Why Airplanes Fly - Voids Above A Planar Sheet

On Oct 5, 1:11 am, Jim Logajan wrote:
Le Chaud Lapin wrote:
I think for the purposes of piloting that one does not need to know the
Navier-Stokes equations.

That's true.

Because quite honestly the real explanation of
lift is to be found in the differential equations (or integral form)
governing mass continuity, momentum, and energy.

Yes, I agree.

All those simple
explanations are just that - simple and obviously incomplete. Rest assured
you're correct in your observations on the inadequate explanations - but
don't make the mistake of assuming a simple _and_ accurate one must exist,
if only you think hard enough on it.

I never thought that my explanation was complete or accurate. I
offered it because, IMO, it has a sificant influence on airfoil
dynamics. But after reading several books that ignore the partial
vacuum, and one book that was wrongly employing Newton's thereom...
[which is intolerable on any grounds, let alone aerodynamics], I had
to read more.

In his book, "The Proficient Pilot", on page 8, Barry Schiff writes:

"There is, for example, this amusing fable: 'Air flowing above the
wing has a greater distance to travel (because of camber) than air
flowing beneath the wing. Therefore, air above the wing must travel
faster so as to arrive at the wing's trailing edge at the same time as
air flowing underneath. This is pure nonsense."

In his book Learning to Fly With Rod Machado, on page 70, Rod Machado
writes:

"Because air flowing over the wing bends, it is forced to travel a
greater distance than the air flowing underneath. Because it travels a
greater distance, the bent air must move faster on its journey over
the wing. It's this relative increase in wind speed above the wing
that lowers pressure and productes lift."

Since I was new to piloting, I asked a few pilots if they understood
aerodynamics about an airfoil, and they all said yes. The reason they
gave is the one that Rod Machado gave. I asked the older pilots if
they knew who Barry Schiff was, and they said yes. I asked them if
they realized that Barry Schiff did not think that was the reason, and
they said I was mistaken, that Barry Schiff would never be as confused
as I seemed to be about flying. I asked them if they knew who Rod
Machado was. They said yes. I asked them if they thought that Rod
Machado and Barry Schiff would agree. They said yes. I asked them if
they were 100% certain, and they said yes.

Thus began my earnest interest in aerodynamics. I had always been
interested in flying, but this accelerated the interest quite a bit.

I took a sheet of paper and blew over it, the trick that we've all
done, and it went up of course, but I suspected that the reason it
went up was not the reason that was being given by so many people.

I visited a few aero/astro departments online, and while no one is
going to argue with the mathematics of field theory...I did get the
feeling that there were experts in the field saying the opposite
things. So before digging into the math [afterall, there is nothing
wrong with math], I decided to refresh my understanding of Bernoulli's
theorem from my old physics book, and while reading that book, it
occured to me that Barry Schiff's view is more likely right than
not...that is, until I read his explanation of relationship between
Newton and downwash on the next 2 pages of his book. I found a couple
of other books that gave the explanation of downwash that was
similar. Most importantly, I also notice that there was a ***HUGE***
amount of hand-waving going on, far more than one would expect in a
field that has been researched for over a century. I still need to
find a book that I can trust.

I went to the WWW and started reading more aero-astro excerpts, and
concluded that not only is theory still in flux, the experts do not
even agree on the basics. The very basics. Huge amounts of money had
been spent on wind-tunnels. But after all that, I could not get two
experts to agree on the basics. And this was a not simply a matter of
different styles, using integral instead of differential form of
equations, for example, or, deciding where to put a constant, as we
electrical engineers do in our expressions of the Fourier
integrals...there was *fundamental* disgreement about what causes lift
on an airplane.

I asked one of the pilot's again..."How sure are you that the aviation
world understands the basics?" He said he was very sure. He started
rattling off things about NASA.

I begin to imagine airflow over a wing and concluded that pinching at
front of wing must be very important, more important than one would
think, reading the explanations. I also concluded that a glider
should have wings that are very long but with a short cord, which aslo
turned out to be true. I then revisited my physics book...and it
_appeared_ that the application of Bernoulli to flying is wrong in
many contexts, but I decided to not discuss that just yet because it
would be too controversial.

