Numerical simulation of dune–flat bed transition and stage‐discharge relationship with hysteresis effect
Numerical simulation of dune–flat bed transition and stage‐discharge relationship with hysteresis effect
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DOI：
10.1029/2008wr006830
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发表时间：
2009-04
影响因子：
5.4
通讯作者：
Y. Shimizu;S. Giri;S. Yamaguchi;J. Nelson
中科院分区：
文献类型：
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作者：
Y. Shimizu;S. Giri;S. Yamaguchi;J. Nelson
这项工作介绍了非恒定流量下床形形态动力学建模的最新进展。本文包括对吉里（Giri）和清水（Shimizu）（2006a）早期提出的形态动力学模型的进一步发展。该模型再现了河流沙丘的时间演变，并准确复制了与床形演变相关的物理特性。模型结果似乎能对任意稳定流的床形几何形状和床形阻力提供准确预测。然而，对形状阻力随时间变化的准确预测是洪水事件期间水位 - 流量关系预测的关键。在此，模型的能力被扩展以复制沙丘 - 平底床的转变，进而复制非恒定流条件下床形随时间增长或衰减所产生的形状阻力变化。进行了一些数值实验，以分析在不同流量的涨水和落水阶段沙丘和平底床状态之间转变所导致的水位 - 流量关系的滞后现象。数值模型成功地模拟了沙丘 - 平底床的转变以及相关的水位 - 流量关系的滞后现象；这与实际观测结果非常吻合，但过去仅使用经验方法进行处理。提出了一个关于泥沙参数（平均步长）的假设关系，作为一级近似，能够再现沙丘 - 平底床的转变。所提出的数值模型展示了其解决与不同流量下床形演变和水流阻力相关的重要实际问题的能力。
This work presents recent advances on morphodynamic modeling of bed forms under unsteady discharge. This paper includes further development of a morphodynamic model proposed earlier by Giri and Shimizu (2006a). This model reproduces the temporal development of river dunes and accurately replicates the physical properties associated with bed form evolution. Model results appear to provide accurate predictions of bed form geometry and form drag over bed forms for arbitrary steady flows. However, accurate predictions of temporal changes of form drag are key to the prediction of stage‐discharge relation during flood events. Herein, the model capability is extended to replicate the dune–flat bed transition, and in turn, the variation of form drag produced by the temporal growth or decay of bed forms under unsteady flow conditions. Some numerical experiments are performed to analyze hysteresis of the stage‐discharge relationship caused by the transition between dune and flat bed regimes during rising and falling stages of varying flows. The numerical model successfully simulates dune–flat bed transition and the associated hysteresis of the stage‐discharge relationship; this is in good agreement with physical observations but has been treated in the past only using empirical methods. A hypothetical relationship for a sediment parameter (the mean step length) is proposed to a first level of approximation that enables reproduction of the dune–flat bed transition. The proposed numerical model demonstrates its ability to address an important practical problem associated with bed form evolution and flow resistance in varying flows.