EXPERIMETAL STUDY OF CHARACTERISTICS OF ROUGH-SURFACE BOUNDARY LAYER PAST GENTLE HILLS

Abstract

Turbulence characteristics of boundary layers past gently curved hills with varying roughness height have been studied by wind-tunnel experiments. The results of the mean velocity distributions indicate that for the gently sloped hills, where no flow reversal occurs, the pressure-gradient and boundary curvature effects and the surface roughness act almost independently and the wall-law similarity similar to the rough boundary layers on flat surface exists. The surface roughness, however, is seen to soften the pressure-gradient effects on both mean velocity and turbulent stresses. Furthermore, the turbulence stresses that are known to be highly anisotropic near the solid surface are made more isotropic due to the surface roughness.