长距离调水工程明渠阻力影响要素机理研究

There are many water supply channels of long-distance water diversion projects in China, which does not take the impact of aquatic plants and litters on open channel flow resistance in different seasons into account, so it greatly reduces the accuracy and efficiency of the open channel hydraulic simulation and regulation. At present, the research on the hydrodynamics of plant-open channel is mainly focused on the water-blocking characteristics of plants and the numerical calculation of plant-open channel flow. While the study on the hydrodynamics of plant-open channel for complex long-distance water diversion projects is blank. .The influence of litter distribution on the energy dissipation and turbulence dissipation of open channel, as well as the influence of litter distribution on the roughness coefficient were firstly analyzed by physical model test, numerical simulation, prototype observation and hydrodynamic analysis. Then the vertical distribution equation of relevant turbulent momentum of aquatic plants under different conditions and response equation of Manning roughness coefficient changing rate of litters were built. Combining the characteristics of long-distance water diversion project, an improved vertical two-dimensional hydrodynamic model along the horizontal integration of channel section were proposed. Finally, through correction and calibration of prototype observation, the two-dimensional hydrodynamic model suitable for long-distance water diversion open channel with the impact of aquatic plants was put forward, which can provide the basic science and technology support for the safety control of complex water diversion project.

在我国有许多长距离调水工程输水渠道，其设计在不同季节水生植物和枯落物对明渠水流垂向紊动阻力的影响上考虑不足，大大降低明渠水力学模拟与调控的准确性。目前国内外对含植物明渠水动力学的研究主要集中在植物阻水特性以及含植物明渠流的数值计算上，而适用于复杂长距离调水工程反向输水渠道的含植物明渠水动力学研究尚属空白。.本项目以物理模型试验、三维数值精细模拟、原型观测、水动力学模拟为手段，分析植物绕流对明渠能量耗散及紊动耗散特性的影响、枯落物对明渠曼宁糙率系数的影响，构建水生植物在不同条件下断面相关紊动量和紊流拟熵的垂线分布方程和枯落物在不同工况组合下明渠曼宁糙率系数变化速率响应方程，结合长距离输水工程的特点，综合考虑准确性和高效性，建立改进的沿断面横向积分的垂向二维水力学模型。再通过原型观测修正率定，最终提出考虑植物影响的适合长距离调水明渠的垂向二维水力学模拟模型，为复杂调水工程安全调控提供支撑。

在设计长距离调水工程时，往往忽略了水生植物和枯落物对明渠水流运动的影响，进而大大降低了明渠水力学模拟的准确性。针对这一问题，本项目采用物理模型试验的方法，观测不同生长状态、不同密度、不同排列方式的水生植物和不同覆盖度的枯落物对水流流速的影响，并根据观测结果改进了垂向二维水动力学模型。研究结果发现：.（1）增加植物叶片数量会增加渠道糙率，减小水流的平均流速。同时最大紊流强度和最大雷诺应力会随着叶片数量的增加呈现先增加后减小的趋势。（2）随着植物密度的增加植物宁糙率系数、雷诺应力和紊流强度也随之增加。（3）在水草数量相同的情况下，均匀分布方式对水流的阻力最大。一边分布情况下含水草一边的雷诺应力和紊流强度最大，不含水草情况下的雷诺应力和紊流强度最小。（4）枯落物的覆盖会明显增加渠道的曼宁糙率系数，减小了底层水流的平均流速，增加底层水流动量交换，但随着覆盖量的增加，曼宁糙率系数变化不大。（5）根据物模试验结果，结合连续方程及动量方程，模拟出改进的明渠垂向二维流水力学方程，并建立雷诺应力紊流模型，将数值模拟结果与试验结果相比较，发现两者结果吻合较好。.本项目研究成果可以提高长距离调水工程模拟精度，为实现调水工程的精准调度奠定基础。