HRT

Abstract

In recent years there has been significant progress made towards understanding t he large-scale structure of wall-bounded shear flows. Most of this work has been conducted with turbulent boundary layers leaving scope for further work in pipe s and channels. Here, the structure of fully-developed turbulent pipe and channel flow has been studied using custom-made arrays of hot-wire probes. R esults reveal long, meandering structures of length up to 25 pipe radii or chann el half-heights. These appear to be qualitatively similar to those reported in t he log region of a turbulent boundary layer. However, for the channel case, larg e-scale coherence persists further from the wall than in boundary layers. Further comparison of the three turbulent flows sh ows that the characteristic structure width in the logarithmic region of a bound ary layer is at least 1.6 times smaller than that in a pipe or channel.