Bifurcation modelling in a meandering gravel–sand bed river
Bifurcation modelling in a meandering gravel–sand bed river
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蜿蜒的砾石-沙床河流的分叉建模
DOI：
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发表时间：
2012
期刊：
影响因子：
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通讯作者：
E. Mosselman
中科院分区：
文献类型：
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作者：
K. Sloff;E. Mosselman
Pannerden的莱茵河分叉口构成了荷兰供水的主要分配点，不仅分配水和泥沙，还分配洪水风险和通航能力。它的形态稳定性几个世纪以来一直是一个令人担忧的问题。我们介绍了20多年来对这种具有砾石砂床和曲折平台的分叉进行数值形态模拟的经验。连续的计算表明了上游接近条件的重要性，包括颗粒分选和冲积粗糙度的物理机制的必要性，以及假设河床活跃层比使用恒定流量的实验室水槽实验所建议的更厚的必要性。模型中的活跃层必须更厚，以考虑河床变化，这是由于在形态建模中过滤掉的高频流量变化引起的。我们讨论了校准和验证方面的限制，但我们认为，尽管有这些限制，2D和3D形态模型是有价值的工具，不仅对于工程问题的实际应用，而且对于揭示既定知识和对相关物理过程的理解的限制。将数值模型应用于Pannerden分叉，似乎揭示了已建立的模型公式中的缺点，这些缺点在其他情况下不会引起特定的问题。因此，这一应用程序对于制定进一步研究的议程特别有用。版权所有©2012 John Wiley&Sons，Ltd.
The Rhine bifurcation at Pannerden forms the major distribution point for water supply in the Netherlands, distributing not only water and sediment but also flooding risks and navigability. Its morphological stability has been a concern for centuries. We present experiences from more than two decades of numerical morphological modelling of this bifurcation with a gravel–sand bed and a meandering planform. Successive computations have shown the importance of upstream approach conditions, the necessity to include physical mechanisms for grain sorting and alluvial roughness, and the need to assume a thicker active layer of the river bed than is suggested by laboratory flume experiments using a constant discharge. The active layer must be thicker in the model to account for river bed variations due to higher‐frequency discharge variations that are filtered out in morphological modelling. We discuss limitations in calibration and verification, but argue that, notwithstanding these limitations, 2D and 3D morphological models are valuable tools, not only for pragmatic applications to engineering problems, but also for revealing the limitations of established knowledge and understanding of the relevant physical processes. The application of numerical models to the Pannerden bifurcation appeared to reveal shortcomings in established model formulations that do not pose particular problems in other cases. This application is therefore particularly useful for setting the agenda for further research. Copyright © 2012 John Wiley & Sons, Ltd.