A mixing‐length‐scale‐based analytical model for predicting velocity profiles of open‐channel flows with submerged rigid vegetation
A mixing‐length‐scale‐based analytical model for predicting velocity profiles of open‐channel flows with submerged rigid vegetation
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DOI：
10.1111/wej.12434
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发表时间：
2018-11
影响因子：
2
通讯作者：
Xiaonan Tang
中科院分区：
文献类型：
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作者：
Xiaonan Tang
在有淹没植被的明渠水流中，垂直流速剖面通常可以用两层来描述：下部区域的植被层和上部无植被区域的表层。本文提出了一种新的涡混合长度尺度，用于预测具有淹没刚性植被的明渠水流的垂直速度分布。流速剖面的分析模型是基于动量方程的流动，其中的湍流涡动粘性假设有一个线性关系与当地的速度。该模型进行了测试，对不同的数据集从文献。所用的22个数据集涵盖了淹没范围[水深（H）/植被高度（h）= 1.25 ~ 3.38]、不同植被密度（ah = 0.11 ~ 1.85）和河床坡度（So = 1.8 × 10−6 ~4.0 × 10−3）。研究表明，该模型能较好地预测各层的流速廓线，且涡旋混合长度尺度（λ）与植被高度（h）和近地层流深（即非植被层的高度H-h）有较好的相关性。对所提出的模型中λ的仔细检查表明，当λ = 0.03 h（H-h）时，除了非常浅的淹没（即H/h < 1.5）外，该模型对所使用的所有数据集都能很好地预测垂直速度剖面。
In open‐channel flows with submerged vegetation, the vertical velocity profile can often be described by two layers: the vegetation layer in the lower region and the surface layer in the upper non‐vegetated region. In this paper, a new mixing‐length scale of eddy is proposed for predicting the vertical velocity profile of flow in an open‐channel with submerged rigid vegetation. The analytical model of velocity profile is based on the momentum equation of flow where the turbulent eddy viscosity is assumed to have a linear relationship with the local velocity. The proposed model was tested against different datasets from the literature. The 22 datasets used cover a range of submergence [flow depth (H)/vegetation height (h) = 1.25 ~ 3.38], different vegetation densities of ah = 0.11 ~ 1.85 (a defined as the frontal area of the vegetation per unit volume) and bed slopes (So = 1.8 × 10−6 ~4.0 × 10−3). This study showed that the proposed model can predict the velocity profiles well against all datasets, and that the mixing length scale of eddies (λ) is well related with both vegetation height (h) and flow depth of surface layer (i.e. the height of non‐vegetation layer, H–h). Close examination of λ in the proposed model showed that when λ = 0.03 h(H-h) , the model predicts vertical velocity profiles well for all datasets used except for very shallow submergence (i.e. H/h < 1.5).