DNS of transition to nonuniform in time and/or space turbulent flows in rotating spherical layers

We have numerically studied the transition to turbulence in a layer of a viscous incompressible fluid confined between concentric counter rotating spherical boundaries. Rotational speeds of one or two boundaries were periodically modulated. The transition to turbulence was caused by an increase in the modulation amplitude. Two different cases of transitions were under consideration. In the first case modulation of outer sphere velocity with constant inner sphere speed was imposed on initial periodical flow state. The obtained solutions reveal cycle-chaos intermittency type - irregular temporal alternation of laminar and turbulent states occupying the whole layer. In the second case both of spheres were opposite-phase oscillated at the same frequency and amplitude about the state of rest. The obtained solutions exhibits chaos-chaos intermittency type of the flow - irregular temporal alternation of weak and strong turbulent states in the limited part of the layer, outside which the flow remains periodical.