Fine Scale Eddy Cluster and Energy Cascade in Homogeneous Isotropic Turbulence
To investigate statistics of the cluster of coherent fine scale eddies and its relation to energy cascade, direct numerical simulation data of homogeneous isotropic turbulence up to Reλ = 287.6 have been analyzed. The cluster of the strong coherent fine scale eddies, which is of the order of the integral length, tends to exist in the region with high strain rate of large scales. Energy transfer from large scales to small scales is also high in the cluster regions. The clusters are composed of the small eddies (<20η), while the large scale eddies (>80η) are distributed outside of the cluster. The high strain rate regions due to different scales in the inertial subrange do not coincide except for the cluster regions. The importance of these structures in SGS stress models of large eddy simulation is discussed.
Keywordsturbulence fine scale structure energy cascade direct numerical simulation SGS model
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