Azimuthal acoustic modes and their impact on an axisymmetric jet

An experimental study is conducted to investigate the impact of azimuthal acoustic forcing on an axisymmetric jet. Understanding the effect of such asymmetric forcing is crucial, as it emulates conditions in annular combustion chambers such as gas turbines or jet engines, where coupling between the unsteady heat release and acoustic waves propagating azimuthally as travelling or standing modes, can have a destructive effect. While various studies have investigated the effect of axisymmetric forcing, those studying the impact of asymmetric azimuthal forcing are minimal. Recently, the response of a jet placed in a standing azimuthal acoustic wave oriented normally to the jet was investigated and jet bifurcation into two or more momentum streams was observed. Here, the effect of travelling azimuthal acoustic waves on the jet development is investigated. To this effect, a novel experimental rig was commissioned and characterized. The jet was also subjected to axisymmetric forcing at the preferred mode. Flow visualization and planar PIV were used to discern the jet's structure and evolution. Preliminary results will be presented to show the changes of the jet's spreading rate in the far field. Instantaneous snapshots will also be used to understand both the jet's spreading rate and its orientation, which in similar studies have been shown to strongly depend on the phase of the azimuthal forcing and induced axisymmetric jet modes.