Numerical simulation of bank erosion processes with composite materials and variations in flow structure
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摘要: 非均质岸滩广泛分布于冲积河流中，其侧蚀过程沿垂向具有分层特点。基于全三维水沙模型及河岸侧蚀坍塌力学模式，提出动态网格跟踪技术，构建了非均质岸滩侧蚀沿垂向差异的三维动力学模拟方法。以连续弯道概化水槽为例，模拟分析了非均质河岸侧蚀过程中三维水流结构的响应特征。研究结果表明：坡脚冲刷后，底部主流向凹岸偏移，在已有弯道环流的基础上，于坡脚处出现一反向次生流；上部粘性土层坍塌后，崩塌土体堆积于坡脚处，上部主流明显左偏，下部次生流消失；随着坡脚堆积体的冲刷搬运，下部主流进一步向凹岸偏移；如此循环，主流不断向凹岸偏移，致使岸坡持续崩退、河道摆动。Abstract: Riverbanks with composite materials are commonly found on alluvial rivers. Lateral erosion processes of such banks are very different along the vertical direction. On the basis of three-dimensional (3-D) flow and sediment transport model and mechanisms of riverbank erosion, a 3-D numerical method was developed for simulating bank erosion processes with composite materials using the adaptive grid scheme. The 3-D numerical method is applied to a conceptual meandering channel, and to simulate the variation of 3-D flow structure as erosion of the bank progresses. Results show that the main flow migrates towards the concave bank after the erosion of bank toes, and then, a new secondary flow structure with reverse direction compared to the initial secondary flow structure is formed on the bank toe. The main flow migrates further towards the concave bank after the collapse of upper layers, and the new secondary flow structure on the bank toe disappears. Again, the main flow migrates towards the concave bank after the erosion of bank toes. Thus, the main flow migrates towards the concave bank step by step, resulting in a continue bank erosion and channel migration.
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