Thanks Fred.

 

This is a very good diagram to explain several personal observations and confirm a very interesting physicist's lecture on wings and lift.  I watched with fascination, a 172 at high idle on the ramp after a rain and where the surface had dried while there was still water in the pavement cracks, the formation of water tornados (sprites?) aft of the prop and moving forward into it in spite of the prop wash.  Indeed, it was strongly obtaining flow from "below the wing", tip vortices notwithstanding.  A friend drew a metal plate on the ground, aft of his prop, into the blade(s), wrecking the prop and scaring the #$$#^%$^ out of us observing as the pieces were flying out in the plane of the prop disk. When someone is starting their engine I am more observant about the ground around the prop and where I am standing.

 

BTW, The physicist mentioned above had a "deer in the headlights" look when I mentioned reflexed wings - like those on our wee Lancairs.