Magnus Force

A fluid flow perpendicular to the axis of a rotating cylinder produces a force perpendicular to both the axis and the flow direction (Figure 1). This force is known as the Magnus Force and can be explained by the Bernoulli effect. In the case shown in the figure, the fluid moves faster over the upper surface of the cylinder than over the lower surface, which results in a lower pressure at the upper surface. This phenomenon is discussed in, for example, Streeter and Wylie (1983) and Massey (1989).

Figure 1. Force on a rotating cylinder.