Enhancement of rotating jet by spirally structured vortex tube in centrifugal bladeless mixer flow

Abstract

The flow characteristics in a centrifugal bladeless mixer were investigated by using particle image velocimetry (PIV) and large eddy simulation (LES). The numerical result is compared with experimental one in terms of the phase-averaged velocities in radial and tangential directions. The result was analyzed by comparing with that of a conventional flat-blade mixer. A spirally structured vortex tube pair was observed around the centrifugal bladeless rotor. In a vertical cross-section of the spirally structured vortex tube pair, a zigzag street of counterrotating vortices like a reverse von Kármán vortex street was formed. It was found that the rotating jet flow was enhanced by the reverse von Kármán vortex street of the spirally structured vortex tube pair. Furthermore, the sustained rotating jet flow constructed a couple of large toroidal structured vortex tube near the tank wall. The large toroidal structured vortex caused a wider circulation in the stirred tank, which was advantage to stir the fluids over the whole field.