Author(s): Chunchen Xia; Hui Liang; Zhixian Cao; Songbai Peng; Youwei Li; Qifeng Liu; Wei Zhang
Linked Author(s):
Keywords: Hydro-sediment-morphodynamic processes; 1D numerical model; Shock-capturing finite volume method; Waterway regulation and management
Abstract: The Changjiang (Yangtze River) is one of the longest rivers in the world and plays a crucial role in waterborne freight in China. The waterway conditions in the middle and lower Yangtze River may not well meet the increasingly demanding requirements of cost-effective navigation in line with the rapid economic development in the region. Quantitative understanding of the water flow, sediment transport and bed evolution is essential for the regulation and maintenance of the waterway, especially since the Three -Gorges Reservoir was put into operation. One-dimensional (1D) modelling is one of the most viable approaches to enhancing the understanding of the hydro-sediment-morphodynamic processes. Yet previous 1D models are simplified, mostly based on rather crude assumptions (especially the quasi-steady flow assumption), of which the effects have so far remained insufficiently understood. Here, a physically-based 1D numerical model is presented, which explicitly incorporates the interactions between the flow, sediment transport and morphological evolution, and features a wide application in natural rivers with unsteady flows and non-uniform sediment transport. The governing equations are numerically solved using the shock-capturing finite volume method with the HLLC approximate Riemann solver for the flow equations and SLIC approximate Riemann solver for the sediment equation respectively. The model is benchmarked against a spectrum of test cases, and then applied to the reach from Yichang to Gong’an in the middle Changjiang Waterway. It shows that the model is able to successfully resolve the propagations of flow and sediment transport and reveals the influences of the discharge in Yichang on the water levels downstream. The present work facilitates a viable and promising approach to the understanding of the Changjiang Waterway, in support of its regulation and management.
Year: 2020