Characteristics of Flow and Intermixing in Ring Vortexes Induced by Rotating Multistage Disks

Ring vortexes which are formed in series by rotating multistage disks in a cylindrical vessel were investigated by flow visualization, torque measurement and concentration response. The vortex behavior, visualized using aluminum powder, is described in the laminar, transition and turbulent states. The critical Reynolds number for the onset of interface oscillation of laminar vortexes is related to the gap width between the rotating disk and vessel wall. Average torque acting on a disk is correlated in terms of the torque coefficient. It was confirmed in a dye experiment that the model of perfectly mixed tank in series is applicable to characterizing the intermixing through the vortex interface. Using this model the intermixing rate was evaluated. The rate through the injection interface is greater than that through the suction interface and the rate in the turbulent vortex varies in proportion to Kolomogoroff's velocity scale. Empirical correlations are given for the intermixing rate and the Reynolds number indicating the transition to turbulent interface.