


The instantaneous pressure, its frequency characteristics and the phase-average values have been measured with a sensitive microphone equipped with a special probe tip.

The velocity field and the spectra measured with a Laser–Doppler anemometer confirmed in all cases the occurrence of PVC and the central recirculation zone (CRZ) that for higher swirl numbers penetrates back into the swirler chamber. The focus was on the characterization of the precessing vortex core (PVC) for a range of swirl numbers S = 1.4–2.4 and Reynolds numbers of 14,460–38,300. We report on experimental and analytical studies of strongly swirling air flow in the near-field of a generic axisymmetric tangential swirler used often as swirl generator in combustors, phase separators or mixing devices.
