含植物明渠水沙運動規(guī)律試驗研究
發(fā)布時間：2018-07-16 16:46
【摘要】：含植物河流是自然生態(tài)的重要組成部分。由于影響因素眾多,水沙運動規(guī)律相對復雜,含植物河流水沙運動特性是河流泥沙動力學中的難點問題之一。本文在資料收集的基礎(chǔ)上,對含植物水流問題的國內(nèi)外研究現(xiàn)狀進行系統(tǒng)的總結(jié),并采用三種仿真柔性植物進行了含植物明渠水沙運動規(guī)律的室內(nèi)水槽試驗；首先分不同區(qū)域(植物帶上游、植物帶和植物帶下游)研究了無草、淹沒型、非淹沒型柔性植物水流阻力特性規(guī)律,繼而對含不同植物明渠水動力運動特性進行深入探討；最后對含不同植物明渠泥沙運動進行詳細分析。全文主要研究以下三個方面的問題： 1.含植物明渠水流阻力特性研究 利用水槽試驗研究了無草、淹沒型、非淹沒型柔性植物水流阻力特性的變化規(guī)律,分析了含植物明渠沿程水面比降和阻力系數(shù)的變化特性。得到各植物阻力系數(shù)變化與尼庫拉茲曲線基本相似,紊流范圍內(nèi)同樣可劃分為紊流光滑區(qū)、紊流過渡區(qū)、紊流粗糙區(qū)；統(tǒng)計各植物經(jīng)不同水流沖擊倒伏后的冠頂高度,分析了植物粗糙度、水流雷諾數(shù)和阻力系數(shù)之間的關(guān)系,并對各植物的水流阻力系數(shù)分區(qū)進行回歸分析,得到各植物水流阻力的分區(qū)經(jīng)驗表達式,該方法能較好地應用于含植物明渠水流阻力系數(shù)的推求。 2.含植物明渠水動力特性試驗研究 利用水槽試驗研究了含不同植物明渠水動力特性,試驗結(jié)果表明,對于淹沒植物,在植物的冠頂上方一定區(qū)域水流流速變化與無草情況下基本相似,但非淹沒植物的水流縱向流速在水深方向呈“S”型分布,并呈明顯的分層現(xiàn)象；水流紊動強度隨植物形態(tài)、沿程分布和距邊壁位置變化而表現(xiàn)出不同特性；-(uv+uv)/u2*是表征水流變化的重要因子,有植物情況下,其與植物形態(tài)和沿程分布等因素密切相關(guān),并隨植物形態(tài)和空間分布而發(fā)生不同規(guī)律的調(diào)整。 3.含植物明渠泥沙運動規(guī)律研究 利用水槽試驗研究了含不同植物明渠泥沙運動規(guī)律,試驗結(jié)果表明：泥沙級配存在明顯的分層現(xiàn)象,呈現(xiàn)“上細下粗”的基本變化規(guī)律,同種植物對細顆粒泥沙的空間分布影響較小,對中、粗顆粒泥沙的影響較大。含植物明渠較無植物明渠,床沙非均勻性減小,其中淹沒型莎草減小幅度最大；對含植物明渠中水流的動量擴散系數(shù)、泥沙擴散系數(shù)和二者比值β進行較詳細研究,得到了三者隨植物形態(tài)和空間分布的變化特征,具體為：動量擴散系數(shù)在垂向總體呈拋物線分布,隨相對水深增加先增大后減小,泥沙擴散系數(shù)總體隨相對水深的增加而逐漸減少,β值變化范圍為0.14-10.0,多數(shù)β值明顯大于1,分析認為,試驗采用輕質(zhì)模型沙,有利于泥沙擴散,泥沙擴散系數(shù)較大所致。
[Abstract]:Vegetative rivers are an important part of natural ecology. Because there are many influencing factors and the law of water and sediment movement is relatively complex, the characteristics of water and sediment movement in vegetative rivers is one of the difficult problems in river sediment dynamics. On the basis of data collection, this paper systematically summarizes the domestic and international research status of water flow problem with plants, and uses three kinds of simulated flexible plants to carry out indoor flume tests on the water and sediment movement laws of open channel containing plants. Firstly, the characteristics of flow resistance of grass free, submerged and non-submerged flexible plants are studied in different regions (upstream, and downstream), and the hydrodynamic characteristics of open channel with different plants are discussed. Finally, the sediment movement in open channel containing different plants is analyzed in detail. This paper mainly studies the following three aspects: 1. Study on the characteristics of flow resistance in open channels containing plants the variation of resistance characteristics of flexible plants without grass submergence and submergence was studied by flume test. The variation characteristics of water surface specific drop and drag coefficient along the open channel with plants are analyzed. The results show that the variation of resistance coefficient of plants is similar to that of Nicuraz curve, and it can also be divided into turbulent smooth region, turbulent transition area and turbulent rough area in turbulent range. The relationships among plant roughness, flow Reynolds number and resistance coefficient are analyzed. The regression analysis of the flow resistance coefficient of each plant is carried out, and the regional empirical expression of the water flow resistance of each plant is obtained. This method can be applied to the calculation of flow resistance coefficient of open channel containing plants. 2. Experimental study on hydrodynamic characteristics of open channel containing plants the hydrodynamic characteristics of open canal containing different plants were studied by flume test. The experimental results show that, for submerged plants, The variation of flow velocity in a certain area above the top of the plant crown is basically similar to that in the case of no grass, but the longitudinal velocity of flow in the non-submerged plant is "S" in the direction of water depth, and there is a distinct stratification phenomenon, and the turbulence intensity of the water flow varies with the plant morphology. (uv) / u ~ (2 *) is an important factor to characterize the change of water flow, which is closely related to plant morphology and distribution along the side. And with the plant morphology and spatial distribution of different laws of adjustment. 3. Study on sediment movement in open channel containing plants the sediment movement in open channel containing different plants is studied by flume test. The results show that there is an obvious stratification phenomenon in sediment gradation. The same plant has little influence on the spatial distribution of fine grain sediment, while the same plant has greater influence on the coarse grain sediment. The inhomogeneity of bed sand in plant-bearing open channel is lower than that in plant-containing open channel, in which submerged Cyperus has the largest decrease, and the momentum diffusion coefficient, sediment diffusion coefficient and ratio 尾 of submerged seagrass in open channel containing plants are studied in detail. The variation characteristics of the three factors with plant morphology and spatial distribution are obtained. The momentum diffusion coefficient distributes parabola in the vertical population, and increases first with the increase of relative water depth and then decreases with the increase of relative water depth. The sediment diffusion coefficient decreases gradually with the increase of relative water depth, and the variation range of 尾 value is from 0.14 to 10.0. Most of the 尾 values are obviously larger than 1. The analysis shows that the light weight model sand is good for sediment diffusion and the sediment diffusion coefficient is larger.
