Modern low-emissions gas turbine combustors commonly employ a twin annular swirling
flow configuration that consists of a central annular inner jet and a surrounding annular outer
jet. This paper investigates the instability dynamics of helical vortices of such a flow
configuration in non-reacting laminar setting with a varying outer jet swirling ratio S⁠. The
corresponding base flow features a centerbody wake (CBW), an outer recirculation zone,
and a lip recirculation zone at low swirl ratios, whereas at high swirl ratios, the CBW is …