Experimental investigation of lift-up and instability of the viscous flow induced by a rotating cone-cylinder in an enclosure

This paper probes into the flow induced by a rotating cone-cylinder model in an enclosure. Two component particle image velocimetry measurements in the symmetry plane reveal that the rotating cone-cylinder causes an outward jet on the cylinder section, which lifts the rotating boundary layers away from the wall. A large-scale counter-rotating vortex pair sets up with its mutual upwash aligned with the lift-up region. Furthermore, the centrifugal instability induces Taylor vortices in the rotating boundary layer, which are convected by the mean flow field and are lifted away from the surface, causing a high standard deviation. The lift-up phenomenon shows two preferred axial locations: below a critical Reynolds number R e b , c , the lift-up occurs close to the cone-cylinder junction, and for the Reynolds number higher than R e b , c , lift-up is pushed away from the cone-cylinder junction, toward the model base. The value of the critical Reynolds number R e b , c lies within 2 × 10 3 − 2.5 × 10 3 for the investigated cases.