Limit Concentration of Suspended Sediment

by Zhaoyin Wang, Inst of Water Conservancy and, Hydroelectric Power Research, Beijing, China,



Document Type: Proceeding Paper

Part of: Hydraulics/Hydrology of Arid Lands (H?AL)

Abstract:

It is found from experiments that there is a limit on suspended sediment concentration. The limit concentration of uniform sediment varies with sediment diameter, and it is about 1000 kg/m³ for cohesionless sediment finer than 0.15 mm and it reduces from 1000 to 200kg/m³ as sediment diameter increases from 0.15 to 5 mm. The limit concentration of sediment of diameter d is not affected by existence of suspended sediment finer than d/10, so that the limit concentration of non-uniform sediment is larger than that of uniform sediment. The concept of limit concentration is verified in a flume experiment. The capacity of flow to carry suspended sediment increases with flow rate in general cases. As the concentration reaches the limit concentration, however, further increasing flow rate and adding sediment raise nothing in suspended sediment concentration. On the other hand, the total concentration can be easily increased to 1200 kg/m³ at the same flow rate if much coarser sediment is added into the flow saturated with finer sediment. The wider the range of sediment size distribution, the easier the flow to carry more suspended sediment. This interpretes the phenomenon of increase in median diameter of suspended load with increasing concentration in hyperconcentrated flow in the Yellow River and its tributories.

Subject Headings: Suspended sediment | Sediment | Fluid flow | Flow measurement | River flow | Flow rates | Rivers and streams | Yellow River

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