Backwash Causes Lift?

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

Le Chaud Lapin writes:

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.

Perhaps you have seen EE from the inside and aerodynamics from the outside.
They may resemble each other far more than you realize. Remember how well
Tesla was received.

2. NASA says it's wrong. From Jim Logajan: http://www.grc.nasa.gov/WWW/K-12/airplane/bernnew.html

The question, though, is who exactly is "NASA"? The organization didn't write
the text (which, by the way, is an explanation for schoolkids); a human being
did. Is an individual human being as reliably correct as all of NASA? This
is another illustration of the dangers of credentialism.

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.

Most of the adjustments in wing shape are intended to reduce drag or raise the
critical angle of attack. Otherwise a flat board would suffice. The very
common misconception is that the curve of the wing somehow is responsible for
the lift. It's not, of course. Only the angle of attack is responsible for
the lift.

The weird thing is that the intuitive impression one has of a wing's function
is essentially correct. It looks like something that would point air down as
it passes, and that's exactly what it does. Only the details of how it does
it are hard to figure out and understand. Fortunately, it works extremely
well even if one doesn't understand the details.

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

The real problem arises when you have a theory that seems to explain all the
observations you make and yet may still be incorrect.

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.

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."

Le Chaud Lapin wrote:
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.html
scrolling 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-


My initial reaction after reading this was sadness, as I hate to see
anyone die while attempting to fly an airplane, but after realizing that
you are probably not a student pilot at all, but a sockpuppet (and not a
very good one at that :-)) these fears won't be realized.
On that note, I'll turn you back to Bertie who seems to need no help
from me in "handling you" on these forums.
All the best of luck anyway........(just in case......so I'll feel
better for having asked you to stay as far away from an airplane as you
possibly can :-)
DH

--
Dudley Henriques

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, 6:38 am, Matt Whiting wrote:
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 truth is that the electrons move, not the protons.

If you are referring to holes http://en.wikipedia.org/wiki/Electron_hole
and electrons in semiconductors http://en.wikipedia.org/wiki/Semiconductor
, where the descriptions of flow of charge through a semiconductor
lattice shows both positive and negative charge flow, in opposite
directions, in the present of an electrical field, the negative charge
being represented by electrons, the positive charge being represented
by holes.

Every book in electrical engineering is likely quite explicit in
telling students up front, (more like forming an agreement with the
students), that the holes are to be modeled as physical particles
because that it is mathematically equivalent to the true phenonmenon,
which is a void moving through the lattice, that, although there are
people who are quite capable of modeling the truth, which is based on
stochastics and energy-band http://en.wikipedia.org/wiki/Energy_band
theory, they will use the one that is simpler since the two models are
functionally equivalent. Note that any professor writing a book
claiming that holes are real particles would probably be barred from
teaching. In the world of electrical engineering, it would be like
saying that the Santa Claus really does exist, knowing that the
professors themselves created the figment of Santa Claus. I cannot
emphasize enough that there is no confusion whatsoever in the minds of
the students about what is actually going on inside the lattice.
There is no doubt in their minds that there are no such thing as
physical particles called holes moving through a lattice. There is no
doubt because professors conscientiously created this fiction, and
tells their students: "We all know that there are no hole
particles...but.." You will notice that the Wikpedia description of
holes uses the word 'conceptual' in the first sentence.

A related concept is something called phonons: http://en.wikipedia.org/wiki/Phonon
These are quantum mechanical pseudo-particles. Electrical engineers
and physicists know that they do not exist. They know because they
made them up, just like the made up the holes.

There is nothing wrong with doing this. In each case, there is no
untruth being spoken, because the scientists say up front: "We are
about to tell you something that is not really true. Just keep in
mind what the real truth is as we go along, please." This implies
that the EE students know the real truth, which they do, because those
same professors tell them that also. The aerodynamicists say: "We are
about to tell you something that is true.", and they say nothing more,
because they think that what they are about to say is not a
mathematically equivalent model of the truth, but truth itself.

Consider the case where one might do a systems problem to find the
voltage across a capacitorhttp://en.wikipedia.org/wiki/Capacitor, and
end up with something like...

V(t) = 12 * Integral(Delta(t)) + u(t)*e^-3t*e[jwt/(4*pi)]

j is the square root of negative one (-1)
w = angular frequency http://en.wikipedia.org/wiki/Angular_frequency
t = time u(t) is Heaviside step function http://en.wikipedia.org/wiki/Unit_step_function
Delta(t) is the Dirac-delta function http://en.wikipedia.org/wiki/Dirac_delta)

This voltage contains complex numbers sitting n an exponential. It
also contains a phenomenon that occurs so quick that is is
mathematically impossible to observe in time, yet its effect during
that brief moment is infinite. This is ridiculous. We know with
certainty that no such things exist in real-life. But that's ok,
because we made these things. Electrical engineers looking at this
will know immediately what the truth is, what the math represents.
What is odd is that one eventually reachs a point where no uneasiness
at all comes from moving between the real and the unreal. They are,
in an abstract sense, in separable.

Futhermore, concerning the point you made, if the above voltage V(t)
is positive, then by the formula for charge on a capacitor, Q=CV,
since C, the capacitance, is [ahemm....always positive...please, if
you are a EE reading this, please don't start up with me about general
impedance converters ], the the charge is possitive, but we just
noted in the semiconductor example above that one does not find
positive charge running around in circuits because the are constrained
to the nuclei of atoms http://en.wikipedia.org/wiki/Atomic_nucleus
with their neutron buddies. This does not bother electrical engineers
because they see the formula and immediately see the image of what is
going on, the truth of physics as it occurs. Note that, if the
formula claims that there is positive charge on one plate of the
capacitor, there really is no positive charge "on the plate" so to
speak, but a depletion of negative charge, which is mathematically
eqivalent model of truth, just as there is no such thing as square-
root of negative number in real life, but if you use Euler's Formula
http://en.wikipedia.org/wiki/Euler's_formula, a Taylor expansion of
the formula about t http://en.wikipedia.org/wiki/Taylor_expansion, you
will see that the V(t) comes out to the nice sine waves that you would
see on an oscilloscopehttp://en.wikipedia.org/wiki/Oscilloscope .

Contrast this with what the aerodynamicists are doing. They are not
issuinig disclaimers saying, "this is not really what is happening, we
all know that, but let us pretend to make the math simpler for now".
They claim what they are illustrating *is* the truth.

-Le Chaud Lapin-

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-

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