Abstract
Turbulent measurements are conducted for flow over rigid vegetation simulated by cylinders with equi-spacing, and the structure of turbulent flow over a vegetated bed is investigated based on the turbulence properties clarified by the experiments. When the water depth is lower than the vegetation height, the velocity profile is uniform and it increases proportionally to the square root of the slope; while, when the depth is higher than the vegetation height, turbulent shear flow profile appears even in the vegetated layer because of the turbulent momentum exchange with the faster surface flow region. The measurements of velocity and the Reynolds stress in this layer and the analysis of them clarify that the mixing length in this layer increases with the distance from the interface of the layer with the surface flow region and that it is non-zero at the interface. This non-zero mixing length at the interface modifies its distribution even in the surface flow region. These facts make it possible to describe the velocity profile of flow over vegetated bed including the vegetated layer.
