Differential Boundary-Layer Separation Effects in the Flow over a Rotating Cylinder

Abstract

When a rotating body is placed in a stream of fluid the viscous drag of the rotating surface moving forward on one side and backwards on the other causes the flow velocity to be lower and hence the pressure on the forward-moving side higher than on the backward-moving side, thus giving a lateral (lift) force L in the direction shown in Fig. 1. This force, known as the Magnus force, is well known to engineers and also to sportsmen. In tennis, for example, top spin is used to swerve a fast ball downwards so that it falls within the required area of play, while in golf the Magnus force causes the all too familiar sliced shot when the club is drawn across the ball at impact.