"Noisy" wind generator solution ? (Just a theory).

[Pseudomax]

This idea is at quite abstract stage, so be warned beforehand.

At least here in Finland various people (factions ?) have expressed their "disappointment" at how terribly noisy (and "lethally dangerous") those bigger wind turbine propeller blades can be.

I wonder if this simple mechanical solution could fix this "serious problem":

Covering the blades with thin layer of fluff (like from amphibious and common plant Typha Latifolia, which has been used previously as fillings for futons, and appears to be quite water resistant and/or "survivable" natural fluffy material). Theory is that it could act like thin layer or air current yielding "feathering", as in birds' wings and thus remove much of the noise generated. I have not researched sensible methods of attaching this "layer of fluff" to propeller blades, nor have I studied the negative effects from it retaining water, and thus getting heavier, in the rain (or prevention of such). Nor have I researched how tightly packed this fluff should be, etc. Nor do I know whether such "turbulence reduction" would be beneficial or adverse for the energy output of the generator (Supposing such could be made without adding significant weight, and without water retaining).

If this is a working theory, perhaps it could have some uses when big scale propeller turbines need to be close to habitations ?

Pseudomax

[jmk]

 What size turbines are you getting noise from? Are they home made? Are the tips tracking? Do the tips come to a point?  

[dinges]

Abstract ideas are not the problem.

First of all: windmill blades being lethally dangerous?! Have I missed something? When was the last time one of those evil blades killed an unsuspecting person? And if so, weren't they trespassing if they got that close to the turbine? perhaps even climbing the tower?

More dangerous than aircraft propellors, or cars for that matter? Do the same people complain about these pieces of mechanics too? Should we install fluff on our car bumpers, instead of a bull-bar?

I suspect a hidden agenda here, from those complainers.

Your solution (to a non-existing problem) wouldn't work, I think, because of extra drag induced. You want the surface of your props as smooth and sharp as possible, to reduce turbulence.

If noise is the problem (though complainers may state this, again, I don't think this is really the underlying problem they have; it's the windturbine they have a bias against, valid or invalid. Trying to rationalize their feelings by commenting on birdkills, noise, horizon pollution, danger of it falling down, de-capitation by props, etc.)

IMHO, there is no problem, so no need to start inventing solutions.

Peter,

The Netherlands.

[dinges]

I forgot: reducing the TSR of props will reduce tip speed, and thus noise level. Your turbine will turn slower though...

Is it just me, or am I the only one who likes the 'wooshing'-sound of blades passing by?

Peter,

The Netherlands.

[johnlm]

I enjoy the sound - unless Im real close to the prop then my hiney starts to pucker especially if the wind is changing directions.

[dinges]

More correctly: you need laminar flow of the air over your blades. The better polished, the smoother, the better. Same thing as with aircraft wings. When I used to still fly gliders, some people severely polished the wings before starting. I never did. I wasn't the best flyer in the club, so whenever I landed sooner than the rest I could always blame it on me not having polished the wings :-) Ever saw a wing with fluff? Turbulence is bad, causes your blades to stall sooner and thus produce less power.

Better use of the fluff would be in those people's ears, so they won't hear the wooshing sound of the turbine. Yess, we even had complaints from people that the gliders were too noisy too... (then again, one person once called the police because they thought an a/c was crashing; it was just me doing some aerobatics :-) I told you I wasn't a good pilot)

To more experienced windgenny builders: when the blades are stalling, do you notice an increase in vibration of the turbine, because of the extra turbulence generated? I.e., one blade hitting the turbulence of the previous blade (wake turbulence)?

Peter,

The Netherlands.

[Pseudomax]

IMPORTANT: The plant (Typha Latifolia) I proposed as a source material for this simulated "feather" / "fluff" layer: apparently causes allergy on some people. Not good source as a solution to such "problem", as it might start to cause real problems for allergics. Also, I'm not sure it could be formed into feathery layer I'm proposing.

*

Indeed they apparently have "unspoken" agendas, as they complain loudly in special media "documentaries" about the "unacceptable dangers" of wind energy as when compared to "traditional" (I.E. not the "new" and "unpredictable" wind energy) centralized powerplants. But this was an excuse enough for me to start looking into this theory about reducing drag and turbulence.