【學位授予單位】：武漢大學
【學位級別】：博士
【學位授予年份】：2014
【分類號】：TV146
本文編號：2127002
[Abstract]:Vegetative rivers are an important part of natural ecology. Because there are many influencing factors and the law of water and sediment movement is relatively complex, the characteristics of water and sediment movement in vegetative rivers is one of the difficult problems in river sediment dynamics. On the basis of data collection, this paper systematically summarizes the domestic and international research status of water flow problem with plants, and uses three kinds of simulated flexible plants to carry out indoor flume tests on the water and sediment movement laws of open channel containing plants. Firstly, the characteristics of flow resistance of grass free, submerged and non-submerged flexible plants are studied in different regions (upstream, and downstream), and the hydrodynamic characteristics of open channel with different plants are discussed. Finally, the sediment movement in open channel containing different plants is analyzed in detail. This paper mainly studies the following three aspects: 1. Study on the characteristics of flow resistance in open channels containing plants the variation of resistance characteristics of flexible plants without grass submergence and submergence was studied by flume test. The variation characteristics of water surface specific drop and drag coefficient along the open channel with plants are analyzed. The results show that the variation of resistance coefficient of plants is similar to that of Nicuraz curve, and it can also be divided into turbulent smooth region, turbulent transition area and turbulent rough area in turbulent range. The relationships among plant roughness, flow Reynolds number and resistance coefficient are analyzed. The regression analysis of the flow resistance coefficient of each plant is carried out, and the regional empirical expression of the water flow resistance of each plant is obtained. This method can be applied to the calculation of flow resistance coefficient of open channel containing plants. 2. Experimental study on hydrodynamic characteristics of open channel containing plants the hydrodynamic characteristics of open canal containing different plants were studied by flume test. The experimental results show that, for submerged plants, The variation of flow velocity in a certain area above the top of the plant crown is basically similar to that in the case of no grass, but the longitudinal velocity of flow in the non-submerged plant is "S" in the direction of water depth, and there is a distinct stratification phenomenon, and the turbulence intensity of the water flow varies with the plant morphology. (uv) / u ~ (2 *) is an important factor to characterize the change of water flow, which is closely related to plant morphology and distribution along the side. And with the plant morphology and spatial distribution of different laws of adjustment. 3. Study on sediment movement in open channel containing plants the sediment movement in open channel containing different plants is studied by flume test. The results show that there is an obvious stratification phenomenon in sediment gradation. The same plant has little influence on the spatial distribution of fine grain sediment, while the same plant has greater influence on the coarse grain sediment. The inhomogeneity of bed sand in plant-bearing open channel is lower than that in plant-containing open channel, in which submerged Cyperus has the largest decrease, and the momentum diffusion coefficient, sediment diffusion coefficient and ratio 尾 of submerged seagrass in open channel containing plants are studied in detail. The variation characteristics of the three factors with plant morphology and spatial distribution are obtained. The momentum diffusion coefficient distributes parabola in the vertical population, and increases first with the increase of relative water depth and then decreases with the increase of relative water depth. The sediment diffusion coefficient decreases gradually with the increase of relative water depth, and the variation range of 尾 value is from 0.14 to 10.0. Most of the 尾 values are obviously larger than 1. The analysis shows that the light weight model sand is good for sediment diffusion and the sediment diffusion coefficient is larger.
【學位授予單位】：武漢大學
【學位級別】：博士
【學位授予年份】：2014
【分類號】：TV146
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