Fig. 2.

Visualizations in a meridional plane of the experiment by Noir et al. (2001) for increasing (in absolute value) precession forcing, illustrating the transition from the laminar base flow with a uniform vorticity flow along an inclined axis (top left), to the bulk filling turbulence (bottom right). Water is seeded with small reflective flakes called Kalliroscope that align preferentially in the flow due to their anisotropy. Lighted here by a meridional light sheet and observed from an angle of ${90}^{\circ }$, Kalliroscope emphasizes preferential domains of the flow, including zones of strong shear. The two steady, geostrophic bands symmetric with respect to the fluid rotation axis in the top left figure result from the non-linear interaction of the conical shear layers emitted at ${30}^{\circ }$ (oscillating flows within conical shear layers are not directly visible using Kalliroscope)