In 1975 Perry and Abell identified significant differences among the then-published experimental measurements of turbulence intensity in pipe flow. They cited inconsistent hot-wire measurement techniques, among other factors, as the reason for the discrepancies. In the years since their observation, a host of improved experimental techniques for measuring turbulence intensity have become available, most notably the non-intrusive methods based on the Doppler effect. However, a survey of single-phase, fully developed turbulent flow in circular pipes shows that significant variations between experimental measurements persist.

This paper surveys some of the available single-phase axial and, where available, radial fluctuating velocity data and sheds light on the differences between the measurements and extracts potential trends. The focus is on the inner portion of the flow where Re effects are minimized. Numerous, heavily-cited published works are surveyed, with Re ranging from 5.3*10^3 to 6.1*10^6, which employ an array of measurement techniques. In addition, new LDV data for water velocity fluctuations at high Re are included in this survey. A dichotomy between the centerline axial fluctuating velocity of experiments conducted in gas (air) and liquid (water) are identified, with velocity fluctuations in water being consistently greater than those in air at similar Re.