【作者】 刘斌；

【导师】 胡旭跃；

【作者基本信息】 长沙理工大学 ， 水力学及河流动力学， 2007， 硕士

【摘要】 天然明渠中生长植物的现象十分普遍。一方面,植物能够保护土壤,避免水土流失,起到固滩固岸的作用;另一方面,植物增加了河床的阻力,使河道水位升高,水流的平均流速减小,降低了河道的行洪能力。因此,探讨植物对水流阻力的影响在水资源可持续利用,河流的生态修复、管理和河道整治等许多方面有重要的科学和实践意义。本文在分析一般明渠阻力分割理论的基础上,推导出新的阻力分割计算公式,并以此公式为基础采用水槽实验对有植物明渠的阻力特性进行了研究。首先,通过分析国外学者已发表的资料,发现了爱因斯坦阻力公式可分别用于明渠边壁与床面的阻力计算,结合连续方程、几何关系推导出一般明渠的阻力计算公式,经验证分析,其计算精度较高,可以满足工程及研究需要。其次,通过实验分析了植物高度、密度不同时边壁平均切应力、植物阻力的变化。边壁平均切应力随植物高度、密度的增加而减小,且这种减小的趋势会随高度、密度的增加而逐渐减小;植物阻力跟植物的倒伏程度、相对淹没度有关,在流量、植物特性不变的情况下,植物阻力随植物高度、密度的增加而增加。再次,通过实验结合一般明渠阻力公式分析了植物粗糙度K_sb的特性。受水流作用,淹没的柔性植物存在倒伏现象, K_sb比植物高度小,当植物高度、密度增加时,与之对应的K_sb也跟着增加,且植物高度、密度越大,植物高度与K_sb在数值上越接近。经过对试验数据的回归分析,推导出粗糙度K_sb的计算式。最后,结合一般明渠阻力公式和植物粗糙度计算式,推导出植物阻力计算式,经分析表明,该公式的推导较为合理,较好地反映了水槽内床面有植物的水流规律。更多还原

【Abstract】 It is universal that vegetation grow in open channel. Vegetation can prevent water loss and soil erosion and protect the side bank. But the vegetation increase the resistance of the bed, raise the water level, it can also low the flow of open channel. So studying vegetation influence to flow resistance is of significant science and practice meanings in water resources sustainable utilization, river ecology rehabilitation and river improvement.In this paper, based on resistance segmentation theory of general open channel, a new calculation formula is derived. And combining with the formula and flume experiment, the resistance characteristic of channel with vegetation is studied.At first, base on analyze of reliable data, it is found the Einstein logarithmic resistance formula can be used calculating in sidewall and bed flow, then combining with flow continuity equation and geometrical relationship , the resistance formula of open channel is derived. The analysis show that the formula has higher precision and can satisfy a engineering and study requirement.Secondly,based on the experiment of different vegetation height and density, analyzing the variation of the average wall shear stress and vegetation resistance. With the vegetation height and density increasing, the wall shear stress would decrease, and the tendency is reverse with the variation of vegetation height and density. The vegetation resistance is related to vegetation laid degree and relative submerged degree, at the constant discharge and vegetation character, along with the vegetation height and density increasing, the vegetation resistance would increase.Thirdly, combining with experiment and resistance formula of open channel, the character of vegetation rough degree K_sb was analyzed. Subjecting to the flow acting, submerged flexible vegetation has falling phenomenon, K_sb is less than vegetation height, while the vegetation height and density increased,related K_sb would increase. And the lager the vegetation height and density, the nearer the numerical value between the vegetation height and K_sb. By the regression analysis to experimental dates, the formula of rough degree K_sb is derived.Finally based on the resistance formula of open channel and the K_sb formula, the formula of vegetation resistance was derived. The analysis of actual measurement show the formula has higher precision and the calculated and measured data has minor relative error.更多还原