Turbulent Flow in the Inlet Region of a Smooth Pipe

Abstract

This paper reports measurements of mean velocities, turbulence intensities, and turbulence (Reynolds) stresses in the inlet region of a smooth pipe. Data are presented for the first 40 diameters of pipe length. Fully developed flow is not attained in this length for a Reynolds number (based on pipe diameter and mean velocity) of 388,000, but the wall shear stress and the static pressure gradient attain their fully developed values within the first 15 diameters. Velocity profiles at successive sections in the inlet region are not similar as assumed in some published calculation methods. Longitudinal convection of turbulence energy is appreciable; except very near the pipe entrance, radial convection is negligible.