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

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

Content Provider	Semantic Scholar
Author	Oberleithner, Kilian Sieber, Moritz Nayeri, Christian Navid Paschereit, Christian Oliver Petz, Christoph Hege, Hans-Christian Noack, Bernd R. Wygnanski, Israel J.
Copyright Year	2011
Abstract	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.
Starting Page	383
Ending Page	414
Page Count	32
File Format	PDF HTM / HTML
DOI	10.1017/jfm.2011.141
Volume Number	679
Alternate Webpage(s)	http://berndnoack.com/publications/2011_JFM_Oberleithner.pdf
Alternate Webpage(s)	https://doi.org/10.1017/jfm.2011.141
Language	English
Access Restriction	Open
Content Type	Text
Resource Type	Article

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