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Mixing Behavior of Absolutely Unstable Axisymmetric Shear Layers Forming Side Jets.


pdf icon Mixing Behavior of Absolutely Unstable Axisymmetric Shear Layers Forming Side Jets. (699 K)
Pitts, W. M.; Johnson, A. W.

IUTAM Symposium. Variable Density Low Speed Turbulent Flows. Volume 41. Fluid Mechanics and Its Applications. 1997, Kluwer Academic Publishers, Fulachier, L.; Lumley, J. L.; Anselmet, F., Editor(s)(s), 17-24 pp, 1997.

Keywords:

absolute instability; axisymmetric jets; concentration measurement; mixing; Raleigh light scattering; side jets

Abstract:

Recently it has been shown that low-density axisymmetric jets can become absolutely unstable and develop highly coherent vortical structures in the near-field shear layer. These jets have several unusual properties when compared to jets which are convectively unstable. The vortical structures grow quickly with downstream distance and rapidly develop three-dimensional structure. Intense pairing of alternative structures is observed. Perhaps the most interesting of all behaviors is the observation of strong ejections of jet fluid, termed "side jets", into the ambient surroundings. Their formation is attributed to the generation of strongly coupled pairs of lontiudinal vortices in the developing shear layer.