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On Dynamics and Secondary Currents in Meandering Confined Turbulent Shallow Jet

On Dynamics and Secondary Currents in Meandering Confined Turbulent Shallow Jet, R. Mullyadzhanov, B. Ilyushin, and K. Hanjalic. International Journal of Heat and Fluid Flow 2015, 56 , 284–289.

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Abstract

We study a shallow turbulent confined jet issuing from a wide duct of the aspect ratio around 0.1 (approximate to H: B = height: width) into a large rectangular reservoir (200H x 267H long in spanwise and streamwise direction) bounded by two parallel plates with the distance H using a wall-resolved Large-eddy simulation. According to statistical and dynamical features of the flow the domain is divided into the near (<40H approximate to 4B), middle and far (> 130H approximate to 13B) field along the streamwise coordinate. The well-known meandering (or flapping) motion of the jet core starts at approximate to 5B generating large-scale planar vortices similar to the von Karman vortex street. We find that the typical smaller scale coherent structure appears to be a vortex tube (with the cross-section diameter < H/2) oriented along the flow with a high value of the streamwise voracity. In the near field a pair of these counter-rotating vortices are produced in each shear layer with the help of the strong entrainment of the ambient fluid into the turbulent jet core and look similar to the braid vortices connecting Kelvin-Helmholtz rolls found in the classical mixing layer. The maximum time-averaged streamwise voracity is reached at the axial distance of 12.5H with monotonic decrease further downstream. In the middle and far fields these streamwise rolls are mostly observed in one shear layer (on one side of the jet) while being suppressed on the other side by the flapping motion. Typically they are organized in a “zig-zag” chain across the “shallow” direction. A simple model is proposed to explain this feature. (C) 2015 Elsevier Inc. All rights reserved.

BibTeX

@article{ ISI:000366961900024,
Author = {Mullyadzhanov, R. and Ilyushin, B. and Hanjalic, K.},
Title = {On Dynamics and Secondary Currents in Meandering Confined Turbulent Shallow Jet},
Journal = {International Journal of Heat and Fluid Flow},
Year = {2015},
Volume = {56},
Pages = {284-289},
Month = {},
Abstract = {We study a shallow turbulent confined jet issuing from a wide duct of the aspect ratio around 0.1 (approximate to H: B = height: width) into a large rectangular reservoir (200H x 267H long in spanwise and streamwise direction) bounded by two parallel plates with the distance H using a wall-resolved Large-eddy simulation. According to statistical and dynamical features of the flow the domain is divided into the near (<40H approximate to 4B), middle and far (> 130H approximate to 13B) field along the streamwise coordinate. The well-known meandering (or flapping) motion of the jet core starts at approximate to 5B generating large-scale planar vortices similar to the von Karman vortex street. We find that the typical smaller scale coherent structure appears to be a vortex tube (with the cross-section diameter < H/2) oriented along the flow with a high value of the streamwise voracity. In the near field a pair of these counter-rotating vortices are produced in each shear layer with the help of the strong entrainment of the ambient fluid into the turbulent jet core and look similar to the braid vortices connecting Kelvin-Helmholtz rolls found in the classical mixing layer. The maximum time-averaged streamwise voracity is reached at the axial distance of 12.5H with monotonic decrease further downstream. In the middle and far fields these streamwise rolls are mostly observed in one shear layer (on one side of the jet) while being suppressed on the other side by the flapping motion. Typically they are organized in a ``zig-zag{''} chain across the ``shallow{''} direction. A simple model is proposed to explain this feature. (C) 2015 Elsevier Inc. All rights reserved.},
DOI = {10.1016/j.ijheatfluidflow.2015.08.004},
ISSN = {0142-727X},
EISSN = {1879-2278},
Unique-ID = {ISI:000366961900024},
}

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