An Experimental Study of Turbulent Mixing in a Tee Mixer Using PIV and PLIF

Turbulent scalar mixing in the near field of a tee mixer (transverse jet in a pipe) is studied using Particle Image Velocimetry (PIV) and Planar Laser Induced Fluorescence (PLIF). Two jet-to-pipe velocity ratios, r = 3.06 and r = 5.04, are investigated for a turbulent pipe flow at a Reynolds number of 20,850. The laser measurement techniques are described, typical flow structures in the near field of tee mixer are examined, and turbulence statistics and scalar statistics are calculated. The general behavior of mixing is analyzed from the jet expansion and the concentration decay along the jet centerline, and the flow condition for jet impingement on the pipe wall is estimated. The mixing mechanism in the near field is revealed from the variation of the scalar PDF across the jet. Results suggest that the mixing on the upstream side of the jet is dominated by largescale structures and on the downstream side by small eddies and turbulent diffusion, where the β-PDF is an excellent approximation.