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arXiv · 2610.28221

Wavepackets in subsonic elliptical jets: coherent-structure eduction and linear modelling

Filipe Ramos do Amaral·Mateus Peixoto Avanci·Jean-Christophe Robinet·Peter Jordan·Jérôme Huber·Grégoire Pont
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Abstract

We study coherent structures extracted from time-resolved particle image velocimetry (TR-PIV) measurements of isothermal elliptical jets with aspect ratio of 1:2, at Mach numbers 0.4 and 0.7. The velocity snapshots are decomposed according to the D$_2$ symmetry. Spectral proper orthogonal decomposition (SPOD) is then used to identify coherent structures. Modelling is performed using three-dimensional parabolised stability equations (3D-PSE) based on linearisation about the time-averaged mean flows. A comparison between SPOD and 3D-PSE results shows alignment of SPOD and single-mode PSE structures of up to 70\%. A linear combination of PSE solutions, obtained from the family of initially unstable local modes, leads to SPOD-PSE alignment of up to 90\%. Limitations are observed at low frequencies and near the nozzle and are attributed to the existence of non-modal amplification mechanisms. The study shows that coherent structures in turbulent elliptical jets can be educed using the D$_2$-SPOD approach, and modelled using 3D PSE.

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Filipe Ramos do Amaral, Mateus Peixoto Avanci, Jean-Christophe Robinet, Peter Jordan, Jérôme Huber, Grégoire Pont. 2026-10-20. Wavepackets in subsonic elliptical jets: coherent-structure eduction and linear modelling. https://arxiv.org/abs/2610.28221

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