Three-dimensional coherent structures in a swirling jet undergoing vortex breakdown: stability analysis and empirical mode construction

By Kilian Oberleithner, Moritz Sieber, C. Nayeri, Christian Oliver Paschereit, Christoph Petz, Hans-Christian Hege, Bernd R. Noack, I. Wygnanski. Journal of Fluid Mechanics, 2011

443 citations recorded by the source corpus.

The spatio-temporal evolution of a turbulent swirling jet undergoing vortex breakdown has been investigated. Experiments suggest the existence of a self-excited global mode having a single dominant frequency. This oscillatory mode is shown to be absolutely unstable and leads to a rotating counter-winding helical structure that is located at the periphery of the recirculation zone. The resulting time-periodic 3D velocity field is predicted theoretically as being the most unstable mode determined by parabolized stability analysis employing the mean flow data from experiments. The 3D oscillatory flow is constructed from uncorrelated 2D snapshots of particle image velocimetry data, using proper orthogonal decomposition, a phase-averaging technique and an azimuthal symmetry associated with helical structures. Stability-derived modes and empirically derived modes correspond remarkably well, yielding prototypical coherent structures that dominate the investigated flow region. The proposed method of constructing 3D time-periodic velocity fields from uncorrelated 2D data is applicable to a large class of turbulent shear flows.

Subfields: Aerospace Engineering, Computational Mechanics

View Paper: https://www.semanticscholar.org/paper/6abd0871fe24eef9f349b9845eade3bf21cc4d03

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Citations in the corpus

Aeroacoustic resonance and self-excitation in screeching and impinging supersonic jets – A review (2019, background): “modes.(189) A travelling wave structure will be defined by a pair of POD modes, with a 90 phase offset between them.”
Coherent structures in a swirl injector at Re = 4800 by nonlinear simulations and linear global modes (2016, background): “The swirl number for spiral vortex breakdown is similar in different swirling flows: S= 0.915 for a vortex breakdown bubble (Ruith et al. 2003; Meliga et al. 2012a) and S= 0.88 for a swirling jet (Oberleithner et al. 2011).”
Coherent structure and sound production in the helical mode of a screeching axisymmetric jet (2014, methodology): “Oberleithner et al. (2011), the oscillating flow field can be expressed rigorously in the subspace spanned by the first two spatial POD modes.”
Recursive dynamic mode decomposition of transient and post-transient wake flows (2016, background): “Yet, only in rare cases have POD modes been found to resemble physically meaningful structures, like stability modes or base-flow deformations (Oberleithner et al. 2011).”
Spectral proper orthogonal decomposition (2015, background): “Coupled modes typically show a similar amount of energy and pair in the POD spectrum (Oberleithner et al. 2011; Oberleithner, Rukes & Soria 2014).”