【摘要】：隨著人們對(duì)生態(tài)型河道建設(shè)意識(shí)的提高,植物在河道護(hù)岸和生態(tài)修復(fù)工程中得到越來(lái)越多的應(yīng)用。在河道中種植植物,有利于凈化水質(zhì),固灘護(hù)岸,美化環(huán)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。因此很有必要對(duì)含植物河道水流特性進(jìn)行研究。本文通過(guò)分析國(guó)內(nèi)外學(xué)者對(duì)含植物河道水流的研究成果和不足,利用理論分析和數(shù)值模擬兩種方法對(duì)含柔性植物的河道水流和含剛性植物的河道水流進(jìn)行研究。主要研究?jī)?nèi)容及結(jié)果如下:(1)提出了一種植物對(duì)河道水流拖曳力計(jì)算的通用公式。總結(jié)前人學(xué)者對(duì)含植物河道水流流速垂線分布的經(jīng)驗(yàn)公式和解析公式,通過(guò)公式的推導(dǎo),找出植物對(duì)河道水流阻力大小的影響因素,建立常規(guī)的河道模型,推導(dǎo)出了植物對(duì)河道水流拖曳力計(jì)算的通用公式。(2)耦合RNG k-ε模型和VOF模型,對(duì)含柔性沉水植物河道的水力特性進(jìn)行三維數(shù)值模擬研究。將柔性沉水植物區(qū)域簡(jiǎn)化為多孔介質(zhì)區(qū)域,以多孔介質(zhì)模型來(lái)模擬柔性植物對(duì)河道水流的影響,以植物帶前后壓強(qiáng)差結(jié)合孔隙率確定多孔介質(zhì)模型的滲透率。模擬結(jié)果給出了河道沿程水位曲線、流速和紊動(dòng)強(qiáng)度等參數(shù)的垂線分布。將數(shù)值模擬結(jié)果和試驗(yàn)實(shí)測(cè)結(jié)果進(jìn)行了對(duì)比,兩者吻合較好。(3)以單邊復(fù)式河道為研究對(duì)象,通過(guò)三維數(shù)值模擬研究在灘地上種樹對(duì)復(fù)式河道水流特性的影響。采用RNG k-ε雙方程湍流模型,VOF法對(duì)河道水面進(jìn)行跟蹤,只考慮樹干對(duì)水流的影響,將樹干簡(jiǎn)化為順直圓柱體,在水流的作用下不發(fā)生變形和擺動(dòng),對(duì)河道水流進(jìn)行三維數(shù)值模擬。分析結(jié)果給出了灘地和主槽的水位曲線、灘地和灘槽交界區(qū)沿垂向流速分布、河道斷面沿橫向流速分布等的變化規(guī)律。研究結(jié)果表明,耦合RNG k-ε雙方程湍流模型和VOF模型可以很好的模擬出含植物河道流速特性的變化規(guī)律。研究成果可應(yīng)用于河道生態(tài)修復(fù)工程中,對(duì)工程實(shí)踐和應(yīng)用有一定的指導(dǎo)價(jià)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.
【學(xué)位授予單位】：天津大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：TV133

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本文編號(hào)：2309026