On Wed, 1 Mar 2006 at 22:43:58 in message
.com,
" wrote:

It discussed the Bernuolli theory of flight- and (if I recall) quite
conclusively proved that one of the _fundamental_ assumptions of the
Bernuolli theory- that air that travels path over the top of the wing
is flowing appreciably faster than air that flows over the bottom- is
simply incorrect in a compressible fluid....

There is not really a Bernoulli theory of lift. Bernoulli's theory
shows the relationship between the velocity and pressure of fluid flow
when energy is not added or removed and the flow is subsonic. It is a
very simple theory which is correct for much of the time. It quite
accurately, at lower speeds, represents the velocity and pressures
between streamlines.

The air does flow faster over the top than the bottom and for the lower
subsonic region air behaves very closely to being incompressible.
Generally pressure changes are transmitted at the velocity of sound.

At high subsonic and of course at supersonic speed the effect of
compressibility cannot be ignored.

Shock waves form, first on places like the top surface of the wing where
the air first reaches the velocity of sound. As the speed rises they
become bigger and move towards the leading and trailing edges. Above
Mach one the air does not detect the approaching aircraft! :-)

I have just read a few more messages in this thread and discussing lift
in this general way without maths and without using at least simple
physics and slowly developing the methods is almost futile.

What's it matter about lift as long as the aircraft fly? !!!!!
--
David CL Francis