Velocity measurements of a free-surface turbulent ow over smooth and roughbeds

Abstract:The effect of different types of surface roughness on a turbulent boundary layer was studied using 1D velocity measurements in a relatively high Reynolds ow. The roughness consisted of trapezoidal ribs with horizontal spacing and roughness height k . The roughness elements were aligned in a direction transverse to the ow. A series of 7 tests of fully rough turbulent subcritical ow over two-dimensional transverse repeated trapezoidal ribs was undertaken, in which the ribs were varied to give uniform rib spacing-to-height ratios of p/k = 6{36. Measurements of the velocity were carried out over a range of Reynolds numbers, 81735 Re 144,110. The results show that the mean pro les of all the surfaces collapse well in the velocity defect form.