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工程科学与技术:2017,49(2):86-91
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植被群河道水流特性试验研究
(1.四川大学 水力学与山区河流开发保护国家重点试验室, 四川 成都 610065;2.山东省淮河流域水利管理局规划设计院, 山东 济南 250100)
Flow Characteristics of Emergent Vegetation Patch in Channel
(1.State Key Lab. of Hydraulics and Mountain River Eng., Sichuan Univ., Chengdu 610065, China;2.Planning and Design Inst. of Huaihe River Water Resources Administration Bureau of Shandong Province, Ji'nan 250100, China)
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投稿时间:2016-07-31    修订日期:2017-01-19
中文摘要: 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。
中文关键词: 植被群  尾流  体积分数  动床  定床
Abstract:In order to study the influence of vegetation patch and bed roughness on flow characteristics in river,this paper used wooden cylinders to simulate emergent circular patch composed by different plant density,with movable bed and fixed bed conditions.By using flow velocity and turbulence kinetic energy,this paper analyzed the formation and development of the upstream adjustment length and the wake flow.Firstly,the results showed that when the diameter of the patch was constant,the upstream adjustment length of patch is independent of vegetation patch density,and in this experiment,the effect of bed roughness could be ignored.Secondly,this paper used the volume fraction φ as a comprehensive characterization of density and diameter of patch.Comparing the contribution of bed roughness and the volume fraction to the complete wake length,it was found that the complete wake length L was related to the volume fraction φ,amely,when φ value was larger the length of the complete wake was smaller.Thirdly,the velocity distribution was mainly controlled by the bed roughness and the volume fraction value backward of the vegetation patchand the steady wake length L1 value was related to the φ value,with L1/D reaching the maximal value in the vicinity of φ=6%.Finally,two turbulence kinetic energy peaks generally appear on the wake region,with its location being mainly affected by the density of patch and the roughness of bed.Due to the different densities of vegetation patch,the development of energy exchange and transverse shear layer was not the same in the wake structure,which was the main factor that affects the position of velocity returning to normal velocity and the formation of stable wake.This paper can provide a reference for the further analysis of the interaction between water flow and vegetation under different bed roughness.
文章编号:201600751     中图分类号:    文献标志码:
基金项目: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)
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李志杰,王丹,朱明明,聂锐华,杨克君.植被群河道水流特性试验研究[J].工程科学与技术,2017,49(2):86-91.
LI Zhijie,WANG Dan,ZHU Mingming,NIE Ruihua,YANG Kejun.Flow Characteristics of Emergent Vegetation Patch in Channel[J].Advanced Engineering Sciences,2017,49(2):86-91.