Structure of square coaxial nozzle flows

Document Type

Conference Proceeding

Publication Date

1-1-1998

Abstract

Flow visualization and measurement results are presented for flows in square coaxial nozzles with parallel sides, and the corresponding geometry of axisymmetric coaxial nozzles, at a co-flow-jet Reynolds number of 19,000 and at two inner-to-outer jet velocity ratio values (0.22 to 0.3). The presence of large-scale periodic structures is evident near the origin of the shear layers, although not as clear as in lower Reynolds number flows. The internal unmixed regions are reduced in size with decreasing velocity ratio. Visualizations and local measurements have indicated mixing enhancement when square nozzles are used compared to the axisymmetric ones. This is largely attributed to the difference in initial velocity profiles between these two configurations. The existence of axis-switching, a phenomenon observed in single non axisymmetric nozzles, is not clearly evident from visualizations and measurements in the square coaxial nozzle. Four distinct regions in the development of the coaxial nozzle flows have been identified on the basis of the measured trends. Scaling of mean velocity and turbulence profiles has also been examined for the three shear layers formed in the near field of axisymmetric and square coaxial flows.

Publication Source (Journal or Book title)

29th AIAA Fluid Dynamics Conference

First Page

1

Last Page

11

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