Numerical Simulation of Negative Magnus Force on a Rotating Sphere

Abstract

Flow characteristics and fluid force on a sphere rotating along with axis perpendicular to mean air flow were investigated using Large Eddy Simulation (LES) at two different Reynolds numbers Re_p of 1.0×10⁴ and 2.0×10⁵. As a result of simulation, opposite flow characteristics around the sphere and displacement of the separation point were visualized depending on the Reynolds number even though rotation speed according to the Reynolds number is the same. When the sphere rotates at some specific rotation velocity and at Re_p = 1.0×10⁴, flow characteristics agree with the flow field explained in the Magnus effect. While sphere rotates at the same rotation velocity while increasing Re_p to 2.0×10⁵, separation point moves in opposite direction and wake appears in the different direction. The reason of the negative Magnus force was discussed in terms of the boundary layer transition on the surface.