坡面植被形态变化的水流阻力特性试验研究

发布时间：2018-04-30 00:02

本文选题：坡面植被 + 偏转角　；参考：《山东科技大学》2017年硕士论文

【摘要】：坡面水流阻力是坡面流水动力特性的参数,是模拟坡面产汇流过程中重要指标,同时对防治坡面水力侵蚀、合理种植防护林和科学建设生态河流均有重要指导意义。植被是影响坡面水流阻力的重要因素,坡面往往存在各种类型和生长状态的植被,这些植被可以改变水流结构,增加动能损失,减缓水流的流速,进而影响坡面水流阻力的变化规律,因此研究植物对坡面水流阻力的作用是揭示坡面流水动力学规律的基础。由于含植物水流复杂多变的特性,仅从理论上分析不能准确掌握植被特性对坡面水流阻力的影响作用,因此要借助试验手段研究植物对坡面水流阻力的影响。目前的大部分模拟试验研究了含植物水流的特性变化,并对试验数据进行分析与内在规律总结,只得到一些定性结果或经验公式,为了更加精确植物对水流的作用,仍需要做进一步定量研究,以期可以得到普遍适用的定律与公式。本文通过室内定床冲刷试验,在变化的水深条件下,模拟研究了植物的不同偏转角和叶片面积在3种坡度(0.00%、0.50%、1.00%)下对水流阻力特性的影响,分析了雷诺数、沿程能量损失和水流阻力系数随平均水深和试验坡度的变化规律,进而揭示植物偏转角度和叶片面积变化对水流特性影响的作用机理。主要得出以下结论:①植物在水流作用下发生偏转,可以增大水流粘滞力,减小水流惯性力,使水流结构更加平稳,减小水流的能量损失与阻力。植物偏转角对雷诺数影响很小,沿程能量损失和Darcy-Weisbach系数都随植物偏转角增大而减小;建立含植物偏转角的Darcy-Weisbach系数计算公式,并用实测数据对该公式进行验证,发现该公式对模拟不同偏转角条件下的水流阻力系数适用性良好。②植物叶片是水流阻力的主要来源,植物叶片面积的增大使水流粘滞力增大,惯性力减小,水流紊动状态减轻。雷诺数随植物叶片面积增大而减小,水流沿程能量损失和Darcy-Weisbach系数随植物叶片面积增大而增大,且随着叶片面积的增大,沿程能量损失和水流阻力系数增大的幅度减小;建立含植物叶片面积的Darcy-Weisbach系数计算公式,通过对实测数据的分析,该公式同样适用于植物不同叶片面积条件下Darcy-Weisbach系数的计算。
[Abstract]:The flow resistance on the slope is the parameter of the hydrodynamic characteristics of the slope and an important index to simulate the process of runoff generation and confluence on the slope. At the same time, it has an important guiding significance for preventing and controlling hydraulic erosion on the slope, planting the shelterbelt reasonably and constructing the ecological river scientifically. Vegetation is an important factor that affects the resistance of the flow on the slope. There are often various types of vegetation on the slope, which can change the structure of the flow, increase the loss of kinetic energy, and slow down the flow velocity. Therefore, the study of the effect of plants on the flow resistance on the slope is the basis of revealing the dynamic law of the flow on the slope. Because of the complex and changeable characteristics of vegetative water flow, the influence of vegetation characteristics on the flow resistance of slope surface can not be accurately grasped by theoretical analysis. Therefore, the effect of plants on the flow resistance of slope surface should be studied by means of experimental means. At present, most of the simulation experiments have studied the characteristic changes of plant-containing water flow, analyzed the experimental data and summarized the inherent laws, and obtained only some qualitative results or empirical formulas, in order to obtain more accurate effects of plants on the water flow. Further quantitative studies are needed to obtain universally applicable laws and formulas. In this paper, the effects of different deflection angles and leaf area of plants on the flow resistance characteristics under three different slopes of 0. 50 and 1. 00 are simulated under the condition of varying water depth by indoor fixed bed scouring test. The Reynolds number is analyzed. The variation of energy loss and flow resistance coefficient along the course with average water depth and experimental slope reveals the mechanism of the influence of plant deflection angle and leaf area on the flow characteristics. The main conclusions are as follows: (1) when the plant deflects under the action of water flow, it can increase the viscous force of the flow, reduce the inertia force of the flow, make the flow structure more stable, and reduce the energy loss and resistance of the flow. The plant deflection angle has little effect on Reynolds number, and the energy loss and Darcy-Weisbach coefficient decrease with the increase of plant deflection angle, the formula of Darcy-Weisbach coefficient with plant deflection angle is established, and the formula is verified by measured data. It is found that this formula is suitable for simulating the flow resistance coefficient under different deflection angles. 2 Plant leaves are the main source of water flow resistance. The increase of plant leaf area increases the viscous force of water flow and decreases the inertia force. The turbulent state of the flow is reduced. The Reynolds number decreases with the increase of leaf area, the energy loss and Darcy-Weisbach coefficient increase with the increase of leaf area, and the amplitude of energy loss and flow resistance coefficient decrease with the increase of leaf area. A formula for calculating the Darcy-Weisbach coefficient of plant leaf area is established. Through the analysis of the measured data, the formula is also applicable to the calculation of Darcy-Weisbach coefficient under different leaf area conditions.
【学位授予单位】：山东科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TV131.22

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