I ask one of the pilots if he thought rarefication had anything to do
with it. He said, "No, it's all Bernoulli." I asked him what would
happen if I did the paper experiment, the one mentioned in my OP, and
he did not know, but said it does not matter because a piece of paper
is not a wing and it does not fly through the air. I asked him if he
understood why the paper would move, and he said, again, it does not
matter. I asked him if he saw any relation between my paper experiment
and the movement of a airfoil, and he said, finally, no, there is
none, because it is all Bernoulli.

I asked a CFI one last time, and he too said it was all Bernoulli,
precisely the argument that Barry Schiff refutes in his book.

So I started imagining, with no mathematics, what goes on with fluids
around surfaces, which lead me to these various experiments.

If you are interested in some books on the subject I'd be happy to make
some suggestions.

Sure.

-Le Chaud Lapin-

Le Chaud Lapin wrote in
oups.com:

On Oct 5, 1:11 am, Jim Logajan wrote:
Le Chaud Lapin wrote:
I think for the purposes of piloting that one does not need to know
the Navier-Stokes equations.

That's true.

Because quite honestly the real explanation of
lift is to be found in the differential equations (or integral form)
governing mass continuity, momentum, and energy.

Yes, I agree.

All those simple
explanations are just that - simple and obviously incomplete. Rest
assured you're correct in your observations on the inadequate
explanations - but don't make the mistake of assuming a simple _and_
accurate one must exist, if only you think hard enough on it.

I never thought that my explanation was complete or accurate. I
offered it because, IMO, it has a sificant influence on airfoil
dynamics.



Ooow! Write Nasa quick! Your research is obviously going to enable the next
critical leap in aeronautical sciences!


Bwawahwhhahwhahwhahwhahwhahwhahwhahawh!


Bertie

Le Chaud Lapin wrote:

I never thought that my explanation was complete or accurate. I
offered it because, IMO, it has a sificant influence on airfoil
dynamics. But after reading several books that ignore the partial
vacuum, and one book that was wrongly employing Newton's thereom...
[which is intolerable on any grounds, let alone aerodynamics], I had
to read more.

Newton had only one theorem? Wow, I always thought he had several...

Matt

"Matt Whiting" wrote in message
...
Le Chaud Lapin wrote:

I never thought that my explanation was complete or accurate. I
offered it because, IMO, it has a sificant influence on airfoil
dynamics. But after reading several books that ignore the partial
vacuum, and one book that was wrongly employing Newton's thereom...
[which is intolerable on any grounds, let alone aerodynamics], I had
to read more.

Newton had only one theorem? Wow, I always thought he had several...

Matt

Not many are familiar with Newton's 4th Law --- "One Fig to a Cookie"

TP

Le Chaud Lapin wrote:
Most importantly, I also notice that there was a ***HUGE***
amount of hand-waving going on, far more than one would expect in a
field that has been researched for over a century. I still need to
find a book that I can trust.

How much math are you willing to deal with?
If you can handle some calculus, then probably the least expensive book I
know of that may fit the bill is:

"Theoretical Aerodynamics" by L. M. Milne-Thomson.
Paperback edition is available from Dover Press.

I went to the WWW and started reading more aero-astro excerpts, and
concluded that not only is theory still in flux, the experts do not
even agree on the basics. The very basics. Huge amounts of money had
been spent on wind-tunnels. But after all that, I could not get two
experts to agree on the basics. And this was a not simply a matter of
different styles, using integral instead of differential form of
equations, for example, or, deciding where to put a constant, as we
electrical engineers do in our expressions of the Fourier
integrals...there was *fundamental* disgreement about what causes lift
on an airplane.

I have no idea what web sites you have visited - all I can say is that
there is _no_ dispute among experts on the very basics. Aerodynamic
models are now run routinely on computers - the field is known as
Computational Fluid Dynamics (CFD) - which would hardly be possible if
the very basics were still in dispute!

I asked one of the pilot's again..."How sure are you that the aviation
world understands the basics?" He said he was very sure. He started
rattling off things about NASA.

