Finspiration: The bumps on the leading edge of the humpback whale’s flipper give it a hydrodynamic advantage. Researchers are discovering that similar bumps could make wind turbines, fan blades, and airplane wings more efficient.
NOAA
Mimicking the bumps on humpback-whale fins could lead to more efficient wind turbines.
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.
Nordic Windpower's two-bladed rotors depart from conventional wind-power design.
A more efficient generator could convert more of the wind's energy into electricity.
Vortex generators & Stall Fences
This is not new.
Vortex generators and stall fences have been attached to the leading edge of wings on airplanes for years.
http://www.centennialofflight.gov/essay/Theories_of_Flight/Transonic_Wings/TH20G6.htm
http://en.wikipedia.org/wiki/Vortex_generator
Randy Mason
Re: Vortex generators & Stall Fences
I was going to make basically the same comment about it being a vortec generator application when I saw your comment. I have been using vortec generators on vehicles for years to increase performance, handling and economy. Very simple, easy, inexpensive and effective technology that could and should be used much more extensively then it is.
Re: Vortex generators & Stall Fences
Please tell us more about the vortex modifications which you make to automobiles. Give the price of gas I interested to see what simple things can be done.
Re: Vortex generators & Stall Fences
A series of small vortex generators across the hood & down the frt fenders @ the front edge -- The same across the front edge of the roof & down the windshield pillars, then again at the rear edges of the vehicle where the airflow leaves the body. Makes a VERY noticable difference in the handling, performance and fuel economy of a vehicle at speeds over about 45MPH
Re: Vortex generators & Stall Fences
There is no question that vortex generators work. Look at the upper surface of the wing next time you fly anywhere. Similarly, stall fences were used in some fighter planes during WW Two to attenuate span-wise stall and span-wise pumping. Neither has been applied with any significant success to wind turbines or fans however.
Tubercles deliver comparable benefits but they are far from identical. First, there is no structural fence. Rather, turbulent streams generated in the intertubercular channel act like virtual fences as they transit the back 60% of chord. Also, very unfence-like, these air flow streams have been accellerated by the channel's shape which works like an air-capped venturi chamber. Similarly, I don't think any known vortex generator produces a flow pattern comparable to the very slow sinuous vorticity produced behind the bumps nor can it match its exceptional attachment. In fact, only the airflow over the root resembles a conventional laminar flow.
The more you know about Tubercle technology, the more you understand that this is not a new design for an airfoil: It is literally a new KIND of airfoil.
Stephen W. Dewar
VP Business Affairs & Director of R&D
WhalePower Corporation
27 Tyrrel Avenue
Toronto, ON M6G 2G1
(tel) 416-651-7559 (fax) CALL FOR CONNECTION
stephen.dewar@whalepower.com
Re: Vortex generators & Stall Fences
Stephen,
This was very exciting to read...I had a couple of questions for you regarding the topic of vortex generators/stall fences and the use of "tubercles" on these fan blades:
1) Is there any similarity between this and the trend of Formula One teams using serrated and stepped leading edges on turning vanes?
For a number of years, now, the leading F1 teams have used stepped upper edges on bargeboards and serrated leading edges on their underbody panels to reduce stall sensitivity and improve performance throughout the operating envelope.
2) In your comment about the Harvard tests (edit: excuse me, that would be the U.S. Naval Academy tests), you make mention of a reduction in drag by 32% and increase in lift of 8%... Was this at the high AoAs you noted just before this or at a neutral AoA?
Thanks!
Patrick
Compared to birds, fish and whales - we've been flying and floating for a much smaller amount of time and our technology shows it, while nature has nurtured and refined it's designs for millions of years.
Can't we just copy perfection?
No, we can't copy nature.
We are too simplistic and limted to copy most things. We do get inspired and most things we created are inspired by nature. That's all we know. Think of a bird's or whale's brain and the adaptive control that comes with it and compare it to a turbine or cockpit controller... There is a huge gap there!!!
Copy may be the wrong phrase. Perhaps "mimic" is better. Why not use 3D scanners, copy the intricacies of a critter's flippers, wings or other anatomical parts that have value to us - then inetgrate these features into propeller designs, or air foils etc. I suspect this approach may cut down development time a whole bunch and since nature tends to evolve things that are more energy efficient overall, then we can benefit too.
I agree completely, just reading the articles on the front page today it seems we are realizing this more and more, that nature has already done a large amount of the work towards the 'most efficient' way to do things.
I wonder if there might be some advantage of tubercles in supersonic flight, eg. softening of the shock waves. There may in fact be none, after all, tubercles evolved in nature in the subsonic regime. Still, if I had the means to build and analyze the models, I'd sure would like to see what happens...
Perhaps it would make better wings for aircraft and drones that have to loiter in an area and allow them to carry higher payloads. A USAF aerial tanker could perhaps benefit greatly with this concept.
Why was no mention of increased or decreased drag mentioned?
