Experimental investigation of enclosed rotor-stator disc flows

Detailed hydrodynamic measurements were obtained in a rotating water-flow rig for an enclosed rotor-stator system with a stationary outer shroud. Three different measuring techniqueslaser-Doppler anemometry, hot-film velocimetry, and the yaw-tube methodwere employed. Measurements include the variation of the mean and some of the fluctuating velocity components across a rotor-stator cavity of aspect ratio 0.127. Several radial locations were examined, and special efforts were made to resolve the near-wall variation. The investigation covers a rotational Reynolds number range, Reθ, from 0.3 106 to 1.6 106. In the detailed picture of the flow structure that emerges, at the higher rotational speeds the Ekman-type boundary layer on the rotor is laminar over the inner half of the cavity and turbulent at the outer radial locations. The stator boundary layer, on the other hand, is turbulent over most of the cavity, and the high near-wall turbulence levels extend further into the core. At lower rotational speeds (Reθ=0.3 106), the rotor boundary layeris laminar over almost the entire cavity but the stator layer remains turbulent. The differing behavior on the rotor and stator surfaces is interfreted as a consequence of convective motion that transports fluid radially outward on the outer surface but radially inward on the stator. Although the present results broadly support an earlier study in a narrower cavity covering a smaller range of Reynolds number, significantly different interpretations are drawn in some respects.