Airplane Pilot's As Physicists

Uncle Al wrote:
2) Bernoulli's law is strictly a 2-D analysis.

Are you sure? I ask because I know the application of Bernoulli's theorem
to airfoils is typically restricted to 2-D and wondering if that is what
you meant. Otherwise there doesn't appear to be any dimensional assumption
in the theory itself or its derivation. Here's one typical presentation of
Bernoulli's theorem:

"In the steady motion of an inviscid fluid the quantity

p/rho + K

is constant along a streamline, where p is the pressure, rho is the density
and K is the energy per unit mass of fluid."

And the definition of streamline also appears void of dimensional
restriction:

"A line drawn in the fluid so that its tangent at each point is in the
direction of the fluid velocity at that point is called a streamline."

Both quotes from "Theoretical Aerodynamics" by L. M. Milne-Thomson.

So unless I'm mistaken (and I could be) it appears that Bernoulli's
theorem:
1) Applies to compressible or incompressible fluids.
2) Does not necessarily apply to viscous fluid flows.
3) Does not necessarily apply to turbulent flow (it's not "steady motion".)
4) Does not itself define the flow streamlines.
5) Is not restricted to 1 or 2 dimensional analysis.

Jim Logajan wrote:

Uncle Al wrote:
2) Bernoulli's law is strictly a 2-D analysis.

Are you sure? I ask because I know the application of Bernoulli's theorem
to airfoils is typically restricted to 2-D and wondering if that is what
you meant. Otherwise there doesn't appear to be any dimensional assumption
in the theory itself or its derivation. Here's one typical presentation of
Bernoulli's theorem:

"In the steady motion of an inviscid fluid the quantity

p/rho + K

is constant along a streamline, where p is the pressure, rho is the density
and K is the energy per unit mass of fluid."

And the definition of streamline also appears void of dimensional
restriction:

"A line drawn in the fluid so that its tangent at each point is in the
direction of the fluid velocity at that point is called a streamline."

Both quotes from "Theoretical Aerodynamics" by L. M. Milne-Thomson.

So unless I'm mistaken (and I could be) it appears that Bernoulli's
theorem:
1) Applies to compressible or incompressible fluids.
2) Does not necessarily apply to viscous fluid flows.
3) Does not necessarily apply to turbulent flow (it's not "steady motion".)
4) Does not itself define the flow streamlines.
5) Is not restricted to 1 or 2 dimensional analysis.

3-D wings are more than Bernoulli's law. If they weren't they
wouldn't vastly benefit from shaped distal winglets to control vortex
shedding. Adding small drag surfaces at the wingtips normal to the
wings' surfaces does not have beneficial - much less hugely beneficial
- effects in 2-D analysis. In the real world airlines madly scrambled
to add winglets to improve fuel economy.

Look at the ratio of surface areas, wing and its winglet. The real
world benefits are wholly disproportional to area ratio. It is a
matter of leverage. A tiny tweaking of vortices rolling off distal
wing ends creates major energy control.

--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/lajos.htm#a2

On Oct 9, 4:08 pm, Le Chaud Lapin wrote:
Comments from anyone who knows physics welcome.

Hee, hee! You obviously don't know sci.physics!

Jim Deutch (JimboCat)
--
"The world is raining knowledge and most
folks use their soupbowls as rain bonnets."
-- Uncle Al

On Oct 10, 11:43 am, JimboCat wrote:
On Oct 9, 4:08 pm, Le Chaud Lapin wrote:

Comments from anyone who knows physics welcome.

Hee, hee! You obviously don't know sci.physics!

You're right.

I've been watching sci.physics for the past few days for first time.

Certainly, while there are some really brilliant people here, not
everyone agrees on controversial topics, which is not a bad thing.

The difference I see between sci.physics and rec.aviation.piloting is
that, if someone attempts to re-examine long-standing accepted
theories, there is genuine debate, at least a lot more than ad hominem
attacks.

Perhaps I should have posed the question here first, then taken a
summary back to rec.aviation.piloting.

-Le Chaud Lapin-

Le Chaud Lapin wrote in
oups.com:

On Oct 10, 11:43 am, JimboCat wrote:
On Oct 9, 4:08 pm, Le Chaud Lapin wrote:

Comments from anyone who knows physics welcome.

Hee, hee! You obviously don't know sci.physics!

You're right.

I've been watching sci.physics for the past few days for first time.

Certainly, while there are some really brilliant people here, not
everyone agrees on controversial topics, which is not a bad thing.

The difference I see between sci.physics and rec.aviation.piloting is
that, if someone attempts to re-examine long-standing accepted
theories, there is genuine debate, at least a lot more than ad hominem
attacks.


No, there is no debate. there is waht is, and then tere are k00ks.

I'll take a wild guess that you just might fall into the latter category.

Bertie

"Le Chaud Lapin" wrote in message
oups.com...