NASA is an excellent and authoritative source and you'll be very pleased
to discover they have web pages that address the VERY SAME COMPLAINTS you
have about many of the bogus explanations of lift that are floating
around. Here are two of the most relevant pages you should read:

http://www.grc.nasa.gov/WWW/K-12/airplane/bernnew.html

Excerpt from the above:
"Arguments arise because people mis-apply Bernoulli and Newton's
equations and because they over-simplify the description of the problem
of aerodynamic lift. The most popular incorrect theory of lift arises
from a mis-application of Bernoulli's equation."

http://www.grc.nasa.gov/WWW/K-12/airplane/wrong1.html

Excerpt from the above:
"There are many theories of how lift is generated. Unfortunately, many of
the theories found in encyclopedias, on web sites, and even in some
textbooks are incorrect, causing unnecessary confusion for students.

The theory described on this slide is one of the most widely circulated,
incorrect explanations. The theory can be labeled the "Longer Path"
theory, or the "Equal Transit Time" theory."


So I started imagining, with no mathematics, what goes on with fluids
around surfaces, which lead me to these various experiments.

It is a great idea to experiment - even with things others already
understand. I do it too.

If you are interested in some books on the subject I'd be happy to
make some suggestions.

Sure.

In addition to the above, there are a couple of other (expensive, alas)
books I would suggest:

"Introduction to Flight" by John D. Anderson, Jr.
Contains a history of the science of flight and also goes into details on
some of the more common mistakes people make in explanations of lift. I
do not own this book, but others also give it great reviews.

"Fundamentals of Aerodynamics" by John D. Anderson, Jr.
A well regarded, though mathematical, text on the subject. I do not own
this book either, but I expect it is good, based on my knowledge of the
next book I mention:

"Computational Fluid Dynamics" By John D. Anderson.
I bought and read through this book a couple years ago and it does a
great job of introducing CFD. I mention it here only because it is how I
know the style and quality of Anderson's writing to confidently recommend
two of his other books (above) that I have not read! He carefully disects
and explains each of the differential equations of the various types used
for computational modeling, among the many things covered.

On Oct 5, 8:31 pm, Jim Logajan wrote:
How much math are you willing to deal with?

I am comfortable with graduate-level mathematics.

If you can handle some calculus, then probably the least expensive book I
know of that may fit the bill is:

"Theoretical Aerodynamics" by L. M. Milne-Thomson.
Paperback edition is available from Dover Press.

Dover. I will assume it is cheap and take a look.

I have no idea what web sites you have visited - all I can say is that
there is _no_ dispute among experts on the very basics.

Well, someone should have told me that Rob Machado and Barry Schiff
are not experts. I did read once that Rod Machado has a Ph.D. in
aviation science, and the foreword to Barry Schiff's book is by Ernest
K. Gann, whom I presumed from his credentials is highly respected in
field. Yet Rob Machado and Barry Schiff said the exact opposite,
Barry clearly stating that what Rob stated was non-sense. Note that
there were not talking about something esoteric how precipitation
beings as condensation on nuclei...they have different opinions on the
most basic phenemenon that _any_ student fascinated with flying would
be inclinded to ask: "Why does the plane stay in the air?" Then we
have Jeppesen, a leaders in edcuation of GA. You would think that,
with such a fine product (no sarcasm meant), that they would have
people whom they trust, experts, at the very high-end of academia, who
could verify what's in the text. But what is in my Jeppensen book and
what Barry Schiff wrote is wrong.

Now I could have gone to some university in the U.S., Germany, France,
and found someone with stratospheric credentials in aero-astro, but
after seeing one expert say that the other is wrong, and then seeing
an incorrect application of Newton's law (yes I still believe it's
incorrect), I had to put on the brakes.

Aerodynamic
models are now run routinely on computers - the field is known as
Computational Fluid Dynamics (CFD) - which would hardly be possible if
the very basics were still in dispute!

Hmm...how shall I say this. It is very similar to what Ron said in my
defense.

In any field of research, there is mind and hand. For artists in the
field, there are those who have a proclivity to use hand more than
mind, and there are those who have a proclivity to use mind more than
hand. In any case, there are typically multiple paths to discovery,
one major path relying heavily on the imagination, the other path
relying on experimentation. Typically there is a combination. Based
on the small amount of the field of aerodynamcis I have seen so far,
and the disputes and inconsistencies, I would not be surprised if
there is an enormous amount of money being spent on experimentation.
Granted, experimentation is very necessary to validate (or invalidate)
what was conceived, but in many fields, there are researchers who
adopt the brute force approach, not completely, but much more than
someone who, lacking $100's of millions in funding would.

