Lift is caused by wind moving at different speeds around the wing. Faster moving air has lower pressure than slowly moving air. Slower air under the wing pushes it upward as lift. The sum of these two forces on a windmill's blades generates a thrust that pulls the blade on its journey through the air, much like it pulls a sailboat through the water. This thrust is greatest when the blade is slicing through the wind.
Airfoil performance is determined by the ratio of lift to drag.
These anemometers measure wind speed by their revolutions per minute. These devices work on the basis of aerodynamic drag. Make Your Own Anemometer . Drag pulls your hand towards the rear of the car. The sum of these two forces on any object generates a thrust that pulls that object through the air.