Main instabilities of coaxial jets

Authors: Segalini, A. S., Talamelli, A.
Document Type: Article
Pubstate: Published
Journal: Proc. iTi Conference on Turbulence IV, Bertinoro, Italy, 2010
Year: 2010


An experimental analysis of the dominant instabilities in the initial merg- ing region of two coaxial jets is presented. 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 in the instability characteristics. Three main in- stabilities 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 velocity ratios nearly unitary the vortex shedding behind the separating wall imposes its own dynamics.