Frictional moment of flow between two concentric spheres, one of which rotates

Frictional moment is investigated experimentally for the flow between a rotating inner sphere and a stationary outer one, and for the flow between a rotating outer sphere and a stationary inner one, respectively. The existence of four basic flow regimes for both is verified, and their extent is mapped over a range of Reynolds number-clearance ratio combinations. An empirical formula for the coefficient of frictional moment is obtained for every flow regime. The coefficient of frictional moment obtained for spherical annulus flow is then correlated with that of the flow around a disk rotating in a confined space, and the effect of the surface curvature of rotating bodies is considered.