Here is my dilemma. I have seen a lot of videos of airfoils in wind tunnels, and I've noticed how the airflow always moves away from the trailing edge parallel to the wing, or at a very small angle away from the wing (link to one of those videos). I've also heard that propellers are nothing more than rotating wings (airfoils), producing lift sideways as opposed to upwards. What confuses me is that in the case of the propeller, the airflow leaves the propeller at a much higher angle, and not straight as is with the wing. In other words, the airflow is deflected backwards from the prop. I just can't understand how the wing and propeller, which are two very similar shapes (maybe not that similar, but they operate by the same principle), deflect air in two radically different directions.
I have a few thoughts non why this happens, but I think it's better if someone tells my first.
Thank you very much!