Low Reynolds Number Turbulent Flow Over Smooth and Transitionally Rough Surfaces

Abstract

This paper reports on experiments conducted to study the structure of turbulent flows over a hydraulically smooth surface and a transitionally rough surface produced using a wire mesh. A high resolution particle image velocimetry (PIV) technique was employed to conduct the velocity measurements. The smooth wall measurements were performed at two different Reynolds numbers while the wire mesh data were obtained for a single Reynolds number. From the PIV data, profiles of the mean velocity, turbulent intensities and Reynolds shear stress as well as two-point velocity correlations were obtained. The results show that the mean velocity and one-point turbulence statistics are similar outside the roughness sublayer. It is also observed that changes in Reynolds number and surface condition do not have significant effects on the average inclination of the hair-pin vortex and the streamwise and transverse extents of the two-point velocity correlations.