Headcut erosion is a very common process occurring at the head of rills, crop furrows and ephemeral gullies. A numerical model of the headcut flow was built to study the wall shear stress characteristics downstream of the scour hole, which is very important in headcut erosion prediction models. The calculated nappe parameters are very close to experimental data and/or equation results. The calculated flow field, velocity centreline of the free jet part and the locations of the maximum velocity in the scour hole are also close to the experimental data. It was found that the upstream flow rate and downstream water level can affect both the maximum value and the distribution of the wall shear stress. Taking into account the affecting factors and referencing the form of the existing relations on the maximum wall shear stress caused by the impinging jet, the relation of the maximum wall shear stress occurring downstream of the headcut is obtained. The wall shear stress distribution can be described by exponential functions. The new prediction equation of the maximum wall shear stress can be used in existing headcut erosion prediction models for calculating equilibrium scour hole depth or scour hole deepening rate.

中文翻译：

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割口下游壁面剪应力的数值模拟

割草侵蚀是在小溪，农作物犁沟和临时沟壑的头部发生的非常普遍的过程。建立了割缝流的数值模型，以研究冲刷孔下游的壁切应力特性，这在割缝侵蚀预测模型中非常重要。计算出的尿布参数非常接近实验数据和/或方程式结果。计算出的流场，自由射流部分的速度中心线以及冲刷孔中最大速度的位置也接近实验数据。发现上游流速和下游水位会影响最大值和壁面剪应力的分布。考虑到影响因素，并参考冲击射流引起的最大壁切应力的现有关系形式，得出了在割口下游发生的最大壁切应力的关系。壁切应力分布可以用指数函数来描述。可以在现有的割口侵蚀预测模型中使用新的最大壁面剪应力预测方程式来计算平衡冲孔深度或冲孔加深率。