Backwash Causes Lift?

Mxsmanic wrote in
:

Bertie the Bunyip writes:

Wanna make a bet about how long it takes you to get your licence?

None of this will influence the time required to get a license.


No fair. you don't get to get into the pool. The horse never bets on
itself.


Bertie

On Oct 6, 8:26 pm, Bertie the Bunyip wrote:
Le Chaud Lapin wrote oups.com:



On Oct 5, 6:32 pm, wrote:
It's familiar because there are many out there who don't
understand or don't agree with the textbooks. Even among experts
there's disagreement. Every so often one of them makes an issue of
it. It's quite normal, especially if they don't use the Google Groups
Search function first to see what the previous arguments have been on
the subject on a particular newsgroup.

I'd like to first note something since I am newly exposed to this
field:

In electrical engineering, we have our own set of fundamental
principles. The "terminal" set of primitives governing electronics
(electrostatics and electrodynamics) is Maxwells Equations
http://en.wikipedia.org/wiki/Maxwell_equation. [Ironically, during
his lifetime, Maxwell was also someone who was a leading expert on
aerodynamics. The notions of gradients, the Laplacian, and scalar
potentials have strong parallels in both fields.] In EE, we have out
own myths, like power lines causing brain cancer, but when they arise,
the experts work hard to show indisputable evidence, verifiable,
rigorous evidence to the contrary, to nip the non-sense in the bud.
We do still have areas of disputes, like what causes shot noise in
circuits [http://en.wikipedia.org/wiki/Shot_noise], but on the bread-
and-butter basics, you won't find a college-leve textbook speaking
untruth. So naturally I am extremely surprised to see this happening
in aerodynamics. You are, after all, the rocket scientists.

It annoys some of us because the same arguments are put forth
repeatedly and we can't figure out why some don't get it. But it's no
different than my classroom, in which every new batch of students
brings the same misunderstandings and doubts and arguments. We were
young once, too, and didn't believe much of what our teachers were
trying to tell us.

Oh, I certainly don't believe what I wrote in the Jeppensen book. I
don't believe what the 3 CFI's told me recently. I don't believe what
my friends friend, the pilot, told me three years ago. And though I
would be highly honored if I could meet him, I don't believe what Rod
Machado, whom I think we would all agree is not exactly dumb nor a bad
teacher, nor ignorant in the field, wrote. I don't believe it for two
reasons:

1. It's obviously wrong if you read and interpret correctly what
Bernoulli wrote.
2. NASA says it's wrong. From Jim Logajan:
http://www.grc.nasa.gov/WWW/K-12/airplane/bernnew.html

Bernoulli said that moving air has a lower pressure than
static air. The air over the top of the wing is moving considerably
faster than that underneath, so it has lower pressure.

People are going to yell and boo me for saying this, but after taking
a nice long ride tonight on my motorcyle tonight, I thought the
venturi/Bernoulli thing through, and I am 95% certain that that is not
the reason the pressure is lower. In fact, I could probably provide an
experiment showing you a situation where air is moving considerably
faster on top than it is on the bottom, with much higher presure on
the top. What is ironic is that Bernoulli would still be right, but
the interpretation of Bernoulli would fall apart.

It's not
rarefaction; it's the increase in dynamic pressure (velocity) that
subtracts from static pressure, the same phenomenon that makes a
turbine engine work so well.

Not to nit-pick, but dynamic pressure is p(t), where t is time, and
velocity is d/dt R(t), where R is position vector, two totally
different things.

Newton said that for every action there's an equal and
opposite reaction. If you look at the diagrams of airflow
here,http://www.av8n.com/how/htm/airfoils.htmlscrolling down to
Figure 3.2, you'll see that there's upwash ahead of the wing as well
as downwash behind it. the upwash is generated by the approaching low
pressure area above the wing. As the wing passes, the upwash is
converted to downwash; if this isn't Newton at work, I don't know
what is. Newton would be just another dead guy.

