Rotating Surfaces

Given what we know so far about wings and lift, it seems logical that a simple cylinder would not produce any lift when immersed in a moving fluid (imagine a plane with wings shaped like cardboard paper-towel tubes). In a simplified world, the air would just flow around the cylinder evenly on both sides, and keep right on going. In reality, the downstream air would be a little turbulent and chaotic, but there still would be no lift created.

However, if we were to begin rotating the cylinder, as in the figure below, the surface of the cylinder would actually drag the surrounding layer of air around with it. The net result would be a pressure difference between the top and bottom surfaces, which deflects the airflow downward. Newton's Third Law states that if the air is being redirected downward, the cylinder must be deflected upward (sounds like lift to me!). This is an example of the Magnus Effect (also known as the Robbins Effect), which holds true for rotating spheres as well as cylinders (see any similarities to curveballs here?)

Believe it or not, in 1926, Anton Flettner built a ship named the Bruckau that used huge spinning cylinders instead of sails to power itself across the ocean.  Learn more about Flettner's Rotorship.