Power laws for rough wall turbulent boundary layers

Abstract

An assessment of the ability of power laws to describe the mean velocity profile in the overlap region of a zero pressure gradient turbulent boundary layer is reported. The experiments were performed in a wind tunnel on smooth and four different types of rough surfaces at moderate Reynolds numbers. A novel modification to the power law velocity profile is proposed to account for the effect of surface roughness in the overlap region. This modification is analogous to the use of a roughness function to produce a downward shift in the logarithmic velocity profile. The roughness parameters in the proposed equation more accurately follow the effect of roughness on skin friction than does the roughness shift Δ U+. The present study shows that power laws can be used to effectively describe the mean velocity profile over a wider range than a log law for both smooth and rough surfaces. © 2003 American Institute of Physics.