Visualization and two-color DPIV measurements of flows in circular and square coaxial nozzles

Document Type

Conference Proceeding

Publication Date

1-1-1998

Abstract

High-resolution, reactive Mie scattering laser-sheet visualizations and two-color DPIV measurements in flows generated by equivalent coaxial circular and square jets are presented. Results were obtained for three square, coaxial configurations and a reference circular coaxial nozzle, at two Reynolds numbers of the outer jet (19,000 and 29,000) and for inner-to-outer jet velocity ratios of 0.15, 0.22 and 0.3. Comparisons between circular and square jet configurations indicated considerable mixing enhancement when square nozzles were used. The presence of large-scale periodic structures was evident near the origin of the shear layers although not as clear as in lower Reynolds-number flows. The internal unmixed regions diminished with decreasing velocity ratio and, at the low velocity ratios, strong evidence of unsteady re-circulation and back-flow was observed at the end of the core of the inner jet. Ensembles of 41 to 113 DPIV images, depending on conditions, were used to obtain mean velocity distributions in the jets' near field. Comparison of DPIV mean velocity profiles with those obtained by Constant-Temperature Anemometry (CTA) are very satisfactory. Errors are higher in regions of high fluctuation intensity as expected.

Publication Source (Journal or Book title)

American Society of Mechanical Engineers, Fluids Engineering Division (Publication) FED

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