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.
A. Segalini, A. Talamelli (2011). Experimental analysis of dominant instabilities in coaxial jets. PHYSICS OF FLUIDS, 23(2), 1-7 [10.1063/1.3553280].
Experimental analysis of dominant instabilities in coaxial jets
TALAMELLI, ALESSANDRO
2011
Abstract
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.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
