Influence of Issued Jet Conditions on Mixing of Confined Flows

The development of the velocity and scalar fields in a coaxial jet mixer has been experimentally investigated applying simultaneously Particle Image Velocimetry (PIV) and Planar Laser Induced Fluorescence (PLIF) methods. Mixing of a turbulent jet (water solution of Rhodamin 6G) issued from a long round nozzle (l/d = 60) with co-flow (water) was studied. Because of the nozzle length the boundary layers of the inner flow already merged upstream of the jet exit. The issued jet conditions were changed installing vortex generators (tabs) at the nozzle exit. The tabs of rectangular and triangular forms with heights of 13 15 % the inner nozzle diameter accelerated mixing significantly but the scalar field developed to the homogeneous state faster than the velocity one. Turbulent characteristics measured downstream of the jet exit gave evidence the mixing specific behind the rectangular and triangular tabs.