Abstract
A qualitative and quantitative comparison between unforced flows emanating from equivalent geometries of axisymmetric (circular) and square coaxial nozzles is presented. The initial state of the jets is turbulent, as in nozzles relevant to practical applications. Flow visualization and velocity measurements were performed at a coflow-jet Reynolds number of 1.9 × 10 4 and at an inner-to-outer jet velocity ratio of 0.3. Scaling of mean velocity and turbulence profiles has been examined for the three shear layers formed in the near field of axisymmetric and square coaxial flows. Visualizations and local velocity measurements have indicated modest mixing enhancement when square nozzles are used compared to the axisymmetric ones, and this is largely attributed to differences in initial velocity profiles between these two configurations. Low-coherence, large-scale periodic structures were observed for both nozzle configurations in the midfield of the inner mixing region, which has wake characteristics
Published Version
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