Fig. 5

General circulation patterns for spherical Couette flow. Flow patterns for the case of outer sphere stationary (a) and rapidly rotating (b). For a, the super-rotating inner sphere pumps fluid out into the bulk in the form of an equatorial jet, with a poloidal return flow. For b, the fluid outside the tangent cylinder spins in solid body with the outer sphere, while the fluid inside the tangent cylinder spins at a rate intermediate between the two spheres, with Ekman pumping along the boundaries of the tangent cylinder. The velocity jump across the boundary of the tangent cylinder is accommodated by the Stewartson layer, a region of high shear. (From Zimmerman 2010)