xerj wrote:

I can understand why a spinning ball would create a circular flow around
itself, but I can't really grasp why a wing would.

There's nothing to grasp, because there is no circular flow.

However, there is the fact that the air flows faster on the upper side
of the wing than below, and it flows even so much faster that it arrives
earlier at the trailing end of the wing. Mathematically, really only
mathematically, this can be described by the overlay of two independant
flows, a straight one and a circular one. But this is strictly a
mathematical model, there really is no circular flow.

I think this "circular flow" thing is a good example of a inadequate
explanation to laypersons. It's a mathematical method and doesn't help
the least bit for a layperson to understand what's going on. It simply
shouldn't appear in basic, purely qualitative explanations.

Stefan