Perhaps the "fluff" was a misleading word: I did not mean for it to "soften" any possible impacts, for I have seen such turbulence reducing on wings: Bird's wings.

To clarify few things: If you build a hydrodynamic model of dolphin, and try to propel / launch it through a body of water, it will not reach the same energy / speed ratios as actual dolphin (of same size, shape, and weight) does. Not unless it has a softening layer of skin and fat that allows water turbulence to "wear itself down" or "flow freely" on the soft recesses it forms, thus reducing drag. (Correct me if this has been proved a hoax, or just been biased research, etc., i.e. if my theory was based on unreliable data). It just seems to me that weathered wings do the same thing with air. If you watch on a film any big bird in mid-flight (especially in smooth slow motion, as the spectacular nature documentaries often like to display it), like albatross or vulture, where it is shown in mid-flight, but remains at the center of the screen (camera with telescope objective has followed it's flight, keeping the observation angle relatively constant), you can see it's individual feathers, and feather-areas being ruffled this way and that, without these turbulences apparently affecting the bird's flight, as the feather layer yields to it. This was my Idea, for turbulence reduction in general, in wings.

This layer of "fluff" I propose, would have to effectively simulate that "feather effect": Light and aerodynamically yielding to minor turbulences. Preferably resistant to water too. This might (or might not) reduce such turbulence effect, drag, twist and noise on many types of wings (depending of the actual airspeeds: I don't think there's much benefit on much higher speeds than for which the feathers seem to have evolved).

I guess I'll have to just get some real feathers and start to test this on small scale models of wind turbines, check their rpm:s and outputs with various "feather" layer simulation techniques at different windspeeds.

Pseudomax

  That's why the poll: "does this type of theoretic musing belong here"

[Gary D]

  To city people, birds singing can be a niusance (especially owls at night), a waterfall, trees leaves blowing in a strong wind, a tractor moving down the road to a different field etc...

  To someone like me, trains, jets, tractor trailers, noisy dirt bikes, and atv's are a nuisance. I doubt that ANY of the things I can get "bothered by" will be stopped becauce of lawsuits, nor would I want them to...

  A 4 foot windgenerator doing a TSR of 4 must have a higher rpm than a 200 foot mill with the same TSR. Would the "complainers" prefer a coal generating plant be built at the same location? If given this as the only alternative, hmmmm...

 Merry Christmas to all  interesting theory  Gary D.

[Pseudomax]

Well, one person I explained this to suggested this, relating to similar phenomenon in aerodynamics:

• According to his knowledge, Golf balls need those small circular recesses. For aerodynamic reasons: Identical golf ball without these recesses apparently can not be played with, as it can't be hit nearly as far as one with the recesses (To test, Golf ball in hardy, flexible pvc layer (or something equal that is smooth but fills and covers the recesses, and can bend to the golf-club impact without breaking).
  
• Apparently, the small recesses create small layer of relatively (to airflow direction)uniform and unobtrusive enough (for aerodynamic purposes), layer of "controlled turbulences". This "controlled turbulence" layer then apparently behaves, just like feather layer: Reduces turbulence effects, smoothens the airflow around the golfball, and thus enable golf ball to fly further with the same amount of energy.
  
• Now, giwen that this turns out to not to be just urban legend, this sounds like something that could be much easier to test on wind turbine propeller blades.
  
  

And after all these IF's: people could wonder what size and depth of tiny recesses, are best at what wind and airspeed (over blade's areas), and where they could be effective (if anywhere at all): the rotation direction edge-area of the blades ? The whole propeller surface area ? Blade side facing the wind ? And so on.

Pseudomax

  If that Golfball thing is bull, do tell me and I'll get back to my experiments with simulated "feather" yielding layers.

Ps: Ignore my recent panicky rants about my "disappearing posts". (It was just me having an "escalated conflict" with my Hotlist program settings.

[dinges]

Yes, the effect you describe is real.

