Chamber Dimension Effects on Induced Flow and Frictional Resistance of Enclosed Rotating Disks

The fundamental fluid mechanics associated with the rotation of a smooth plane disk enclosed within a right-cylindrical chamber have been studied both experimentally and theoretically. In order to acquire further and systematic information pertinent to this problem, which has received much attention in the past, torque data were obtained over a range of disk Reynolds numbers from 103 to 107 for axial clearance-disk radius ratios s/a from 0.0127 to 0.217 for a constant small radial tip clearance and velocity and pressure data were obtained for laminar and turbulent flows. The existence of four basic flow regimes in the axial gap between the disk and casing wall was verified, and these regimes, the existence and extent of which are governed by the Reynolds number-axial spacing combinations, have been delineated. A new approximate theoretical analysis has accounted for axial-clearance effects for the case of separate boundary layers on the disk and end wall; this theory has been checked against test results. Velocity and pressure data have shown that the concept of a fluid “core” rotation in the case of separate boundary layers must be modified because of secondary flows and skewed boundary layers.