Backwash Causes Lift?

flightoffancy wrote in
:

In article ,
says...
The downwash thing is wrong. Yes, there is some dispacemtn of air that
causes lift, but it' only a minor contribution in the bigger scheme of
things.



I admit to being a relative retard on this issue (not as retarded as a
non-pilot probably is, but not as educated as an aeronautical engineer).

I thought I had read in numerous books during training that the primary
component of lift is the air that gets knocked downward by the wing. I
was calling that "downwash". Maybe my concept of downwash is wrong,
maybe it's a separate consideration from the air that gets knocked
downward by the airfoil. Hell I might not be remembering any of that
correctly.

Anyway you say downwash is minor.

Well okay. But then what are the major contributions that cause lift in
the bigger scheme of things?


Bernoulli, Period, Full stop, end of story, finito, spaghettio, Finis
sayonara, Good lucko,



Bertie

Mxsmanic wrote in
:

Bertie the Bunyip writes:

Actually, yes it is.

Show me an aircraft that does this.


Does what?
Makes a period?

Bertie

Mxsmanic wrote in
:

Le Chaud Lapin writes:

If that is the case, what is pushing the air?

You may be able to get past this by considering that the airfoil
actually turns the flow, rather than push or pull it. It turns the
flow downwards, and this acceleration of the air mass engenders an
upward force that is lift.


Mmm, nope.

Bertie

Mxsmanic wrote in
:

Le Chaud Lapin writes:

The airfoil turns the flow downward....

What air gets turn downward....the air on top of the wing or the air
on the bottom of wing?

Both, but mostly air from above the wing (a great deal of air, in fact).


Nope


Bertie

Le Chaud Lapin wrote:
"the molecules stay in contact with the solid body"...?????????????

Why?

It's what gases do. The particles are constantly bouncing away from each
other. This is pretty simple physics - something that should almost be
intuitive. If you have a cylinder of gas with an air-tight piston and pull
back on the piston and double the size of the volume do you seriously think
the gas will not expand into the other half as fast as it can to try and
stay in contact with the piston?

If you are having this much trouble on a basic concept of gases, then I see
no value in you or anyone else investing time in dealing with your
questions, which you chose to post to an inappropriate newsgroup anyway.

Grumble. Now I recall why I had established a personal policy to stay away
from discussions of aerodynamics on this newsgroup: futility avoidance.

flightoffancy wrote in
:

In article ,
says...
flightoffancy wrote:

http://www.grc.nasa.gov/WWW/K-12/airplane/lift1.html

And if you click on "turning" you can see this explanation of the
term (and hopefully why "turning" was chosen):

http://www.grc.nasa.gov/WWW/K-12/airplane/right2.html

And this is what aerodynamicists call "downwash" :

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


Thanks James!

As LCL does I appreciate these links. If even NASA has it wrong, then
I'd say the chance that anybody on this thread having it right is
close to nil.


Nasa on't have it wrong, but that site is far from complete.


Bertie

Matt Whiting wrote in news:lRdOi.234$2n4.16576
@news1.epix.net:

Bertie the Bunyip wrote:
flightoffancy wrote in
news:MPG.2172e043702d7a5d989681
@news-server.hot.rr.com:

In article ,
says...

"Nope, wrong" to which claims I made?

I freely admit that my knowledge of aerodynamics is lacking. But I'm
absolutely correct about Lapin's training (or utter lack thereof, in
this case).

It's completely absurd for someone who has not studied aeronautical
engineering to stand up on a soap box and announce that the work of
several generations of aeronautical engineers is WRONG -- and that
he's
leading the charge to finding out what the facts of aerodynamics
really
are.

Lapin does this kind of thing on countless other news groups,
especially
computer science groups. He denounces decades worth of work as
inadequate or completely wrong, claims he has the right answer or
merely
wishes to find the right answer, with the result that nearly
everyone
on
the group calls him a crank. Anyone who is really an expert in the
area
he's challenging quickly figures out his meager explorations of the
subject are not worth spending any time participating in.

Lapin believes that he is here to TEACH us.

If you can find hundreds of threads started by LCL on Google groups.
He's an incorrigible usenet troll.




The downwash thing is wrong. Yes, there is some dispacemtn of air
that
causes lift, but it' only a minor contribution in the bigger scheme
of
things.

Bertie

And what about a hovering helicopter? What is holding it up?

Air?

Bertie

Matt

How does a gyrocopter fly because the airflow over it's "wing" is going up.

"Gig 601XL Builder" wrDOTgiaconaATsuddenlink.net wrote in
:

How does a gyrocopter fly because the airflow over it's "wing" is
going up.




They're gliders. The same rules apply.


Bertie

On Oct 7, 7:10 pm, Le Chaud Lapin wrote:
On Oct 7, 5:54 pm, flightoffancy wrote:





In article ,
says...

The downwash thing is wrong. Yes, there is some dispacemtn of air that
causes lift, but it' only a minor contribution in the bigger scheme of
things.

I admit to being a relative retard on this issue (not as retarded as a
non-pilot probably is, but not as educated as an aeronautical engineer).

I thought I had read in numerous books during training that the primary
component of lift is the air that gets knocked downward by the wing. I
was calling that "downwash". Maybe my concept of downwash is wrong,
maybe it's a separate consideration from the air that gets knocked
downward by the airfoil. Hell I might not be remembering any of that
correctly.

Just wanted to reiterate what I said in my OP and each subsequent post
for you benefit since you just joined the discussion.

If you have an aifoil, and you move it forward, there will be
compression beneath the wing. Newton's law will be at play here, and
there will be downwash. This downwash results from the induced
pressure gradient.

That is not what I was talking about. The books that I have been
reading are talking about downwash that is _on top of_ the wing. The
pictures show air moving at an angle, backward and downward near the
trailing edge of the wing.

Note that these are two "downwashes".

I am saying that downwash on top of the wing does not generate a force
on the wing that causes the wing to move upward.

Anyway you say downwash is minor.

Well okay. But then what are the major contributions that cause lift in
the bigger scheme of things?

-Le Chaud Lapin-- Hide quoted text -

- Show quoted text -

If the airflow on top of the wing doesn't contribute to lift, then how
can we explain the phenomenon of the wing stalling? When the wing
stalls, it is the airflow over the top of the wing that detaches from
the curve of the wing and becomes turbulent. This causes a radical
loss of lift. To me, this indicates that the airflow over the top of
the wing plays an essential role in providing lift.

I know the Bernoulli effect has been invoked historically to (at least
partially) explain the lift produced by the top surface of a wing. I
think another way to look at it is the Coanda effect (
http://en.wikipedia.org/wiki/Coand%C4%83_effect ). The airflow tends
to follow the curve of the top of the wing, and is displaced
downward. As long as the air flow follows the curve faithfully, you
have good lift. When the airflow detaches in a stall, you lose most
of your lift. This top surface lift is combined with the downward
displacement of air by the bottom of the wing. The wing is
essentially throwing air downward using both the top and bottom
surfaces. This is why a curved wing is a better lift producer than a
simple flat wing. The top surface curve helps contribute to the lift.

Now, how does the wing feel the lift? It feels high pressure on its
bottom surface, and it feels low pressure on its upper surface. It is
pushed up from below, and sucked up from above. That is how the
airplane experiences the effects of the downward displacement of air.

Phil