At 07:36 PM 20/08/05 +1000, you wrote:
> There was an interesting article in the SMH recently which describes
>use of high frequency sound vibrations to prevent breakaway at high angle
>of attack - thus reducing stall speed. refer to:
>http://smh.com.au/articles/2005/08/18/1123958182084.html?oneclick=true Is
>this something we might see in gliders some day? Dave Shorter
What's he's doing is turbulating the air - lots of light aircraft already
do this, you can buy vortex generator kits for many types. A lot of light
twins have the vortex generators on the fin too for increased rudder
effectiveness and lower Vmc.
Anyway he's about two steps behind Dr Sinha. What he describes has been
known for a long time and even some so called "low turbulence" wind tunnels
showed better performance on some test airfoils than they showed in the
real world. The Wortmann FX 67K170 was one of these. This was used on a
large number of gliders in the 1970's - Nimbus, Mini Nimbus, Mosquito, Pik
20, LS3.
Dr Sinha found that vibrating strips reduced drag, then found the drag
reduction even when the strips weren't powered hence the current direction
of his research.
Mike
Borgelt Instruments - manufacturers of quality soaring instruments
phone Int'l + 61 746 355784
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Int'l + 61 429 355784
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