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