I asked one of the pilot's again..."How sure are you that the aviation
world understands the basics?" He said he was very sure. He started
rattling off things about NASA.

NASA is an excellent and authoritative source and you'll be very pleased
to discover they have web pages that address the VERY SAME COMPLAINTS you
have about many of the bogus explanations of lift that are floating
around. Here are two of the most relevant pages you should read:

I will read that...but there seems to be a contradiction of what you
are saying. OTOH, you're saying that there is no disputes amond
experts. On the other hand, you're saying that other people
(institutions) are complaining about the same thing.

http://www.grc.nasa.gov/WWW/K-12/airplane/bernnew.html

Excerpt from the above:
"Arguments arise because people mis-apply Bernoulli and Newton's
equations and because they over-simplify the description of the problem
of aerodynamic lift. The most popular incorrect theory of lift arises
from a mis-application of Bernoulli's equation."

Ok, I just read that entire page, and yes, it is comforting to see
that NASA is at least dispelling the myth that is being put forth by
Jeppensen's book and Rod Machado's book. I guess Barry Schiff was
right.

Excerpt from the above:
"There are many theories of how lift is generated. Unfortunately, many of
the theories found in encyclopedias, on web sites, and even in some
textbooks are incorrect, causing unnecessary confusion for students.

Entirely unnecessary.

The theory described on this slide is one of the most widely circulated,
incorrect explanations. The theory can be labeled the "Longer Path"
theory, or the "Equal Transit Time" theory."

So I started imagining, with no mathematics, what goes on with fluids
around surfaces, which lead me to these various experiments.

It is a great idea to experiment - even with things others already
understand. I do it too.

Oh, I plan to.

In addition to the above, there are a couple of other (expensive, alas)
books I would suggest:

"Introduction to Flight" by John D. Anderson, Jr.
Contains a history of the science of flight and also goes into details on
some of the more common mistakes people make in explanations of lift. I
do not own this book, but others also give it great reviews.

"Fundamentals of Aerodynamics" by John D. Anderson, Jr.
A well regarded, though mathematical, text on the subject. I do not own
this book either, but I expect it is good, based on my knowledge of the
next book I mention:

"Computational Fluid Dynamics" By John D. Anderson.
I bought and read through this book a couple years ago and it does a
great job of introducing CFD. I mention it here only because it is how I
know the style and quality of Anderson's writing to confidently recommend
two of his other books (above) that I have not read! He carefully disects
and explains each of the differential equations of the various types used
for computational modeling, among the many things covered.

A lot of J. D. Anderson.

Another note:

On my way to and from a party tonight, I thought in more detail about
Bernoulli's theorem, and I am more certain that not that I understand
the venturi tube, why the fluids, move, the distribution of pressures,
etc. Bernoulli's theorem is, indeed, at work over an airfoil, but is
has nothing to do with the descriptions that are being put forward by
the incorrect texts [really nothing]. All that business about one
side being longer is *not* the reason.

I guess the most important thing I learned from this experiences is
that, if it is true that the field of aerodynamics is fully-cooked,
the experts need to tell everyone else so that they stop printing (as
late as 2006) erroneous information in textbooks about the very
basics.

-Le Chaud Lapin-

Le Chaud Lapin writes:

Well, someone should have told me that Rob Machado and Barry Schiff
are not experts.

It's best not to worry too much about credentials or hearsay.

Then we
have Jeppesen, a leaders in edcuation of GA. You would think that,
with such a fine product (no sarcasm meant), that they would have
people whom they trust, experts, at the very high-end of academia, who
could verify what's in the text. But what is in my Jeppensen book and
what Barry Schiff wrote is wrong.

Jeppesen probably depends on credentials, like so many other entities and
people. It's easier to go by credentials than to test actual qualifications.
If someone has fancy credentials, he may get the job, even if he doesn't
actually know the answers.

