RE: Raskin's Coanda effect article

[Marlyn Jakub <mjakub@physics.otago.ac.nz>]

Bill Beaty wrote:
> From: William Beaty <billb@eskimo.com>
> To: list physics teaching <PHYS-L@atlantis.uwf.edu>
> Subject: Raskin COANDA EFFECT article
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>
>
> The Airfoil-Lifting-Force article from QUANTUM magazine is now online on
> Jeff Raskin's website:
>
>    http://freebie.cfcl.com/jef/
>
> Lots of good material regarding the incorrect "Bernoulli effect" 
> explanation of lifting force. It includes some A. Einstein history which I
> have never before enountered.  Apparently Einstein designed an airfoil
> during WWI, but his thinking was based upon the usual incorrect
> explanation of aerodynamic lift, and his design didn't work Einstein
> found:
>
>  "Although it is probably true that the principle of flight can be most
>  simply explained in this [Bernoullian] way it by no means is wise to
>  construct a wing in such a manner!" 
>
> Not only does the "longer path gives faster flow" misconception suck in
> students, educators, and textbook authors, it sucked in Albert too!
Bill, 
On 13DEC95, I wrote a criticism of this article for Phys-L readers. Again, I
would strongly urge readers of Raskin's logic to add lots of salt before
believing any of Raskin's claims.

In short, Raskin uses air jets which are smaller than the wing object. This
can be totally misleading. E.g. blow through in inverted small (5mm) funnel
and you can hold a ping-pong ball inside the funnel...but with a downward
blast of ping pong ball diameter, there's no lift for the ball to stay in
the larger funnel.

Raskin never mentions circulation because he cannot have much with flow only
over the top of the wing. With circulation, flows over the wing are much
larger than those under the wing, so the 2% figure only shows that he needed
circulation in his model to get the better velocity estimates. 

Raskin claims that the back of the airfoil is most important, but the
primary pressure lift profile is at the front third of the typical wing,
where Raskin's arguments would seem to lead to the opposite conclusions. The
semi-stall condition for wings is when the lift-off point moves forward from
the rear edge of the airfoil, but there is still some lift...and a lot more
drag.

I have no conformation on the claim about Einstein's wing design or on
Raskin's role in developing the Mac computer...perhaps Jobs or Wosniak can
help on the latter.