Effects of a Ground Plate on Magnus Effect of a Rotating Cylinder

We present the effects of a ground plate (stationary or moved) on the Magnus effect of a rotating circular cylinder. Measurements were carried out for Reynolds number Re identical with 6.6x10 super(4) and velocity ratio alpha identical with 1. The surface pressure distributions on the cylinder were measured with a highly sensitive pressure transducer for the various clearances between the cylinder and the ground plate. The drag and lift forces on the cylinder were calculated from those surface pressure distributions. As a result, it was found that the lift suddenly changes at a certain clearance, and this behavior is not caused by the transition of the boundary layer from laminar to turbulent. This phenomenon is related to a change in the flow pattern, and each pattern was measured with a hot-wire anemometer. These flow patterns show that one of the flows through the clearance is along the cylinder surface, and another is along the ground plate. It is interesting that this phenomenon is unstable and hysteretic.