灌木植被水流的流速垂向分布

Vertical profile of horizontal velocity of flow through shrubs

速度分布是植被水流动力学研究的基础问题之一。与明槽水流的对数流速分布不同,植被水流在垂直方向差别较大,一般分为植间水流和植上水流两部分,垂向分布较为复杂。本文在考虑水流动量平衡的基础上,借助于混合长度紊流模型,并考虑植被形态的垂向差异,建立了表征流速垂向分布的微分方程;以灌木植被的形状为原型,在假定灌木直径垂向分布的前提下,得到了更为普适的流速垂向分布公式。将所得到的解析公式和室内试验数据及Baptist公式进行对比分析,发现本文公式与试验数据吻合得更好,能准确地反映植间流速的垂向变化。

This paper presents an analytical solution of vertical profile of horizontal velocity for vegetated open channel flow.Owing to vegetation effects,the vertical profile is often complicated and difficult to express analytically.To simplify the analysis,the flow is divided vertically into two layers,a vegetable-occupied bottom layer and a layer over it.Then a differential equation for horizontal velocity can be established by using the momentum theorem and mixing-length turbulence model and considering the differences of the two layers.Shrub vegetation is analyzed here.The stem diameter is assumed a hyperbolic form over the depth,and an analytical profile is easy to derive through solving the equation.A comparison with experimental data and Baptist formula shows that the analytical solution gives a better agreement than Baptist formula,especially for the vegetation layer.