> > And someone tell us how to explain how circulation induces lift
> > to a budding pilot.
>
> Track the path of a single air particle as the airfoil approaches and
> p*****. It will move, roughly, in a circle (aka circulation). A
particle
> going over the wing will initially move forward and up due to positive
> pressure from the leading edge, then get pulled back and down along the
top
> surface. A particle going under will go the opposite direction.
However,
> the particles won't end up where they started...they'll both be lower
than
> they were initially (assuming positive angle of attack). Net result is
> downward momentum transfer to the air, which results in an upward force
on
> the wing (lift).
>
> Any shape which imparts downward momentum to the airstream will generate
> lift. Airfoil design is all about getting the maximum lift for the drag
and
> avoiding problematic flows (separation, shocks, etc.)
>
> > Oh, yeah, FWIW, a supercritical wing produces lift because it's at an
> > angle of attack, just like a symmetrical or plane surface airfoil is
to
> > develop lift.
>
> True, because a supercritical wing gives imparts momentum to the
airstream
> just like a flat plate or normal airfoil. The major point with a
> supercritical thing is that it will continue to do that efficiently
(with
> low drag) at a higher speed than a conventional airfoil.
>
> Tom.
Here is the best downwash/waketurbulence picture I have seen at this
site :
http://www.airliners.net/open.file/239080/L/
It,s taken by a pilot in a meeting plane at FL350
Jan-Olov Newborg
|
