....and the plane pulls up on the earth.

The air pushes up on the plane and the plane pushes down on the air;
essentially transferring the earth's continuous flow of downward
momentum acting on the plane to a much greater mass of air.

That air keeps that downward momentum, diffusing it through more and
more volume...

....until it eventually transfers it back to the Earth; countering the
aircraft's upward pull on it.

I'm willing to send that to any Ph.D. in Aeronautics that anyone cares
to name and post the answer back here.

Anyone game?

--
Alan Baker
Vancouver, British Columbia
<http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg>

Alan Baker wrote:
> ...and the plane pulls up on the earth.
>
> The air pushes up on the plane and the plane pushes down on the air;
> essentially transferring the earth's continuous flow of downward
> momentum acting on the plane to a much greater mass of air.
>
> That air keeps that downward momentum, diffusing it through more and
> more volume...
>
> ...until it eventually transfers it back to the Earth; countering the
> aircraft's upward pull on it.
>
> I'm willing to send that to any Ph.D. in Aeronautics that anyone cares
> to name and post the answer back here.
>
> Anyone game?

LOL

Alan Baker wrote:
> ...and the plane pulls up on the earth.
>
> The air pushes up on the plane and the plane pushes down on the air;
> essentially transferring the earth's continuous flow of downward
> momentum acting on the plane to a much greater mass of air.
>
> That air keeps that downward momentum, diffusing it through more and
> more volume...
>
> ...until it eventually transfers it back to the Earth; countering the
> aircraft's upward pull on it.
>
> I'm willing to send that to any Ph.D. in Aeronautics that anyone cares
> to name and post the answer back here.
>
> Anyone game?

Send that to Scott Eberhardt.

http://home.comcast.net/~clipper-108/Professional.html
To email me:
Copy/Paste > Send


Next, don't miss "A slightly more technical paper, which targets physics
students and teachers, titled The Newtonian Description of Lift of a
Wing, is also available online (in PDF format)" at the bottom of the
webpage. You'll notice his email address at the top of that paper, the
same as on the webpage.

As the paper says, the amount of air below that is pushed is negligible.
See "the wrong-Newtonian description of lift" on page 3.

See the "virtual scoop" in Figure 5. Air from overhead is pulled down by
the plane. The plane must, in turn, be pulled up. You imagined a plane
at the top of an air column, pushing down. It's more like a plane at the
bottom of a suction bubble, pulling down. Oh, you like differential
pressure, you don't like air to pull? Too bad, he talks about air
pulling on page 5.

Nothing is said about downwash continuing to the surface. The paper does
say that if a plane flies over a large scale, the weight of the airplane
would be measured. Excited?
Well, an acoustically levitated scale would register its own weight too.
Or turn that upside down, and the scale sees the earth's weight
acoustically levitated above the scale. Same thing, and no upwash or
downwash in sight, just a standing pressure wave with a scale caught at
a node between positive and negative.
Almost sort of like a wing between a strong little suction bubble and a
big weak pressure bubble. Is the wing almost sort of caught in a
standing wave? I don't know.

In article >,
Beryl > wrote:

> Alan Baker wrote:
> > ...and the plane pulls up on the earth.
> >
> > The air pushes up on the plane and the plane pushes down on the air;
> > essentially transferring the earth's continuous flow of downward
> > momentum acting on the plane to a much greater mass of air.
> >
> > That air keeps that downward momentum, diffusing it through more and
> > more volume...
> >
> > ...until it eventually transfers it back to the Earth; countering the
> > aircraft's upward pull on it.
> >
> > I'm willing to send that to any Ph.D. in Aeronautics that anyone cares
> > to name and post the answer back here.
> >
> > Anyone game?
>
> Send that to Scott Eberhardt.

OK, I will.

>
> http://home.comcast.net/~clipper-108/Professional.html
> To email me:
> Copy/Paste > Send

Thanks, I've got it covered.

>
>
> Next, don't miss "A slightly more technical paper, which targets physics
> students and teachers, titled The Newtonian Description of Lift of a
> Wing, is also available online (in PDF format)" at the bottom of the
> webpage. You'll notice his email address at the top of that paper, the
> same as on the webpage.
>
> As the paper says, the amount of air below that is pushed is negligible.
> See "the wrong-Newtonian description of lift" on page 3.
>
> See the "virtual scoop" in Figure 5. Air from overhead is pulled down by
> the plane. The plane must, in turn, be pulled up. You imagined a plane
> at the top of an air column, pushing down. It's more like a plane at the
> bottom of a suction bubble, pulling down. Oh, you like differential
> pressure, you don't like air to pull? Too bad, he talks about air
> pulling on page 5.
>
> Nothing is said about downwash continuing to the surface. The paper does
> say that if a plane flies over a large scale, the weight of the airplane
> would be measured. Excited?
> Well, an acoustically levitated scale would register its own weight too.
> Or turn that upside down, and the scale sees the earth's weight
> acoustically levitated above the scale. Same thing, and no upwash or
> downwash in sight, just a standing pressure wave with a scale caught at
> a node between positive and negative.
> Almost sort of like a wing between a strong little suction bubble and a
> big weak pressure bubble. Is the wing almost sort of caught in a
> standing wave? I don't know.


You certainly don't.

--
Alan Baker
Vancouver, British Columbia
<http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg>

In article >,
Beryl > wrote:

> Alan Baker wrote:
> > ...and the plane pulls up on the earth.
> >
> > The air pushes up on the plane and the plane pushes down on the air;
> > essentially transferring the earth's continuous flow of downward
> > momentum acting on the plane to a much greater mass of air.
> >
> > That air keeps that downward momentum, diffusing it through more and
> > more volume...
> >
> > ...until it eventually transfers it back to the Earth; countering the
> > aircraft's upward pull on it.
> >
> > I'm willing to send that to any Ph.D. in Aeronautics that anyone cares
> > to name and post the answer back here.
> >
> > Anyone game?
>
> Send that to Scott Eberhardt.
>
> http://home.comcast.net/~clipper-108/Professional.html
> To email me:
> Copy/Paste > Send
>
>
> Next, don't miss "A slightly more technical paper, which targets physics
> students and teachers, titled The Newtonian Description of Lift of a
> Wing, is also available online (in PDF format)" at the bottom of the
> webpage. You'll notice his email address at the top of that paper, the
> same as on the webpage.
>
> As the paper says, the amount of air below that is pushed is negligible.
> See "the wrong-Newtonian description of lift" on page 3.
>
> See the "virtual scoop" in Figure 5. Air from overhead is pulled down by
> the plane. The plane must, in turn, be pulled up. You imagined a plane
> at the top of an air column, pushing down. It's more like a plane at the
> bottom of a suction bubble, pulling down. Oh, you like differential
> pressure, you don't like air to pull? Too bad, he talks about air
> pulling on page 5.
>
> Nothing is said about downwash continuing to the surface. The paper does
> say that if a plane flies over a large scale, the weight of the airplane
> would be measured. Excited?
> Well, an acoustically levitated scale would register its own weight too.
> Or turn that upside down, and the scale sees the earth's weight
> acoustically levitated above the scale. Same thing, and no upwash or
> downwash in sight, just a standing pressure wave with a scale caught at
> a node between positive and negative.
> Almost sort of like a wing between a strong little suction bubble and a
> big weak pressure bubble. Is the wing almost sort of caught in a
> standing wave? I don't know.

Oh, you should check out what he says in his book:

"The wing develops lift by transferring momentum to the air. Momentum is
mass times velocity. In straight and level flight, the momentum is
transferred toward the earth. This momentum eventually strikes the
earth."

<http://books.google.com/books?id=wmuPXQuZnGoC&printsec=frontcover&dq=und
erstanding+flight+anderson&cd=1#v=onepage&q=downwash&f=false>

Page 11.

--
Alan Baker
Vancouver, British Columbia
<http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg>

Alan Baker wrote:
> In article >,
> Beryl > wrote:
>
>> Alan Baker wrote:
>>> ...and the plane pulls up on the earth.
>>>
>>> The air pushes up on the plane and the plane pushes down on the air;
>>> essentially transferring the earth's continuous flow of downward
>>> momentum acting on the plane to a much greater mass of air.
>>>
>>> That air keeps that downward momentum, diffusing it through more and
>>> more volume...
>>>
>>> ...until it eventually transfers it back to the Earth; countering the
>>> aircraft's upward pull on it.
>>>
>>> I'm willing to send that to any Ph.D. in Aeronautics that anyone cares
>>> to name and post the answer back here.
>>>
>>> Anyone game?
>> Send that to Scott Eberhardt.
>>
>> http://home.comcast.net/~clipper-108/Professional.html
>> To email me:
>> Copy/Paste > Send
>>
>>
>> Next, don't miss "A slightly more technical paper, which targets physics
>> students and teachers, titled The Newtonian Description of Lift of a
>> Wing, is also available online (in PDF format)" at the bottom of the
>> webpage. You'll notice his email address at the top of that paper, the
>> same as on the webpage.
>>
>> As the paper says, the amount of air below that is pushed is negligible.
>> See "the wrong-Newtonian description of lift" on page 3.
>>
>> See the "virtual scoop" in Figure 5. Air from overhead is pulled down by
>> the plane. The plane must, in turn, be pulled up. You imagined a plane
>> at the top of an air column, pushing down. It's more like a plane at the
>> bottom of a suction bubble, pulling down. Oh, you like differential
>> pressure, you don't like air to pull? Too bad, he talks about air
>> pulling on page 5.
>>
>> Nothing is said about downwash continuing to the surface. The paper does
>> say that if a plane flies over a large scale, the weight of the airplane
>> would be measured. Excited?
>> Well, an acoustically levitated scale would register its own weight too.
>> Or turn that upside down, and the scale sees the earth's weight
>> acoustically levitated above the scale. Same thing, and no upwash or
>> downwash in sight, just a standing pressure wave with a scale caught at
>> a node between positive and negative.
>> Almost sort of like a wing between a strong little suction bubble and a
>> big weak pressure bubble. Is the wing almost sort of caught in a
>> standing wave? I don't know.
>
> Oh, you should check out what he says in his book:
>
> "The wing develops lift by transferring momentum to the air. Momentum is
> mass times velocity. In straight and level flight, the momentum is
> transferred toward the earth. This momentum eventually strikes the
> earth."
>
> <http://books.google.com/books?id=wmuPXQuZnGoC&printsec=frontcover&dq=und
> erstanding+flight+anderson&cd=1#v=onepage&q=downwash&f=false>
>
> Page 11.