Goes for golfballs, and I know that sports engineers have designed swimming suits and ice-skating suits with 'shark teeth' marks in them. They deliberately cause a little bit. Apparently, this gives slightly less resistance than laminar flow. However, this is so specialistic; in 99.9% (?) of cases, you'd be best served by keeping things simple and laminar; unless you want to go for that extra .01% of extra generated power by your turbine. Hmm, I don't even know any glider pilots (some real competitive guys out there) that use turbulator strips (term?); the better they are, the more they clean & polish their aircraft...

in short: laminar=good; turbulent=bad.

I forgot: they have an extremely smooth surface, and deliberately reduce this a bit; this is not the same as starting out with a rough, untreated surface and claiming it to be a state-of-the-art turbulator. :-)

Also, turbulent flow will cause less output and more wear on the turbine.

So, just KISS, unless you're an aerodynamics engineer looking for a Ph.D. subject...

But now, if you're any real scientist, you'll ignore what I and we just said and do it anyway. It's usually these type of guys that get the Nobel-prizes...

Peter,

The Netherlands.

[paradigmdesign]

Instead of putting a "fluff" layer on, why not just let the material that you use have a "print-through", basicially don't sand the outside layer, and use a thick fiberglass cloth.  You would have to do it in a open lay-up situation so the excess resin on the outside could drip off.

Wind mill blades are different than a golf ball is that they interact with the wind in a completely different way.  Being that the blades at the tip are hitting most of the wind with the leading edge, and the further you go down the blade, the more the wind goes twords the chord of the blade.  So to keep up a "uniform turblience" the divits in the blade would need to get smaller as they got further down the blade.

I was talking to a guy from Bergey about the blade noise, and he said they were having problems with blade noise, that they solved by placing a strip of fiberglass tape down the downwind side of the blades, to help breakup some of the vaccume pressure on that side of the blade.  It should be noted that bergey gennys do not use twist-tapered blades, so this siloution may not work for every one here.

[drdongle]

Some of the so called "greens" will always find fault now matter what one does to make them happy. In fact there is a small faction that thinks that Humanity need to disappear so as to eliminate our evil influence.

[rotornuts]

Laminar is best if you can keep it laminar and keep the AoA's low. turbulent boundry layers are best over a broad range of AoA's because they suffer much less under adverse contitions than laminar flow. When laminar flow breaks down (which it does easier than non-laminar) the airfoil suffers greatly as turbulence propagates foward on the profile and sideways as well affecting the area of laminar flow adjacent (laminar boundry profiles are not entirely laminar anyway). For the same reason that golf balls have dimples many turbine blades use non-laminar blade profiles and can also incorporate vortex generators of some sort(golf ball dimples). Of course you could use a laminar profile and use flow agmentation as well but from what I understand a laminar profile is not simply a polished one. Not as easy to build in your basement.

The feather idea isn't all that half cocked, it has merit in the theory. The thing though is that non-feather looking approches have accomplished the same results without some of the drawbacks such as feather maintenance and collection, kidding of course.

I think if you placed feather like devices with a spring action in the stall zone (transition point) on the cambered surface of the profile you would probably see delayed stall like you would with vortex generators possibly with better results. It would be like having self adjusting VG's rising and lowering with the thickness of the boundry layer. This is pure speculation on my behalf but I believe the theory is sound.

Suggested reading for some folks would be:

http://www.aerospaceweb.org/question/aerodynamics/q0215.shtml

http://142.26.194.131/aerodynamics1/Drag/Page2.html

http://www.princeton.edu/~asmits/Bicycle_web/blunt.html

http://www.aviation-history.com/theory/lam-flow.htm

http://www.avweb.com/news/reviews/182564-1.html

http://www.standardcirrus.org/OilFlows.html

http://www.standardcirrus.org/Turbulators.html

The two adove links speak about turblators and sailplanes. Turbulators are a form of vortex generator. Sailplanes ideed I believe always use laminar profiles but flow seperation and turbulent boundry layers still haunt. Hmmmm....

Low Re info:

http://www.nd.edu/~mav/belgium.pdf

turbulence propagation:

http://www.efluids.com/efluids/gallery/gallery_pages/spot_page.htm

Home the above link if you like fluid dynamics visuals.

