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Thin shear layers in high Reynolds number turbulence - DNS results

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Data analysis of high resolution DNS of isotropic turbulence with the Taylor micro-scale Reynolds number R = 1131 on 4096^3 grid points shows that there are significant thin shear layers of thickness of the order of Taylor micro-scale, consisting of a cluster of strong vortex tubes with typical diameter of order 10 eta (eta is the Kolmogorov length scale) . There are big velocity jumps of the order of the rms of the fluctuation velocity across the layers. The locally averaged energy dissipation rate in the layers is much greater than the mean energy dissipation rate, and contributes disproportionately to the overall mean dissipation rate. Up scale and down scale energy transfer to small eddies is largest within and just outside these layers (where the most intense vortices and dissipation occur). The statistics (based on a systematic study) of the layers will be presented and their Reynolds number dependence will be discussed.

Author(s):

Takashi Ishihara    
Nagoya University
Japan

Julian Hunt    
University College London
United Kingdom

Yukio Kaneda    
Aichi Institute of Technology
Japan