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Effects of large-scale structures on inner layer in high Reynolds number turbulent channel flow

Yoshinobu Yamamoto
Department of Mechanical Engineering University of Yamanashi 4-3-11, Takeda, Kofu, 400-8511, Japan

Yoshiyuki Tsuji
KTH Mechanics, Royal Institute of Technology, 100 44 Stockholm, Sweden; Department of Energy Science and Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8503, Japan

Sinopsis

Direct numerical simulations of turbulent channel flows up to Reτ = 8000 were carried out. Present resolution of DNS database ensures over twice fine resolution of Kolmogorov wave length at all wall-normal heights. In case of Reτ = 8000, 8640 (Δx+=14.8), 4096 (Δy+=0.6-8.0), and 6144 (Δz+=8.3) grid points (resolutions in wall-units) were adapted for stream, wall-normal, and spanwise directions, respectively. As the results, a logarithmic profile of the mean velocity and a second peak of the production/dissipation rate of the turbulent energy were clearly observed for Reτ > 4000. The second peak of premultiplied spectrum at overlap regions in streamwise turbulent velocity was appeared in cases of Reτ = 4000 and 8000. The wave-length of this second peak is almost 5h, where, h is channel-half height. In this overlap region, 90 < y+ < 200, the formation of the intermediate scale structures between large-scale structures and primary structures near the wall were visually observed. The characteristics of these intermediate scale structures might be regarded as the high-Reynolds number effects.