Velocity distributions in plane turbulent channel flows

Abstract

Measurements of time-mean velocity have been made in a flat channel (aspect ratio 12 to 28), one of whose walls consists of a belt which can be moved in the direction of air blown through the channel or in the opposite direction. The wall layers generated in twenty-six turbulent flows, including plane Poiseuille and plane Couette cases, are compared with analytical results obtained by Kader & Yaglom and by Townsend. Empirical descriptions are developed for the viscous, logarithmic and gradient portions of these wall layers. The core regions of both Couette-type and Poiseuille-type flows are also described empirically. Parallels are drawn with developing boundary layers, and phenomena are identified that relate to the relaminarization of boundary layers.