I sent this thread to a team 237 Mentor who is a Aeronautical Engineer by Degree, and this is what he sent me back.
It's a doozy.
Quote:
OK, so you have a lot of people not understanding the question or the answer and inferring too many of their own thoughts and experiences into it.
Because the question does not say specifically whether the plane's speed (that the conveyor is matching) is relative to the ground or to the air, you could argue both sides.
I believe the intent of the question is to imply that the plane never makes ground speed because the conveyor inhibits it. If this is the case, the plane will not fly since it sees no air movement over the wings (think of a glider being towed on the same conveyor- it cannot create air movement over
the wings as the conveyor matches the forward speed of the towing vehicle).
To further muddy the waters: Add Boundary Layer theory to the
equation.....
The speed of the air that the conveyor sees at it's intersection with
the air (basically the surface of the treadmill) is different than the
speed of the air the plane's wing sees (a few feet off the ground). This is
because relative air speed is slower the closer you get to the ground. If taken
to the extreme, there is no air movement at the physical intersection of
the ground and air regardless of the wind speed measured any distance away
from the surface, mainly due to frictional forces.
Now pull that friction into the equation..........
The frictional forces (acting on the air from the surface of the treadmill) will eventually begin to create air movement in the boundary layer. The boundary between still air and moving air will be higher off the surface of the treadmill as it's speed increases until eventually the plane's wing experiences air movement. Again taken to the extreme, once the air movement (call it wind) created by the friction between the conveyor & air, reaches the speed at which the wing will create enough lift, the plane will "hover" over the treadmill.
Of course, once the wheels are not in contact with the treadmill won't
the treadmill stop? Which begs the question: Does the Plane then
immediately fall to the ground and the treadmill start again?
I'll leave the theory of lift to another day (but I did see some discussion of it in the thread you showed me). I can only point out that "lift" is a misnomer. Wings do not lift a plane off the ground. They cause a condition ("adverse pressure gradient") where they are sucked off the ground.
Therefore, in future posts all references to "lift" should be changed to "suck".
Just kidding. Now you know why I don't post on CD or our forum. I tend to ramble.
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Sorry about the bad formatting of the text. I tried to fix it up as much as possible.
Elgin