Modeling of Breaching Due to Overtopping Flow and Waves Based on Coupled Flow and Sediment Transport

Water

Liang Zhao¹  Thomas Pähtz¹  Peng Hu¹  Zhiguo He¹  Gangfeng Wu² 

[1] Ocean College, Zhejiang University, Hangzhou 310058, China;School of Civil Engineering and Architecture, Ningbo Institute of Technology, Zhejiang University, Ningbo 31510, China;

关键词: dam breaching;    overtopping flow;    wave;    coupled;    sediment transport;    bed erosion;   

DOI  :  10.3390/w7084283

来源: DOAJ

【 摘 要 】

Breaching of earthen or sandy dams/dunes by overtopping flow and waves is a complicated process with strong, unsteady flow, high sediment transport, and rapid bed changes in which the interactions between flow and morphology should not be ignored. This study presents a depth-averaged two-dimensional (2D) coupled flow and sediment transport model to investigate the flow and breaching processes with and withoutwaves. Bed change and variable flow density are included in the flow continuity and momentum equations to consider the impacts of sediment transport. The model adopts the non-equilibrium approach for total-load sediment transport and specifies different repose angles to handle non-cohesive embankment slope avalanching. The equations aresolved using an explicit finite volume method on a rectangular grid with the improved Godunov-type central upwind scheme and the nonnegative reconstruction of the water depth method to handle mixed-regime flows near the breach. The model has been tested against two sets of experimental data which show that it well simulates the flow characteristics, bed changes, and sediment transport. It is then applied to analyze flow and morphologic changes by overtopping flow with and without waves. The simulated bed change and breach cross-section shape show a significant difference if waves are considered. Erosion by flow without waves mainly occurs at the breach and is dominated by vertical erosion at the initial stage followed by the lateral erosion. With waves, the flow overtops the entire length of the dune to cause faster erosion along the entire length. Erosion mainly takes place at the upper layer at the initial stage and gradually accelerates as the height of the dune reduces and flow discharge increases, which indicates the simulated results with waves shall be further verified by physical experimental evidence.

【 授权许可】

Unknown