Characterization of trailing vortices generated by a Rushton turbine

The discharge flow of a Rushton turbine is characterized by a counter-rotating vortex pair generated behind the impeller blade. The objective here is to characterize these trailing vortices. To this end, PIV measurements were synchronized with blade position. These measurements were performed to identify and locate the trailing vortices, according to an identification technique proposed to detect a vortical region. The advantage of this method for determining the trailing vortex is highlighted after comparison to previous techniques. The trajectory of the vortices is deduced and it is shown to follow the phase-averaged velocity field induced by the impeller. The trailing vortices were characterized in terms of size and velocity circulation within the vortex. The interactions between these organized structures and turbulence were also illustrated. (C) 2004 American Institute of Chemical Engineers