基于运动波方程的地面集水时间计算及参数研究
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摘要
地面集水时间是推理公式法计算城市雨水管道设计流量的重要参数,其取值大小将对排水安全和工程造价带来较大影响。采用运动波方程组描述城市地表汇流过程,并与城市暴雨强度公式联立求解地面集水时间,对方程组中地面粗糙系数、汇流长度、坡度、重现期和径流系数进行敏感性分析,得出光滑地面下坡度对集水时间的影响最为显著。进一步进行数值模拟试验,得出汇流长度为50～200 m时光滑平坦的地面集水时间在《室外排水设计规范》推荐值范围内,但坡度变大时(S_0> 0. 03)集水时间快速减小,此时不宜使用《室外排水设计规范》推荐值。集水时间随粗糙系数的增大而增大,在平坦地面下粗糙系数> 0. 15时,集水时间> 30 min,超出《室外排水设计规范》推荐值,设计时可考虑适当增大集水时间。
Time of concentration is an important parameter in the evaluation of the design flow for urban storm drainage systems. And it has a significant effect on the system reliability and engineering cost. Kinematic wave equations were used to describe the process of concentration and in combination with the urban storm rainfall intensity formula to solve the time of concentration. The impact of factors including surface roughness coefficient,flow distance,slope,return period and runoff coefficient were considered in the sensitivity analysis. It was concluded that the slope parameter determined the time of concentration on smooth surface. Further numerical evaluations showed that,when the flow distances was between 50 m and 200 m,the time of concentration on smooth and flat surface followed the recommended range in Code for Design of Outdoor Wastewater Engineering. However,as the slope increased (S_0>0. 03),time of concentration decreased rapidly and fell out of the recommended range. Furthermore,time of concentration increased with the increase of the surface roughness coefficient. When the roughness coefficient was beyond 0. 15 on a flat surface,time of concentration was over 30 min and exceeded the recommended range in the code. Larger time of concentration should be considered in the design under such circumstance.
Time of concentration is an important parameter in the evaluation of the design flow for urban storm drainage systems. And it has a significant effect on the system reliability and engineering cost. Kinematic wave equations were used to describe the process of concentration and in combination with the urban storm rainfall intensity formula to solve the time of concentration. The impact of factors including surface roughness coefficient,flow distance,slope,return period and runoff coefficient were considered in the sensitivity analysis. It was concluded that the slope parameter determined the time of concentration on smooth surface. Further numerical evaluations showed that,when the flow distances was between 50 m and 200 m,the time of concentration on smooth and flat surface followed the recommended range in Code for Design of Outdoor Wastewater Engineering. However,as the slope increased (S_0>0. 03),time of concentration decreased rapidly and fell out of the recommended range. Furthermore,time of concentration increased with the increase of the surface roughness coefficient. When the roughness coefficient was beyond 0. 15 on a flat surface,time of concentration was over 30 min and exceeded the recommended range in the code. Larger time of concentration should be considered in the design under such circumstance.
引文
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[4]张大伟,赵冬泉,陈吉宁,等.芝加哥降雨过程线模型在排水系统模拟中的应用[J].给水排水,2008,34(S1):354-357.Zhang Dawei,Zhao Dongquan,Chen Jining,et al.Application of Chicago approach in urban drainage network modeling[J].Water&Wastewater Engineering,2008,34(S1):354-357(in Chinese).
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