Newton did say that. And I looked at that diagram very carefully.
[Thanks for link] The upwash is not casued by an approaching low
pressure. The upwash is caused by a gradient in pressure, going from
high pressure at the leading ede, to low pressure, right above and
slightly-back of the wing, due to rarefication of the wing in motion.
The area above the rarefication is normal atmosphere that has a
propensity to move toward the lower-pressure, rarefied air. The
combination of that normal atmosphere air, combine with the high
velocity of the molecules from the leading edge of the wing, results
in the flow paths (streams) that you see. I haven't looked yet, but I
imagine that there are aerodynamicists, all over the world, who, if
not for appreciation of the hypothesis I am proposing here, have at
least figured this out empircally, and are fretting day and night
trying to find the optimal shape of the leading edge of the wing.
They have two conflicting objectives:

1. Make the shape in such a way so as to minimize drag.
2. Make the shape in such a way so as to increase pressure to impart
high velocity to air molecules moving up/backwards.

I'll be the first to admit that i don't have the capacity to do so at
this moment, but imagine that that one shape of the leading edge is
not appropriate for all speeds of the aircraft. For a given set of
context variables like density, temperature, pressure, angle-of-
attack, airspeed, what-the-plane-was-doing-20-milliseconds-ago,
turbulences...wind, etc...there is an optimal shape for that leading
edge, depending on what you are trying to do. It would be quite wild
if someone were to design a wing that could morph, dynamically by
control of a computer, into an instaneously-optimal shape.

For the average PPL or CPL this should be sufficient. It's
true
enough, even if it doesn't give the detail that the physicist would
like. As I said, most pilots have other careers and interests and
they find that Newton and Bernoulli jibe with what they experience in
the air, so they're satisfied. Making textbooks thicker or filling
them with competing theories does nothing but confuse these people.

I believe it should be possible to explain a venturi tube, Bernoulli's
principle, and a decent part of why a wing has lift, in about 2-3
pages of written text, with pictures, using no formulas, not even
grade-school mathematics.

If a student wants to argue that the physics as presented are
all wrong he should do extensive research and publish a book on the
subject, not argue with pilots who have been trusting their soft pink
bodies to Bernoulli and Newton for decades.

I definitely agree a paper should be written, and there should be an
element of rigor, obviously lacking in my posts.

However, I honestly think pilot's have been trusting neither Bernoulli
nor Newton. They are dead. But they each left a legacy, which,
according to the NASA links, have been misinterpreted and abused by
countless theoritsts and educators in this field. So one could say
that the pilots have been trusting these theorists and educators, but
perhaps not even that is the case. I think what Ron hinted at is most-
likely the case, that there is a phenomenon that would allow even a
Neanderthal to achieve technical advancement:

The Neanderthal starts with a contraption that works, and through much
trial-and-error, finds better and better rendentions of that same
contraption. Eventually, he will have something that works so well,
that the question of "Why" would hardly need be asked. Naturally,
theorists will tag along and try to explain with rigorous scientific
principles what he has accomplished with only raw will of spirit, but
the theory does not necessarily have to be right or complete get the
thing in the air. Of course, the Wright Brothers were high-minded
individuals, but I think you get the point.

One might ask, "Well if that is the case, then what is the point of
nit-picking with theory?"

It is because a theory that correctly explains observed phenomenon
generally opens up an entirely new world of order and efficiency.

-Le Chaud Lapin-

Wanna make a bet about how long it takes you to get your licence?

Let's have a pool!

I got never!

90 hours to solo

george wrote in
ps.com:

On Oct 6, 8:26 pm, Bertie the Bunyip wrote:
Le Chaud Lapin wrote
oups.com:



On Oct 5, 6:32 pm, wrote:
It's familiar because there are many out there who don't
understand or don't agree with the textbooks. Even among experts
there's disagreement. Every so often one of them makes an issue of
it. It's quite normal, especially if they don't use the Google
Groups Search function first to see what the previous arguments
have been on the subject on a particular newsgroup.

