visualisation of the lift distribution over a wing

In article ,
Jim Logajan wrote:

Alan Baker wrote:
In article ,
Beryl wrote:

Alan Baker wrote:

It's like the downwash argument. You can say "IT DOESN'T MATTER",
when people argue that the air behind an aircraft is not deflected
downward, but it *does* matter. Having an accurate understanding of
the physical processes of flight matters.

It isn't really deflected downward, not for long anyway. It's
churning in a torus. Like a smoke ring.

No.

It really *is* deflected downward.

It's also deflected upward. ;-)

Here's why:
Because the airplane and the Earth have zero relative vertical velocity
during straight and level flight, conservation of momentum requires the
net vertical flow of air to also be zero.

Therefore in subsonic flows where the fluid is assumed incompressible, to
the extent any fluid is moving downward, conservation of mass requires an
equal amount of mass must be moving upward (the continuity requirement.)

Hence airplanes must cause air to move in circles.

Nope. Wrong.

The aircraft is experience an force upward the entire time it is in
flight. That force means there must be an equal force acting on the air,
and since the air was not moving vertically (in our idealized case for
this discussion) before the aircraft arrived, the force exerted on it
must mean that it is moving downward afterward it has passed.


The edges of the deflected area churn, and the air that is deflected
ends up getting diffused among all the other air below *it*, but it
really is deflected downward.

Yes some deflection downward occurs. But I don't know that it could be
said to "diffuse" in any sense due to conservation of mass and momentum
requirements.

As the air the plane has forced downward encounters more air, the
momentum is diffused so that a greater and greater mass of air moves
downward at smaller and smaller velocities (net)...

....until it encounters the ground.


And eventually, that downward deflection makes it way until it -- very
diffusely -- impacts upon the surface of the earth. That is the only
thing that finally stops it.

That assertion is not true in general. What appears to happen instead is
that any downward deflection is quickly reversed, leading to what is
known as a shed vortex. Here are some links on the subject:

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

Sorry, but the vortex is an edge effect. The net flow is downward.

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

While the deflected flow doesn't need to reach the surface of the earth
for the airplane to stay aloft, an increase in air _pressure_ would
eventually make its way to the surface.

--
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:
It's like the downwash argument. You can say "IT DOESN'T MATTER", when
people argue that the air behind an aircraft is not deflected downward,
but it *does* matter. Having an accurate understanding of the physical
processes of flight matters.
It isn't really deflected downward, not for long anyway. It's churning
in a torus. Like a smoke ring.
No.

It really *is* deflected downward.


The edges of the deflected area churn, and the air that is deflected
ends up getting diffused among all the other air below *it*, but it
really is deflected downward.

And eventually, that downward deflection makes it way until it -- very
diffusely -- impacts upon the surface of the earth. That is the only
thing that finally stops it.
After more than 100 years of flight, the atmosphere still hasn't been
pushed down to the earth's surface.

Sorry, Beryl, but you're just wrong.

As I said, the atmosphere isn't getting any shorter. Do you disagree
with that?
Repeating that "the net flow is downward" isn't making progress.

Alan Baker wrote:
...

As the air the plane has forced downward encounters more air, the
momentum is diffused so that a greater and greater mass of air moves
downward at smaller and smaller velocities (net)...

...until it encounters the ground.

Yikes! Eventually, ALL of the air will be on the ground!

And eventually, that downward deflection makes it way until it -- very
diffusely -- impacts upon the surface of the earth. That is the only
thing that finally stops it.
That assertion is not true in general. What appears to happen instead is
that any downward deflection is quickly reversed, leading to what is
known as a shed vortex. Here are some links on the subject:

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

Sorry, but the vortex is an edge effect. The net flow is downward.

Mankind needs to set up fans IMMEDIATELY to move air back up into the sky!

In article ,
Beryl wrote:

Alan Baker wrote:
In article ,
Beryl wrote:

Alan Baker wrote:
In article ,
Beryl wrote:

Alan Baker wrote:
It's like the downwash argument. You can say "IT DOESN'T MATTER", when
people argue that the air behind an aircraft is not deflected downward,
but it *does* matter. Having an accurate understanding of the physical
processes of flight matters.
It isn't really deflected downward, not for long anyway. It's churning
in a torus. Like a smoke ring.
No.

It really *is* deflected downward.


The edges of the deflected area churn, and the air that is deflected
ends up getting diffused among all the other air below *it*, but it
really is deflected downward.

And eventually, that downward deflection makes it way until it -- very
diffusely -- impacts upon the surface of the earth. That is the only
thing that finally stops it.
After more than 100 years of flight, the atmosphere still hasn't been
pushed down to the earth's surface.

