Local dissipation scales and energy dissipation-rate moments in channel flow

Local dissipation-scale distributions and high-order statistics of the energy dissipation rate are examined in turbulent channel flow using very high-resolution direct numerical simulations at Reynolds numbers Re-tau = 180, 381 and 590. For sufficiently large Re-tau, the dissipation-scale distributions and energy dissipation moments in the channel bulk flow agree with those in homogeneous isotropic turbulence, including only a weak Reynolds-number dependence of both the finest and largest scales. Systematic, but Re-tau-independent, variations in the distributions and moments arise as the wall is approached for y(+) less than or similar to 100. In the range 100 < y(+) < 200, there are substantial differences in the moments between the lowest and the two larger values of Re-tau. This is most likely caused by coherent vortices from the near-wall region, which fill the whole channel for low Re-tau.