I'd like to first note something since I am newly exposed to this
field:

In electrical engineering, we have our own set of fundamental
principles. The "terminal" set of primitives governing electronics
(electrostatics and electrodynamics) is Maxwells Equations
http://en.wikipedia.org/wiki/Maxwell_equation. [Ironically, during
his lifetime, Maxwell was also someone who was a leading expert on
aerodynamics. The notions of gradients, the Laplacian, and scalar
potentials have strong parallels in both fields.] In EE, we have
out own myths, like power lines causing brain cancer, but when they
arise, the experts work hard to show indisputable evidence,
verifiable, rigorous evidence to the contrary, to nip the non-sense
in the bud. We do still have areas of disputes, like what causes
shot noise in circuits [http://en.wikipedia.org/wiki/Shot_noise],
but on the bread- and-butter basics, you won't find a college-leve
textbook speaking untruth. So naturally I am extremely surprised to
see this happening in aerodynamics. You are, after all, the rocket
scientists.

It annoys some of us because the same arguments are put
forth
repeatedly and we can't figure out why some don't get it. But it's
no different than my classroom, in which every new batch of
students brings the same misunderstandings and doubts and
arguments. We were young once, too, and didn't believe much of
what our teachers were trying to tell us.

Oh, I certainly don't believe what I wrote in the Jeppensen book.
I don't believe what the 3 CFI's told me recently. I don't believe
what my friends friend, the pilot, told me three years ago. And
though I would be highly honored if I could meet him, I don't
believe what Rod Machado, whom I think we would all agree is not
exactly dumb nor a bad teacher, nor ignorant in the field, wrote.
I don't believe it for two reasons:

1. It's obviously wrong if you read and interpret correctly what
Bernoulli wrote.
2. NASA says it's wrong. From Jim Logajan:
http://www.grc.nasa.gov/WWW/K-12/airplane/bernnew.html

Bernoulli said that moving air has a lower pressure than
static air. The air over the top of the wing is moving
considerably faster than that underneath, so it has lower
pressure.

People are going to yell and boo me for saying this, but after
taking a nice long ride tonight on my motorcyle tonight, I thought
the venturi/Bernoulli thing through, and I am 95% certain that that
is not the reason the pressure is lower. In fact, I could probably
provide an experiment showing you a situation where air is moving
considerably faster on top than it is on the bottom, with much
higher presure on the top. What is ironic is that Bernoulli would
still be right, but the interpretation of Bernoulli would fall
apart.

It's not
rarefaction; it's the increase in dynamic pressure (velocity) that
subtracts from static pressure, the same phenomenon that makes a
turbine engine work so well.

Not to nit-pick, but dynamic pressure is p(t), where t is time, and
velocity is d/dt R(t), where R is position vector, two totally
different things.

Newton said that for every action there's an equal and
opposite reaction. If you look at the diagrams of airflow
here,http://www.av8n.com/how/htm/airfoils.htmlscrolling down to
Figure 3.2, you'll see that there's upwash ahead of the wing as
well as downwash behind it. the upwash is generated by the
approaching low pressure area above the wing. As the wing passes,
the upwash is converted to downwash; if this isn't Newton at work,
I don't know what is. Newton would be just another dead guy.

Newton did say that. And I looked at that diagram very carefully.
[Thanks for link] The upwash is not casued by an approaching low
pressure. The upwash is caused by a gradient in pressure, going
from high pressure at the leading ede, to low pressure, right above
and slightly-back of the wing, due to rarefication of the wing in
motion. The area above the rarefication is normal atmosphere that
has a propensity to move toward the lower-pressure, rarefied air.
The combination of that normal atmosphere air, combine with the
high velocity of the molecules from the leading edge of the wing,
results in the flow paths (streams) that you see. I haven't looked
yet, but I imagine that there are aerodynamicists, all over the
world, who, if not for appreciation of the hypothesis I am
proposing here, have at least figured this out empircally, and are
fretting day and night trying to find the optimal shape of the
leading edge of the wing. They have two conflicting objectives:

1. Make the shape in such a way so as to minimize drag.
2. Make the shape in such a way so as to increase pressure to
impart high velocity to air molecules moving up/backwards.

