Coherent structures in subsonic elliptical jets

In this paper we address coherent structures extracted from stereo particle image velocimetry (stereo PIV) databases of 1:2 aspect-ratio elliptical jets measured at Mach number 0.4 under isothermal conditions. The snapshots are decomposed in terms of D-2-symmetry, taking advantage of the geometry invariance under reflection about the ellipse major and minor axes. Spectral proper orthogonal decomposition (SPOD) is applied to each symmetry component to identify coherent structures. To explore the underpinning physical mechanisms the SPOD modes are compared to solutions of the parabolized stability equations (PSE). Similarity metrics between SPOD solutions and PSE solutions of 0.7 are attained, in agreement with previous studies for round jet flows.