Experimental analysis of dominant instabilities of coaxial jets

Authors: Segalini, A. S., Talamelli, A.
Document Type: Article
Pubstate: Published
Journal: Phys. Fluids
Volume: 23   024103
Year: 2011


An experimental analysis of the dominant instabilities in the near field of two coaxial jets is presented and discussed. Different inner/outer jet velocity pairs ??Ui , Uo?? have been tested in order to investigate the effect of both velocity ratio ru = Uo / Ui and Reynolds number. Three main instabilities have emerged depending on the velocity ratio. For ru<0.75, the coaxial jets dynamic is driven by the inner shear layer. For ru>1.6, the outer shear layer dominates the near field vortex dynamics while for ru nearly unitary, the vortex shedding behind the separating wall imposes its own dynamics. A new scaling relationship is proposed to improve the estimation of the shedding frequency with respect to the one found in literature.