422 Statistics of the Cluster of Coherent Fine Scale Eddies in Homogeneous Isotropic Turbulence

To investigate the statistics of the clusters of coherent fine scale eddies, direct numerical simulation database of homogeneous isotropic turbulence up to Re_λ=256.1 have been analyzed. The cluster of the strong coherent fine scale eddies tends to exist in the region with high local turbulent kinetic energy, which is defined as local average in the cube of integral length scale, and with high strain rate in large scales. Even in the Kolmogorov length unit, the most expected diameter of the coherent fine scale eddies depend on the characteristics of the integral length box. The diameter in each integral length boxes can be scaled by the local Kolmogorov scale (ηl). The most expected diameter is about 10_<ηl>. These characteristics of coherent fine scale eddies are similar to those in the near-wall turbulence. Moreover, the large scale eddies tend to exist in the region around the cluster where the energy transfer from GS to SGS is strong.