Stability, non-uniqueness and transition to turbulence in the flow between two rotating spheres

Experimental and numerical stability analyses of viscous incompressible fluid flow between two concentric coaxially rotating spheres are presented for a wide range of similarity parameters. The stability curves for different gap sizes are found. The non-uniqueness of the secondary flows for the same supercritical values of the parameters are shown both experimentally and numerically. The regions of the existence of different regimes in the space of similarity parameters are found. The transition to turbulence in wide gap case is investigated by spectral and correlation analyses of radial velocity fluctuations.