Small-scale statistics in direct numerical simulation of turbulent channel flow at high-Reynolds number

Small-scale statistics in turbulent channel flow are studied by high resolution direct numerical simulations with the friction Reynolds number up to Re_τ = 2560. The second order velocity statistics in the inertial subrange of the log-low region are found to be not far from those predicted by Kolmogorov's universal equilibrium theory, although the agreement is not perfect. The shear parameter S* decreases with the distance y⁺ from the wall and S* ≲ 0.1 in y⁺ > 400 for large Re_τ, where S* is the ratio of the Kolmogorov time scale to the mean shear time scale. For larger Re_τ, the y ⁺-dependence of S* is closer to a simple theoretical estimate in the log-low region.