Anyhow, the more one learns the less likely one is to speak with absolute authority, I think?

Have fun and if you think it will work give it a try, I say it can't hurt unless you expect total sucess on your first attempt.

Just to avoid confusion, as I understand it all profiles have a combination of laminar and turbulent flow. The issue is controlling the transition point and the flow aft of the transition to yield a desired effect dependant on one's objectives. How long do you want to keep it laminar? does it make sense to keep it laminar beyond a certain point? will the profile have any apreciable lift left after you kill yourself making it supper dupper laminar. What the hell is laminar anyway?

Mike

[IntegEner]

Need anyone say more when debates like these arise over a simple question? The study of aerodynamics may be some 100 years in the process now but seems still lost in a tangle of nomenclature and conflicting theories. My engineering degree is from the same U. of Notre Dame mentioned in these links and I support the UND PIV (Particle Image Velocimetry) groundbreaking work, at the micro level far removed from macro applications like wind energy though it continues to be. Go Irish!

I long ago forsook all these questions about what happens at the surface of the airfoil, even those about whether the flow above or below the wing arrives at the trailing edge first. In a word, atmospheric air is a block of mass occupying a large volume and unless this is accepted at the very outset, my eyes glaze over and I begin to turn the page. What is missing from most of these studies is what happens to the airflow mass at some distance away from the airfoil. This matters to the exclusion of practically everything else. It bothers me no end to see the almost universal lack of insight on this.

What is also noticeable here is the absence of commentary from the sailors, whose company I greatly prefer despite the pokiness of sailing vs. the speed of flight. It is when a person sees the airflow deflecting power of large, thin objects like sails that one comes to understand the basic questions about how wings work and how wind turbine blades convert energy. So it is that my airfoils for the small wind rotators as seen on my website are thin and "sail-like". This avenue of approach is far more productive than worrying about small surface features as is found when actually putting something together that runs. Thin and "sail-like". Wind energy has yet to discover the importance of thin and "sail-like". In this instance the thinness of bird wings is being overlooked in favor of studying the fluffiness of their feathers.

More to be said in the wonderful opportunities on this discussion list of posting rants and diaries, which I have some inclination to do on these topics later.

Anthony (Yes, I am still the "Knucks") Chessick

www.integener.com

[finnsawyer]

Bats don't have feathers, but they fly very quietly.  Check out the propeller set-up on the new Virginia class of submarines.

[finnsawyer]

You pop up in the strangest places.  I believe some time ago I recommended that you examine the (known) solutions for fluid flow around a sphere and a cylinder.  Did you?  If you did you will find that these solutions predict that the fluid far from the surface is disturbed.  There should be no surprise there, and the disturbance is different for each shape.  The fact is that these disturbances are caused by the presence of the object.  So, how does the presence of the object affect the 'air mass'.  The answer is by imposing conditions on the air flow at the objects surface, namely by requiring that there can be no movement of air into or at right angles to the surface of the object.  Since you claim to be an Engineer, you must know that this is called a 'Boundary Value Problem'.  The upshot is that one can not hope to solve the problem of airflow around an object without taking into account the nature of the surface of an object and the interaction of the surface of that object with the airflow.  This is true of any physical object including sails.  You are still hung up on the idea of a windmill blade deflecting the air when it is clear that the blade gets power from the air by slowing down the velocity of the air.  A theory of deflection by itself is insufficient.

[elvin1949]

Peter

 I used to mess with racing boats [power].

The hull was faster if it was not glass smooth.

later

elvin

[IntegEner]

When I said sailors I didn't mean submarine sailors so much, though it is true they carry on their own traditions. Are the propellers on these submarines like bat wings? Regardless, bat wings are even thinner than bird wings, supporting what I have claimed. Airfoil deflection is the whole answer since anyone who knows their vectors knows that to deflect the wind velocity to be directed so as to be opposite to the airfoil velocity vector in the moving frame of reference is to net out (reduce) its velocity in the standing-still frame of reference. No turbulence or drag. No smoke and mirrors. Even a knucklehead like me has always assumed this to be hardly even needing to be mentioned in so many words.

BTW, "sisu" = "attitude".

