From: "JACK L. URETSKY (C)1998; HEP DIVISION, ARGONNE NATIONAL LAB ARGONNE, IL 60439" <JLU@HEP.ANL.GOV>
Date: Fri, 27 Aug 1999 17:05:03 -0500
Hi Bill-
I think that you are misunderstanding John, and clearly misunderstanding
the underlying physics.
The point is then in the relevant fluid dynamics context it is
incorreect to make microscopic arguments of the nature of "this piece of
wing here is related somehow to that parcel of air over there". What one
does in fact is to solve the Laplace equation in a infinite reqion subject
to certain local boundary conditions and conditions "at infinity". Whatever
the conditions at any part of the region affects the solution everywhere
else. Until one grasps this essential mathematical truth, the subject of
aerodynamics is guaranteed to remain mysterious.
I suggest that you acquire a good book on aerodynamics and study some
of the solutions. Two dimensions is easy, three dimensions cannot be done
in closed form except for some simple shapes (that also can be done in
electrostatics). My view is that there is no easy road to undeerstanding -
that is the point of my message - which you might wish to reread.
You wrote, incorrectly:
******************************************************************************
Correct me if I'm wrong, but John Denker disagrees with me. Instead he
says that, over time, a 3D wing in high-altitude flight DOES NOT need to
impose a net downwards momentum-change upon the air-parcels it passes.
****************************
Regards,
Jack
"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