Wake instability behind a streamwise and transversely rotating sphere

The wake instabilities associated with a streamwise and transversely rotating sphere at very high rotational speeds are not clearly understood. This article attempts to address typical wake instability characteristics when the sphere rotates along the streamwise and transverse directions through direct numerical simulations. We have found that a larger streamwise rotation makes the wake bifurcate into large-scale shear-layer structures. In contrast, the azimuthal stretching during transverse rotation splits the wake into a twin jet-type flow pattern, resulting in the transverse expansion of the wake.