Reynolds number dependence of inner peak turbulence intensity in pipe flow

Abstract

Streamwise turbulence statistics in the range from Reτ = 990 to Reτ = 20 750 at the High Reynolds Number Actual Flow Facility at the National Metrology Institute of Japan are presented, specifically focusing on the Reynolds number dependence of the inner peak turbulence intensity. Velocity measurements are conducted using laser Doppler velocimetry (LDV), taking account of problems specific to this method, with the aim of providing reliable experimental results. The control volume and the fringe pattern of LDV, both of which influence turbulence statistics, are directly measured using a rotary wire device, and they are used to correct the measured turbulence intensity using methods developed in this study. The present results for mean velocity and turbulence intensity profiles agree well with direct numerical simulation data. The inner peak turbulence intensity in this pipe experiment increases with the increasing Reynolds number. It is found that the Reynolds number dependence of the inner peak up to Reτ = 20 750 is very similar to that in a turbulent boundary layer (TBL). The slope of the outer logarithmic region in the turbulence intensity profile is twice the slope obtained from the relation between the inner peak and the Reynolds number. This relation is also consistent with that for TBL flow.