Singing Wings

[Neil Allison]

I noticed this today: http://www.newscientist.com/article.ns?id=dn7867

"In wind tunnel tests, Salmon stuck sections of plastic piezo-electric
film to wing segments. This film vibrates when an electrical signal is
applied, producing sound.

Tests using a barely audible sinusoidal tone of about 400 hertz showed
22% increase in lift, compared with a standard wing"

I've not found the entire paper but wonder: what thoughts or experience
does anyone have on this topic as it might relate to gliding?

Apart from the obvious about giving your aircraft a "tune up" ;)

Cheers,
Neil
--
Christchurch, NZ

[Derrick Steed]

look up stuff relating to Sinha and his film for boundary layer control
- he also tried an active surface with the intent of accoustic response
of the boundary surface.

Rgds,

Derrick Steed

[Frank Whiteley]

I think applying the electrical signal (requiring an active input)
would not be allowed for competition, badges, or records in gliders
unless there was a rethinking of the rules. There have been other
suggestions of electrical discharge and powered blow holes, but these
are 'thrusted' strategies requiring additional batteries and, as a
result, are 'powered' flight. Thermaling at 25-30kts would be
interesting though. Maybe catch up with those hawks, eh?

Regarding the article, what if the input wire to one wing fails?
Instant spin? Could be cheaper to put the funds into more training and
proficiency flying so the pilots of the 4-8 passenger planes wouldn't
stall or overload their aircraft to begin with. I'd hazard a guess
that overloading is an all too frequent contributing factor. They are
already saying the pilots are slow to react to the existing stall
warning indicators. Really think another gadget will save them from
themselves?

Frank

[Bill Daniels]

"Neil Allison" > wrote in message
...
> I noticed this today: http://www.newscientist.com/article.ns?id=dn7867
>
> "In wind tunnel tests, Salmon stuck sections of plastic piezo-electric
> film to wing segments. This film vibrates when an electrical signal is
> applied, producing sound.
>
> Tests using a barely audible sinusoidal tone of about 400 hertz showed
> 22% increase in lift, compared with a standard wing"
>
> I've not found the entire paper but wonder: what thoughts or experience
> does anyone have on this topic as it might relate to gliding?
>
> Apart from the obvious about giving your aircraft a "tune up" ;)
>
> Cheers,
> Neil
> --
> Christchurch, NZ
>
This falls into the category of "active boundary layer control". It's a
fascinating area of aerodynamics that started with Gus Raspet's suction
scheme 50 years ago. Dr. Sinha's "deturbulator" films and this vibrating
plastic film are attempts to make it more practical. All of these have
produced impressive results in controlled experiments but developing them to
the point of practicality so they can survive in the field has been the
problem.

If it ever gets to the point that one of these schemes can be applied to an
older glider for a 25% increase in performance, I'd expect to see a lot of
people doing it.

Bill Daniels