Now I could have gone to some university in the U.S., Germany, France,
and found someone with stratospheric credentials in aero-astro, but
after seeing one expert say that the other is wrong, and then seeing
an incorrect application of Newton's law (yes I still believe it's
incorrect), I had to put on the brakes.

Lift is bizarre because it's easy to use and very reliable and practical, and
the overall principle is easy to understand correctly, but it's very difficult
to analyze in detail. But that is true of many things in the physical world:
the more closely you look at them, the more confusing they become.

In any field of research, there is mind and hand. For artists in the
field, there are those who have a proclivity to use hand more than
mind, and there are those who have a proclivity to use mind more than
hand. In any case, there are typically multiple paths to discovery,
one major path relying heavily on the imagination, the other path
relying on experimentation. Typically there is a combination. Based
on the small amount of the field of aerodynamcis I have seen so far,
and the disputes and inconsistencies, I would not be surprised if
there is an enormous amount of money being spent on experimentation.
Granted, experimentation is very necessary to validate (or invalidate)
what was conceived, but in many fields, there are researchers who
adopt the brute force approach, not completely, but much more than
someone who, lacking $100's of millions in funding would.

Not understanding aerodynamics doesn't prevent you from developing elaborate
computer models, it just prevents you from developing models that produce
accurate answers. Just running something through a computer doesn't validate
it.

A lot of J. D. Anderson.

Everyone has his favorite "experts."

I guess the most important thing I learned from this experiences is
that, if it is true that the field of aerodynamics is fully-cooked,
the experts need to tell everyone else so that they stop printing (as
late as 2006) erroneous information in textbooks about the very
basics.

There are still many mysteries in aerodynamics, as in so many other areas of
physical reality. It seems unlikely that human beings could have gone for
thousands of years understanding almost nothing of the subject and then
suddenly could have progressed to omniscience in a single century.

Mxsmanic wrote in
:

Le Chaud Lapin writes:

Well, someone should have told me that Rob Machado and Barry Schiff
are not experts.

It's best not to worry too much about credentials or hearsay.

Then we
have Jeppesen, a leaders in edcuation of GA. You would think that,
with such a fine product (no sarcasm meant), that they would have
people whom they trust, experts, at the very high-end of academia,
who could verify what's in the text. But what is in my Jeppensen
book and what Barry Schiff wrote is wrong.

Jeppesen probably depends on credentials,


Actualy, they rely on pilots, which you are not.


Bertie

Le Chaud Lapin wrote:
Well, someone should have told me that Rob Machado and Barry Schiff
are not experts. I did read once that Rod Machado has a Ph.D. in
aviation science, and the foreword to Barry Schiff's book is by Ernest
K. Gann, whom I presumed from his credentials is highly respected in
field.

As far as I know, Machado, Schiff, and Gann are experts in piloting, not
aerodynamics. There is very large difference in having a degree in
"Aviation Science" and Aerodynamics. The former seems to typically
include only one course in aerodynamics and an associates degree can be
obtained in only two years. Since no calculus is required, the
aerodynamics presented is likely to be qualitative and not quantitative.
An aerodynamics engineering degree, on the other hand, is at least four
years and a couple years of aerodynamic courses. Calculus is required and
is intended to impart enough knowledge to a student so they could design
aircraft.

But what is in my Jeppensen book and
what Barry Schiff wrote is wrong.

It could also be considered incomplete, rather than outright wrong.

Now I could have gone to some university in the U.S., Germany, France,
and found someone with stratospheric credentials in aero-astro, but
after seeing one expert say that the other is wrong, and then seeing
an incorrect application of Newton's law (yes I still believe it's
incorrect), I had to put on the brakes.

I don't agree with your approach to how you handled the contradictions
you encountered. If you can handle the math and physics, I think you
should move on to that level, not "put on the brakes." The problem is not
one of piloting, but rather understanding the physics and aerodynamics,
so I'm not sure why you chose to post to a piloting group. I would
suggest you post a query asking for authoritative texts and material to
one or more of these groups:

sci.physics
sci.mech.fluids
sci.physics.computational.fluid-dynamics
sci.aeronautics

I guess the most important thing I learned from this experiences is
that, if it is true that the field of aerodynamics is fully-cooked,
the experts need to tell everyone else so that they stop printing (as
late as 2006) erroneous information in textbooks about the very
basics.

