基于运动波模拟的雨水管网设计流量计算方法

Calculation method for stormwater network design flow based on kinematic wave simulation

雨水管网中管段的设计流量计算一般以恒定均匀流理论为基础,由于偏离了雨水管网实际流态,当应用于较大规模管网时,产生的误差会逐步累积。因此,该文提出一种基于运动波模拟的雨水管网设计流量计算方法,在地表产汇流阶段,基于管网设计参数等价原则,采用径流系数与φ指数法结合的方式进行产流计算,并与等流时线法耦合,完成产汇流阶段设计条件的等价设置;采用暴雨洪水管理模型(storm water management model,SWMM)运动波模块,计算管段汇流过程,并基于GDAL(geospatial data abstraction library)开发技术,实现雨水管网设计流程。对某区雨水管网进行实例验证,结果表明:与恒定均匀流计算相比,采用运动波模拟法得到的雨水管段集水时间短、设计流量大,且随汇水时间和汇水面积的增长,2种方法的流量计算差值呈递增趋势;在超标降雨情景下,运动波模拟法设计的方案具有更好的防涝性能,提高了管网的可靠性。

[Objective]The pipe section collection time is typically based on the theory of steady full pipe uniform flow when using the reasoning formula method to calculate the design flow of a storm pipe network,but the actual water flow in the storm pipe is non-steady,causing errors in the calculation of the design flow that,when applied to a larger scale pipe network,gradually reduce the calculation accuracy.In this context,the paper suggests a design flow computation method for storm pipe networks based on kinematic wave simulation.[Methods]In this paper,the design flow of pipe sections is solved using kinematic waves under the condition of ensuring the equivalent setup of model parameters and storm pipe network starting design parameters.This paper combines the Horton infiltration model and the index method to calculate infiltration intensity in the surface rainwater runoff stage.The runoff generation is calculated with the objective of achieving equivalence of the volumetric runoff coefficient and discharge runoff coefficient.Taking surface catchment time and linear confluence curve type as input,and coupling with the isochrones model,the equivalence setting of design conditions and stormwater outlet inflow process line calculation are completed.In the pipe section confluence process,the pipe section flow process line is calculated by inputting the corresponding stormwater inlet inflow process line into the node inflow mode and computing the pipe section confluence process using the stormwater management kinematic wave model.The stormwater inlet inflow process line of the designed pipe section and the upstream pipe section flow process line connected with it are superimposed to complete the calculation of the pipe section design flow process line.Combined with the hydraulic design of the stormwater pipe section,the whole storm pipe network design is realized based on the geospatial data abstraction library development technology process.[Results]The results of a storm pipe network example in a particular area(with a total size of 4.506 km2)showed that:(1)When compared to the reasoning formula method,the stormwater pipe section created using the kinematic wave simulation approach had a quick catchment time and a greater design flow rate.(2)The flow calculation difference between the two approaches increased over time as catchment time and catchment area increased,reaching a maximum increase of 39.45%.(3)Under the 10-year rainfall scenario,the design storm pipe network obtained by the two calculation methods of equivalent design conditions reduced the number of overflow nodes,total overflow volume,and length of pipe section overload by 8.57%,28.57%,and 38.48%,respectively,compared to the reasoning formula method.[Conclusions]By comparing the differences in the design results obtained by the two calculation methods for different catchment times and catchment areas,it can be seen that for large projects,it is advisable to use the kinematic wave simulation method to calculate the design flow of the storm pipe network.In a simulated analysis with a 10-year exceedance of rainfall,the storm pipe network designed by the kinematic wave simulation method has better flood prevention performance.