高レイノルズ数円管流れに関する実験的研究

－乱流強度分布に対する計測体積の影響－

抄録

LDV (Laser Doppler Velocimetry) measurement has been performed in the high Reynolds number turbulent pipe flow (1000 ≤ Re_τ ≥ 20,000) using water flow facility at AIST, NMIJ, to clarify the space resolution issue. When the measurement volume is larger than the viscous length scale, the spatial resolution affects on the measurement. In this research, we measured velocity by changing the wall-normal direction width of measurement volume, and verified the effect on the mean and turbulence intensity profile. Even though the measurement width increased, the mean velocity profile didn't change, but the turbulence intensity profile remarkably increased at near wall region, (y⁺ < 50). We compared the PDFs at y⁺ = 15 (Re_τ = 8400) among different volume sizes, and found that their shape widely spread. But the PDFs at y⁺ = 50 were not spread. Based on this result, we conclude that the effect of measurement width appears only near the wall where the mean velocity gradient is large.