0208 遷移域チャネル流の大規模な乱れ間欠性に関する数値的・実験的研究(OS2-2 乱流の計測・解析・制御,オーガナイズドセッション)

抄録

The turbulent stripe, which was found by previous DNS (direct numerical simulation) studies on a turbulent channel flow at transitional Reynolds numbers, was investigated numerically using large-scale DNSs and experimentally by flow visualizations. The bulk Reynolds number at the transition from turbulent to intermittent flow was varied from 2800 to 1580, and the intermittency factor was measured. During the determination of the intermittency factor, the threshold value of the detector function based on the wall-normal turbulent intensity was verified by flow visualizations. Conditional averaging revealed that, in the quasi-laminar region, the Reynolds shear stress was almost negligible but the streamwise and spanwise velocity fluctuations were still significant.