The flow resistance factors of non-submerged rigid vegetation in open channels were analyzed. The formulas of drag coefficient CD and equivalent Manning＇s roughness coefficient na were derived by analyzing the force ...The flow resistance factors of non-submerged rigid vegetation in open channels were analyzed. The formulas of drag coefficient CD and equivalent Manning＇s roughness coefficient na were derived by analyzing the force of the flow of non-submerged rigid vegetation in open channel. The flow characteristics and mechanism of non-submerged rigid vegetation in open channel were studied through flume experiments.展开更多
在风生流的形成中风应力起决定性作用,风应力拖曳系数决定了大气与湖泊间的动量传输率。风应力拖曳系数随风速而变化,与水面粗糙度有关。本文采用五种与风速有关的风应力拖曳系数表达式进行水槽风生流和太湖风生流的数值模拟,与将其视...在风生流的形成中风应力起决定性作用,风应力拖曳系数决定了大气与湖泊间的动量传输率。风应力拖曳系数随风速而变化,与水面粗糙度有关。本文采用五种与风速有关的风应力拖曳系数表达式进行水槽风生流和太湖风生流的数值模拟,与将其视为常数情况相比较,发现风应力拖曳系数取为和风速有关的表达式时,计算结果的精度有较明显提高。对比各表达式模拟结果,采用Large and Pond给出的风应力拖曳系数公式的模拟效果为最好。展开更多
Results of several Large Eddy Simulations （LES） this article. It is shown that the vegetation can make the flow of open channel flows with non-submerged vegetation are presented in structure in the mainstream direct...Results of several Large Eddy Simulations （LES） this article. It is shown that the vegetation can make the flow of open channel flows with non-submerged vegetation are presented in structure in the mainstream direction uniform for both supercritical and subcritical flows. For subcritical flows, the LES results of the ensemble-average of time-averaged velocity distributions at four vertical sections around a single plant are in good agreement with measurements. The velocity sees double peaks at the upper and lower positions of flows. For supercritical flows, the ensemble-average velocities see some discrepancy between LES and measurement results. Some secondary flow eddies appear near the single plant, and they just locate in the positions of the double peaks in stream-wise velocity profiles. It is also found that the vegetation drag coefficient deceases as the Froude number increases.展开更多
文摘The flow resistance factors of non-submerged rigid vegetation in open channels were analyzed. The formulas of drag coefficient CD and equivalent Manning＇s roughness coefficient na were derived by analyzing the force of the flow of non-submerged rigid vegetation in open channel. The flow characteristics and mechanism of non-submerged rigid vegetation in open channel were studied through flume experiments.
文摘在风生流的形成中风应力起决定性作用,风应力拖曳系数决定了大气与湖泊间的动量传输率。风应力拖曳系数随风速而变化,与水面粗糙度有关。本文采用五种与风速有关的风应力拖曳系数表达式进行水槽风生流和太湖风生流的数值模拟,与将其视为常数情况相比较,发现风应力拖曳系数取为和风速有关的表达式时,计算结果的精度有较明显提高。对比各表达式模拟结果,采用Large and Pond给出的风应力拖曳系数公式的模拟效果为最好。
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 10972163, 51079102)the State Water Pollution Control and Management of Major Special Science and Technology (Grant No. 2008ZX07104-005)the Fundamental Rsearch Funds for the Central Universities (Grant N0. 2104001)
文摘Results of several Large Eddy Simulations （LES） this article. It is shown that the vegetation can make the flow of open channel flows with non-submerged vegetation are presented in structure in the mainstream direction uniform for both supercritical and subcritical flows. For subcritical flows, the LES results of the ensemble-average of time-averaged velocity distributions at four vertical sections around a single plant are in good agreement with measurements. The velocity sees double peaks at the upper and lower positions of flows. For supercritical flows, the ensemble-average velocities see some discrepancy between LES and measurement results. Some secondary flow eddies appear near the single plant, and they just locate in the positions of the double peaks in stream-wise velocity profiles. It is also found that the vegetation drag coefficient deceases as the Froude number increases.
