Author(s): Wei Huang, Huai Han Liu, Bo Jiang, Guoping Lei, Zupeng Gu, Hongwei Kuang, Fei Chen
Linked Author(s): Wei Huang
Keywords: Poor sorted sediments, gravel to sand transition, numerical study, sensitive analysis.
Abstract: In natural rivers, bed sediment size tends to decrease from upstream to downstream. Interestingly, sediment size does not decrease gradually. Bed material can change from gravel to sand abruptly with paucity of some sizes accompanying abrupt change in bed slope. Although many studies have investigated features and mechanisms of the gravel to sand transition (GST), details about flow, sediments and bed are not investigated during formation and evolution of GST. In the present paper, a nonuniform sediment transport model is applied to investigate formation and evolution of GST feeding with poor sorted sediments at the upstream inlet. Results show that bed shear stresses, sediment transport, medium size of bed sediment and Shields number all change abruptly at some locations during formation and evolution of GST. It should be noted that abrupt changes for different variables do not appear at the same location, which implies that variations for flow and sediment characteristics exist some spatial lags. Sensitive analyses of flow and sediment discharges on GST show that gravel front migrates downstream further in relation to a larger flow discharges. However, influence of sediment discharge on GST is not monotonous, e. g. , in the initial period, GST moves faster in relation to a larger sediment discharge. However, it moves slower after a certain period
Year: 2017