Androcles writes:

Tell it to a bumble bee (BB).

Bees are not aircraft.

Tell it to a bumble bee (BB).

On 17 Okt, 03:03, Bertie the Bunyip <S...@rt.1> wrote:
Le Chaud Lapin <jaibudu...@gmail.com> wrote
innews:1192547842.109495.1581
0@v23g2000prn.googlegroups.com:





On Oct 16, 6:31 am, Thomas <thomas.s...@gmail.com> wrote:
On 9 Oct, 21:08, Le Chaud Lapin <jaibudu...@gmail.com> 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/gallery/gallery_pages/Morris_4.jsp

http://www.efluids.com/efluids/gallery/gallery_pages/Morris_3.jsp

Le Chaud Lapin <jaibudu...@gmail.com> wrote innews:1192547842.109495.15810@v23g2000prn.googlegroups.com:





On Oct 16, 6:31 am, Thomas <thomas.s...@gmail.com> wrote:
On 9 Oct, 21:08, Le Chaud Lapin <jaibudu...@gmail.com> 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 -

Thomas <thomas.s...@gmail.com> wrote:
You may want to check out my web pages
http://www.physicsmyths.org.uk/bernoulli.htmand
http://www.physicsmyths.org.uk/drag.htm for a closer examination of
the physics behind the aerodynamicliftand drag.

You might want to actually _include_Bernoulli'stheorem somewhere in your
pages. You talk aboutBernoulli'sequation,Bernoulli'sprinciple, andBernoulli'slaw. And yet none of them are actually presented. Are you
saying they all the same or all different? Why not use the terminology used
by the professionals and stick with "Bernoulli'stheorem"? How about
including references to relevant texts on your pages? It's not like serious
texts and lab experiments haven't been done on the subject for a zillion
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 labeled
arrows. Then present the assumptions and math needed to show your work and
why you think the vertical magnitudes sum to zero. Just saying they do, or
they only yield a torque, isn't good enough. It is more useful to _show_ -
not pontificate and hand-wave.

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

On Oct 16, 3:31 pm, Thomas <thomas.s...@gmail.com> wrote:





On 16 Oct, 19:41, Jim Logajan <Jam...@Lugoj.com> wrote:

Thomas <thomas.s...@gmail.com> wrote:
You may want to check out my web pages
http://www.physicsmyths.org.uk/bernoulli.htmand
http://www.physicsmyths.org.uk/drag.htmfora closer examination of
the physics behind the aerodynamicliftand drag.

You might want to actually _include_Bernoulli'stheorem somewhere in your
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 terminology used
by the professionals and stick with "Bernoulli'stheorem"? How about
including references to relevant texts on your pages? It's not like serious
texts and lab experiments haven't been done on the subject for a zillion
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 labeled
arrows. Then present the assumptions and math needed to show your work and
why you think the vertical magnitudes sum to zero. Just saying they do, or
they only yield a torque, isn't good enough. It is more useful to _show_ -
not pontificate and hand-wave.

P.S. Chapter section 40-3 in volume 2 of Feynman's Lectures on Physics 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 -

- Visa citerad text -

On 16 Okt, 20:41, Jim Logajan <Jam...@Lugoj.com> wrote:
Thomas <thomas.s...@gmail.com> wrote:
You may want to check out my web pages
http://www.physicsmyths.org.uk/bernoulli.htmand
http://www.physicsmyths.org.uk/drag.htm for a closer examination of
the physics behind the aerodynamicliftand drag.

You might want to actually _include_Bernoulli'stheorem somewhere in
your pages. You talk aboutBernoulli'sequation,Bernoulli'sprinciple,
andBernoulli'slaw. And yet none of them are actually presented. Are
you saying they all the same or all different? Why not use the
terminology used by the professionals and stick with
"Bernoulli'stheorem"? How about including references to relevant
texts on your pages? It's not like serious texts and lab experiments
haven't been done on the subject for a zillion 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
labeled arrows. Then present the assumptions and math needed to show
your work and why you think the vertical magnitudes sum to zero. Just
saying they do, or they only yield a torque, isn't good enough. It is
more useful to _show_ - not pontificate and hand-wave.

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


Nobelprizewinner Feynman made a good statement about the fluid
Bernoulli equation was valid for, "ideal fluid".

Feynman called the perfect fluid for "dry water" and it did not
exsist i a real world, only the mathematical world.

On 17 Okt, 01:48, Le Chaud Lapin <jaibudu...@gmail.com> wrote:
On Oct 16, 3:31 pm, Thomas <thomas.s...@gmail.com> wrote:





On 16 Oct, 19:41, Jim Logajan <Jam...@Lugoj.com> wrote:

Thomas <thomas.s...@gmail.com> wrote:
You may want to check out my web pages
http://www.physicsmyths.org.uk/bernoulli.htmand
http://www.physicsmyths.org.uk/drag.htmfora closer examination
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 -

- Visa citerad text -

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.

