TURBULENCE IN HELICALLY CORRUGATED PIPE FLOW

Results are reported of experimental measurements of friction factor, mean and turbulent velocities, and Reynolds stresses in fully developed flow through a helically corrugated pipe. Helical corrugations induce a strong rotational component in the mean flow near the wall but this decreases rapidly toward the pipe axis. Turbulence intensities and axial shear are generally smaller in this flow than in nonrotating pipe flow and the reduction is attributed to rotation. Reynolds stress measurements extrapolated to the wall are in agreement with pressure drop measurements. Both show that pipe friction factor is less in helically corrugated pipe than in normally corrugated pipe, other factors being the same. The axial component of the mean flow is well fitted by the two-dimensional semilogarithmic law-of-the-wall for rough pipes. It is also fitted by the defect law but the numerical parameters of the latter behave as in an adverse pressure gradient boundary layer, indicating less shear stress than in nonrotating pipe flows. This is consistent with reduced friction factor.