Er, right. His book "which targets the general public", rather than the
more technical paper "which targets physics students and teachers."

Alan Baker > wrote:
> Oh, you should check out what he says in his book:
>
> "The wing develops lift by transferring momentum to the air. Momentum
> is mass times velocity. In straight and level flight, the momentum is
> transferred toward the earth. This momentum eventually strikes the
> earth."

The momentum is transferred toward the earth at essentially the speed of
sound and appears as a rise in static pressure.

.... OR ...

_Your_ contention has *always* been that it is transferred much slower.
In fact you contend that the speed of that transfer decreases at some
unknown rate. By inference, it seems you also appear to contend that the
transfer eventually happens due to a rise in dynamic pressure, not static
pressure.

You appear to continue to treat the problem as a "rocket" problem, which
yields non-physical aspects like holes and voids in the atmosphere above
the aircraft. (Because you've already claimed no air moves upward *until*
the downwash reaches the earth's surface.)

So please help me understand your view of the situation by considering
the following hypothetical case and answering as many of the questions I
ask as you can:

Imagine a toy helicopter in a large room (or even a vertically oriented
denser-than-water submarine in a box fully filled with water):

========================== <-- Top
| |
| |
B --> | --------- | < -- B
| | |
| (===0 |
| |
... ... (Height of room/box could be large or
| | small, relative to blade width.)
| |
========================== <-- Bottom
(Width of room/box could be large or
small, relative to blade width.)

Given a downwash through the blades (depicted by "---------" in the
figure above) of the copter/submarine sufficient to hold the
copter/submarine stationary, can you describe to me roughly how you see
the flow of fluid above the helicopter occuring such that no fluid flows
upward anywhere *through* the plane "B" made by the blades *before* the
first bit of downwash created by the *blades* has reached the bottom of
the room/box?

That is - if the copter/submarine begins moving 1 kg/s of fluid down, do
you see a void immediately forming above the blades?

If not, which direction is the fluid flowing from so as to keep a void
from forming? If so, what keeps fluid from filling that void?

If a void above the blades is avoided by sideways fluid flow, does
that mean you see voids forming along the walls above the blades?

If you see voids forming anywhere, what keeps fluid from filling
them?

Are voids consistent with the assumption of incompressible flow?

Alan Baker > wrote:
> Oh, you should check out what he says in his book:
>
> "The wing develops lift by transferring momentum to the air. Momentum
> is mass times velocity. In straight and level flight, the momentum is
> transferred toward the earth. This momentum eventually strikes the
> earth."

The momentum is transferred toward the earth at essentially the speed of
sound and appears as a rise in static pressure.

.... OR ...

_Your_ contention has *always* been that it is transferred much slower.
In fact you contend that the speed of that transfer decreases at some
unknown rate. By inference, it seems you also appear to contend that the
transfer eventually happens due to a rise in dynamic pressure, not static
pressure.

You appear to continue to treat the problem as a "rocket" problem, which
yields non-physical aspects like holes and voids in the atmosphere above
the aircraft. (Because you've already claimed no air moves upward *until*
the downwash reaches the earth's surface.)

So please help me understand your view of the situation by considering
the following hypothetical case and answering as many of the questions I
ask as you can:

Imagine a toy helicopter in a large room (or even a vertically oriented
denser-than-water submarine in a box fully filled with water):

========================== <-- Top
| |
| |
B --> | --------- | < -- B
| | |
| (===0 |
| |
... ... (Height of room/box could be large or
| | small, relative to blade width.)
| |
========================== <-- Bottom
(Width of room/box could be large or
small, relative to blade width.)

Given a downwash through the blades (depicted by "---------" in the
figure above) of the copter/submarine sufficient to hold the
copter/submarine stationary, can you describe to me roughly how you see
the flow of fluid above the helicopter occuring such that no fluid flows
upward anywhere *through* the plane "B" made by the blades *before* the
first bit of downwash created by the *blades* has reached the bottom of
the room/box?

That is - if the copter/submarine begins moving 1 kg/s of fluid down, do
you see a void immediately forming above the blades?

If not, which direction is the fluid flowing from so as to keep a void
from forming? If so, what keeps fluid from filling that void?

If a void above the blades is avoided by sideways fluid flow, does
that mean you see voids forming along the walls above the blades?

If you see voids forming anywhere, what keeps fluid from filling
them?

Are voids consistent with the assumption of incompressible flow?

In article >,
Beryl > wrote:

> Alan Baker wrote:
> > In article >,
> > Beryl > wrote:
> >
> >> Alan Baker wrote:
> >>> ...and the plane pulls up on the earth.
> >>>
> >>> The air pushes up on the plane and the plane pushes down on the air;
> >>> essentially transferring the earth's continuous flow of downward
> >>> momentum acting on the plane to a much greater mass of air.
> >>>
> >>> That air keeps that downward momentum, diffusing it through more and
> >>> more volume...
> >>>
> >>> ...until it eventually transfers it back to the Earth; countering the
> >>> aircraft's upward pull on it.
> >>>
> >>> I'm willing to send that to any Ph.D. in Aeronautics that anyone cares
> >>> to name and post the answer back here.
> >>>
> >>> Anyone game?
> >> Send that to Scott Eberhardt.
> >>
> >> http://home.comcast.net/~clipper-108/Professional.html
> >> To email me:
> >> Copy/Paste > Send
> >>
> >>
> >> Next, don't miss "A slightly more technical paper, which targets physics
> >> students and teachers, titled The Newtonian Description of Lift of a
> >> Wing, is also available online (in PDF format)" at the bottom of the
> >> webpage. You'll notice his email address at the top of that paper, the
> >> same as on the webpage.
> >>
> >> As the paper says, the amount of air below that is pushed is negligible.
> >> See "the wrong-Newtonian description of lift" on page 3.
> >>
> >> See the "virtual scoop" in Figure 5. Air from overhead is pulled down by
> >> the plane. The plane must, in turn, be pulled up. You imagined a plane
> >> at the top of an air column, pushing down. It's more like a plane at the
> >> bottom of a suction bubble, pulling down. Oh, you like differential
> >> pressure, you don't like air to pull? Too bad, he talks about air
> >> pulling on page 5.
> >>
> >> Nothing is said about downwash continuing to the surface. The paper does
> >> say that if a plane flies over a large scale, the weight of the airplane
> >> would be measured. Excited?
> >> Well, an acoustically levitated scale would register its own weight too.
> >> Or turn that upside down, and the scale sees the earth's weight
> >> acoustically levitated above the scale. Same thing, and no upwash or
> >> downwash in sight, just a standing pressure wave with a scale caught at
> >> a node between positive and negative.
> >> Almost sort of like a wing between a strong little suction bubble and a
> >> big weak pressure bubble. Is the wing almost sort of caught in a
> >> standing wave? I don't know.
> >
> > Oh, you should check out what he says in his book:
> >
> > "The wing develops lift by transferring momentum to the air. Momentum is
> > mass times velocity. In straight and level flight, the momentum is
> > transferred toward the earth. This momentum eventually strikes the
> > earth."
> >
> > <http://books.google.com/books?id=wmuPXQuZnGoC&printsec=frontcover&dq=und
> > erstanding+flight+anderson&cd=1#v=onepage&q=downwash&f=false>
> >
> > Page 11.
>
> Er, right. His book "which targets the general public", rather than the
> more technical paper "which targets physics students and teachers."

You think he rights things into his book which aren't true? You think
that simply because he makes the language more plain he's included
falsehoods?

Really?

He never says *once* in his "more technical paper" that "The plane must,
in turn, be pulled up." That is you.

He does say in his "more technical paper":

"Lift requires power

When a plane passes overhead the formally still air gains a downward
velocity."

Read that over and over until you get it:

"When a plane passes overhead the formally still air gains a downward
velocity."

He also says right at the top of this "more techical paper":

"This material can be found in more detail in Understanding Flight 1st
and 2nd editions by David Anderson and Scott Eberhardt, McGraw-Hill,
2001, and 2009"

IOW, the author of the "more technical paper" declares the book the more
detailed explanation.

