高レイノルズ数円管流れにおけるPMS解析

抄録

In this study, we report first results of streamwise spectrum analysis at fully developed turbulent pipe flow up to Re_τ=20000 using laser Doppler velocimetry (LDV). The distribution of Pre-Multiplied Spectra (PMS) measured by LDV were nice agreement with previous ones measured by hot wire. We focus on very-large-scale-motion (VLSM) and large-scale-motion (LSM) which have different sizes with radius R scale away from the wall, and discuss the change of energydominant structures from the overlap region to the wake region. The dominant structure in the overlap region is VLSM, and it changes to LSM in the wake region. The peak value of PMS for VLSM; P_V-peak increases with Reynolds number with the relation of P_V-peak=0.137ln(Re_τ)-0.140. On the other hands, the peak value of PMS for LSM is independent with Reynolds number at wake region.