WhalePower Corp is commercializing this
WhalePower Corp in Toronto has been pursuing this commercially.
Here's our independent coverage:
http://peswiki.com/index.php/Directory:WhalePower_Corp
The company website is http://whalepower.com
Re: WhalePower Corp is commercializing this
We know . There's a link to whalepower in the article .
"The Harvard research validates the first controlled wind-tunnel tests of model flippers..."
Theoretical predictions are validated by experiments, not the other way around. Such a misunderstanding of science perpetuated the ridiculous claims of Aristotle and St. Thomas Aquinas.
Guest (andrewm)
Science works in both directions. An experiment can validate a blue sky theory, and developing a theory to explain experimental data can allow developing the application beyond the immediately visible instance. Either way we end up understanding our universe better.
That's right...it's called "Inductive vs. Deductive" reasoning.
I've heard many different versions of this, but here's my $0.02...others should certainly jump in.
It reflects approaching a physical problem or question from two different directions:
1) Deductive - you observe behavior in a physical system and take measurements about the surroundings, the environment, and the interactions. You then attempt to deduce the cause of the behavior from that data and use controlled experiments to validate your understanding of the relationships between the system, surroundings, environment, etc.
2) Inductive - you start from a theoretical model and basic equations, then design a theoretical system of constrations and interactions. You design tests and experiments to validate the assumptions and constraints in your theoretical model and refine your understanding of the system.
It's two sides of the same coin, but I'd submit it as proof that while you can start with one or the other, you eventually need at least some of both (experimental observation and theoretical induction) to develop the body of knowledge that defines a physical system. It sounds like they've done it here and there' some substantial benefit to be had in airfoil design!
I wonder if engineering should include bio
That "bump" i guess its because it is a "muscles". Somemore if one follow the design of a whale, it will be very dangerous. Cos u fly up then down.
o ya
muscles contract and relax. If one can make the wings of an airplane like that. That would be wonderful. Somemore its flight is because of a wonderful thrust while it is in the water and it lost it while in the air and thats why it falls back down.
Winds changes its form easily. If someone really want to improve it then the wings able to adapt to its surrounding just like that cute little big whale. The wings can be change due to weather and pressure difference and its soft. can change its shape by little though but at least it does change.
for the nowadays flying tech i guess its very nice already. but why not make it with different design.. Whale gave idea not on tech but rather the design more. It would be cute to see a whale flying on the sky.
I'd like to suggest the application of this new design to fans used in computers. It should be relatively cheep to design, build, and test on the fans that cool our computers. The lessons learned could lead to reduced R&D cost on other more expensive fan blades or air wings.
If these claims are true, then a wind + CAES scheme would be very interesting. Consider:
- Wind would be much cheaper, even in areas with lower wind resources, as output would increase dramatically but costs wouldn't rise a lot. Although, for the time being, they may licence/sell their technology for a serious premium ;)
- Tubercles could be integrated in new designs fairly easily and quickly, and older windmills could even be retrofitted with new tubercle blades.
- CAES is already the cheapest method for bulk energy storage, and the majority of the US and many other countries as well have suitable geology for developing the resevoir/aquifer.
- Compressors and expanders used in CAES could be significantly more efficient but again not much more expensive, increasing the round trip efficiency of CAES, making it cheaper.
The development of cost-effective no-fuel CAES such as AACAES would make the scheme even more attractive.
Considering how poorly wind power correlates with electrical demand, it could make sense to bypass the electrical generator in the windmill altogether, replacing it with a compressor. Large wind parks of say at least a few GW each, would all have their own large resevoir. The windmills directly charging the compressed air storage resevoir. It saves the cost of expensive electrical generators, and could also have the advantage of being able to exploit the strongest winds, which is problematic for electrical generators but easier with more robust compressors. Especially because, with tubercles, the blades would be stronger so they could also take stronger winds.
If what they claim is true, then this could be the most important breakthrough for wind in years.
Can you patent something from Mother Nature? God might take you to court.
Stall is seperation of the boundary layer. In golf balls and other 'trips' the flow is forced to be turbulent which although creates more drag, stays attached to the surface for longer.
Adaptable wings? already being researched using electro morphing material to alter the camber of the wings to match the speed.
There's always the under-exploited aerodynamics of delta wings. Better at slower speeds. Different to normal wings and not just streched out and chopped to fit into a Mach cone either.
I always fancied a simple single blade wind turbine based entirely on a sycamore seed. Cheap and the best aerodynamics known afaik.
Just read the note on the effect of the nodules being found 60% back down the flipper. Maybe this is the same as the attached vortex in delta wings..?..
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nucinc
2 Comments
Whale-Inspired Windmills
Whale-Inspired Windmills should be corrected to Whale-Inspired Wind Turbines.
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tadswana
1 Comment
Re: Whale-Inspired Windmills
Yes, these sort of devices are already being used on wind turbine blades - however some of the other concepts discussed in the article are not fully implemented yet.
I'm discussing this in further detail on my blog:
windmeup
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