In article ,
Bruce wrote:

Here is a stab at a simple explanation -

The crux of the matter is that aircraft fly by the transfer of energy. Fluid

Point of order: transfer of *momentum*. In order to fly, a
heavier-than-air aircraft must apply a certain force to the air,
transferring momentum to it. The amount of momentum transferred is
constant across the aircraft's performance envelope, whereas the energy
transfer varies.

dynamics and physics provide us with a variety of tools to model how this
happens.

A famous quote from IT applies - "All models are false, some models are
useful"

Depending on the situation one or another model may be more useful and/or
accurate, but they remain models. We are generally concerned with low
Reynolds
numbers and laminar flow over low lift+low drag wings. In this regime the
contribution of upper surface lift is apparently no less than 1/3 of the
total,
and at low angle of attack it may be greater than 50%.

The net result of Bernoulli, Prantl et al is that a moving wing transmits
kinetic energy to the air. As long as the air flows around the wing in a
relatively orderly fashion, the reaction is lift (varying amounts of suck and
blow), if the flow becomes chaotic (stalled) we get primarily drag.(Very
simple.)

Conversely - calculating how much will be created, and optimising efficiency
over a range of performance requires serious computational power and a head
for
calculus. (very complex)

Nyal Williams wrote:
Newton explains it better than Bernoulli. The FAA
written for PSEL no longer requires the Bernoulli answer
about lift.

Go to Amazon.com or Bookfinder.com and look for a book
by Gale Craig, titled, 'Stop Abusing Bernoulli! - How
Airplanes Really Fly '. (Search under Craig, Gale.)
Gale is a physicist who enquired into this subject.
Used copies are listed there, but the book is self-published
and you can order fresh copies from him. He lives
in Anderson, Indiana. Anyone who is interested in
that address should write me and I will get it for
you.

At 17:00 09 January 2006, Marty wrote:

Stick the cambered side of a standard spoon under a
running tap! Ease
the cambered side of the spoon gradually into the running
SNIP

--
Alan Baker
Vancouver, British Columbia
"If you raise the ceiling 4 feet, move the fireplace from that wall
to that wall, you'll still only get the full stereophonic effect
if you sit in the bottom of that cupboard."