Direct numerical simulations of the turbulent annular jet with different diameter ratio

We performed direct numerical simulations (DNS) of the turbulent annular jet flow for the Reynolds number Re = 8900 with three different values of the inner-to-outer diameter ratio (a = d / D = 0.3, 0.5, 0.7). The time-averaged velocity fields and fluctuations were analyzed. The low aspect ratio results in the shortest recirculation zone while for high a value the stagnation point features high level of turbulent kinetic energy. This is the evidence of the accompanying low-frequency oscillations of the recirculation zone.