Hi Dick,
This may seem out of topic and rather controversial but:
Have you ever wondered why golf balls have dimples?
Just look at the leading edge of any Learjet and you'll find little machined diamonds attached nearby.
It is claimed to create counter-rotating vortices at either side of each leading-edge bump.
The vortices "inject momentum into the fluid flow, which keeps the flow attached to the upper surface rather than allowing it to separate".
Don't be surprised if you see some models with knobbly-knotty leading edges in the future…

Here's further source of information:
http://www.ascribe.org/cgi-bin/spew4...=2004&public=1

http://scitation.aip.org/getabs/serv...cvips&gifs=Yes