Anthony "Knucks the Knuckleheaded KnotHead" Chessick

www.integener.com

[finnsawyer]

Actually, "sisu" = "intestinal fortitude" aka "guts".  I should know since I am of Finnish descent and was raised in a Finnish American community.  That's why the "fin" in "finsawyer".  As far as your vector rantings are concerned, a vector has both direction and magnitude.  You must include changes in both aspects in any type of meaningful physical analysis involving vectors.  And phenomenon that appear to be the same at first glance can be quite different.  For instance, an airplane propeller can be 83% efficient in converting mechanical energy to thrust, while a windmill blade assembly can not be more than 59% efficient in converting wind energy to mechanical energy.  This implies that the physical processes that govern the two are somewhat different.  Instead of being dogmatic, you should open up your mind to the possibility that you are missing something.

The comment that you were responding to had to do with noise.  Since an attack submarine has to be ultra silent, I felt the propeller arrangement of the new Virginia Class of Submarines might have a bearing on the subject.  Oh yeah, I had also responded to your comment.  You might check it out.

[ghurd]

Trivia. The very first Wright Brother's prop was over 70% efficient and 3 layers of laminated spruce.  Very soon after, they approached modern efficiencies. Impressive, IMHO.

Makes me wonder how history will interpret the various designs found here.

Like the Wright Brothers first designs, can windmill blades only get 15% better than we all ready have?

[TomW]

As long as I am in a crappy mood, I feel I should inject my personal opinion here.

This thread reminds me of usenet postings a decade plus back where these [supposedly] concerned folks posted comments to the Linux community threads about things like:

"I heard Linux will Ruin your hard drive, is this true? How can I avoid this?"

"I understand the GPL will infect your code so you can never build proprietary code after you use GPL code..."

It eventually became obvious that it was all a big FAT smokescreen by Gates and Co. to get as much negative press as possible online concerning Linux and GPL.

Well, In my Humble Opinion, this type of [so called] story is exactly the same excrement in a different dish. Much like mountainman insulting us about conservation.

Anyone with any real sense and the brains to type some text into google will soon discover that the noise is trivial. the dead birds stuff is bull and the loss of life from turbine accidents is on a par with that of being killed by a meteor.

Do not feed the trolls like stray cats once you feed them they return. You remember Mister Pants don't you?

These types only get away with this stuff because the average user is to nice to say anything. Not me.

Just my personal rant not likely to be possessed by others.

/end rant and goodbye for awhile.

Cheers.

TomW

[elvin1949]

Tomw

jcp has been gone a LONG time.

You are still here.

nuf said

later

elvin

[IntegEner]

In doing routine checking of how well wind turbines perform both from their published power production curves and actual in site data it is always found both for the small and large turbine categories and for every manufacturer that at their rated power they invariably produce no more than one half of the Betz limit, which itself is only a little over one half of the energy in the wind. For the small turbines, the "wind is free" and it doesn't matter much but in extending this to the large turbines, it does. As far as some other comments herein they have the continual flavor about them of a parent scolding a child, every one! Amazing and I am sure this is now clear. The idea of wind velocity deflection by the blades is central to wind energy and it sure seems that more needs to be said about this. Central to wind energy. More later and possibly in the Diaries.

(It may also be found that this aforementioned power deficit goes into the production of the noise being discussed here and solving the one problem solves the other.)

Anthony Chessick

www.integener.com

[finnsawyer]

Rather than "parent" to "child", I have tried time and again to involve you in a discussion of your theory on the merits by introducing various physical insights.  You have chosen not to respond, which does not speak well of either your attitude or training.  For the sake of those who might be tempted to send you money for a treatise on a "will-o-the wisp" theory, I will try one more thing.  To wit:  Take a child's wagon and mount a two foot square piece of plywood vertically on it.  Place the wagon against the garage.  Throw a rubber ball against the square.  The ball will bounce back some distance, say 15 feet.  Now place the wagon two feet in front of the garage.  Repeat the experiment.  The wagon moves and the ball doesn't bounce back as far.  This is simple Newtonian physics.  That is, it is the basis for the Newtonian Principle.  You may refine the experiment to any level of detail you like, so that the ball bounces back initially in the same direction (same vector direction).  But the vector velocity will always have a smaller magnitude when the wagon moves.  In fact, just changing the vector director for an object results in no energy being delivered by the object.  Since air is composed of molecules, when air imparts energy to a windmill blade the average speed of the impacting molecules must also decrease.  This shows up in a decrease in the average wind speed (the magnitude of the average wind velocity vector).  So much for a theory involving only deflection.

