浮叶植物对明渠流水动力特性的影响研究

Influence of Floating-leaved Vegetation on the Hydraulic Characteristics of Open Channel Flow

浮叶植物广泛存在于水生态系统中,对水域的生态环境和水动力特性均有显著的影响。本文采用理论模型与实验研究相结合的方法,研究了浮叶植物对明渠流水动力特性的影响,采用人工材料模拟浮叶植被开展水槽实验,建立了纵向流速垂向分布的数值解模型。结果表明,将水流沿垂向分为浮叶主导区和河床主导区,基于改进的混合长度理论,可得到纵向流速垂向分布的数值解,且理论模型与实测数据吻合良好。浮叶植被通过浮叶、茎秆和河床对水体的共同作用影响水流结构,底部层和顶部层均有较大的流速梯度,流速和流速梯度均随着相应的临界距离值增大而减小;中间层的流速近似为均匀分布,且不受临界距离值的影响。

The floating-leaved vegetation is widely found in the aquatic ecosystem,and can affect the hydraulic characteristics of the flow and provide a wide range of ecosystem functions.Bionic lotus leaves fixed on circular wooden cylinders were used to imitate floating-leaved vegetation,and their effects on the open channel flow were investigated by laboratory experiments.The flow region was divided into the leaf-dominated region and bed-dominated region,and a numerical model was built based on the modified mixing length hypothesis to solve the vertical distribution of streamwise velocity.The model predicted results agreed well with the experimental data.The floating-leaved vegetation altered the flow structure through the combined action of floating leaves,stems,and the channel bed.Large velocity gradients appeared at the bottom and top layers,and the velocity and velocity gradient decreased with the increase of the critical distance Lm,while the velocity remained approximately constant in the internal region and was not affected by the critical distance Lm.