--
Alan Baker
Vancouver, British Columbia
<http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg>

Alan Baker wrote:
> In article >,
> Beryl > wrote:
>
>> Alan Baker wrote:
>>> In article >,
>>> Beryl > wrote:
>>>
>>>> Alan Baker wrote:
>>>>> ...and the plane pulls up on the earth.
>>>>>
>>>>> The air pushes up on the plane and the plane pushes down on the air;
>>>>> essentially transferring the earth's continuous flow of downward
>>>>> momentum acting on the plane to a much greater mass of air.
>>>>>
>>>>> That air keeps that downward momentum, diffusing it through more and
>>>>> more volume...
>>>>>
>>>>> ...until it eventually transfers it back to the Earth; countering the
>>>>> aircraft's upward pull on it.
>>>>>
>>>>> I'm willing to send that to any Ph.D. in Aeronautics that anyone cares
>>>>> to name and post the answer back here.
>>>>>
>>>>> Anyone game?
>>>> Send that to Scott Eberhardt.
>>>>
>>>> http://home.comcast.net/~clipper-108/Professional.html
>>>> To email me:
>>>> Copy/Paste > Send
>>>>
>>>>
>>>> Next, don't miss "A slightly more technical paper, which targets physics
>>>> students and teachers, titled The Newtonian Description of Lift of a
>>>> Wing, is also available online (in PDF format)" at the bottom of the
>>>> webpage. You'll notice his email address at the top of that paper, the
>>>> same as on the webpage.
>>>>
>>>> As the paper says, the amount of air below that is pushed is negligible.
>>>> See "the wrong-Newtonian description of lift" on page 3.
>>>>
>>>> See the "virtual scoop" in Figure 5. Air from overhead is pulled down by
>>>> the plane. The plane must, in turn, be pulled up. You imagined a plane
>>>> at the top of an air column, pushing down. It's more like a plane at the
>>>> bottom of a suction bubble, pulling down. Oh, you like differential
>>>> pressure, you don't like air to pull? Too bad, he talks about air
>>>> pulling on page 5.
>>>>
>>>> Nothing is said about downwash continuing to the surface. The paper does
>>>> say that if a plane flies over a large scale, the weight of the airplane
>>>> would be measured. Excited?
>>>> Well, an acoustically levitated scale would register its own weight too.
>>>> Or turn that upside down, and the scale sees the earth's weight
>>>> acoustically levitated above the scale. Same thing, and no upwash or
>>>> downwash in sight, just a standing pressure wave with a scale caught at
>>>> a node between positive and negative.
>>>> Almost sort of like a wing between a strong little suction bubble and a
>>>> big weak pressure bubble. Is the wing almost sort of caught in a
>>>> standing wave? I don't know.
>>> Oh, you should check out what he says in his book:
>>>
>>> "The wing develops lift by transferring momentum to the air. Momentum is
>>> mass times velocity. In straight and level flight, the momentum is
>>> transferred toward the earth. This momentum eventually strikes the
>>> earth."
>>>
>>> <http://books.google.com/books?id=wmuPXQuZnGoC&printsec=frontcover&dq=und
>>> erstanding+flight+anderson&cd=1#v=onepage&q=downwash&f=false>
>>>
>>> Page 11.
>> Er, right. His book "which targets the general public", rather than the
>> more technical paper "which targets physics students and teachers."
>
> You think he rights things into his book which aren't true? You think
> that simply because he makes the language more plain he's included
> falsehoods?
>
> Really?

I think so.

> He never says *once* in his "more technical paper" that "The plane must,
> in turn, be pulled up." That is you.

Correct. He never said the next sentence "You imagined a plane at the
top of an air column, pushing down" either.

> He does say in his "more technical paper":
>
> "Lift requires power
>
> When a plane passes overhead the formally still air gains a downward
> velocity."
>
> Read that over and over until you get it:
>
> "When a plane passes overhead the formally still air gains a downward
> velocity."

He actually says that? Still air always seems very casual to me.

> He also says right at the top of this "more techical paper":
>
> "This material can be found in more detail in Understanding Flight 1st
> and 2nd editions by David Anderson and Scott Eberhardt, McGraw-Hill,
> 2001, and 2009"

Not on the pdf I downloaded.
http://home.comcast.net/~clipper-108/Lift_AAPT.pdf
Maybe you're looking at something else.

> IOW, the author of the "more technical paper" declares the book the more
> detailed explanation.

I don't see any such notion on his webpage either.

In article >,
Beryl > wrote:

> Alan Baker wrote:
> > In article >,
> > Beryl > wrote:
> >
> >> Alan Baker wrote:
> >>> In article >,
> >>> Beryl > wrote:
> >>>
> >>>> Alan Baker wrote:
> >>>>> ...and the plane pulls up on the earth.
> >>>>>
> >>>>> The air pushes up on the plane and the plane pushes down on the air;
> >>>>> essentially transferring the earth's continuous flow of downward
> >>>>> momentum acting on the plane to a much greater mass of air.
> >>>>>
> >>>>> That air keeps that downward momentum, diffusing it through more and
> >>>>> more volume...
> >>>>>
> >>>>> ...until it eventually transfers it back to the Earth; countering the
> >>>>> aircraft's upward pull on it.
> >>>>>
> >>>>> I'm willing to send that to any Ph.D. in Aeronautics that anyone cares
> >>>>> to name and post the answer back here.
> >>>>>
> >>>>> Anyone game?
> >>>> Send that to Scott Eberhardt.
> >>>>
> >>>> http://home.comcast.net/~clipper-108/Professional.html
> >>>> To email me:
> >>>> Copy/Paste > Send
> >>>>
> >>>>
> >>>> Next, don't miss "A slightly more technical paper, which targets physics
> >>>> students and teachers, titled The Newtonian Description of Lift of a
> >>>> Wing, is also available online (in PDF format)" at the bottom of the
> >>>> webpage. You'll notice his email address at the top of that paper, the
> >>>> same as on the webpage.
> >>>>
> >>>> As the paper says, the amount of air below that is pushed is negligible.
> >>>> See "the wrong-Newtonian description of lift" on page 3.
> >>>>
> >>>> See the "virtual scoop" in Figure 5. Air from overhead is pulled down by
> >>>> the plane. The plane must, in turn, be pulled up. You imagined a plane
> >>>> at the top of an air column, pushing down. It's more like a plane at the
> >>>> bottom of a suction bubble, pulling down. Oh, you like differential
> >>>> pressure, you don't like air to pull? Too bad, he talks about air
> >>>> pulling on page 5.
> >>>>
> >>>> Nothing is said about downwash continuing to the surface. The paper does
> >>>> say that if a plane flies over a large scale, the weight of the airplane
> >>>> would be measured. Excited?
> >>>> Well, an acoustically levitated scale would register its own weight too.
> >>>> Or turn that upside down, and the scale sees the earth's weight
> >>>> acoustically levitated above the scale. Same thing, and no upwash or
> >>>> downwash in sight, just a standing pressure wave with a scale caught at
> >>>> a node between positive and negative.
> >>>> Almost sort of like a wing between a strong little suction bubble and a
> >>>> big weak pressure bubble. Is the wing almost sort of caught in a
> >>>> standing wave? I don't know.
> >>> Oh, you should check out what he says in his book:
> >>>
> >>> "The wing develops lift by transferring momentum to the air. Momentum is
> >>> mass times velocity. In straight and level flight, the momentum is
> >>> transferred toward the earth. This momentum eventually strikes the
> >>> earth."
> >>>
> >>> <http://books.google.com/books?id=wmuPXQuZnGoC&printsec=frontcover&dq=und
> >>> erstanding+flight+anderson&cd=1#v=onepage&q=downwash&f=false>
> >>>
> >>> Page 11.
> >> Er, right. His book "which targets the general public", rather than the
> >> more technical paper "which targets physics students and teachers."
> >
> > You think he rights things into his book which aren't true? You think
> > that simply because he makes the language more plain he's included
> > falsehoods?
> >
> > Really?
>
> I think so.

Even you don't believe that.

>
> > He never says *once* in his "more technical paper" that "The plane must,
> > in turn, be pulled up." That is you.
>
> Correct. He never said the next sentence "You imagined a plane at the
> top of an air column, pushing down" either.
>

I'm not responsible for what you imagine I'm thinking.


> > He does say in his "more technical paper":
> >
> > "Lift requires power
> >
> > When a plane passes overhead the formally still air gains a downward
> > velocity."
> >
> > Read that over and over until you get it:
> >
> > "When a plane passes overhead the formally still air gains a downward
> > velocity."
>
> He actually says that? Still air always seems very casual to me.

Yes: that is the actually quote. Obviously an uncaught typo for the word
"formerly".

<http://home.comcast.net/~clipper-108/Flightrevisited.pdf>

>
> > He also says right at the top of this "more techical paper":
> >
> > "This material can be found in more detail in Understanding Flight 1st
> > and 2nd editions by David Anderson and Scott Eberhardt, McGraw-Hill,
> > 2001, and 2009"
>
> Not on the pdf I downloaded.
> http://home.comcast.net/~clipper-108/Lift_AAPT.pdf
> Maybe you're looking at something else.

