Swirling jets undergoing vortex breakdown are dominated by a strong coherent structure
that is characterized by a precessing vortex core and the large-scale roll-up of the shear
layers. These fully synchronized flow dynamics play an important role for the stabilization of
swirl flames commonly applied in gas-turbine combustion. It is now well accepted that these
flow dynamics are the manifestation of a saturated global instability triggered by a
hydrodynamic feedback loop. Yet, the origin of this instability is still discussed …