Main Instabilities of Coaxial Jets
An experimental analysis of the dominant instabilities in the initial merging region of two coaxial jets is presented. Different inner/outer jet velocity pairs (U i ,U o ) have been tested in order to investigate the effect of both velocity ratio r u = U o /U i and Reynolds number in the instability characteristics. Three main instabilities have emerged depending on the velocity ratio. For r u < 0.75 the coaxial jets dynamic is driven by the inner shear layer. For r u > 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.
KeywordsShear Layer Flow Turbulence Combust Velocity Ratio Strouhal Number Absolute Instability
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