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. Author manuscript; available in PMC: 2019 Jul 11.
Published in final edited form as: J Acoust Soc Am. 2005 Jul;118(1):410–427. doi: 10.1121/1.1862251

FIG. 6.

FIG. 6

Schematic of global structure of a jet formed at a sudden expansion in a duct. The top half of the figure shows the distribution of particle velocity (and local momentum) as a function of distance from the centerline, at four axial locations. The bottom half shows the growth in size of the coherent structures through diffusion, as well as the breakdown of coherent structures. Note that the outer edge of the jet is curved due to the recirculatory flow caused by entrainment of stagnant region air by friction with the jet. Dj is the diameter of the duct at the jet formation location, Uj is the particle velocity at that location, Lh is the “step height,” Lr is the recirculation length, and δi is the spacing between shear layer coherent structures. Note that δi=Uc/fus, where Uc is the convection speed of the vortical structure and fus is the jet instability frequency. The relationship between Ls and Lr depends upon the Reynolds number UjDj/ν.