Stability characteristics of eccentric spherical annulus flow

Experimental results are presented concerning the stability characteristics of the flow of a viscous incompressible fluid within an eccentric spherical annulus. The flow is driven by the rotation of the inner sphere, which is not centered (along the axis of rotation), relative to the stationary outer sphere. The stability characteristics are found to be dependent upon the radius ratio of the two spheres and the relative eccentricity. As the eccentricity is increased from zero (concentric spheres), the flow first becomes more stable, then less stable, and finally more stable again as the eccentricity approaches one (both spheres touching). Such characteristics are observed for both the initial transition of the basic flow to another laminar flow and the transition to turbulence.