I was. This:

<http://home.comcast.net/~clipper-108/Flightrevisited.pdf>

In the one you looked at, he says this:

"It should not be surprising that wings also produce lift by
accelerating air in the downward direction."

And it also says this:

"It is worth noting that the wing produces lift by transferring
momentum to the air. In straight-and-level flight this momentum is
directed towards the ground. If the airplane were to fly over a large
scale the weight of the airplane would be measured. The earth does not
get lighter when the airplane takes off."

It also says this:

"One might ask how large m& is for a typical airplane. Take for example
the Cessna 172 that weighs about 2300 lb (1045 kg). Traveling at a
speed of 140 mph (220 km/h), and assuming an effective angle of attack
of 5 degrees, we get a vertical velocity for the air of about 11.5 mph
(18 km/h) right at the wing. If we assume that the average vertical
velocity of the air diverted is half that value then we calculate m& to
be on the order of 5 ton/s."

Please note if there is an average velocity downward, then the updrafts
in the tip vortices cannot possibly be cancelling out all the downward
motion.

>
> > IOW, the author of the "more technical paper" declares the book the more
> > detailed explanation.
>
> I don't see any such notion on his webpage either.

Read the paper I looked at. You can't blame me for picking a different
"PDF" on the same page when you fail to provide the actual URL.

--
Alan Baker
Vancouver, British Columbia
<http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg>

Alan Baker wrote:

> Read the paper I looked at. You can't blame me for picking a different
> "PDF" on the same page when you fail to provide the actual URL.

I told you, exactly:
Next, don't miss "A slightly more technical paper, which targets physics
students and teachers, titled The Newtonian Description of Lift of a
Wing, is also available online (in PDF format)" at the bottom of the
webpage.

In article >,
Beryl > wrote:

> Alan Baker wrote:
>
> > Read the paper I looked at. You can't blame me for picking a different
> > "PDF" on the same page when you fail to provide the actual URL.
>
> I told you, exactly:
> Next, don't miss "A slightly more technical paper, which targets physics
> students and teachers, titled The Newtonian Description of Lift of a
> Wing, is also available online (in PDF format)" at the bottom of the
> webpage.

There was more than one PDF listed at the bottom of the page and neither
the one you cited nor the one I cited says that the air pulls the plane
up.

The one you cited does say:

"It is worth noting that the wing produces lift by transferring
momentum to the air. In straight-and-level flight this momentum is
directed towards the ground."

I can't help but notice that you snipped that along with a lot of other
text to which you obviously could not find an adequate reply...

--
Alan Baker
Vancouver, British Columbia
<http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg>

On Dec 11, 11:23*pm, Alan Baker > wrote:
> In article >,
>
> *Beryl > wrote:
> > Alan Baker wrote:
>
> > > Read the paper I looked at. You can't blame me for picking a different
> > > "PDF" on the same page when you fail to provide the actual URL.
>
> > I told you, exactly:
> > Next, don't miss "A slightly more technical paper, which targets physics
> > students and teachers, titled The Newtonian Description of Lift of a
> > Wing, is also available online (in PDF format)" at the bottom of the
> > webpage.
>
> There was more than one PDF listed at the bottom of the page and neither
> the one you cited nor the one I cited says that the air pulls the plane
> up.
>
> The one you cited does say:
>
> "It is worth noting that the wing produces lift by transferring
> momentum to the air. In straight-and-level flight this momentum is
> directed towards the ground."
>
> I can't help but notice that you snipped that along with a lot of other
> text to which you obviously could not find an adequate reply...
>
> --
> Alan Baker
> Vancouver, British Columbia
> <http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg>

Arguments like this could go on forever but solve little or nothing.
Along with the flamers who try to elevate themselves by dissing
everyone else, these scraps are the sort of thing that have ruined the
rec.aviation groups as a whole and have driven most of us to moderated
groups where this isn't tolerated. There are so few individuals
following this thread anymore that it's sad. Nothing is being solved,
and won't be.

Adherents to either Newton or Bernoulli have argued the sources of
lift at least since the Wright brothers did their thing, and probably
before that. It still hasn't been settled. There is downwash, for
sure, and that supports Newton, but Bernoulli's pressure differential
also causes that downwash as the air, accelerated over the top of the
wing, follows its curvature and leaves it at a descending angle.
Downwash. Big deal. Air has enormous damping properties and downwash
seldom reaches the surface, even from an airliner 100 feet up on final
approach. I regularly drive under the approach path of a large
airport, where the runway threshold is a few feet from the road, and I
never notice litter or dust blowing around after an airliner has
skimmed over and landed. Air resists movement and stops moving soon
after it has been agitated. That's not to say that downwash isn't
involved in lift; it very likely is, and since the air is supported by
the earth's surface, the airliner's flight does not reduce the earth's
gross weight while it's off the ground. And that would be true even if
Newton wasn't involved and only Bernoulli was.

Orchardists have used light aircraft, flying VERY low and slow with
considerable flap, over their fields on frosty nights to drive warmer
air from a few feet up down into the trees to try to prevent the
fruit's freezing. It's debatable as to the overall effectiveness of
the method. Cropsprayers also fly with the wheels practically in the
crop so that the downwash drives the spray into the plants. In both
cases, the flight is extremely low, so low that it's dangerous.
Spraying from 20 feet up is far less effective. The downwash is
already dissipated.

The Clark Y airfoil generates lift at angles of attack as low as minus
4 degrees. At that angle there is no reason to expect downwash of any
sort, yet lift is generated. The bottom of the airfoil is angled
upward at about seven degrees in such flight.

So the argument could go on and on with neither side convinced, like
it has on and off for the last ten years I've followed these groups,
and the net result will be a handful of angry posters and and
otherwise empty forum. Is that what we want?

Dan

In article
>,
wrote:

> On Dec 11, 11:23*pm, Alan Baker > wrote:
> > In article >,
> >
> > *Beryl > wrote:
> > > Alan Baker wrote:
> >
> > > > Read the paper I looked at. You can't blame me for picking a different
> > > > "PDF" on the same page when you fail to provide the actual URL.
> >
> > > I told you, exactly:
> > > Next, don't miss "A slightly more technical paper, which targets physics
> > > students and teachers, titled The Newtonian Description of Lift of a
> > > Wing, is also available online (in PDF format)" at the bottom of the
> > > webpage.
> >
> > There was more than one PDF listed at the bottom of the page and neither
> > the one you cited nor the one I cited says that the air pulls the plane
> > up.
> >
> > The one you cited does say:
> >
> > "It is worth noting that the wing produces lift by transferring
> > momentum to the air. In straight-and-level flight this momentum is
> > directed towards the ground."
> >
> > I can't help but notice that you snipped that along with a lot of other
> > text to which you obviously could not find an adequate reply...
> >
> > --
> > Alan Baker
> > Vancouver, British Columbia
> > <http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg>
>
> Arguments like this could go on forever but solve little or nothing.
> Along with the flamers who try to elevate themselves by dissing
> everyone else, these scraps are the sort of thing that have ruined the
> rec.aviation groups as a whole and have driven most of us to moderated
> groups where this isn't tolerated. There are so few individuals
> following this thread anymore that it's sad. Nothing is being solved,
> and won't be.
>
> Adherents to either Newton or Bernoulli have argued the sources of
> lift at least since the Wright brothers did their thing, and probably
> before that. It still hasn't been settled. There is downwash, for
> sure, and that supports Newton, but Bernoulli's pressure differential
> also causes that downwash as the air, accelerated over the top of the
> wing, follows its curvature and leaves it at a descending angle.
> Downwash. Big deal. Air has enormous damping properties and downwash
> seldom reaches the surface, even from an airliner 100 feet up on final
> approach. I regularly drive under the approach path of a large
> airport, where the runway threshold is a few feet from the road, and I
> never notice litter or dust blowing around after an airliner has
> skimmed over and landed. Air resists movement and stops moving soon
> after it has been agitated. That's not to say that downwash isn't
> involved in lift; it very likely is, and since the air is supported by
> the earth's surface, the airliner's flight does not reduce the earth's
> gross weight while it's off the ground. And that would be true even if
> Newton wasn't involved and only Bernoulli was.
>
> Orchardists have used light aircraft, flying VERY low and slow with
> considerable flap, over their fields on frosty nights to drive warmer
> air from a few feet up down into the trees to try to prevent the
> fruit's freezing. It's debatable as to the overall effectiveness of
> the method. Cropsprayers also fly with the wheels practically in the
> crop so that the downwash drives the spray into the plants. In both
> cases, the flight is extremely low, so low that it's dangerous.
> Spraying from 20 feet up is far less effective. The downwash is
> already dissipated.
>
> The Clark Y airfoil generates lift at angles of attack as low as minus
> 4 degrees. At that angle there is no reason to expect downwash of any
> sort, yet lift is generated. The bottom of the airfoil is angled
> upward at about seven degrees in such flight.
>
> So the argument could go on and on with neither side convinced, like
> it has on and off for the last ten years I've followed these groups,
> and the net result will be a handful of angry posters and and
> otherwise empty forum. Is that what we want?
>
> Dan

Dan, I appreciate your efforts, but the existence of lift absolutely
demands that there is downwash.

Lift is a force up on the plane. Where's it come from? The air.

Therefore there is a force down on the air from the plane.

