Jose wrote:
You can also generate an upward force on an airplane by
creating low pressure over the upper surface of the wing while
the pressure below the wing remains at ambient. I dunno if
there are any airfoils that leave the air below the wing exactly
the same as ambient, but if there were, it would fly. There is
no NEED to throw anything downward.

I suppose a wing that gobbled up air molecules from the top of the wing
and beamed them into outer space would do the trick.

Or blew them out the rear for thrust.

Another way would
be to supercool the top surface, and let the general gas law reduce the
pressure above. But doing either one, air above the air above the wing
would rush down, as the air below the wing pushes the wing up into that
same space. The two will collide, or the wing will have passed by then.
In the latter case, downward momentum has been imparted to the air
above the air above the wing, which gets dissipated as I argued for
conventional wings.


Yes and that is what a conventional wing does. It creates lower
pressure above the wing so that the ambient or near ambient
pressure below the wing pushes up on the wing creating lift.

The air from above that low pressure region begins moving down
into that region but doesn't get there until after the wing has
passed. Downwash occurs, as you describe in the paragraph
above. It is a consequence of lift, not the cause. In fact the
energy put into the air by the downwash phenomenum is wasted.
A more efficient wing will produce less downwash than a less efficient
one, for the same lift.

--

FF

not the cause.

Jose
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