Magnus Effect

The Magnus effect or Magnus force is the phenomenon whereby a spinning object flying in a fluid creates a whirlpool of fluid around itself, and experiences a force perpendicular to the line of motion. The overall behaviour is similar to that around an airfoil (see lift force) with a circulation which is generated by the mechanical rotation, rather than by aerofoil action. The Magnus effect is often considered a demonstration of Bernoulli's principle, but this is incorrect, as the viscosity of the air — assumed to be negligible in Bernoulli's principle — is central to understanding the magnitude of the force.

In many ball sports, the Magnus effect is responsible for the curved motion of a spinning ball. The effect also affects spinning missiles, and is used in rotor ships and Flettner aeroplanes.