Force *is* change of momentum with respect to time, so a force down on
the air means a change in the airs momentum downward.

Period. End. Full stop.

The fact that the downwash quickly spreads itself among more and more
air doesn't make that momentum go away. The law of conservation of
momentum tells it can't. It has literally never once been found to have
been violated. So while more air may now share the momentum, that only
means that the average speed of the air is reduced in inverse proportion
to the amount of air that is then moving.

--
Alan Baker
Vancouver, British Columbia
<http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg>

On 12/12/2009 2:01 PM, Alan Baker wrote:
> In article
> >,
> wrote:
>
>> On Dec 11, 11:23 pm, Alan > wrote:
>>> In >,
>>>
>>> > wrote:
>>>> Alan Baker wrote:
>>>
>>>>> Read the paper I looked at. You can't blame me for picking a different
>>>>> "PDF" on the same page when you fail to provide the actual URL.
>>>
>>>> I told you, exactly:
>>>> Next, don't miss "A slightly more technical paper, which targets physics
>>>> students and teachers, titled The Newtonian Description of Lift of a
>>>> Wing, is also available online (in PDF format)" at the bottom of the
>>>> webpage.
>>>
>>> There was more than one PDF listed at the bottom of the page and neither
>>> the one you cited nor the one I cited says that the air pulls the plane
>>> up.
>>>
>>> The one you cited does say:
>>>
>>> "It is worth noting that the wing produces lift by transferring
>>> momentum to the air. In straight-and-level flight this momentum is
>>> directed towards the ground."
>>>
>>> I can't help but notice that you snipped that along with a lot of other
>>> text to which you obviously could not find an adequate reply...
>>>
>>> --
>>> Alan Baker
>>> Vancouver, British Columbia
>>> <http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg>
>>
>> Arguments like this could go on forever but solve little or nothing.
>> Along with the flamers who try to elevate themselves by dissing
>> everyone else, these scraps are the sort of thing that have ruined the
>> rec.aviation groups as a whole and have driven most of us to moderated
>> groups where this isn't tolerated. There are so few individuals
>> following this thread anymore that it's sad. Nothing is being solved,
>> and won't be.
>>
>> Adherents to either Newton or Bernoulli have argued the sources of
>> lift at least since the Wright brothers did their thing, and probably
>> before that. It still hasn't been settled. There is downwash, for
>> sure, and that supports Newton, but Bernoulli's pressure differential
>> also causes that downwash as the air, accelerated over the top of the
>> wing, follows its curvature and leaves it at a descending angle.
>> Downwash. Big deal. Air has enormous damping properties and downwash
>> seldom reaches the surface, even from an airliner 100 feet up on final
>> approach. I regularly drive under the approach path of a large
>> airport, where the runway threshold is a few feet from the road, and I
>> never notice litter or dust blowing around after an airliner has
>> skimmed over and landed. Air resists movement and stops moving soon
>> after it has been agitated. That's not to say that downwash isn't
>> involved in lift; it very likely is, and since the air is supported by
>> the earth's surface, the airliner's flight does not reduce the earth's
>> gross weight while it's off the ground. And that would be true even if
>> Newton wasn't involved and only Bernoulli was.
>>
>> Orchardists have used light aircraft, flying VERY low and slow with
>> considerable flap, over their fields on frosty nights to drive warmer
>> air from a few feet up down into the trees to try to prevent the
>> fruit's freezing. It's debatable as to the overall effectiveness of
>> the method. Cropsprayers also fly with the wheels practically in the
>> crop so that the downwash drives the spray into the plants. In both
>> cases, the flight is extremely low, so low that it's dangerous.
>> Spraying from 20 feet up is far less effective. The downwash is
>> already dissipated.
>>
>> The Clark Y airfoil generates lift at angles of attack as low as minus
>> 4 degrees. At that angle there is no reason to expect downwash of any
>> sort, yet lift is generated. The bottom of the airfoil is angled
>> upward at about seven degrees in such flight.
>>
>> So the argument could go on and on with neither side convinced, like
>> it has on and off for the last ten years I've followed these groups,
>> and the net result will be a handful of angry posters and and
>> otherwise empty forum. Is that what we want?
>>
>> Dan
>
> Dan, I appreciate your efforts, but the existence of lift absolutely
> demands that there is downwash.
>
> Lift is a force up on the plane. Where's it come from? The air.
>
> Therefore there is a force down on the air from the plane.
>
> Force *is* change of momentum with respect to time, so a force down on
> the air means a change in the airs momentum downward.
>
> Period. End. Full stop.
>
> The fact that the downwash quickly spreads itself among more and more
> air doesn't make that momentum go away. The law of conservation of
> momentum tells it can't. It has literally never once been found to have
> been violated. So while more air may now share the momentum, that only
> means that the average speed of the air is reduced in inverse proportion
> to the amount of air that is then moving.
>

the horse has been dead for quite a while

In article >,
Ray Adair > wrote:

> On 12/12/2009 2:01 PM, Alan Baker wrote:
> > In article
> > >,
> > wrote:
> >
> >> On Dec 11, 11:23 pm, Alan > wrote:
> >>> In >,
> >>>
> >>> > wrote:
> >>>> Alan Baker wrote:
> >>>
> >>>>> Read the paper I looked at. You can't blame me for picking a different
> >>>>> "PDF" on the same page when you fail to provide the actual URL.
> >>>
> >>>> I told you, exactly:
> >>>> Next, don't miss "A slightly more technical paper, which targets physics
> >>>> students and teachers, titled The Newtonian Description of Lift of a
> >>>> Wing, is also available online (in PDF format)" at the bottom of the
> >>>> webpage.
> >>>
> >>> There was more than one PDF listed at the bottom of the page and neither
> >>> the one you cited nor the one I cited says that the air pulls the plane
> >>> up.
> >>>
> >>> The one you cited does say:
> >>>
> >>> "It is worth noting that the wing produces lift by transferring
> >>> momentum to the air. In straight-and-level flight this momentum is
> >>> directed towards the ground."
> >>>
> >>> I can't help but notice that you snipped that along with a lot of other
> >>> text to which you obviously could not find an adequate reply...
> >>>
> >>> --
> >>> Alan Baker
> >>> Vancouver, British Columbia
> >>> <http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg>
> >>
> >> Arguments like this could go on forever but solve little or nothing.
> >> Along with the flamers who try to elevate themselves by dissing
> >> everyone else, these scraps are the sort of thing that have ruined the
> >> rec.aviation groups as a whole and have driven most of us to moderated
> >> groups where this isn't tolerated. There are so few individuals
> >> following this thread anymore that it's sad. Nothing is being solved,
> >> and won't be.
> >>
> >> Adherents to either Newton or Bernoulli have argued the sources of
> >> lift at least since the Wright brothers did their thing, and probably
> >> before that. It still hasn't been settled. There is downwash, for
> >> sure, and that supports Newton, but Bernoulli's pressure differential
> >> also causes that downwash as the air, accelerated over the top of the
> >> wing, follows its curvature and leaves it at a descending angle.
> >> Downwash. Big deal. Air has enormous damping properties and downwash
> >> seldom reaches the surface, even from an airliner 100 feet up on final
> >> approach. I regularly drive under the approach path of a large
> >> airport, where the runway threshold is a few feet from the road, and I
> >> never notice litter or dust blowing around after an airliner has
> >> skimmed over and landed. Air resists movement and stops moving soon
> >> after it has been agitated. That's not to say that downwash isn't
> >> involved in lift; it very likely is, and since the air is supported by
> >> the earth's surface, the airliner's flight does not reduce the earth's
> >> gross weight while it's off the ground. And that would be true even if
> >> Newton wasn't involved and only Bernoulli was.
> >>
> >> Orchardists have used light aircraft, flying VERY low and slow with
> >> considerable flap, over their fields on frosty nights to drive warmer
> >> air from a few feet up down into the trees to try to prevent the
> >> fruit's freezing. It's debatable as to the overall effectiveness of
> >> the method. Cropsprayers also fly with the wheels practically in the
> >> crop so that the downwash drives the spray into the plants. In both
> >> cases, the flight is extremely low, so low that it's dangerous.
> >> Spraying from 20 feet up is far less effective. The downwash is
> >> already dissipated.
> >>
> >> The Clark Y airfoil generates lift at angles of attack as low as minus
> >> 4 degrees. At that angle there is no reason to expect downwash of any
> >> sort, yet lift is generated. The bottom of the airfoil is angled
> >> upward at about seven degrees in such flight.
> >>
> >> So the argument could go on and on with neither side convinced, like
> >> it has on and off for the last ten years I've followed these groups,
> >> and the net result will be a handful of angry posters and and
> >> otherwise empty forum. Is that what we want?
> >>
> >> Dan
> >
> > Dan, I appreciate your efforts, but the existence of lift absolutely
> > demands that there is downwash.
> >
> > Lift is a force up on the plane. Where's it come from? The air.
> >
> > Therefore there is a force down on the air from the plane.
> >
> > Force *is* change of momentum with respect to time, so a force down on
> > the air means a change in the airs momentum downward.
> >
> > Period. End. Full stop.
> >
> > The fact that the downwash quickly spreads itself among more and more
> > air doesn't make that momentum go away. The law of conservation of
> > momentum tells it can't. It has literally never once been found to have
> > been violated. So while more air may now share the momentum, that only
> > means that the average speed of the air is reduced in inverse proportion
> > to the amount of air that is then moving.
> >
>
> the horse has been dead for quite a while

The facts are the facts.

