Re: End Plate Effect
You fill your pocket with nickels, and the weight of the nickels tears a hole in the bottom and the nickels start leaking out.
An end plate plugs the leak, so the nickels stay in your pocket. And the "fluid" (air or water) stays on the airfoil, instead of falling off the end.
You see them on aircraft wings these days too, they call them "winglets", the small vertical plate on the end of the wing. Same thing, keeps the nickels from rolling off.