Published online by Cambridge University Press: 04 July 2016
Axial, normal (radial) and tangential turbulence intensity measurements have been carried out in the past in pipe and two-dimensional channel flows, e.g. Refs. 1-9. A similarity in the distribution of these turbulence intensities is observed. They are all minimum at the centreline, increasing steadily as the wall is approached, until they reach some maximum values close to the wall, then they start to decrease as the wall is approached further. Furthermore, the three components of turbulence intensity have been observed to vary in a similar way with the Reynolds number.
On the other hand, the Prandtl mixing length theory assumes that the turbulent fluctuations are proportional to the product of a local mixing length and a velocity gradient. This implies that the turbulence fluctuations are directly proportional to each other. It is, therefore, found worthwhile examining the possibility of a relationship between the turbulence intensities. Smooth pipe and channel flows are chosen for this purpose.