DNS of turbulent channel flow at very low Reynolds numbers

Direct numerical simulation (DNS) of a fully developed turbulent channel flow for very low Reynods numbers has been executed with larger computational box-sizes than those of common DNS. The present Reynolds number is decreased down to Re _T = 64, where Re _T is based on the friction velocity and the channel half width δ. For Re _T=80 with using the largest box of 51.2δ × 2δ × 22.5δ, the periodic weak-turbulence regions are observed. This type of locally disordered flow is similar to a turbulent puff observed in a transitional pipe flow. Various turbulence statistics such as turbulent intensities, vorticity fluctuations, Reynolds stresses are provided. Especially, their near-wall asymptotic behavior and budget terms of turbulence kinetic energy are obtained and discussed with respect to Reynolds number dependence and an influence of the comptational box-size. In addition, two-point correlation coefficients, visualized instantaneous flow fields and the pre-multiplied energy spectra are presented in order to examine turbulence structures.