有植被的河道水流试验研究

【作者】 王忖；

【导师】 赵振兴； 黄本胜；

【作者基本信息】 河海大学 ， 水力学及河流动力学， 2003， 硕士

【摘要】 近来，流经植被的水流的运动特性，正在逐渐引起人们的注意。水中植被的存在抬高了河道水位，改变了河道水流的结构，减小了河道水流的平均流速，在促进地貌稳定的同时，也使河道的行洪能力降低。但是，到目前为止，植被的存在对河道水流的影响仍处于研究阶段。因此，有必要对有植被的河道水流问题进一步探讨。本文较系统地总结了前人对有植被的河道水流问题的研究成果，将有植被的河道水流问题分为两大类：(1)流经柔性植被的河道水流问题，(2)流经刚性植被的河道水流问题，本文分别进行试验研究。主要研究内容如下：1．对流经柔性植被的河道水流进行了试验研究。利用三维超声波多普勒流速仪(ADV)量测不同位置、不同流量下的瞬时流场。分析了测点位置和水深与植被高度比对时均流速分布的影响。本文还给出了种树段紊动强度及雷诺应力的垂线分布。分析其水力特性和所测流速分布，推导出新的垂线流速分布表达式。根据力的平衡建立了一个一维简单模型分析植被对水流的阻力。2．在前人研究的基础上对河滩上种有树木的复式断面渠道的水流特性进行了试验研究，着重分析了滩地种树密度、排列方式对水流的影响。3．采用ADV对滩地种树前后滩槽交界区域的流速场进行了量测。分析了滩槽交界区域的垂线流速、紊动强度和雷诺应力的变化。将滩槽交界的动量传递描述为一表观应力，这个表观应力可以看作是交界面处的脉动函数并将其定量化。更多还原

【Abstract】 Recently, an increase in awareness of the hydrodynamic behavior in vegetated channels has spurred additional studiesPresence of vegetation in the flow modifies the velocity distribution,and hence,produces high resistance to flow,and,as a result,has a large impact on the capacity of flood carrying as well as promoting geomorphic stability.But the quantitative influence ofvegetation are still not well understood. Therefore,it is significant to carry out further experimentaly studies on the flow characteristics of vegetation.In this paper,based on achievement of flow with partly vegetated channel of predecessors,according to vegetation types ,the flow over flexible bottom vegetation and rigid one is experimentally studied.The main researches as follows:1 .Open channel flow over flexible bottom vegetation is studied experimentally. A three-dimensional-acoustic doppler velocimeter is used to measure the velocity components of the flow field in all three coordinate directions for different discharge and measurement site.The influence of measurement site and the depth/vegetation height ratio on the measured velocity profile and turbulence intensity and the Renolds stress is analyzed.The characteristics of the measured velocity distributions and the results of the previous investigators are used to select an analytical expression for the shape of the velocity profile. A simple model based on force equilibrium is proposed to evaluate the vegetative roughness coefficient.2.Based on the achievement of predecessors physical modeling and fundamental theory of hydrodynamic behavior of compound channel with rigid vegetated floodplains are studied in this paper.Hydrodynamic behavior of compound with rigid vegetated floodplains is conclued. Attention is focused on the influence of vegetation density and arranging pattern on the measured Hydrodynamic behavior.3.A three-dimensional-acoustic doppler velocimeter has been used to measure the velocity and turbulence in a compound channel with vegetated and unvegetated flood -plains.Particulary in the interface region between main channel and floodplain.The distribution in three coordinate directions of velocity and turbulence intensities andthe Renolds stresses are presented.The momentum transfer at the main channel flood -plain interface can be described as an apparent shear stress which can be quantified as a function of the local turbulence at the interface.更多还原