There is no upward force without a downward force.

An unbalanced for always accelerates that which it acts upon.

Momentum is always conserved.

--
Alan Baker
Vancouver, British Columbia
<http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg>

Alan Baker wrote:

> So while more air may now share the momentum, that only
> means that the average speed of the air is reduced in inverse proportion
> to the amount of air that is then moving.

'Traveling at a speed of 140 mph, and assuming an effective angle of
attack of 5 degrees, we get a vertical velocity for the air of about
11.5 mph right at the wing.'
Eberhardt then assumes the average vertical velocity is half that. I'll
assume that *miles* away from the wing it's nothing.

In article >,
Beryl > wrote:

> Alan Baker wrote:
>
> > So while more air may now share the momentum, that only
> > means that the average speed of the air is reduced in inverse proportion
> > to the amount of air that is then moving.
>
> 'Traveling at a speed of 140 mph, and assuming an effective angle of
> attack of 5 degrees, we get a vertical velocity for the air of about
> 11.5 mph right at the wing.'
> Eberhardt then assumes the average vertical velocity is half that. I'll
> assume that *miles* away from the wing it's nothing.

You can assume all you want...

....if you want to be wrong.

Fact: momentum is always conserved.

--
Alan Baker
Vancouver, British Columbia
<http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg>

On Dec 12, 2:27 pm, Alan Baker > wrote:
> In article >,
> > Eberhardt then assumes the average vertical velocity is half that. I'll
> > assume that *miles* away from the wing it's nothing.
>
> You can assume all you want...
>
> ...if you want to be wrong.
>
> Fact: momentum is always conserved.


See what I mean? Endless, endless back-and-forth. Miles away from the
wing it's nothing. Even a couple hundred yards away it's pretty much
undetectable apart from the sound. The air dampens all movement,
turning it into heat (due to friction between agitated molecules) and
nothing more. Newton is right, OK? For every action there is an equal
and opposite reaction. In our case, the air dissipates the action
(downwash) to such an extent that you are wasting time looking for it
anywhere but near the wing. You'd be better informed to look for a
temperature rise in the wake of the wing.

Dan

In article
>,
wrote:

> On Dec 12, 2:27 pm, Alan Baker > wrote:
> > In article >,
> > > Eberhardt then assumes the average vertical velocity is half that. I'll
> > > assume that *miles* away from the wing it's nothing.
> >
> > You can assume all you want...
> >
> > ...if you want to be wrong.
> >
> > Fact: momentum is always conserved.
>
>
> See what I mean? Endless, endless back-and-forth. Miles away from the
> wing it's nothing. Even a couple hundred yards away it's pretty much
> undetectable apart from the sound. The air dampens all movement,
> turning it into heat (due to friction between agitated molecules) and
> nothing more. Newton is right, OK? For every action there is an equal
> and opposite reaction. In our case, the air dissipates the action
> (downwash) to such an extent that you are wasting time looking for it
> anywhere but near the wing. You'd be better informed to look for a
> temperature rise in the wake of the wing.
>
> Dan

No. That is wrong. Friction changes where the *energy* the air had ends
up, but momentum is conserved. When friction slows one object, it speeds
up the object that was the source of the friction and momentum is
conserved.

Friction splits the momentum among more and more molecules in the air,
but it cannot make it go away.

--
Alan Baker
Vancouver, British Columbia
<http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg>

wrote:
> Arguments like this could go on forever but solve little or nothing.

I respectfully disagree - the universe as we know it probably has a
finite life span, which should eventually cut these threads short. ;-)

More seriously, sometimes some interesting things come out of them. And
I suspect even some of the people who go off and cherry pick supporting
data for untenable (or even tenable) positions are likely to grow a
glimmer of doubt. Doubt about one's own positions sometimes grows a bit
of humility, which I think is a good thing. (At least I hope it does -
sometimes I have my doubts about that....)

> Orchardists have used light aircraft, flying VERY low and slow with
> considerable flap, over their fields on frosty nights to drive warmer
> air from a few feet up down into the trees to try to prevent the
> fruit's freezing. It's debatable as to the overall effectiveness of
> the method. Cropsprayers also fly with the wheels practically in the
> crop so that the downwash drives the spray into the plants. In both
> cases, the flight is extremely low, so low that it's dangerous.
> Spraying from 20 feet up is far less effective. The downwash is
> already dissipated.

This is one of those interesting things I think comes out of these
threads. I came across research that has been done on using the downwash
of helicopters to clear fog. It appears that the downwash of most
helicopters is unable to clear fog more than about 1000 ft thick. Here's
a report (about 4 megabytes long):

http://www.dtic.mil/cgi-bin/GetTRDoc?AD=AD753357&Location=U2&doc=GetTRDoc.pdf

> So the argument could go on and on with neither side convinced, like
> it has on and off for the last ten years I've followed these groups,
> and the net result will be a handful of angry posters and and
> otherwise empty forum. Is that what we want?

I can only say in my defense as one of the contributors you probably
have in mind is that I wanted to insure that posters who pontificate
on the subject actually know the basic governing conservation laws
and take them all into account in their explanations.

> More seriously, sometimes some interesting things come out of them. And
> I suspect even some of the people who go off and cherry pick supporting
> data for untenable (or even tenable) positions are likely to grow a
> glimmer of doubt. Doubt about one's own positions sometimes grows a bit
> of humility, which I think is a good thing. (At least I hope it does -
> sometimes I have my doubts about that....)
luv it !

On Dec 12, 4:28 pm, Alan Baker > wrote:

> No. That is wrong. Friction changes where the *energy* the air had ends
> up, but momentum is conserved. When friction slows one object, it speeds
> up the object that was the source of the friction and momentum is
> conserved.
>
> Friction splits the momentum among more and more molecules in the air,
> but it cannot make it go away.

From Wiki:

The kinetic energy in the moving cyclist and the bicycle can be
converted to other forms. For example, the cyclist could encounter a
hill just high enough to coast up, so that the bicycle comes to a
complete halt at the top. The kinetic energy has now largely been
converted to gravitational potential energy that can be released by
freewheeling down the other side of the hill. (Since the bicycle lost
some of its energy to friction, it will never regain all of its speed
without further pedaling. Note that the energy is not destroyed; it
has only been converted to another form by friction.)

If air is disturbed by the wing, some of the kinetic energy it
acquires is converted to heat through friction. The heat comes at the
expense of lost momentum. It isn;t additional energy.

Dan

In article
>,
wrote:

> On Dec 12, 4:28 pm, Alan Baker > wrote:
>
> > No. That is wrong. Friction changes where the *energy* the air had ends
> > up, but momentum is conserved. When friction slows one object, it speeds
> > up the object that was the source of the friction and momentum is
> > conserved.
> >
> > Friction splits the momentum among more and more molecules in the air,
> > but it cannot make it go away.
>
> From Wiki:
>
> The kinetic energy in the moving cyclist and the bicycle can be
> converted to other forms. For example, the cyclist could encounter a
> hill just high enough to coast up, so that the bicycle comes to a
> complete halt at the top. The kinetic energy has now largely been
> converted to gravitational potential energy that can be released by
> freewheeling down the other side of the hill. (Since the bicycle lost
> some of its energy to friction, it will never regain all of its speed
> without further pedaling. Note that the energy is not destroyed; it
> has only been converted to another form by friction.)
>
> If air is disturbed by the wing, some of the kinetic energy it
> acquires is converted to heat through friction. The heat comes at the
> expense of lost momentum. It isn;t additional energy.
>
> Dan

No. Energy and momentum are not the same thing. And you're quite wrong.

Imagine two billiard balls: when they collide head on, almost no energy
is lost and the total momentum after collision is the same as it was
before.

Now, imagine two equal balls made of modeling clay: when they collide,
they stick together and a lot of energy becomes heat. In fact, half the
kinetic energy they had will be converted to heat.

But is any momentum lost? No. None. I know this sounds
counter-intuitive, but it is absolutely true.


If one of the ball both with mass b was doing speed x m/s before
collision and after collision they are stuck together, the new speed
will be x/2. Momentum before was 0 * b (for the still ball) + xb (for
the moving one) = xb and afterwards, it will be x/2 * 2b = xb.

Kinetic energy before was b/2 * 0 (for the still ball) + b/2 * x^2 (for
the moving one = (bx^2)/2

Afterwards, the kinetic energy will be 2b * (x/2)^2 = (2bx^2)/4 = (bx^)/2

This is very basic high school physics guys.

Momentum doesn't disappear due to friction. Kinetic energy does, but
momentum is conserved.

Always.

--
Alan Baker
Vancouver, British Columbia
<http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg>

It's all trolling noise, and, to my mind, began with an incorrect assertion
that one can not "pull" on air.



http://www.northsailsod.com/articles/article6-1.html

In article >,
cavelamb > wrote:

> It's all trolling noise, and, to my mind, began with an incorrect assertion
> that one can not "pull" on air.
>
>
>
> http://www.northsailsod.com/articles/article6-1.html

Air cannot pull on a surface. Any pressure at all means the air is
*pushing* on the surface.

