On 27 Okt, 17:10, Bertie the Bunyip wrote:
jon wrote groups.com:





On 26 Okt, 08:24, Bertie the Bunyip wrote:
jon wrote
innews:1193336318.130848.213230@i13g2000pr
f.googlegroups.com:

On 17 Okt, 01:48, Le Chaud Lapin wrote:
On Oct 16, 3:31 pm, Thomas wrote:

On 16 Oct, 19:41, Jim Logajan wrote:

Thomas wrote:
You may want to check out my web pages
http://www.physicsmyths.org.uk/bernoulli.htmand
http://www.physicsmyths.org.uk/drag....serexamination
of
the physics behind the aerodynamicliftand drag.

You might want to actually _include_Bernoulli'stheorem
somewhere in y
our
pages. You talk aboutBernoulli'sequation,Bernoulli'sprinciple,
and
Bernoulli'slaw. And yet none of them are actually presented.
Are you
saying they all the same or all different? Why not use the
terminolog
y used
by the professionals and stick with "Bernoulli'stheorem"? How
about including references to relevant texts on your pages?
It's not like s
erious
texts and lab experiments haven't been done on the subject for
a zill
ion
years. It helps to show you know what you're talking about by
showing you've first read the professional literature on the
subject and done
your
own relevant research.

You might also want to redraw your figures so they include
vertical l
abeled
arrows. Then present the assumptions and math needed to show
your wor
k and
why you think the vertical magnitudes sum to zero. Just saying
they d
o, or
they only yield a torque, isn't good enough. It is more useful
to _sh
ow_ -
not pontificate and hand-wave.

P.S. Chapter section 40-3 in volume 2 of Feynman's Lectures on
Physic
s is
as good a place as any to start.

Bernoulli'stheorem is not a fundamental physical law and thus not
required to understand the principle behind the aerodynamiclift.
And its misinterpretation and misapplication quite evidently
leads to incorrect physical conclusions, like the claim that a
moving gas would inherently have a lower static pressure than a
stationary one. The net flow velocity of a gas has per se
nothing to do with the static pressure.

I so agree. The amout of hand-waving that goes on when
(presumably technically-inclined) individuals invokeBernoulliis
perplexing. Oddly, my college physics book is almost as guilty -
after chapters and chapters of Newtonian mechanics that are quite
clear, they seem to imply just that.

As a thought experiment, consider a large tank containing gas
with a pipe attached to it which leads into a vacuum space.
Assume first this pipe is closed at the end; then the flow
velocity in the pipe is zero because the molecules heading
outwards will be reflected at the end and reverse their velocity
(assume for simplicity that the molecules do not collide with
each other but only with the walls of the pipe and the tank). If
one now opens the pipe, the only thing that changes is that the
molecules heading outwards will not be reflected anymore at the
end but simply carry on heading into the vacuum space (with the
corresponding loss of molecules being replaced from the large
tank). So we now have a net flow velocity within the pipe
without that either the density nor the speed of the molecules
has changed in any way. This means that the pressure exerted on
the inside wall of the pipe is unchanged despite the fact that
we now have a net flow velocity within it. SoBernoulli'stheorem
would quite evidently give a wrong result here.

Hmmm...technically, someone could argue that, in the vicinity of
the exit hole of the tank, there would be resulting decrease in
pressure, which would be true.

The misapplication, I think, results from too much hand-waving and
not being very specific about what pressure decreases over what. A
venturi apparutus, for example, very clearly demonstrates a drop
in pressure, and that drop is real, but the points chosen to
measure the pressure in the apparutus is very specific.

-Le Chaud Lapin-- Dölj citerad text -

- Visa citerad text -- Dölj citerad text -

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The venturi pipe is mostly misunderstood. To get through the
narrow section, the fluid must be pressed against the convergent
part with a higher pressure. The Coanda effect forces the fluid to
follow the walls in the divergent part.

All early speed sensors in 1920 used only the divergent part of the
venturi pipe.

Look att Bleriot and other planes. Look at Piper Colt 1953 model
with its backpart venturi. The front convergent part was not
needed.

Piper Colt 1953 model?

Unh unh. First flew in 1960 you fjukkwit.

Backpart Venturi?

Bwawhahwhahwhahwhahwhahwha!

Changing the airflow direction over and under the wing, creates the
local pressure gradients + or - .

Nope.

Bertie

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The backpart of a venturi is sitting also on the Piper Colt 1960-64
models, like it does on the 1953 TriPacer of the same family.

They didn't make the colt from 60-64, fjukkwit.

One does not need the convergent entrance part, to measure the
airspeed.

One doesn't need a venturi to measure airspeed either, fjukkktard.

OH, BTW, we met real life once. the other pilots in the room nearly
****ed their pants laughing about you in the bar afterwards.

Why don't you tell he bois and gurls here what you do for a living?

Bertie- Dölj citerad text -

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Since you are such a superexpert Bertie, Bombardier needs your help to
fix the landinggear problem!

Now 9 incidents happened with failed landinggear!

We can not block more runways with Q400 anymore and we need your help
Bertie, since you know everything in the

aviation world.


And you still believe the aircrafts are sucked up in the sky, like
Apollo went to the moon?