Lumpy Leading Edges

[Dan M]

There's been some research into the lumps on the leading edges of humpback whale fins.  They are said to improve the performance of sailboat keels, rudders, etc.

There's also been some small scale wind-tunnel testing to determine their effect in a compressible fluid (air) and the results seem to indicate more lift, a LOT LESS drag, and a considerably higher angle of attack prior to stalling.

A guy named Fish (how appropriate) supposedly has a patent on a lumpy leading edge wing design.

Here's a link to one of the articles:

http://www.ascribe.org/cgi-bin/spew4th.pl?ascribeid=20040511.071106&time=07%2026%20PDT&year=



2004&public=1

Has anyone tried anything like this on a wind generator blade?

-Dan M

[windstuffnow]

  That's interesting.   Sometime back when I was heavy into flying and building aircraft there was some reasearch being done on a similar note. The wing was etched with tiny V's through the entire length of the wing and I believe was called a vortex generator.  Apparently it helped the air follow the wing allowing a higher angle with no stall and added an enormous amount of lift.  Also, it didn't have as much turbulance leaving the wing at the trailing edge.

  I'm not sure the extra amount of work would be benifited from the few watts that might be gained from our efforts.

  It would be interesting to see some test results from one though.

Have Fun

Windstuff Ed

[DanB]

Bergey puts little lumps on the backs of their blades right over the thickest part of the airfoil I believe...

(I always use it as the excuse that a lumpy/sloppy finish on the back of the blade might even work better ;-)  )

[LEXX]

I like it, what do you feel would be the best way to utillize this.  A few years back i saw a news article about boeing that showed how they wanted to get rid of their rivet dimples and they came to about the same findings, they found that when they smoothed them out their wing was less efficient, they compared their findings to a golf ball however, not a whale.

LEXX

[monte350c]

Or instead of the lumps/bumps, one could add vortex generators. These are little tabs usually about an inch long positioned about 10% chord back from the L/E. They are usually mounted in pairs, with the pairs being slightly angled towards each other at their front edges.

If you're dealing with an aviation application, there has to be a lot of paperwork, and approved parts, but if a guy wanted to try this on a wind turbine, I think a lot could be done with some aluminum sheet, tinsnips, a vice, and some good adhesive.

One of the more popular GA manufacturers of these things has a good site. Check the photo gallery for ideas...

http://www.microaero.com/index.html

Looks like fun!

Ted.

[wooferhound]

In full size Gliders that people fly in. there is a turbulance tape that is applied to the leading edges of the wings that is anout 1/32 inch thick and in a long Z pattern

like ////////

They said that if the air is turbulant in the layer of air next to the surface of the wing it was more slippery.

[gibsonfvse]

Hmm... I suspect that the operating Reynolds number has a lot to do with whether or not such things would help or hurt efficiency.  Also, the airfoil shape matters quite a bit... this would only hurt the performance of laminar-flow airfoils.  However, I'm sure most of us aren't carving laminar-flow blades in our garages

As whales move through the water, the tubercles disrupt the line of pressure against the leading edge of the flippers. The row of tubercles sheers the flow of water and redirects it into the scalloped valley between each tubercle, causing swirling vortices that roll up and over the flipper to actually enhance lift properties.

If this is the explanation, then the comments about vortex generators should also apply.  Of course (like everything in aerodynamics), it's more than a matter of just sticking tabs on blades.  I found a good article on generators some time ago: here.

[Jerry]

My plastic blades have a slight orange peal surface texture. I think this is a micro version of the above discusion? They are also very thin but gain stringth from there cup and twist. 23 degrees at the root to almost flat at the tip.

                                JK TAS Jerry

[elvin1949]

i don't see why it wont work in air.

it work's on racing boat bottom's.

i used to build hydroplane's

b class [20 ci motor] 280 lb driver glass

smooth bottom 65 mph.

same boat, motor, and driver bottom roughed up to

trap a thin film of air, 72 mph.

that is a VERY large gain

later

elvin

ps that was 22 yr's ago