Originally Posted by Chesty Morgan
Regarding the infinite aerofoil. Again I'm only guessing. Wake vortex is essentially caused by the span wise flow of air along the wing, due to the high and low pressure areas. If you take the infinite aerofoil, theoretically there would be no span wise flow and therefore no induced drag and wake vortex. Lots of profile drag though! Is that correct or am I completely rudderless now?!
Look forward to hearing the answer!
I doubt whether an infinite airfoil wouldn´t have induced drag. After all, it can either be unloaded - just profile drag, pressures equal on both sides, no lift, no vortex sheet, just profile drag - or loaded at a nonzero angle of attack, in which case it would generate lift all along the airfoil, and have some extra, induced drag in addition to the profile drag.
An infinite airfoil in a slipping or oblique airflow ought to have spanwise flow, but no wake vortex, as the high pressure should be uniform over the airfoil length...