The effects of bed roughness on the distribution of turbulent intensities in open-channel flow

In this paper, the systematic longitudinal turbulent intensity measurements of flow in a gravel open-channel have been conducted with a highly accurate one-dimensional LDA-system. The channel bed was roughened with gravels of uniform and non-uniform diameters respectively, and a wide range of H /Ks were considered. In comparison with the smooth bed results, it was found that the bed roughness makes the flow turbulence become well-distributed in the region near the bed and in the case of small H jK% values. With regard to the flow over a non-uniform gravel bed, only the flow region below the maximum gravels is affected by the rough bed, and outside this region, the turbulent intensity distributions could collapse on to a single curve.