Effect of bed-load concentration on friction factor in narrow channels

摘要

Many studies concern the influence of bed-load on flow resistance in wide open channels and flumes. In this work the effect of bed-load concentration on the friction factor was investigated experimentally in a narrow channel. Tests were performed both in clear water and sediment transport conditions, using a roughened fixed bed. The present approach revises the Einstein side-wall correction procedure for the decomposition of flow resistance between the bed and the walls, which are of different material and, consequently, different roughness. From the velocity profiles, measured through micro-propellers, it was possible to obtain the bed shear velocities and, then, the mean bed and wall friction factors. An equivalent friction factor was finally obtained. The effects of the sediment concentration on velocities and resistance was analyzed. Also the influence of the walls on the velocity distributions was observed and commented on.