Characterization of flow behavior in an enclosed cylinder with a partially rotating end wall

Abstract

The vortex breakdown phenomena in an enclosed cylindrical chamber with a rotating disk whose radius is smaller than that of the chamber were investigated by a numerical model based on the steady, axisymmetric Navier-Stokes equations. The flow behaviors were investigated over a wide range of parameters. The main recirculation region remains unchanged if the cylinder-to-disk ratio, the ratio of the chamber radius to the disk radius, is beyond the recirculation-invariance ratio. The recirculation-invariance ratio displays a generally linear relationship with the vertical ratio, the ratio of the chamber height to disk radius. The trends of the vortex breakdown boundary curves at different cylinder-to-disk ratios suggest that three regions, namely the quasi whole end-wall rotating region, the vortex-breakdown boundary invariance region, and the mixed region, can be used to characterize the occurrence of vortex breakdown. Depending on the specific conditions, the presence of the stationary end wall either serves to precipitate or delay the onset of vortex breakdown. The stationary end wall has the effect of reducing the physical aspect ratio but it also dissipates the fluid's angular momentum along its surface. These two opposite effects lead to different trends of the vortex-breakdown boundary curves in different regions, depending on which effect is dominant. © 2007 American Institute of Physics.