The Study of the Suspended-load on Fixed bed with Large Roughness

Abstract

There are many studies of the mechanics of suspended load laden flow, and many theoretical formula to estimate the concentration of suspended load have been proposed so far. But all has common problems;
(1) The relation between the characteristics of the turbulence of flow and the behaviour of suspended load is not so much reflected on the formula.
(2) It's necessary to know a reference concentration at a reference level to evaluate the formula. The reference level has not been set up theoretically.
And there are few studies of the suspended load on the torrential bed condition, in comparison with that on the alluvial bed condition.
This study was made by using a steep channel with large roughness on its bed. The results were analyzed using the diffusion model in order to check the suitability. The results are;
(1) The similarity between the dispersion of suspended load and the momentum transfer of flow was not always shown.
(2) The concentration distribution below roughness height decrease with decreasing height in some cases.
(3) It's more reasonable that the reference level is set up at the point with the roughness height from the theoretical bed.
In order to figure out mechanics of suspended load laden flow, especially on the torrential bed condition, the structure of the turbulence of the flow, the behaviour of suspended load near the bed and the behaviour of suspended load there should be studied.