A Level 1 AOA clarification

Hilton wrote:
Greg Esres wrote:
No, for subsonic flight, it's perpendicular to the *local* relative
wind, the relative wind that is modified by wingtip vortices. If lift
were perpendicular to the chordline, you would have induced drag in a
wind tunnel, and you don't.

Come on Greg, you're telling me that wings in wind tunnels have no induced
drag? That's ridiculous. How about if the wind tunnel was 1000 miles
long
by 10 miles high - would the wings in that wind tunnel have induced drag?
(I seem to remember this same argument a few months ago)

Just to follow-up my own post, here is a line from the NASA web site:
"During the winter, with the aid of their wind tunnel, they began to
understand the role of high induced drag on their aircraft's poor
performance."

http://www.grc.nasa.gov/WWW/Wright/airplane/drag1.html

Sorry Greg, "no induced drag in a wind tunnel" is simply not true.

Hilton

Sorry Greg, "no induced drag in a wind tunnel" is simply not true.

Once again, you don't understand.

If you put a 3-D wing in a wind tunnel, you will get induced drag.

The article you posted even documents the effect:

----------snip--------------
This drag occurs because the flow near the wing tips is distorted
spanwise as a result of the pressure difference from the top to the
bottom of the wing. Swirling vortices are formed at the wing tips, and
there is an energy associated with these vortices.
----------snip--------------


See that? Flow "near the wing tips is distorted"....vortices are
formed at the wing tips


2-D flow is achieved when the wing tips are flush against the sides of
the wind tunnel. No wing tips = no pressure leaking around the wing
tips = no wingtip vortices = no induced drag.