Frequency response of swirl flow behind an axial swirler

This paper deals with the frequency response of swirl flow behind an axial swirler. Vortex breakdown resulting in the formation of a precessing vortex core is considered. The influence of the swirl intensity and the nozzle confinement effect on the frequency response of the PVC is studied. Regimes with the presence of PVC were determined using two microphones. The Strouhal number depends linearly on the swirl parameter and weakly on the Reynolds number. The measurement results are used to derive an empirical dependence of the Strouhal number on a modified geometric swirl number. This allows a generalization of the frequency characteristics of swirling flows with a PVC for the class of axial vane swirlers, which are most widely used in engineering.