含植物明渠水沙运动规律试验研究
发布时间：2018-07-16 16:46
【摘要】：含植物河流是自然生态的重要组成部分。由于影响因素众多,水沙运动规律相对复杂,含植物河流水沙运动特性是河流泥沙动力学中的难点问题之一。本文在资料收集的基础上,对含植物水流问题的国内外研究现状进行系统的总结,并采用三种仿真柔性植物进行了含植物明渠水沙运动规律的室内水槽试验；首先分不同区域(植物带上游、植物带和植物带下游)研究了无草、淹没型、非淹没型柔性植物水流阻力特性规律,继而对含不同植物明渠水动力运动特性进行深入探讨；最后对含不同植物明渠泥沙运动进行详细分析。全文主要研究以下三个方面的问题： 1.含植物明渠水流阻力特性研究 利用水槽试验研究了无草、淹没型、非淹没型柔性植物水流阻力特性的变化规律,分析了含植物明渠沿程水面比降和阻力系数的变化特性。得到各植物阻力系数变化与尼库拉兹曲线基本相似,紊流范围内同样可划分为紊流光滑区、紊流过渡区、紊流粗糙区；统计各植物经不同水流冲击倒伏后的冠顶高度,分析了植物粗糙度、水流雷诺数和阻力系数之间的关系,并对各植物的水流阻力系数分区进行回归分析,得到各植物水流阻力的分区经验表达式,该方法能较好地应用于含植物明渠水流阻力系数的推求。 2.含植物明渠水动力特性试验研究 利用水槽试验研究了含不同植物明渠水动力特性,试验结果表明,对于淹没植物,在植物的冠顶上方一定区域水流流速变化与无草情况下基本相似,但非淹没植物的水流纵向流速在水深方向呈“S”型分布,并呈明显的分层现象；水流紊动强度随植物形态、沿程分布和距边壁位置变化而表现出不同特性；-(uv+uv)/u2*是表征水流变化的重要因子,有植物情况下,其与植物形态和沿程分布等因素密切相关,并随植物形态和空间分布而发生不同规律的调整。 3.含植物明渠泥沙运动规律研究 利用水槽试验研究了含不同植物明渠泥沙运动规律,试验结果表明：泥沙级配存在明显的分层现象,呈现“上细下粗”的基本变化规律,同种植物对细颗粒泥沙的空间分布影响较小,对中、粗颗粒泥沙的影响较大。含植物明渠较无植物明渠,床沙非均匀性减小,其中淹没型莎草减小幅度最大；对含植物明渠中水流的动量扩散系数、泥沙扩散系数和二者比值β进行较详细研究,得到了三者随植物形态和空间分布的变化特征,具体为：动量扩散系数在垂向总体呈抛物线分布,随相对水深增加先增大后减小,泥沙扩散系数总体随相对水深的增加而逐渐减少,β值变化范围为0.14-10.0,多数β值明显大于1,分析认为,试验采用轻质模型沙,有利于泥沙扩散,泥沙扩散系数较大所致。
[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.
【学位授予单位】：武汉大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TV146
本文编号：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.
【学位授予单位】：武汉大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TV146
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