From: "JACK L. URETSKY (C)1998; HEP DIVISION, ARGONNE NATIONAL LAB ARGONNE, IL 60439" <JLU@HEP.ANL.GOV>
Date: Fri, 15 Jan 1999 13:40:56 -0600
Hi all-
William Beatty writes:
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Here is a central problem: in 2D, the air far upstream from the wing is
flowing horizontally, right? And the air far downstream is also flowing
horizontally, correct? These flows come about through the superposition
of circulation and constant horizontal flight. It seems to me that this
guarantees a ZERO change in momentum of the air. It looks as if the 2D
flow diagram is symmetrical about a vertical line, and upwash exactly
equals downwash.
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Wrong. Newton's laws work very well in both wind tunnels and 2-D
aerodynamics.
The air downstream of a 2-D ideal lifting airfoil has a net
downward component. A classic work is Glauert, "Airfoil and Airscrew
Theory", but I'm sure that there are many other texts available. I
haven't yet checked Brittannica, but that's usually a good place to
start.
"I scored the next great triumph for science myself,
to wit, how the milk gets into the cow. Both of us
had marveled over that mystery a long time. We had
followed the cows around for years - that is, in the
daytime - but had never caught them drinking fluid of
that color."
Mark Twain, Extract from Eve's
Autobiography