Air flow in a tube with a diverging inlet: II. Measurement and correlation of confirmed fully developed turbulent flow

Abstract

Mean local velocities were measured in the section of a tube where turbulent flow was experimentally confirmed to be fully developed. Over Reynolds numbers from 9,000 to 56,0 00, the velocities correlated, using a logarithmic distribution, almost identically to those of Deissler. Because of the limited data for γ+< 26, no meaningful correlation near the wall was obtained. Using these data as a basis, a comparison of the various correlations for fully developed turbulent flow in the core region was performed. Although measurements in the laminar sublayers were limited, some discussion of correlations applicable over the entire cross‐section of the tube is included. Pai's equation, valid from the wall to the center‐line, was found to correlate all of the data best for the several approaches tested. In the turbulent core, the improved universal velocity distribution correlation suggested by Bogue but in simplified form, correlated the data equally well. Using the method of Wasan et al, this logarithmic distribution could be joined without a discontinuity to other suitable correlaions valid near the wall.