I'll be the first to admit that i don't have the capacity to do so
at this moment, but imagine that that one shape of the leading edge
is not appropriate for all speeds of the aircraft. For a given set
of context variables like density, temperature, pressure, angle-of-
attack, airspeed, what-the-plane-was-doing-20-milliseconds-ago,
turbulences...wind, etc...there is an optimal shape for that
leading edge, depending on what you are trying to do. It would be
quite wild if someone were to design a wing that could morph,
dynamically by control of a computer, into an instaneously-optimal
shape.

For the average PPL or CPL this should be sufficient. It's
true
enough, even if it doesn't give the detail that the physicist
would like. As I said, most pilots have other careers and
interests and they find that Newton and Bernoulli jibe with what
they experience in the air, so they're satisfied. Making textbooks
thicker or filling them with competing theories does nothing but
confuse these people.

I believe it should be possible to explain a venturi tube,
Bernoulli's principle, and a decent part of why a wing has lift, in
about 2-3 pages of written text, with pictures, using no formulas,
not even grade-school mathematics.

If a student wants to argue that the physics as presented
are
all wrong he should do extensive research and publish a book on
the subject, not argue with pilots who have been trusting their
soft pink bodies to Bernoulli and Newton for decades.

I definitely agree a paper should be written, and there should be
an element of rigor, obviously lacking in my posts.

However, I honestly think pilot's have been trusting neither
Bernoulli nor Newton. They are dead. But they each left a legacy,
which, according to the NASA links, have been misinterpreted and
abused by countless theoritsts and educators in this field. So one
could say that the pilots have been trusting these theorists and
educators, but perhaps not even that is the case. I think what Ron
hinted at is most- likely the case, that there is a phenomenon that
would allow even a Neanderthal to achieve technical advancement:

The Neanderthal starts with a contraption that works, and through
much trial-and-error, finds better and better rendentions of that
same contraption. Eventually, he will have something that works so
well, that the question of "Why" would hardly need be asked.
Naturally, theorists will tag along and try to explain with
rigorous scientific principles what he has accomplished with only
raw will of spirit, but the theory does not necessarily have to be
right or complete get the thing in the air. Of course, the Wright
Brothers were high-minded individuals, but I think you get the
point.

One might ask, "Well if that is the case, then what is the point of
nit-picking with theory?"

It is because a theory that correctly explains observed phenomenon
generally opens up an entirely new world of order and efficiency.

-Le Chaud Lapin-

Wanna make a bet about how long it takes you to get your licence?

Let's have a pool!

I got never!

90 hours to solo



A control-line model


Bertie

Le Chaud Lapin wrote:

In electrical engineering, we have our own set of fundamental
principles. The "terminal" set of primitives governing electronics
(electrostatics and electrodynamics) is Maxwells Equations
http://en.wikipedia.org/wiki/Maxwell_equation. [Ironically, during
his lifetime, Maxwell was also someone who was a leading expert on
aerodynamics. The notions of gradients, the Laplacian, and scalar
potentials have strong parallels in both fields.] In EE, we have out
own myths, like power lines causing brain cancer, but when they arise,
the experts work hard to show indisputable evidence, verifiable,
rigorous evidence to the contrary, to nip the non-sense in the bud.
We do still have areas of disputes, like what causes shot noise in
circuits [http://en.wikipedia.org/wiki/Shot_noise], but on the bread-
and-butter basics, you won't find a college-leve textbook speaking
untruth. So naturally I am extremely surprised to see this happening
in aerodynamics. You are, after all, the rocket scientists.

Really? Many books still can't agree on the definition of current.
Some say it is the movement of electrons and some say it is the movement
of positive charge and some say it us both. Which is the absolute
truth, Mr. Wizard?

Matt

Matt Whiting writes:

Really? Many books still can't agree on the definition of current.
Some say it is the movement of electrons and some say it is the movement
of positive charge and some say it us both. Which is the absolute
truth, Mr. Wizard?

