Numerical simulation of three‐dimensional, time‐averaged flow structure at river channel confluences
Numerical simulation of three‐dimensional, time‐averaged flow structure at river channel confluences
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DOI：
10.1029/2000wr900011
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发表时间：
2000-09
影响因子：
5.4
通讯作者：
K. Bradbrook;S. Lane;K. Richards
中科院分区：
文献类型：
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作者：
K. Bradbrook;S. Lane;K. Richards
目前的汇流研究强调三个广泛的控制流动结构的产生：（1）平面形状曲率;（2）地形转向;（3）与流动分离和剪切层动力学相关的各向异性湍流。这些过程在解释观测到的流动结构中的相对重要性是有争议的，这种情况可能与不同的研究人员已经研究了不同的汇流配置的事实有关。本文使用三维数值模型，具有完全椭圆形解、自由表面处理，以及基于重整化群（RNG）的湍流模型，以帮助为实验室和（矩形）和一个场汇流（Kaskaskia河和铜斯劳的汇合处），并确定观察特定流动结构的特定条件。结果表明，对于对称配置，可以与背靠背曲折进行类比，但随着汇流不对称性的增加，这种状态将逐渐发散。在不对称的情况下，由于流线曲率和地形转向的影响，双单元结构可能仅限于连接处附近。这些差异可以通过考虑动态压力场来解释，动态压力场可能是每个汇流配置所特有的。因此，这项研究部分地调和了关于控制河道汇流中时均流结构的不同观点，尽管需要进一步研究这些过程与瞬时速度波动的相互作用。
Current confluence research emphasizes three broad controls on flow structure generation: (1) planform curvature; (2) topographic steering; and (3) anisotropic turbulence associated with flow separation and shear layer dynamics. The relative importance of these processes in explaining observed flow structures is controversial, a situation that may be related to the fact that different investigators have examined different confluence configurations. This paper uses a three‐dimensional numerical model, with a fully elliptic solution, a free surface treatment, and a turbulence model based on a renormalized group (RNG) to help to provide a physically based explanation of the controls upon flow structure generation for both a laboratory (rectangular) and a field confluence (the confluence of the Kaskaskia River and Copper Slough) and to identify the particular conditions under which particular flow structures are observed. Results suggest that an analogy with back‐to‐back meanders is possible for symmetrical configurations but that there will be progressive divergence from this state as confluence asymmetry increases. In asymmetric situations a dual‐cell structure may be limited to the immediate vicinity of the junction because of the effects of streamline curvature and topographic steering. These differences can be explained by consideration of the dynamic pressure field, which may be specific to each confluence configuration. As such, this study partially reconciles differing views over what controls time‐averaged flow structures in river channel confluences, although further research into the interaction of these processes with instantaneous velocity fluctuations is required.