植被群河道水流特性试验研究

发布时间：2018-01-25 02:09

本文关键词： 植被群尾流体积分数动床定床　出处：《工程科学与技术》2017年02期 　论文类型：期刊论文

【摘要】：为研究河道中植被群的存在及床面糙率对植被群上下游的水流特性产生的影响,分别设计动床与定床情况下的试验,试验中采用木质圆柱模拟植株组成疏密不同的非淹没圆形植被群。通过研究含植被群水流的流速和紊动动能的分布,分析植被群上游水流调整长度和尾流的形成与发展过程。试验研究表明:当植被群的直径不变时,植被群上游的水流调整长度与植被群的密度无关,在该试验条件下,床面糙率对其影响可以忽略;提出体积分数φ作为综合表征植被群密度与植被群直径的参数,比较床面糙率与体积分数φ对完整尾流长度的贡献,发现植被群后形成的完整尾流长度L的大小主要与体积分数φ值有关,且φ值越大L值就越小;植被群后的流速分布主要受床面糙率和体积分数φ值影响,稳定尾流长度L1的形成主要与φ值有关,并且在φ=6%附近,L1/D出现最大值;植被群后的尾流结构中一般会出现2个紊动动能的波峰,其位置主要受植被群的密度及床面糙率影响。由于植被群密度的不同,尾流结构中水体的能量交换和横向剪切层的发展也不相同,这是影响植被群后的流速恢复至正常流速的位置和稳定尾流形成的主要因素。本文所得结果可为进一步分析不同床面糙率下水流与植被的相互作用提供参考。
[Abstract]:In order to study the existence of vegetation groups and the effect of bed roughness on the flow characteristics of the upper and lower reaches of the vegetation groups, the experiments of moving bed and fixed bed were designed respectively. In the experiment, wood columns were used to simulate plants to form non-submerged circular vegetation groups with different density. The distribution of flow velocity and turbulent kinetic energy was studied. This paper analyzes the formation and development process of water flow adjustment length and wake flow in the upper reaches of vegetation group. The experimental study shows that when the diameter of vegetation group is constant, the water flow adjustment length of upstream vegetation group is independent of the density of vegetation group. Under the experimental conditions, the effect of bed roughness on it can be neglected. Volume fraction 蠁 is used as a parameter to characterize the density and diameter of vegetation group, and the contribution of bed roughness and volume fraction 蠁 to the complete wake length is compared. It is found that the size of the complete wake length L is mainly related to the volume fraction 蠁, and the larger the 蠁 value is, the smaller the L value is. The velocity distribution after vegetation group is mainly affected by the roughness of bed surface and volume fraction 蠁. The formation of stable wake length L1 is mainly related to 蠁 value, and the maximum value of L ~ (1 / D) appears in the vicinity of 蠁 ~ (6%). There are usually two peaks of turbulent kinetic energy in the wake structure of vegetation group, the location of which is mainly affected by the density of vegetation group and roughness of bed surface, because of the different density of vegetation group. The energy exchange and the development of transverse shear layer in the wake structure are also different. This is the main factor that affects the position of velocity returning to normal velocity and the formation of steady wake after vegetation swarm. The results obtained in this paper can provide a reference for further analysis of the interaction between water flow and vegetation under different bed roughness.
【作者单位】：四川大学水力学与山区河流开发保护国家重点试验室;山东省淮河流域水利管理局规划设计院;
【基金】：国家自然科学基金重点资助项目(51539007);国家自然科学基金资助项目(51479128)
【分类号】：TV133
【正文快照】： 植被的生长与分布是河流系统中一个重要的组成部分,研究植被与水流的相互作用具有重要意义。例如,河流中的植被为一些生物提供的生境就与弗劳德数有关[1];水生植物会影响水流结构进而影响水体污染物的扩散能力与方式[2];水流与植被的相互作用影响了营养物质的输移,在漫滩水流

【相似文献】