【作者】 李冬；

【导师】 胡旭跃；

【作者基本信息】 长沙理工大学 ， 水力学及河流动力学， 2007， 硕士

【摘要】 流经床面有植被明渠水流的运动特性正在逐渐引起人们的注意。在河流岸滩种植植被,能起到固岸护滩的作用,植被作为一种生物控导工程措施,对于水生生态环境的保护和修复,维持河流湖泊和海滨区的高质量水环境具有非常重要的意义。但水中植被的存在,改变了河道水流的结构,减小了河道水流的平均流速,导致河道的泄洪能力降低。因此探讨植被与水流的相互影响,深入理解植被与水流之间的作用机理,在水资源可持续利用,河流及湖泊的生态修复、管理和河道整治等方面都有重要的科学和实践意义。植被的存在对明渠水流的影响仍不十分清楚,有必要对有植被明渠的水力特性做进一步研究。本文在资料查新的基础上,对有植被明渠水流问题国内外的研究现状进行了较详细的总结。并对有柔性植被的明渠水流进行了试验研究,主要研究内容如下。对流经有柔性植被的明渠水流结构进行了试验研究。利用三维超声波多普勒流速仪(ADV)量测不同位置、不同流量下的流场,分析了测点位置和水深与植被高度比对时均流速、紊动强度及雷诺应力垂线分布的影响。通过水槽试验,研究了植被层以下和植被层以上垂线流速的分布律。建立了植被层以下垂线流速的三次函数公式和植被层以上垂线流速的对数公式,同时提出了相关系数的确定方法,并通过试验数据和其它水槽的流速资料进行了验证,发现所提出的明渠流速分布律可以比较好的描述有植被明渠实际的流速分布。将植被当成大阻力单元,用植被高度表示有植被床面的粗糙突起程度,以高度的方差表示它的非均匀性。在植被密度和直径不变的情况下,进行了一系列的水槽试验研究,较系统地考虑了植被几何特征的非均匀性对水流阻力的影响,得出植被高度非均匀性对水流阻力影响的初步规律,丰富了人们对床面上存在植被的明渠流动特性的认识,为进一步深入研究奠定了基础。更多还原

【Abstract】 Recently, the hydrodynamic behavior in vegetated channels has drew researchers’attention. Planting vegetation on the riverbank can prevent soil erosion and maintain flat. As a biological measure, vegetation has various functions, including stabilizing river channel, adjusting flow and fixing beach and bank. To preserve and restore water ecological environment, maintain water of high quality in the river, sea and seaside, the biological measure has very important meaning. The existence of vegetation in the channel will disturb the flow and change it’s structure. It can decrease the velocity of flow, so resulting to the rise of the water level and the deposition of sediment. So exploring influence and profoundly comprehending mechanism of action between vegetation with flow is of significant science and practice meanings in water resources sustainable utilization, river ecology rehabilitation and river improvement.The quantitative influence of vegetation is still not well understood. Therefore, it is important to understand the flow characteristics of the channel with vegetation. In this paper, based on the data and investigation, we summarize the study on the flow characteristics of the channel with vegetation, and then research the flow over flexible bottom vegetation. The main researches are shown as follows.Open channel flow over flexible 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, turbulence intensity and Reynolds stress is analyzed. The present paper reviews the distribution law of vertical velocity of water flow inside and above the vegetation by water channel experiment, developing the relationship of Cubic- and logarithmic-function to describe the velocity distribution of water flow inside and above vegetation, suggesting the ascertain method of correlative and then verifying it by experiment data and other water channels. The result shows that the velocity distribution law given by authors is in accordance with the real velocity distribution in open channel.In this paper, the bed roughness height is expressed by the corrective height of vegetation. The non-uniformity of the vegetation is expressed by the variance of the height. As the density and diameter are constant, experiments study is carried out to analyze the resistance characteristics of open channel flow with the vegetation composed of different non-uniformity properties. This influence is studied systematically based on flume experiment here, and the relationships have been established between vegetation height non-uniformity and flow resistance. This analysis has made the knowledge about resistance of non-uniformity of the vegetation height more understandable.更多还原