Asymmetric vortex shedding in the wake of an abruptly expanding annular jet

In this paper, the structure of turbulent wake behind inner tube a suddenly expanding annular jet flow is studied. The field measured using tomographic particle image velocimetry and analyzed proper orthogonal decomposition (POD). It was found that both instantaneous time-averaged central wakes pipe are highly asymmetric despite axisymmetric geometry. This asymmetry result bifurcation at low Reynolds numbers which persists up to regime. induces pair counter-rotating vortices in aligned with main direction. Moreover, also dynamical field. Analyzing structures POD shows oscillates around equilibrium position very Strouhal number order 0.01. On top motion, shear layer range 0.1-0.3. oscillation causes an shedding hairpin type layer. As such, local region intensive mixing induced near stagnation point.