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Triple decomposition of the velocity gradient tensor is exploited to investigate the role of the simple-shear, normal-strain, and rigid-body rotation, in the turbulent kinetic energy transfer of a forced, high-Reynolds-number homogeneous isotropic turbulent flow. Splitting the total energy flux into three elementary partial fluxes shows that the rigid-body rotation has a secondary contribution to turbulent kinetic energy transfer, while within 80% of the total energy flux is produced through the simple-shear and normal-strain processes. Energy is dominantly extracted through the shearing process from larger motion scales and injected into smaller scales by the normal-straining process. In addition, each partial energy flux contains a strong conservative part and a weak non-conservative part. Besides the total kinetic energy transfer, all partial energy fluxes also show scale-invariance behaviour over the inertial subrange. Statistically, total energy flux shows a strong correlation with the simple-shear and normal-strain processes. However, the relatively poor correlation between these two dominant processes, implies a fairly low efficiency for turbulent kinetic energy transfer. These results can provide new insights into sub-grid scale turbulence modelling based on the physical mechanism of simple-shear and normal-strain processes.
Fathali et al. (Sun,) studied this question.