupe spent running CFD code on that leading edge could could keep our whole economy employed for a month lol.

Essentially, a delta wing could do the job better, it's cheaper, was discovered I think a day after the caveman sparked fire, and even looks sexier (FWIW). This reminds me of those 32-word title masters dissertations I had to endure about the regurgitation of the millionth decimal place optimization, and I could always come up with two carbon epoxy boards and a ruler in one hand and a fist on my other hand to punch myself in the face during said defense to pretend to my advisor I cared about my job (I didn't), and make a planform to achieve 95% their desired result in the time it took them to pitch the profs the idea in the first place. Then again that's kinda why I gave up on trying to get a soon-to-be-offshored Lockmart job and followed my lazy heart to my true calling, become a government pilot *grabs some cheddar cheese while dos gringos plays in the background*

Oh that's intellectual property above and my billing rate is $3,547.34/post. Here to help

[LockheedFix]

Bingo. That leading edge is a disaster for transonic flight. The concept is very much an extension of vortex generation applications. Great in theory for extending the usable AOA range, but rather limited in its ability to optimize, or even make possible, supersonic flight. Wave drag issues and a highly dynamic set of mach critical sections on a leading edge of that shape is counter-productive for a dedicated fighter. I can see the utility for marine applications where sonar considerations lend themselves to organic architecture, rather than internal moving parts, to affect a shape, but for flight, not even a halfway decent choice. Of course the 20,000 man hours some underpaid dupe spent running CFD code on that leading edge could could keep our whole economy employed for a month lol.

Essentially, a delta wing could do the job better, it's cheaper, was discovered I think a day after the caveman sparked fire, and even looks sexier (FWIW). This reminds me of those 32-word title masters dissertations I had to endure about the regurgitation of the millionth decimal place optimization, and I could always come up with two carbon epoxy boards and a ruler in one hand and a fist on my other hand to punch myself in the face during said defense to pretend to my advisor I cared about my job (I didn't), and make a planform to achieve 95% their desired result in the time it took them to pitch the profs the idea in the first place. Then again that's kinda why I gave up on trying to get a soon-to-be-offshored Lockmart job and followed my lazy heart to my true calling, become a government pilot *grabs some cheddar cheese while dos gringos plays in the background*

Oh that's intellectual property above and my billing rate is $3,547.34/post. Here to help

This is the squadron bar. You can't talk like that here.

[FourFans]

This is the squadron bar. You can't talk that here.

Are you trying to tell me that he was actually trying to communicate? With aircrew?

[busdriver]

I will pistol whip the next mother fucker who says Reynold's number, and god help you if you bring up Laplace transforms.

[HoHum]

god help you if you bring up Laplace transforms.

Is this a service Linda performs for engineering types?

[SurelySerious]

This thread has to do with wind turbines... close enough:

Large Wind Farms Increase Temperatures Near Ground

Large wind farms slightly increase temperatures near the ground as the turbines' rotor blades pull down warm air, according to researchers who analyzed nine years of satellite readings around four of the world's biggest wind farms.

The study showed for the first time that wind farms of a certain scale, while producing clean, renewable energy, do have some long-term effect on the immediate environment.

Using sensors aboard a NASA satellite, researchers at the University at Albany-State University of New York, and the University of Illinois systematically tracked a cluster of wind farms in central Texas as the installations grew from a few dozen turbines in 2003 to more than 2,350 by 2011.

On average, the nighttime air around the wind farms became about 0.72 degree Celsius warmer over that time, compared with the surrounding area, the scientists reported Sunday in the peer-reviewed journal Nature Climate Change.

"The warming trend corresponds very well with the growth of the wind turbines," said wind-energy expert Somnath Baidya Roy at the University of Illinois, who was part of the research group. "The warming is going to level off when you stop adding more turbines."

Despite long-standing interest in the environmental impacts of such large-scale alternative-energy installations, this is the first time anyone has measured how wind turbines can alter local temperatures over the long term, the scientists said. So far, the scientists don't know if these higher temperatures affect local rainfall or other weather patterns.

"We don't know whether there is a change in weather due to the temperature change," said atmospheric scientist Liming Zhou at the University at Albany, who led the study, which was funded by the National Science Foundation. "The temperature change is small."

As wind farms become popular and much more widespread, however, they "might have noticeable impacts on local-to-regional weather and climate," Mr. Zhou said. But more research is needed, he said.

The researchers didn't identify the companies operating the wind farms in the region where they monitored temperature changes. To track the growing numbers of wind turbines in the area, the scientists used records kept by the Federal Aviation Administration of construction projects that might interfere with air safety.

Texas has more wind-turbine capacity than any other U.S. state, with many large commercial wind farms. Typically, these commercial wind turbines each sit atop a tower about 250 feet tall, capturing the wind with rotor blades that are about 100 feet long, Mr. Roy said.

Normally, the nighttime air is a layer cake of cool and warm air, caused as hot air rises and cold air sinks, with the coolest air closest to the ground. As the giant rotor blades churn the air, they draw the warmer nighttime air down to the surface.

"If you have a wind turbine spinning, there is a lot of turbulence in the wake just like a boat in the water," said Mr. Roy. "The turbine pulls warm air from aloft and pulls it down and takes cooler air underneath and pushes it up. That creates a warming effect near the surface."

Although the researchers detected some daytime warming because of the wind farms, the temperature changes were highest in the predawn hours, when the air normally is still and not so turbulent, the researchers said.

Write to Robert Lee Hotz at sciencejournal@wsj.com

A version of this article appeared April 30, 2012, on page A6 in some U.S. editions of The Wall Street Journal, with the headline: Large Wind Farms Increase Temperatures Near Ground.

The irony.

[guineapigfury]

Wait ... isn't this what we have had on high speed booms since forever?

[Breckey]

I will pistol whip the next mother fucker who says Reynold's number, and god help you if you bring up Laplace transforms.

What about Fourier Transforms?