The difference I see between sci.physics and rec.aviation.piloting is
that, if someone attempts to re-examine long-standing accepted
theories, there is genuine debate, at least a lot more than ad hominem
attacks.

Guys like Kelly Johnson didn't design the P-38, U-2 and the SR-71 Blackbird
by not understanding aerospace physics. Basically, you came into r.a.p.
popping off like a sophomoric twit, and got called on it by everybody who
bothered to respond.

When I look out the window at 5,000 feet and see my wings continue to work
as described in the manual and the textbooks, just like they do in every
airplane I've flown, I'm dramatically more inclined to believe the physics
of the engineers who actually proved their worth by designed airplanes than
some usenet-know-it-all.

Perhaps I should have posed the question here first, then taken a summary
back to rec.aviation.piloting.

Perhaps before you come out here blathering about possible errors you see in
your flight computer, you should at least know what it's called. It's an
E6B, not an EB-6. (Been that way since before World War II.) Why invest
effort in a "genuine debate" with somebody who can't even correctly identify
his own tool? Even most student pilots learning in, as you called it,
"monkey mode", know that one.

"My question is: How many graduated students, in your opinion, have true
understanding of what is going on and how many have learned by
iliarity?" -you

-c
r.a.p.

On Oct 15, 5:32 pm, "Gatt" wrote:
"Le Chaud Lapin" wrote in
Guys like Kelly Johnson didn't design the P-38, U-2 and the SR-71 Blackbird
by not understanding aerospace physics. Basically, you came into r.a.p.
popping off like a sophomoric twit, and got called on it by everybody who
bothered to respond.

The fact remains that there is still considerable dispute about the
fundamentals of the dynamics of airfoils from multipile prominent
organizations involved in the theory of flight.

In the 2-3 weeks that I have been searching, I have found, with help
of others, countless examples of the fundamentals being disputed by
people who write textbooks, scientific papers, etc. There is also the
link at NASA that claims that many of the textbooks are wrong. I read
last night in another piloting book, again, that the common belief
about the dynamics of airfoils is wrong, but the explanation of what
was right contrasted with the other textbook's explanation.

When I look out the window at 5,000 feet and see my wings continue to work
as described in the manual and the textbooks, just like they do in every
airplane I've flown, I'm dramatically more inclined to believe the physics
of the engineers who actually proved their worth by designed airplanes than
some usenet-know-it-all.

Who said your textbooks are right? How do you determine that your
textbook is right and the others are wrong? It is not necessary for
you to have (true) understanding of airfoil dynamics to be able to fly
an aircraft. Many pilots might not understand the physics of
electrogmagnetic propagation, but they still use the radio.

My question was a statement of my opinion, something that I, like all
USENET posters, are entitled to. If you disagree with my opinion, it
is your right to not participate in the conversation.

The insults are really unnecessary. I read my original posts, and
there were little in them to warrant personal attacks other than that
I was broaching a subject that you and others felt should not be
discussed, at least by someone like me.

Perhaps before you come out here blathering about possible errors you see in
your flight computer, you should at least know what it's called. It's an
E6B, not an EB-6. (Been that way since before World War II.) Why invest
effort in a "genuine debate" with somebody who can't even correctly identify
his own tool? Even most student pilots learning in, as you called it,
"monkey mode", know that one.

E6B, EB-6...this has little to do with my original question. And what
it is called has no bearing on how it functions. And the topic I
introduced had nothing to do with an E6B, nor did I ever dispute teh
operation of it.

-Le Chaud Lapin-

"Le Chaud Lapin" wrote in message
ups.com...

I read last night in another piloting book, again, that the common belief
about the dynamics of airfoils is wrong,

Yeah? Which one?

I'm dramatically more inclined to believe the physics
of the engineers who actually proved their worth by designed airplanes
than
some usenet-know-it-all.

Who said your textbooks are right?

No kidding. I mean, HOW DO I KNOW THE AIRPLANE I'M FLYING ACTUALLY FLIES?!


How do you determine that your textbook is right and the others are wrong?

Why do you repeatedly snip the bits about Kelly Johnson, the SR-71, etc?

E6B, EB-6...this has little to do with my original question.

It shows your lack of understanding of the subject matter and your lack of
attention to detail. As I told you before, physics is an exact science.
If you're unable to properly name the hammer, you're not going to convince
anybody you're a useful carpenter.

-c

Gatt writes:

Guys like Kelly Johnson didn't design the P-38, U-2 and the SR-71 Blackbird
by not understanding aerospace physics.

Actually there was a lot of trial and error involved. They experimented and
found what worked.

Mxsmanic wrote in
:

Gatt writes:

Guys like Kelly Johnson didn't design the P-38, U-2 and the SR-71
Blackbird by not understanding aerospace physics.

Actually there was a lot of trial and error involved. They
experimented and found what worked.



Like you'd know, fjukkwit.

Bertie