Author(s): F. Canovaro; E. Paris; L. Solari
Linked Author(s):
Keywords: Flow resistance; Experiments; Mountain streams; Macro-scale roughness
Abstract: A physically based model for average velocity distribution profile over a bed with macro roughness elements, such as mountain streams, is developed herein. Such model allows to investigate how flow resistance is affected by concentration and planimetric disposition of the macro roughness elements. The model is based on the partitioning of total bed shear stress induced by the flow into two contributions: a drag component associated to the flow around the macro-roughness elements and a surface friction component. The model requires some input data that have been obtained through an experimental activity. The experiments have been carried out in a flume characterized by steep slope and large relative roughness conditions. For a given flow discharge and bed slope various experiments have been carried out according to different pattern and spacing of the roughness elements constituted by rounded river pebbles. During the experiments flow depth and velocity have been measured at different locations in the flume. Application of the model suggests the existence of a concentration of the macro-roughness elements which produces the maximum flow resistance. In such condition the model suggests that the ratio of drag induced shear stress to the total bed shear stress is maximum too.
Year: 2003