I do not know what the best efficiency attained by a windmill blade assembly is, but I do know that drag and tip vortices can affect that value.  Apparently you do not take those into account either.

 

[TomW]

fin;

Nice explanation of that Newtonian bit. Very clear at least to me. I am fairly clueless on these things so I just read the stuff thats posted. I do like the ability to experiment with it like your ball and wagon which gels it up in my mind.

I would like to understand this Bent Air thing but Anthony seems unable to describe it with any clarity I can decipher. Certainly interested in various theories of how things work but faith is one thing i do not have simply because someone keeps repeating the statements.

Please continue and I will sit on the side and try to glean understanding from any discussion you can prize loose.

Anthony, Please accept the challenge to describe what you are promoting and do it here for free which is the whole point of this site. Free exchange of information and ideas. Probably millions of dollars in free ideas have been provided for you to peruse at no charge so please try to understand that it is a 2 way street. I guess I do not understand why some feel others should pay for an idea or bit of knowledge. I guess it is your right to do so. It does make me wonder if your only reason for participating is for financial gain which would be sad.

Cheers.

TomW

[IntegEner]

"You are still hung up on the idea of a windmill blade deflecting the air when it is clear that the blade gets power from the air by slowing down the velocity of the air. A theory of deflection by itself is insufficient."

I suddenly realized from these words the root cause of the problem here. I would love to explain some of these otherwise neglected (my website, for example, which goes into these considerations) details but, as they say, the words get in the way. The short answer to what is being asked here is that acceleration also occurs rotationally as well as straight ahead. This means that an object can continue on at the same speed but still experience acceleration while moving in a circle. Rephrase your questions and maybe I can answer them better. More lengthy diatribes are on their way and will be posted later. Let's just say my Newtonian-like (again, others invented these words) explanations are because I was and continue to be highly unsatisfied with what I see out there.

AVC

www.integener.com

[finnsawyer]

Well, if words won't do try mathematical equations.  Some of us understand and can deal with vector calculus, let alone vector algebra.  As far as rotational acceleration is concerned, the classical example is an object in a circular orbit.  This too is Newtonian, and the object's velocity vector changes constantly, but no work is done as the magnitude of the velocity vector never changes.  Only it's direction does.  You need to be careful of the conclusions you draw from 'rotational acceleration'.  I had a go around with a fellow by the name of Harry some time ago on this.  Like you he did not wish to entertain the merits of the argument.  Harry, are you out there?  How's it going?

[finnsawyer]

I was wondering if anyone was following this thread.  I appreciate your support, but have to say I think it's gone about as far as it can.  Like you, I am willing to entertain any new idea if an honest attempt is made to present it, and if the person advocating it is willing to engage in a meaningful dialogue or can present some practical results that advance the topic.  We don't seem to have that here.  Anthony has indicated that he will continue to preach.  The problem is that it is easy for someone to buy into it without proof.  It's the old idea that if you claim something long enough people begin to believe it.  Perhaps it's time for someone else to try rebutting him.  Anyway, thanks for the comment!

[SmoggyTurnip]

"In a word, atmospheric air is a block of mass occupying a large volume and unless this is accepted at the very outset, my eyes glaze over and I begin to turn the page. What is missing from most of these studies is what happens to the airflow mass at some distance away from the airfoil."

Ummm - which word is it?

[TomW]

fin;

I hear you!

Lets buy his "info" then publish on a website where everyone can see it for free [beyond US jurisdiction].

I will toss in $5 as seed money. Then later we can sell it along with some open source stuff on EbaY on a CD.

Just an idea since I guess he is holding back for the $$ or maybe, just maybe, he already knows its wrong but cannot admit it.

??

Cheers.

TomW