2000 Volume 44 Pages 665-670
The fractional transport of graded sediment and the resultant sorting are the key factors to understand the sediment transport phenomena in alluvial stream. Ordinary approach is to apply the sediment transport law, which is proposed for the uniform sediment, for each fractions of graded sediment, with estimating the critical bottom shear stress based on the Egiazaroff s formula. In other words, the particle/particle interaction was not considered directly in the previous studies of the graded sediment; while the interaction between the different size sediments are predominant factor of the transport process of the graded sediment. In this study, the Movable Bed Simulator-the numerical code of granular material based on the Distinct Element Method-is applied to the fractional transport of graded sediment. The critical bottom shear stress and the fractional sediment transport rate estimated by the present code show satisfactory agreement with the previous experimental data. Furthermore, the velocity profile of the sediment particles and the thickness of the sediment moving layer are calculated by the present simulation to estimate the internal structure of the transport process of graded sediment.
