Hydrodynamic processes in sharp meander bends and their morphological implications
Hydrodynamic processes in sharp meander bends and their morphological implications
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DOI：
10.1029/2010jf001806
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发表时间：
2011-01-29
影响因子：
3.9
通讯作者：
Blanckaert, K.
中科院分区：
文献类型：
--
作者：
Blanckaert, K.
曲流急弯的迁移率具有较大的变异性，表明某些急弯趋于稳定。这些观察结果仍然无法解释。本文研究了三个水动力过程中的急弯与固定银行，并讨论了其形态的影响：二次流饱和，外银行细胞，和内银行流动分离。降阶水动力模型的预测表明，非线性水动力相互作用限制了二次流的增长。这个过程称为二次流的饱和。对于外岸细胞和内岸流动分离，分析依赖于水槽研究中的实验结果，在固定和移动的床通道。实验结果表明，外银行细胞存在附近的陡峭以及搁置银行和扩大与陡峭度和粗糙度的外银行，特别是增加曲率。流分离的影响，在内银行被认为是强烈的条件下的流-沙相互作用，这导致增加冲刷深度附近的外银行和增加的速度附近的脚趾，银行。总的来说，结果表明，二次流饱和度和外银行细胞往往抑制曲流迁移，而内银行分离可能会增强迁移。这三个水动力过程的相对重要性取决于水力，几何和沉积条件，这是一致的，在观察到的迁移率的大的变化。结果表明，大型浅水河流具有最动态的曲流行为，而稳定的曲流的发生似乎有利于在狭窄的河流。
The migration rate of sharp meander bends exhibits large variance and indicates that some sharply curved bends tend to stabilize. These observations remain unexplained. This paper examines three hydrodynamic processes in sharp bends with fixed banks and discusses their morphological implications: secondary flow saturation, outer-banks cells, and inner-bank flow separation. Predictions from a reduced-order hydrodynamic model show that nonlinear hydrodynamic interactions limit the growth of the secondary flow. This process is called the saturation of the secondary flow. For outer-bank cells and inner-bank flow separation, the analysis relies on experimental findings from flume studies in channels with fixed and mobile beds. The experiments reveal that outer-bank cells exist near steep as well as shelving banks and amplify with increasing steepness and roughness of the outer bank, and especially with increasing curvature. The effects of flow separation at the inner bank are found to be strongly conditioned by flow-sediment interactions, which lead to an increased scour depth near the outer bank and increased velocities near the toe of that bank. Overall the results suggest that secondary flow saturation and outer-bank cells tend to inhibit meander migration, whereas inner-bank separation may enhance migration. The relative importance of these three hydrodynamic processes depends on hydraulic, geometric, and sedimentologic conditions, which is consistent with the large variance in observed migration rates. The results suggest that large shallow rivers have the most dynamic meandering behavior, while the occurrence of stabilized meanders seems to be favored in narrow rivers.