Re: refutation of the scoop theory

[John Denker <jsd@MONMOUTH.COM>]

At 12:15 PM 8/21/99 -0500, David_Anderson wrote:
> Our physical description was not intended to be a calculation tool.

I read and take note of that statement, but I cannot reconcile it with
other things the authors say.  For one thing, the authors have sent me
calculations using their theory, purporting to show its usefulness and
accuracy.  In addition, in the very next sentence, the authors go on to say:

> It was intended to impart the true physics of flight to pilots.

We seem to have radically different notions of what "true physics" means.
  *) To me, "true physics" requires getting *all* the relevant physics
right, to some consistent level of approximation.
  *) To me, "true physics" means when the model makes a clear and
calculable prediction, it is OK to do the calculation.

Otherwise it's not "true physics";  it should perhaps be classified as a
"just so story" such as the one about how the leopard got his spots.

> We, of course dispute your statement on the error in the "scoop model" by
> the same 600%.  What if we were off by a factor of two?

If it were off by a factor of two, then .....
it would be off by a factor of two!

Sure enough, there are cases where the scoop theory makes predictions that
are only off by a factor of two.  Specifically:
  *) In the case of formation flight with three airplanes, the theory gets
the induced drag wrong by a factor of three.
  *) In the case of formation flight with two airplanes, the theory gets
the induced drag wrong by a factor of two.
  *) In the case of a degenerate formation of only one airplane, the theory
makes no prediction about induced drag.  I say "no prediction" because the
theory contains an arbitrary adjustable parameter -- the size of the scoop
-- that must be adjusted _a posteriori_.  Then the theory can make an
accurate postdiction of the orthodox result.  (In contrast, note that the
standard theories in engineering textbooks contain no such arbitrary
adjustments.)
  *) In the more complicated case I sent to Prof. Eberhardt, where the
chord is changing as well as the span, the theory is off by something like
600%.  Anybody who believes I made a math error while doing the calculation
is free to go over the calculation and give us a more accurate measure of
the discrepancy.

==============

One wonders whether the authors stand by the statement in their paper that
%...air is pulled up at the leading edge. This upwash actually
%contributes to negative lift and more air must be diverted
%down to compensate for it.

When I look at pressure and velocity fields near the leading edge, such as in
  http://www.monmouth.com/~jsd/how/htm/airfoils.html#fig_stall_wrng
I see high pressure below the wing and low pressure above the wing.  I
don't see anything pulling down on the wing.  The upwashing air below the
wing is actually decelerating as it climbs into a region of
higher-than-atmospheric pressure -- exactly the opposite of what would
would expect if the air were being "pulled" up in that region.

So tell me, what is the "true physics" here?