Effects of surface roughness element spacing on boundary-layer velocity profile parameters

Abstract Turbulent boundary-layer velocity profiles over rough surfaces depend on the size, shape and spacing of the roughness elements. In this study, simple theoretical equations to predict the aerodynamic roughness length and displacement height as functions of element spacing density are developed when cubes are used as roughness elements. These parameters are also evaluated from wind-tunnel tests for various element spacing densities. The experimental results agree well with the theoretical equations. Dependence of the shear velocity (or surface drag coefficient), turbulence intensity and longitudinal turbulent length scale on the element spacing density are also evaluated from the experiments.

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