Lumley Decomposition of the Turbulent Round Jet Far-field. Part 2 - Dynamics

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In the current work the reconstruction of the far-field region of the turbulent axi-symmetric jet is performed in order to investigate the modal turbulence kinetic energy production contributions. The reconstruction of the field statistics is based on a semi-analytical Lumley Decomposition (LD) of the PIV sampled field using stretched amplitude decaying Fourier modes (SADFM), derived in Hodžić et al. 2019, along the streamwise coordinate. It is shown that, a wide range of modes obtain a significant amount of energy directly from the mean flow, and are therefore not exclusively dependent on a Richardson-like energy cascade even in the κ-range in which the energy spectra exhibit the −5/3-slope. It is observed that the −7/3-range in the cross-spectra is fully reconstructed using a single mode in regions of high mean shear, and that shear-stresses are nearly fully reconstructed using the first two modes. These results indicate that most of the energy production related to shear-stresses is related to the first LD mode.
Original languageEnglish
JournalJournal of Fluid Mechanics
Publication statusSubmitted - 2019

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ID: 191604686