Airplane Pilot's As Physicists

jon wrote in
ups.com:

On 17 Okt, 03:03, Bertie the Bunyip wrote:
Le Chaud Lapin wrote
innews:1192547842.109495.1581
:





On Oct 16, 6:31 am, Thomas wrote:
On 9 Oct, 21:08, Le Chaud Lapin wrote:
You may want to check out my web
pageshttp://www.physicsmyths.org.uk/bernoulli.htm
andhttp://www.physicsmyths.org.uk/drag.htmfor a closer examination
of the physics behind the aerodynamicliftand drag.

The main point I am making there is that it is physically nonsense
to claim that changing merely the tangential velocity of the air
stream relative to the surface would in any way produce a
resultant force (at least for a non-viscous gas).

What one needs for a pressure change
(and thus a force) on the surface is a change in the numbers
and/or the velocity of the molecules hitting it, i.e. it is only
the vertical component of the velocity that is relevant here. Only
this can produce theliftfor an airfoil, either because of the
increased number of collisions on the lower side or the decreased
number of collisions on the upper side (both situations lead to
alift).

I agree, but there are some that seem to think the contrary, as you
know, with the Coanda effect.
http://en.wikipedia.org/wiki/Coand%C4%83_effect

What is troubling about many of these theories is that, at the
precise moment where the reader is most alert in anticipation of
the meat of the explanation, the hand-waving begins. In the link
above, the clause entitled Causes, it is written:

"The effect of a spoon apparently attracting a flow of water is
caused by this effect as well, since the flow of water entrains
gases to flow down along the stream, and these gases are then
pulled, along with the flow of water, in towards the spoon, as a
result of the pressure differential. "

Hmmm...."and these gases are then pulled"...

pulled? By what?

And it should be
obvious that for this to be the case, one must either have the
lower side of the wing facing to a certain degree into the
airstream, and/or the upper side facing to a certain degree
opposite to the airstream. This is why one either needs a certain
'angle of attack' or a correspondingly shaped airfoil. And it
should be obvious that in order to have an asymmetric force (i.e.
a higher upward than downward force) one needs the surfaces of the
airfoil to be orientated in some way asymmetrical relatively to
the airstream. So a perfectly symmetrical airfoil (front to back)
at a zero angle of attack (like I indicated in Fig.1 on my
pagehttp://www.physicsmyths.org.uk/bernoulli.htm) should not
produce anyliftas the upward force (from the rear part) is exactly
equal to the downward force (from the front part). All that would
happen is that the wing experiences an anti-clockwise torque. This
is the reason why the rear part of the wing (behind the apex) must
always have a larger surface than the front part. At least I have
yet to see an airfoil where this is not the case and where it can
be used at a zero angle of attack. (theBernoulliprinciple is in
direct contradiction to this as it would also predict aliftfor a
perfectly symmetric airfoil in this sense).

I just read both your web pages.

BTW, your explanation of d'Alembert's Paradox and the
blow-over-paper- attached-to-table experiment could both use
diagrams. I am trying the blow over the paper experiment now and I
am not sure if I am doing it as you described. Could you provide a
more vivid description so I can make sure?

MAybe if you took your head out of your ass first..

Bertie- Dölj citerad text -

- Visa citerad text -

But Bertie, you were considered to be an idiot, already 3 years ago.

You seems not to have improved!

Here you see the vertical airflow due to wings AOA and downwash from a
heavy jet:

http://www.efluids.com/efluids/galle...s/Morris_4.jsp




Oh goodie, it's the huigh priest of fjukktardedeness, Jon.


He that would argue that up is down and vice versa just because he
thinks the numbers say so.

The Jehova's witness of lift.

Oh Anthony! A special friend for you.


Bertie