That remains the reality, regardless of a website that uses less than
precise language.

--
Alan Baker
Vancouver, British Columbia
<http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg>

Alan Baker wrote:
> In article >,
> cavelamb > wrote:
>
>> It's all trolling noise, and, to my mind, began with an incorrect assertion
>> that one can not "pull" on air.
>>
>>
>>
>> http://www.northsailsod.com/articles/article6-1.html
>
> Air cannot pull on a surface. Any pressure at all means the air is
> *pushing* on the surface.
>
> That remains the reality, regardless of a website that uses less than
> precise language.
>

You didn't even look.

In article >,
cavelamb > wrote:

> Alan Baker wrote:
> > In article >,
> > cavelamb > wrote:
> >
> >> It's all trolling noise, and, to my mind, began with an incorrect assertion
> >> that one can not "pull" on air.
> >>
> >>
> >>
> >> http://www.northsailsod.com/articles/article6-1.html
> >
> > Air cannot pull on a surface. Any pressure at all means the air is
> > *pushing* on the surface.
> >
> > That remains the reality, regardless of a website that uses less than
> > precise language.
> >
>
> You didn't even look.

I did look, and I even read.

It shows a diagram of "pressure" with the arrows pointed *away* from
from the sail. Pressure doesn't act away from a surface.

--
Alan Baker
Vancouver, British Columbia
<http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg>

Alan Baker wrote:
> In article >,
> cavelamb > wrote:
>
>> Alan Baker wrote:
>>> In article >,
>>> cavelamb > wrote:
>>>
>>>> It's all trolling noise, and, to my mind, began with an incorrect assertion
>>>> that one can not "pull" on air.
>>>>
>>>>
>>>>
>>>> http://www.northsailsod.com/articles/article6-1.html
>>> Air cannot pull on a surface. Any pressure at all means the air is
>>> *pushing* on the surface.
>>>
>>> That remains the reality, regardless of a website that uses less than
>>> precise language.
>>>
>> You didn't even look.
>
> I did look, and I even read.
>
> It shows a diagram of "pressure" with the arrows pointed *away* from
> from the sail. Pressure doesn't act away from a surface.
>


Alan, It's ALL about suction.
It's just CALLED a blow-job.

In article >,
cavelamb > wrote:

> Alan Baker wrote:
> > In article >,
> > cavelamb > wrote:
> >
> >> Alan Baker wrote:
> >>> In article >,
> >>> cavelamb > wrote:
> >>>
> >>>> It's all trolling noise, and, to my mind, began with an incorrect
> >>>> assertion
> >>>> that one can not "pull" on air.
> >>>>
> >>>>
> >>>>
> >>>> http://www.northsailsod.com/articles/article6-1.html
> >>> Air cannot pull on a surface. Any pressure at all means the air is
> >>> *pushing* on the surface.
> >>>
> >>> That remains the reality, regardless of a website that uses less than
> >>> precise language.
> >>>
> >> You didn't even look.
> >
> > I did look, and I even read.
> >
> > It shows a diagram of "pressure" with the arrows pointed *away* from
> > from the sail. Pressure doesn't act away from a surface.
> >
>
>
> Alan, It's ALL about suction.

And suction is actually higher pressure pushing something towards a
region of lower pressure.

--
Alan Baker
Vancouver, British Columbia
<http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg>

(Since this was partially written a couple days ago, I decided to
complete it and post it anyway even though I'm sure some were hoping the
the discussion had died. :-))

Alan Baker > wrote:
> Jim Logajan > wrote:
>> To that question I say: "Nothing in the physics rules it out." The
>> math appears to allow a solution wherein the fluid moves such that
>> the *forces*, *momentum*, and *mass flows* are *all* conserved _long
>> before_ any downwash strikes the earth.
>
> Sorry, but you're wrong.

Tsk. Here's the math that shows there are solutions wherein momentum is
conserved yet yields zero average mass flow. It uses two conservation
laws (one of them being the first derivative of conservation of
momentum):

A toy helicopter is hanging from a line in a sealed room initially at
rest, and is released from the line and engine started at the same time
so it remains stationary. The law of conservation of mass requires that
the net flow of mass through the surface of any volume in an
incompressible fluid must be zero. For this problem the volume of the
room bounded by the walls above the plane made by helicopter blades and
said plane is used for one of the needed constraints.

The vertical forces through the plane made by the blades is described by
two areas: the area made by the blades (call it A1, in m^2) and the
remaining area of that same plane (call it A2, in m^2; the area from the
blade disk to the walls):

(1) F1 = M1d*V1
(2) F2 = M2d*V2

Where:
F1: Force of downwash through A1, in N. Positive number.
F2: Force of any upward flow through A2, in N. Positive number.
M1d: Average mass flow, in kg/s, of through A1. Positive number.
M2d: Average mass flow, in kg/s, of through A2. Positive number.
V1: Average velocity, in m/s, of flow through A1. Positive number.
V2: Average velocity, in m/s, of flow through A2. Positive number.

Since the chosen volume remains completely filled with fluid at all times
due to the constraints on it, its center of mass never moves, indicating
zero net force. The helicopter never moves either, so the force the
helicopter exerts on that volume, the force any upflow exerts on it, and
the force of gravity on the helicopter must all sum to zero:

(3) Fz - F1 + F2 = 0
Where:
Fz: Gravitational force, in N, on helicopter. Positive number.

Substituting (1) and (2) into (3):

(4) Fz - M1d*V1 + M2d*V2 = 0

(5) M1d - M2d = 0
{Conservation of mass; that is, the net flow of mass through the
surface of any volume in an incompressible fluid must be zero. So
the net flow into our chosen volume must be zero.}

Solving for V2 in terms of M1d, V1, and Fz (exercise left for the reader;
see also note [1])) yields:

(6) V2 = V1 - Fz/M1d {for F1 > Fz, i.e. V1 > Fz/M1d}

Now an example:

Given a downward gravity force of
Fz = 10 N
with a downwash of
V1 = 6 m/s
M1d = 2 kg/s
the equations yield the following average upward flow values:
V2 = 1 m/s
M2d = 2 kg/s

Plugging those back into equations (4) and (5) indicates they are valid
solutions. Forces balance and momentum is conserved. Mass flow is
conserved (no sinks, no sources.) So the SOLID PART part of the earth
DOES NOT have to move up to insure conservation of momentum because part
of the FLUID PART of the earth has already moved up and done that job.

[1] The M1d and M2d variables actually contain V1 and V2 respectively;
e.g. M1d = rho*A1*V1 where rho = density of the fluid in kg/m^3 and A1 =
area in m^2 that V1 is measured through.

> The only way to get momentum is to have mass in motion. That it is
> greater and greater mass as the system evolves means it is moving more
> and more slowly, but it is still moving until it can transfer its
> momentum to something else.

You've contradicted yourself. You are now saying there is a reduction in
velocity of the downwash. That can only happen if a force is acting
upward on it. That upward force, that you inadvertently overlook, would
be due to the air itself. It has inertia and transmits the pressure
exerted on it to the ground much as a solid object would - at the speed
of sound in that material.

Here's what really happens: the instant the blades started to move the
first tiny bit of fluid downward, conservation of mass in a fluid
required an equal tiny bit of mass of the fluid to flow upward. The fluid
flow starts as a tiny closed circular-like flow and grows into a large
circular-like flow. Whatever their shape and size, the flows form closed
circuits.

Meanwhile, the fluid masses that are forced to move cause pressure waves
to move out at the speed of sound (which is infinite in a perfectly
incompressible flow) and it is those pressure changes that will appear
elsewhere, such as the earth's surface. The earth accelerates upward
until the downward pressure balances the upward gravitational pull
yielding net zero force: in the idealized case of a perfectly
incompressible fluid, the instantaneous rise in pressure at the surface
yields a net force just balancing the pull of the aircraft's mass and the
earth doesn't move upward at all.

>> I can't adjust my thinking to your way of thinking until you explain
>> which directions the fluid is flowing in my hypothetical case to my
>> satisfaction.
>
> Your trying to obfuscate and I'm not buying it.

You obfuscate - I clarify: I've just presented a simplified mathematical
model (more than you've presented) and a better conceptual model for
incompressible flow as it relates to flight than yours.

You've already admitted ignorance of fluid mechanics when you said the
law of conservation of masses was only relevant to chemistry - so I
should really be charging you tuition.

> Net force up on plane: net force down on air.

That's correct.

> Net force down on air: net momentum down.

Transmitted at the speed of sound, not at the speed of the downwash.

> Net momentum down: net velocity down.

Transmitted at the speed of sound, not at the speed of the downwash.

In article >,
Jim Logajan > wrote:

> (Since this was partially written a couple days ago, I decided to
> complete it and post it anyway even though I'm sure some were hoping the
> the discussion had died. :-))
>
> Alan Baker > wrote:
> > Jim Logajan > wrote:
> >> To that question I say: "Nothing in the physics rules it out." The
> >> math appears to allow a solution wherein the fluid moves such that
> >> the *forces*, *momentum*, and *mass flows* are *all* conserved _long
> >> before_ any downwash strikes the earth.
> >
> > Sorry, but you're wrong.
>
> Tsk. Here's the math that shows there are solutions wherein momentum is
> conserved yet yields zero average mass flow. It uses two conservation
> laws (one of them being the first derivative of conservation of
> momentum):

Where to begin? There is so much nonsense in this post.

