Wall effects on a rotating sphere

The flow induced by a spherical particle spinning in the presence of no-slip planar boundaries is studied by numerical means. In addition to the reference case of an infinite fluid, the situations considered include a sphere rotating near one or two infinite plane walls parallel or perpendicular to the axis of rotation and a sphere centred within a cube. The hydrodynamic force and couple acting on the sphere exhibit a complex behaviour under the sometimes competing, sometimes cooperating action of viscous, inertial and centrifugal effects