Effect of the computational domain on direct simulations of turbulent channels up to Re_τ = 4200

The effect of domain size on direct numerical simulations of turbulent channels with periodic boundary conditions is studied. New simulations are presented up to Re_τ = 4179 in boxes with streamwise and spanwise sizes of 2πh × πh, where h is the channel half-height. It is found that this domain is large enough to reproduce the one-point statistics of larger boxes. A simulation in a box of size 60πh × 6πh is used to show that a contour of the two-dimensional premultiplied spectrum of the streamwise velocity containing 80% of the kinetic energy closes at λ_x ≈ 100h.