植物对河道水流特性的影响研究

发布时间：2018-11-03 20:59

【摘要】：随着人们对生态型河道建设意识的提高,植物在河道护岸和生态修复工程中得到越来越多的应用。在河道中种植植物,有利于净化水质,固滩护岸,美化环境。但是河道中植物的存在也增加了河道水流阻力,降低了河道的行洪能力。因此很有必要对含植物河道水流特性进行研究。本文通过分析国内外学者对含植物河道水流的研究成果和不足,利用理论分析和数值模拟两种方法对含柔性植物的河道水流和含刚性植物的河道水流进行研究。主要研究内容及结果如下:(1)提出了一种植物对河道水流拖曳力计算的通用公式。总结前人学者对含植物河道水流流速垂线分布的经验公式和解析公式,通过公式的推导,找出植物对河道水流阻力大小的影响因素,建立常规的河道模型,推导出了植物对河道水流拖曳力计算的通用公式。(2)耦合RNG k-ε模型和VOF模型,对含柔性沉水植物河道的水力特性进行三维数值模拟研究。将柔性沉水植物区域简化为多孔介质区域,以多孔介质模型来模拟柔性植物对河道水流的影响,以植物带前后压强差结合孔隙率确定多孔介质模型的渗透率。模拟结果给出了河道沿程水位曲线、流速和紊动强度等参数的垂线分布。将数值模拟结果和试验实测结果进行了对比,两者吻合较好。(3)以单边复式河道为研究对象,通过三维数值模拟研究在滩地上种树对复式河道水流特性的影响。采用RNG k-ε双方程湍流模型,VOF法对河道水面进行跟踪,只考虑树干对水流的影响,将树干简化为顺直圆柱体,在水流的作用下不发生变形和摆动,对河道水流进行三维数值模拟。分析结果给出了滩地和主槽的水位曲线、滩地和滩槽交界区沿垂向流速分布、河道断面沿横向流速分布等的变化规律。研究结果表明,耦合RNG k-ε双方程湍流模型和VOF模型可以很好的模拟出含植物河道流速特性的变化规律。研究成果可应用于河道生态修复工程中,对工程实践和应用有一定的指导价值。
[Abstract]:With the improvement of people's awareness of ecological river course construction, plant has been applied more and more in river revetment and ecological restoration engineering. Planting plants in the river channel is beneficial to purify water quality, protect the beach and beautify the environment. However, the presence of plants in the river also increases the flow resistance and reduces the flood discharge capacity. Therefore, it is necessary to study the flow characteristics of vegetated river channel. In this paper, by analyzing the achievements and shortcomings of domestic and foreign scholars on the flow of vegetated river channels, two methods of theoretical analysis and numerical simulation are used to study the flow of river channels with flexible plants and river flows with rigid plants. The main contents and results are as follows: (1) A general formula for calculating the towing force of plants to river flow is proposed. This paper summarizes the empirical and analytical formulas for the vertical distribution of flow velocity in river channels containing plants, finds out the factors that affect the resistance of river flow caused by plants, and establishes a conventional channel model. A general formula for calculating the towing force of plant to river flow is derived. (2) coupled with RNG k- 蔚 model and VOF model, the hydraulic characteristics of river channels with flexible submerged plants are studied by three-dimensional numerical simulation. The flexible submerged plant region is simplified as a porous medium region. The influence of the flexible plant on the channel flow is simulated by the porous media model. The permeability of the porous media model is determined by the pressure difference before and after the plant belt and the porosity. The simulation results show the vertical distribution of water level, velocity and turbulence intensity along the river course. The numerical simulation results are compared with the experimental results. (3) the effects of planting trees on the channel flow characteristics are studied by 3D numerical simulation. The RNG k- 蔚 two-equation turbulence model and VOF method are used to track the water surface of the river, only considering the influence of the trunk on the flow, the trunk is simplified as a straight cylinder, and no deformation or swing occurs under the action of the current. Three-dimensional numerical simulation of river flow is carried out. The results show that the water level curve of the beach and the main channel, the distribution of vertical velocity along the boundary area between the beach and the channel, and the distribution of the transverse velocity of the river section, etc. The results show that the coupled RNG k- 蔚 two-equation turbulence model and the VOF model can well simulate the variation of the velocity characteristics of the river channel containing plants. The research results can be used in river ecological restoration engineering, and have certain guiding value to engineering practice and application.
【学位授予单位】：天津大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TV133

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