Sorry, Beryl, but you're just wrong.

As I said, the atmosphere isn't getting any shorter. Do you disagree
with that?
Repeating that "the net flow is downward" isn't making progress.

The net flow is downward until it hits the ground and the momentum is
transfer to the earth.

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

Alan Baker wrote:
Beryl wrote:
Alan Baker wrote:
Beryl wrote:
Alan Baker wrote:
Beryl wrote:
Alan Baker wrote:

It's like the downwash argument. You can say "IT DOESN'T
MATTER", when people argue that the air behind an
aircraft is not deflected downward, but it *does* matter.
Having an accurate understanding of the physical
processes of flight matters.
It isn't really deflected downward, not for long anyway.
It's churning in a torus. Like a smoke ring.

No.

It really *is* deflected downward.

The edges of the deflected area churn, and the air that is
deflected ends up getting diffused among all the other air
below *it*, but it really is deflected downward.

And eventually, that downward deflection makes it way until
it -- very diffusely -- impacts upon the surface of the
earth. That is the only thing that finally stops it.

After more than 100 years of flight, the atmosphere still
hasn't been pushed down to the earth's surface.

Sorry, Beryl, but you're just wrong.

As I said, the atmosphere isn't getting any shorter. Do you
disagree with that? Repeating that "the net flow is downward" isn't
making progress.

The net flow is downward until it hits the ground and the momentum is
transfer to the earth.

Has to be an equal upward flow. Somewhere. Where?

Imagine riding in a C-130 Hercules. You're flying an RC model airplane
in the cabin! (That's why I picked a C-130)
The model's weight is applied to the cabin floor, of course, but the
"downwash" from the model's wing doesn't pile up on the floor.

http://www.efluids.com/efluids/galle...s/Morris_4.jsp
The column of downward flow in the center doesn't really flow down so
far, does it?

In article ,
Beryl wrote:

Alan Baker wrote:
Beryl wrote:
Alan Baker wrote:
Beryl wrote:
Alan Baker wrote:
Beryl wrote:
Alan Baker wrote:

It's like the downwash argument. You can say "IT DOESN'T
MATTER", when people argue that the air behind an
aircraft is not deflected downward, but it *does* matter.
Having an accurate understanding of the physical
processes of flight matters.
It isn't really deflected downward, not for long anyway.
It's churning in a torus. Like a smoke ring.

No.

It really *is* deflected downward.

The edges of the deflected area churn, and the air that is
deflected ends up getting diffused among all the other air
below *it*, but it really is deflected downward.

And eventually, that downward deflection makes it way until
it -- very diffusely -- impacts upon the surface of the
earth. That is the only thing that finally stops it.

After more than 100 years of flight, the atmosphere still
hasn't been pushed down to the earth's surface.

Sorry, Beryl, but you're just wrong.

As I said, the atmosphere isn't getting any shorter. Do you
disagree with that? Repeating that "the net flow is downward" isn't
making progress.

The net flow is downward until it hits the ground and the momentum is
transfer to the earth.

Has to be an equal upward flow. Somewhere. Where?

Imagine riding in a C-130 Hercules. You're flying an RC model airplane
in the cabin! (That's why I picked a C-130)
The model's weight is applied to the cabin floor, of course, but the
"downwash" from the model's wing doesn't pile up on the floor.

http://www.efluids.com/efluids/galle...s/Morris_4.jsp
The column of downward flow in the center doesn't really flow down so
far, does it?

Yes, it does.

All the way to the ground.

Spread out among lots and lots of air, but that's where the momentum
*has* to go.

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

Alan Baker wrote:
In article ,
Beryl wrote:

Alan Baker wrote:
Beryl wrote:
Alan Baker wrote:
Beryl wrote:
Alan Baker wrote:
Beryl wrote:
Alan Baker wrote:
It's like the downwash argument. You can say "IT DOESN'T
MATTER", when people argue that the air behind an
aircraft is not deflected downward, but it *does* matter.
Having an accurate understanding of the physical
processes of flight matters.
It isn't really deflected downward, not for long anyway.
It's churning in a torus. Like a smoke ring.
No.

It really *is* deflected downward.

The edges of the deflected area churn, and the air that is
deflected ends up getting diffused among all the other air
below *it*, but it really is deflected downward.

And eventually, that downward deflection makes it way until
it -- very diffusely -- impacts upon the surface of the
earth. That is the only thing that finally stops it.

After more than 100 years of flight, the atmosphere still
hasn't been pushed down to the earth's surface.

Sorry, Beryl, but you're just wrong.

