Recent studies have clearly shown the important role of swirl fluctuations (or, more precisely,
fluctuations in axial vorticity) in the response of premixed flames to flow oscillations. An
important implication of this mechanism is that the axial location of the swirler plays a key
role in the phase between the acoustic flow excitation source and the resulting axial vorticity
fluctuation at the flame. Similar to the previously well recognized role of azimuthal vorticity
fluctuations, these swirl fluctuations are vortical and convect at the mean flow velocity, unlike …