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

On 26 Okt, 08:24, Bertie the Bunyip <S...@rt.1> wrote:
jon <newb...@algonet.se> wrote
innews:1193336318.130848.213230@i13g2000pr
f.googlegroups.com:





On 17 Okt, 01:48, Le Chaud Lapin <jaibudu...@gmail.com> wrote:
On Oct 16, 3:31 pm, Thomas <thomas.s...@gmail.com> wrote:

On 16 Oct, 19:41, Jim Logajan <Jam...@Lugoj.com> wrote:

Thomas <thomas.s...@gmail.com> wrote:
You may want to check out my web pages
http://www.physicsmyths.org.uk/bernoulli.htmand
http://www.physicsmyths.org.uk/drag.htmforacloser examination
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 -

- Visa citerad text -

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



- Dölj citerad text -

- Visa citerad text -- Dölj citerad text -

- Visa citerad text -


You must be very stupid Bertie, when don´t even know when Piper Colt
was introduced:

Piper PA-22 Tri-Pacer

The Pacer was originally designed as a tailwheel aircraft and thus had
somewhat limited forward visibility on the ground and more demanding
ground-handling characteristics. To help introduce more pilots to
easier, safer flying, in 1953 the PA-20 was redesigned and offered as
the PA-22 Tri-Pacer with a nosewheel in place of the tailwheel landing
gear. Additionally, the Tri-Pacer offered higher-powered engine
options in the form of 150 hp (112 kW) and 160 HP (120 kW) engines,
whereas the largest engine available to the original Pacer had an
output of 135 hp (100 kW).[1] At the time the tricycle undercarriage
became a popular preference and 1953 saw the PA-22 Tri-Pacer outsell
the Pacer by a ratio of six to one.

P.S., do tell th eboys and gurls what you do for a living.

jon <newb...@algonet.se> wrote innews:1193336318.130848.213230@i13g2000prf.googlegroups.com:





On 17 Okt, 01:48, Le Chaud Lapin <jaibudu...@gmail.com> wrote:
On Oct 16, 3:31 pm, Thomas <thomas.s...@gmail.com> wrote:

On 16 Oct, 19:41, Jim Logajan <Jam...@Lugoj.com> wrote:

Thomas <thomas.s...@gmail.com> wrote:
You may want to check out my web pages
http://www.physicsmyths.org.uk/bernoulli.htmand
http://www.physicsmyths.org.uk/drag.htmforacloser examination
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 -

- Visa citerad text -

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



- Dölj citerad text -

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On 26 Okt, 08:24, Bertie the Bunyip <S...@rt.1> wrote:
jon <newb...@algonet.se> wrote
innews:1193336318.130848.213230@i13g2000pr
f.googlegroups.com:





On 17 Okt, 01:48, Le Chaud Lapin <jaibudu...@gmail.com> wrote:
On Oct 16, 3:31 pm, Thomas <thomas.s...@gmail.com> wrote:

On 16 Oct, 19:41, Jim Logajan <Jam...@Lugoj.com> wrote:

Thomas <thomas.s...@gmail.com> wrote:
You may want to check out my web pages
http://www.physicsmyths.org.uk/bernoulli.htmand
http://www.physicsmyths.org.uk/drag.htmforacloser examination
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 -

- Visa citerad text -

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



- Dölj citerad text -

- Visa citerad text -- Dölj citerad text -

- Visa citerad text -

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.

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

On 26 Okt, 08:24, Bertie the Bunyip <S...@rt.1> wrote:
jon <newb...@algonet.se> wrote
innews:1193336318.130848.213230@i13g2000pr
f.googlegroups.com:

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.

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

jon <newb...@algonet.se> wrote innews:1193336318.130848.213230@i13g2000prf.googlegroups.com:





On 17 Okt, 01:48, Le Chaud Lapin <jaibudu...@gmail.com> wrote:
On Oct 16, 3:31 pm, Thomas <thomas.s...@gmail.com> wrote:

On 16 Oct, 19:41, Jim Logajan <Jam...@Lugoj.com> wrote:

Thomas <thomas.s...@gmail.com> wrote:
You may want to check out my web pages
http://www.physicsmyths.org.uk/bernoulli.htmand
http://www.physicsmyths.org.uk/drag.htmforacloser examination
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 -

- Visa citerad text -

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



- Dölj citerad text -

- Visa citerad text -- Dölj citerad text -

- Visa citerad text -