Turbulent Flow Over Urban-Type Roughness Using PIV

Wind tunnel measurements of turbulent boundary layers over rough and smooth surfaces have been carried out using PIV. The roughness elements used were an urban-type surface with 5-mm square, random-height elements and the ratio of the mean roughness height to the boundary thickness was h/delta = 0.042. The Reynolds number based on the momentum thickness was about Re(theta) = 12,500. By using PIV measurements, the effects of surface roughness on the mean flow and Reynolds stresses across the entire boundary layer were examined and compared with that of a smooth wall. Spatial correlation data, extracted from the PIV images were used to provide information about eddy structures and comparisons have been made with previous data for the uniform cube surface.