The absolute truth is unknown, and the real proof of wizardry is the ability
to say "I don't know."

Mxsmanic wrote in
:

Matt Whiting writes:

Really? Many books still can't agree on the definition of current.
Some say it is the movement of electrons and some say it is the
movement of positive charge and some say it us both. Which is the
absolute truth, Mr. Wizard?

The absolute truth is unknown, and the real proof of wizardry is the
ability to say "I don't know."




And the proof of your idiocy is that you can actualy say that with a
presumably straight face.

Matt, come on, you're better than that. You have to know what you're
talking about re current flow is simply accepting one convention or
another. In either case (using a plus or a minus sign consistantly
when writing loop equations for example) the calculations and
observations match fairly well.

The hand waving about lift is equally funny: people are attaching
names to various theories, but the reality is the physics used in the
analysis of lift work well enough to predict performance. The 'wise
fools' will wave their hands and argue, those knowing what they are
doing will design airplanes.

"Tina" wrote in message
ps.com...
Matt, come on, you're better than that. You have to know what you're
talking about re current flow is simply accepting one convention or
another. In either case (using a plus or a minus sign consistantly
when writing loop equations for example) the calculations and
observations match fairly well.

The hand waving about lift is equally funny: people are attaching
names to various theories, but the reality is the physics used in the
analysis of lift work well enough to predict performance. The 'wise
fools' will wave their hands and argue, those knowing what they are
doing will design airplanes.

BADA BING!

(I'm a southerner so spelling or usage may or may not be correct)

On Oct 6, 8:53 am, Tina wrote:
The hand waving about lift is equally funny: people are attaching
names to various theories, but the reality is the physics used in the
analysis of lift work well enough to predict performance. The 'wise
fools' will wave their hands and argue, those knowing what they are
doing will design airplanes.

This I definitely agree with. Even if aerodynamicists (is that even a
word) were so inept at physics that could not even calculate F=ma,
after so many iterations, they would still be able to make highly
refined airfoils simply because nature provides feedback to help one
distinguish between good designs and bad designs.

However, I must point out something I noted yesterday, that if you
have theory as well as the practice, the correct theory, there might
be opportunity to experience and entiely new realm of order and
efficiency.

I re-read the chapter on fluid mechanics in my physics book last night
and it says exactly what that NASA article refutes. Naturally, I was
bit perturbed - this physics book is same one used by some very good
universities. It also read in it a near verbatim explanation of
downwash as an example of Newton's law at work, that I found in the
Jeppesen book, the same explanation with is rigorously refuted by
NASA. I remember reading this chapter over and over a long time ago,
and "not getting it", and now I realize that it's because it is most
likely wrong.

In any case, there is something to be said for re-examining the
theory. There might be a bit of opportunity here.

I *think* I understand the physics behind reduced pressure above a
moving, appropriately shaped airfoil. *If* my suspicions are correct,
then it should be possible to make an entirely new type of aircraft,
where the mechanims to keep the aircraft flying are entirely different
from what they are today. I won't say too much now. I know no one
will consider it anyway. I'll just start fiddling, albeit slowly,
with my copy of SolidWorks that is coming in the mail soon.

I plan eventually to make a small-scale model. Hopefully, someday, I
might find someone involved in aerodynamics/flight to help make a
prototype.

-Le Chaud Lapin-

Tina wrote:
Matt, come on, you're better than that. You have to know what you're
talking about re current flow is simply accepting one convention or
another. In either case (using a plus or a minus sign consistantly
when writing loop equations for example) the calculations and
observations match fairly well.

I was simply making a point that there are different ways of looking at
the same thing. Much the same with lift and Bernoulli and Newton. Does
the difference in pressure between the top and bottom of the airfoil
cause the downward airflow behind the airfoil, or does the mechanical
deflection of the airflow cause the different in pressure between the
top and bottom of the wing? Inquiring minds want to know? :-)

Matt