I do not the fault the experts. They have authored much material on the
subject. But it's a complex subject - just as complex as quantum
mechanics, for example. But some people insist on seeking easy to
undertand or otherwise "intuitive" explanations for systems where
multiple constraints are operating simultaneously. So when explanations
are reduced to comprehensible bits something has to give. I'm not sure
why you appear shocked by this.

On Oct 6, 1:59 pm, Jim Logajan wrote:
As far as I know, Machado, Schiff, and Gann are experts in piloting,
not
aerodynamics. There is very large difference in having a degree in
"Aviation Science" and Aerodynamics. The former seems to typically
include only one course in aerodynamics and an associates degree can be
obtained in only two years. Since no calculus is required, the
aerodynamics presented is likely to be qualitative and not quantitative.
An aerodynamics engineering degree, on the other hand, is at least four
years and a couple years of aerodynamic courses. Calculus is required and
is intended to impart enough knowledge to a student so they could design
aircraft.

Hmm....do you think then that it is reasonable to expect a person with
Ph.D. in aviation science (that's what I read somewhere) to know what
causes lift on an airplane, without math?

But what is in my Jeppensen book and
what Barry Schiff wrote is wrong.

It could also be considered incomplete, rather than outright wrong.

In this case, it is outright wrong. I have the book here with me. I
can retype the entire section, the copy and paste from the NASA link
that you gave earlier, and it will be plainly obvious that two
descriptions are polar opposites.

I don't agree with your approach to how you handled the contradictions
you encountered. If you can handle the math and physics, I think you
should move on to that level, not "put on the brakes." The problem is not
one of piloting, but rather understanding the physics and aerodynamics,
so I'm not sure why you chose to post to a piloting group. I would
suggest you post a query asking for authoritative texts and material to
one or more of these groups:

By "putting on the brakes", I mean that I stopped reading books that
seem to have erroneous explanations of what causes lift.

sci.physics
sci.mech.fluids
sci.physics.computational.fluid-dynamics
sci.aeronautics

I thought about the fluids group, but I thought this group might be a
bit open-minded. Not to say that the fluid dynamicists are not open-
minded, but..after all, unless Jeppesen has fluid-dynamicists on
staff, it is they who started promulgating wrong information in the
first place. Also, if there are scientists lurking in the room who
are thorougly convinced that the NASA article, for example, is
wrong...there might be a tendency to ask me questions like:

1. "Do you have any experience in fluid dynamics?"
2. "Do you understand more than high school math?"
3. "Are you really trained as an engineeer?"

I thought I could avoid all of that by presenting a qualitative
exposition, without the numbers first, to an audience that is almost
guaranteed to have visceral experiences with the descriptions, then,
if there was something more to discuss, move on to rigorous
exploration. I barely got past the double-sheet-of-paper experiment.

I do not the fault the experts. They have authored much material on the
subject. But it's a complex subject - just as complex as quantum
mechanics, for example. But some people insist on seeking easy to
undertand or otherwise "intuitive" explanations for systems where
multiple constraints are operating simultaneously. So when explanations
are reduced to comprehensible bits something has to give. I'm not sure
why you appear shocked by this.

Hmm...I guess that's fair enough. Bernoulli, IMO, is at play above the
wing, but as the NASA article pointed out, it has nothing to do with
the description given by Jeppensen or even an online aero-astro text I
was reading yesterday. I guess it is possible that, a long time ago,
during a conference, someone mentioned Bernoulli and above-the-wing in
same sentence, and people started printing untruth. So maybe the
truth has always been known. But so far, the vast majority of
textbooks I see have printed the opposite of what that NASA article is
saying.

That downwash-Newton-thing, is simply inexcusable. Newton's law of
reciprocity is not complicated at all. Someone who understands this
law could look at the the description and see that it is incorrect
while understanding essentially zero about aerodynamics.

I just realized that when I take my KT, there is a good chance that
there will be a question that asks about the theory of lift. If that
NASA article is correct, there will be a small white lie for the
points.

Also, since you are the one who posted the NASA link, I have two
questions:

1. Do you understand thoroughly NASA's explanation why they think the
other authors are wrong?
2. Do you agree with them?

-Le Chaud Lapin-