High Reynolds Number Experimental Facilities for Turbulent Pipe Flow at NMIJ

In this paper, we report on high Reynolds number and highly accurate experimental facilities for turbulent pipe flow established by the National Metrology Institute of Japan (NMIJ). One of the facilities, called the High Reynolds number actual flow facility (Hi-Reff), is capable of handling a maximum bulk Reynolds number of \({Re}_\mathrm{D} = 2.0 \times 10^7\). The most remarkable feature of this facility is its highly accurate flow rate measurements. The expanded uncertainty of the volumetric flow rate is estimated as 0.040–0.10%. Such a low flow rate measurement uncertainty contributes to extremely accurate estimations of inner-scale variables such as friction velocity. This paper presents the details and advantages provided by this NMIJ facility in relation to turbulent pipe experiments.