Abstract
The friction factor of flow on a flat bed consisting of sands decreases when the sands on the bed are transported by the flow. In this paper, the equations of velocity distribution and friction factor on a flat movable bed are derived on the basis of a two layer flow model with water flow layer and sand-water flow layer. Theoretical values of velocity distribution are compared with the experimental ones and show good agreement with them. As the results, the differences in the velocity and the friction factor between the fixed and movable beds are crarified.
