Why can't a nozzle that is already in relative motion to the air produce thrust by speeding up the air that passes through inside it?
So let's pretend you're in a glider with two converging nozzles (without fans or burning fuel), one attached to each wing. Shouldn't the air passing through speed up due to continuity, and provide a forward force on the plane?
Obviously this does not work in real life so I would like to know why. Is it because the bottom an top surfaces essentially function as a diffuser, which slow the air around?