The Effect of Sphere Rotation on Vortex Shedding from a Sphere in Uniform Flow

Abstract

Vortex shedding from a rotating sphere in uniform flow is investigated experimentally. Two hot wires are used to examine the three-dimensional behaviour of vortex shedding and to measure the vortex shedding frequency. It is shown that, when the sphere is rotating, both high and low modes of vortex shedding similar to those of a nonrotating sphere exist. However, it is shown that when the sphere is rotating, the high mode can be found at Reynolds numbers higher than that of the nonrotating sphere case. The phases of velocity fluctuations are the same in the rotating direction for the high mode, but phases for the low mode differ when the sphere is in rotation. The phase difference for the low mode is greater than the angular rotational speed of the sphere. In the rotating sphere case, a new mode with its frequency about twice that of the low mode is found. The direction of the phase velocity of this new mode is found to be opposite to that of the low mode.