Experimental study on the effect of rough surfaces with systematically varied effective slope and skewness on turbulent frictional resistance

Abstract

In order to investigate the effect of geometrical characteristics of rough surfaces on turbulent frictional resistance, we performed particle image velocimetry (PIV) measurements on the turbulent flows over systematically varied rough surfaces. The present study focused on two characteristics parameters, namely the skewness factor and effective slope, which are respectively related to the probability density of roughness elevations and the wavelength of the surface undulations. It is found that the frictional resistance is large for the surface with peak-dominated steep rough surface, which is characterized by the positive skewness factor and large effective slope value. The characteristic parameters are found to have a minor influence on the asymptotic behavior toward the fully rough regime.