I was looking at the great site code7700.com, but I don't really understand their explanation of lift and drag. Actually I think they are wrong, and I ask here for confirmation.
This is what they describe as a wing with no induced drag:
The so-called infinite wing displaces air for a while, but the air particles return to their original positions along the relative wind. The relative wind experience up wash as it approaches the airfoil and down wash as it leaves the airfoil. But the up wash and down wash are equal so the net effect is cancelled. Because of this, the aerodynamic force occurs perpendicular to the relative wind and their is no induced drag. In other words, all of the aerodynamic force is producing lift, none of it is pulling the wing backwards.
In this description the airstreams return to there initial height after the wing has passed, but lift is created. It seems this is a big confusion. Afaik, the origin of lift is the reaction to the downwash; lift is created because air is deflected by the wing (so in this case AF should be null).
Could someone just confirm that lift is created solely by the downwash and Newton's 3rd law? (Why air is deflected is not part of the question.)
Newton's Laws on Wikipedia.