As I said, the atmosphere isn't getting any shorter. Do you
disagree with that? Repeating that "the net flow is downward" isn't
making progress.
The net flow is downward until it hits the ground and the momentum is
transfer to the earth.
Has to be an equal upward flow. Somewhere. Where?

Imagine riding in a C-130 Hercules. You're flying an RC model airplane
in the cabin! (That's why I picked a C-130)
The model's weight is applied to the cabin floor, of course, but the
"downwash" from the model's wing doesn't pile up on the floor.

http://www.efluids.com/efluids/galle...s/Morris_4.jsp
The column of downward flow in the center doesn't really flow down so
far, does it?

Yes, it does.

All the way to the ground.

Spread out among lots and lots of air, but that's where the momentum
*has* to go.

Say where the _air_ has to go.

Beryl wrote:
Alan Baker wrote:
In article ,
Beryl wrote:

Alan Baker wrote:
Beryl wrote:
Alan Baker wrote:
Beryl wrote:
Alan Baker wrote:
Beryl wrote:
Alan Baker wrote:
It's like the downwash argument. You can say "IT DOESN'T
MATTER", when people argue that the air behind an
aircraft is not deflected downward, but it *does* matter.
Having an accurate understanding of the physical processes of
flight matters.
It isn't really deflected downward, not for long anyway.
It's churning in a torus. Like a smoke ring.
No.

It really *is* deflected downward.

The edges of the deflected area churn, and the air that is
deflected ends up getting diffused among all the other air
below *it*, but it really is deflected downward.

And eventually, that downward deflection makes it way until
it -- very diffusely -- impacts upon the surface of the
earth. That is the only thing that finally stops it.

After more than 100 years of flight, the atmosphere still
hasn't been pushed down to the earth's surface.

Sorry, Beryl, but you're just wrong.

As I said, the atmosphere isn't getting any shorter. Do you
disagree with that? Repeating that "the net flow is downward" isn't
making progress.
The net flow is downward until it hits the ground and the momentum is
transfer to the earth.
Has to be an equal upward flow. Somewhere. Where?

Imagine riding in a C-130 Hercules. You're flying an RC model
airplane in the cabin! (That's why I picked a C-130)
The model's weight is applied to the cabin floor, of course, but the
"downwash" from the model's wing doesn't pile up on the floor.

http://www.efluids.com/efluids/galle...s/Morris_4.jsp
The column of downward flow in the center doesn't really flow down so
far, does it?

Yes, it does.

All the way to the ground.
Spread out among lots and lots of air, but that's where the momentum
*has* to go.

Say where the _air_ has to go.


Please!

I think maybe we are talking about very different things.

I'm talking flow.

In article ,
Beryl wrote:

Alan Baker wrote:
In article ,
Beryl wrote:

Alan Baker wrote:
Beryl wrote:
Alan Baker wrote:
Beryl wrote:
Alan Baker wrote:
Beryl wrote:
Alan Baker wrote:
It's like the downwash argument. You can say "IT DOESN'T
MATTER", when people argue that the air behind an
aircraft is not deflected downward, but it *does* matter.
Having an accurate understanding of the physical
processes of flight matters.
It isn't really deflected downward, not for long anyway.
It's churning in a torus. Like a smoke ring.
No.

It really *is* deflected downward.

The edges of the deflected area churn, and the air that is
deflected ends up getting diffused among all the other air
below *it*, but it really is deflected downward.

And eventually, that downward deflection makes it way until
it -- very diffusely -- impacts upon the surface of the
earth. That is the only thing that finally stops it.

After more than 100 years of flight, the atmosphere still
hasn't been pushed down to the earth's surface.

Sorry, Beryl, but you're just wrong.

As I said, the atmosphere isn't getting any shorter. Do you
disagree with that? Repeating that "the net flow is downward" isn't
making progress.
The net flow is downward until it hits the ground and the momentum is
transfer to the earth.
Has to be an equal upward flow. Somewhere. Where?

Imagine riding in a C-130 Hercules. You're flying an RC model airplane
in the cabin! (That's why I picked a C-130)
The model's weight is applied to the cabin floor, of course, but the
"downwash" from the model's wing doesn't pile up on the floor.

http://www.efluids.com/efluids/galle...s/Morris_4.jsp
The column of downward flow in the center doesn't really flow down so
far, does it?

Yes, it does.

All the way to the ground.

Spread out among lots and lots of air, but that's where the momentum
*has* to go.

Say where the _air_ has to go.

The aircraft starts the air moving downward. Net downward momentum.

The ground stops that net downward motion.

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

On second thought, no, I don't want to get sucked back into this troll.