Double vortices and single-eyed vortices in a rotating cylinder under thermal gradients

In this paper we use nonlinear simulations to show the generation of single-cell vortices, two-cell vortices and double vortices in a cylinder non-homogeneously heated from below in a rotating reference frame. For moderate rotation rates we show the transition from an axisymmetric one-cell vortex, characterized by an updraft at the center of the cell, to an axisymmetric two-cell vortex, characterized by a central downdraft surrounded by updraft, i.e., a vortex that develops a central eye. This transition can be explained through a force balance analysis. When the thermal gradient increases beyond a certain threshold the axisymmetric single-eyed vortex loses the axisymmetry, the eye displaces from the center and tilts. For larger rotation rates the axisymmetric one-cell vortex bifurcates to a double vortex.