Absolute instability of a double ring jet – numerical study

The paper is aimed at analyzing the influence of external flow on absolutely unstable modes of a ring jet with recirculation zone. The double ring jet is also considered. The investigation is carried out by means of the linearized, inviscid spatio-temporal stability theory. Calculations are based on the shooting method for asymmetric azimuthal mode. During the numerical experiment, absolutely unstable modes were identified. No major influence of the external stream on the stability of the flow was also proved.