Drag Reduction by means of flow control over a surface

[Jman]

Found and interesting article on Sciencedaily.com . I've posted a small teaser paragraph below.

"The most promising actuators are the so called synthetic jet or oscillatory jet actuators which are embedded in the surface of the body (an airplane wing for example), and essentially perform injection and suction of the fluid from the surface in a periodic manner," said Agarwal. He has demonstrated that the transonic drag of an airplane wing can be reduced by 12 to 15 percent with the incorporation of three-ounce actuators, about 20 to 30 spaced optimally on the surface of the wing.

[GESchwarz]

A related article linked to the same page Wings That Waggle Could Cut Aircraft Emissions By 20% speaks about a subject that was covered in this forum about a week ago. I'm thinking that this may be why birds were built with feathers.

It almost makes you want to tar and feather your airplane.

Seriously, these ideas may have merit.

[lr27]

There was a great article by Peter Garrison relating to this in the September, 1990 Flying magazine. I enjoyed the article a lot, but I don't necessarily buy all of it. However, it is highly recommended. Not sure how you could find it, though.

[autoreply]

Loek Boermans does a lot of research in it (low-speed only). It's extremely efficient (think 50% less drag on the most optimised profile possible), but in reality it's almost impossible to achieve since the holes are so tiny they are immidiately blocked by dust in a real-life environment. I'm afraid (and heard from others too) that this idea has less or more the same problem, it's a perfect solution, but might not work in reality because it's too tiny and too vulnerable (think -50 centigrade and some ice).

Nice idea nevertheless, but realistic? I don't believe so..

[Topaz]

Surface blowing or suction in strategic locations has been known since the 1960's to give tremendous drag reduction. These schemes all fall down on the same basis that autoreply is talking about: whether slot or hole, keeping them clean and free of obstruction is virtually impossible in the real world. The weight penalty of all those holes (or slots) in the skin can also be substantial, since the skin loses some or all of its ability to resist twisting for the wing.