Comment by somat

I did not say reflector as implied by that link but deflector, a thing put in the fluidstream to move it somewhere else. airplanes lift because you are moving air down. People get hung up about the convex side of the airfoil but what else is the fluid going to do, stay a vacuum? it is going to move in the way the deflector shaped, adding to(actually providing most of) the downward flow. There is a lot of engineering that goes into it but at the end of the day an airfoil is the shape that moves enough enough air downward with the least drag. The only reason it is a thick teardrop shape is it has to be strong enough to support itself and the airplane. otherwise the ideal shape would be super thin shaped like the upper surface of the wing bending slightly from the cord(aspect directly into the stream) to the trailing edge(a few degrees of slope).