>
> A toy helicopter is hanging from a line in a sealed room initially at
> rest, and is released from the line and engine started at the same time
> so it remains stationary. The law of conservation of mass requires that
> the net flow of mass through the surface of any volume in an
> incompressible fluid must be zero. For this problem the volume of the
> room bounded by the walls above the plane made by helicopter blades and
> said plane is used for one of the needed constraints.

Well right off the bat, air is not an incompressible fluid.

>
> The vertical forces through the plane made by the blades is described by
> two areas: the area made by the blades (call it A1, in m^2) and the
> remaining area of that same plane (call it A2, in m^2; the area from the
> blade disk to the walls):
>
> (1) F1 = M1d*V1
> (2) F2 = M2d*V2
>
> Where:
> F1: Force of downwash through A1, in N. Positive number.
> F2: Force of any upward flow through A2, in N. Positive number.
> M1d: Average mass flow, in kg/s, of through A1. Positive number.
> M2d: Average mass flow, in kg/s, of through A2. Positive number.
> V1: Average velocity, in m/s, of flow through A1. Positive number.
> V2: Average velocity, in m/s, of flow through A2. Positive number.
>
> Since the chosen volume remains completely filled with fluid at all times
> due to the constraints on it, its center of mass never moves, indicating
> zero net force. The helicopter never moves either, so the force the
> helicopter exerts on that volume, the force any upflow exerts on it, and
> the force of gravity on the helicopter must all sum to zero:

The centre of mass of the notional volume never moves, no. The fluid
most definitely moves. You could say exactly the same thing about fluid
moving through a pipe. Would you claim that that fluid had no momementum?


>
> (3) Fz - F1 + F2 = 0
> Where:
> Fz: Gravitational force, in N, on helicopter. Positive number.
>
> Substituting (1) and (2) into (3):
>
> (4) Fz - M1d*V1 + M2d*V2 = 0
>
> (5) M1d - M2d = 0
> {Conservation of mass; that is, the net flow of mass through the
> surface of any volume in an incompressible fluid must be zero. So
> the net flow into our chosen volume must be zero.}
>
> Solving for V2 in terms of M1d, V1, and Fz (exercise left for the reader;
> see also note [1])) yields:
>
> (6) V2 = V1 - Fz/M1d {for F1 > Fz, i.e. V1 > Fz/M1d}
>
> Now an example:
>
> Given a downward gravity force of
> Fz = 10 N
> with a downwash of
> V1 = 6 m/s
> M1d = 2 kg/s
> the equations yield the following average upward flow values:
> V2 = 1 m/s
> M2d = 2 kg/s
>
> Plugging those back into equations (4) and (5) indicates they are valid
> solutions. Forces balance and momentum is conserved. Mass flow is
> conserved (no sinks, no sources.) So the SOLID PART part of the earth
> DOES NOT have to move up to insure conservation of momentum because part
> of the FLUID PART of the earth has already moved up and done that job.

I'm sorry, but you're wrong. Remove the atmosphere for a moment, the
force of gravity means that the helicopter exerts a force upward on the
earth equal to its own weight.

>
> [1] The M1d and M2d variables actually contain V1 and V2 respectively;
> e.g. M1d = rho*A1*V1 where rho = density of the fluid in kg/m^3 and A1 =
> area in m^2 that V1 is measured through.
>
> > The only way to get momentum is to have mass in motion. That it is
> > greater and greater mass as the system evolves means it is moving more
> > and more slowly, but it is still moving until it can transfer its
> > momentum to something else.
>
> You've contradicted yourself. You are now saying there is a reduction in
> velocity of the downwash. That can only happen if a force is acting
> upward on it. That upward force, that you inadvertently overlook, would
> be due to the air itself. It has inertia and transmits the pressure
> exerted on it to the ground much as a solid object would - at the speed
> of sound in that material.

There is a force acting upward on it as the flow of downward moving air
encounters air that is not yet moving. But the force interaction between
the moving air and the non-moving air ensures that the total momentum is
unchanged. IOW, more air moving more slowly.


>
> Here's what really happens: the instant the blades started to move the
> first tiny bit of fluid downward, conservation of mass in a fluid
> required an equal tiny bit of mass of the fluid to flow upward. The fluid
> flow starts as a tiny closed circular-like flow and grows into a large
> circular-like flow. Whatever their shape and size, the flows form closed
> circuits.

No. Your conservation law means that when a bit of fluid exits a volume,
an equal amount must enter (we'll ignore for the moment that the law
actually only applies to incompressible fluids), it says nothing about
it having to be traveling in the opposite direction to that which exits.

>
> Meanwhile, the fluid masses that are forced to move cause pressure waves
> to move out at the speed of sound (which is infinite in a perfectly
> incompressible flow)

Which, of course, air is not.

> and it is those pressure changes that will appear
> elsewhere, such as the earth's surface. The earth accelerates upward
> until the downward pressure balances the upward gravitational pull
> yielding net zero force: in the idealized case of a perfectly
> incompressible fluid, the instantaneous rise in pressure at the surface
> yields a net force just balancing the pull of the aircraft's mass and the
> earth doesn't move upward at all.

Waves cannot carry momentum continuously.

>
> >> I can't adjust my thinking to your way of thinking until you explain
> >> which directions the fluid is flowing in my hypothetical case to my
> >> satisfaction.
> >
> > Your trying to obfuscate and I'm not buying it.
>
> You obfuscate - I clarify: I've just presented a simplified mathematical
> model (more than you've presented) and a better conceptual model for
> incompressible flow as it relates to flight than yours.
>
> You've already admitted ignorance of fluid mechanics when you said the
> law of conservation of masses was only relevant to chemistry - so I
> should really be charging you tuition.
>
> > Net force up on plane: net force down on air.
>
> That's correct.
>
> > Net force down on air: net momentum down.
>
> Transmitted at the speed of sound, not at the speed of the downwash.

Find me a single reference that agrees with you...

>
> > Net momentum down: net velocity down.
>
> Transmitted at the speed of sound, not at the speed of the downwash.

Complete and utter nonsense.

--
Alan Baker
Vancouver, British Columbia
<http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg>

Alan Baker > wrote:
> Jim Logajan > wrote:
>> Alan Baker > wrote:
>> > Net force down on air: net momentum down.
>> Transmitted at the speed of sound, not at the speed of the downwash.
> Find me a single reference that agrees with you...

Since we have made differing claims that are actually testable by simple
experiments, why not use them to determine the real truth? Nothing else
would be as definitive at resolving the claims than an experiment simple
enough that anyone could run independently, so anyone having any doubts is
not slaved to trust the claims of others. The methodology would also be
open to independent analysis and critique. I.E. we use good old scientific
method.

I can think of a possible experiment that uses a large box (cardboard may
suffice) hanging from a ceiling from four vertical strings (or wires or
ropes) so that it can swing back and forth with two opposite ends that can
be opened and closed.

A small fan can be taped in place inside the center of the box and some
tests run - first with the ends opened (to measure the thrust of the fan
using some simple trig on displacement and known weight of the fan+box, and
thence compute the average wind speed of the fan) and then with the ends
closed. Based on how much the closed box swings when the fan is turned on,
one should be able to determine which of our theories is correct.

If your claim is correct, the box will swing more than what my claim
predicts (because the wind from the fan travels slower than the speed of
sound, so if you are correct the fan would push the box farther along in
its swing before the force of that wind hits the interior wall of the box.)
The approximate amount of swing (which could be recorded several simple
ways) should be predictable for both our theories based on several factors
that should be measurable using common equipment like a ruler and weight
scale (though a bathroom scale might not be precise enough to measure the
box+fan weight, though such scales are fairly common.)

So if you think the above is reasonable, or you need more insight into what
I am proposing before you commit, I am willing to flesh out the proposed
experiment in more detail.

In article >,
Jim Logajan > wrote:

> Alan Baker > wrote:
> > Jim Logajan > wrote:
> >> Alan Baker > wrote:
> >> > Net force down on air: net momentum down.
> >> Transmitted at the speed of sound, not at the speed of the downwash.
> > Find me a single reference that agrees with you...
>
> Since we have made differing claims that are actually testable by simple
> experiments, why not use them to determine the real truth? Nothing else
> would be as definitive at resolving the claims than an experiment simple
> enough that anyone could run independently, so anyone having any doubts is
> not slaved to trust the claims of others. The methodology would also be
> open to independent analysis and critique. I.E. we use good old scientific
> method.

It seems to me you're making a tacit admission that you can find no
supporting reference, and I note also that you've snipped by factual
refutations of your earlier "theory" about how air moves.

Why is this such a problem for you?

A fan on a table moves air, doesn't it? You can feel a column of moving
air coming from it, right?

Well once that air is moving it has momentum and all you can do with
that momentum is transfer it to something else.

If the air slows down as it move further away from the fan, it can't be
because the momentum just disappears. Momentum is always conserved.
ALWAYS. Therefore, if the air is moving more slowly, more air -- more
mass -- must be moving.

Period.

<snipped deflection by proposed "experiment">

--
Alan Baker
Vancouver, British Columbia
<http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg>