Study On Optimization Model Of Rainwater Pipe Network Based On NSGA-Ⅱ Algorithm

In the past few years,the frequent occurrence of urban floods has not only caused great damage to urban facilities,but also caused a lot of inconvenience to people’s lives.While flooding caused damage to the original environment,it also had a serious impact on public safety.The urban rainwater pipe network is an important component of the flood control and drainage system.Its main function is to collect and discharge surface runoff and discharge rainwater on the road in time.However,the rainwater pipe network in the old urban areas of many cities in China has exposed many disadvantages,such as the low value of the rainstorm return period,the original design does not meet the long-term urban planning,the lack of a sound management and maintenance mechanism in operation,or the design by the designer based on traditional experience.The resulting subjective influence,etc.,can not achieve the optimal design.Therefore,this article uses mathematical methods to establish a rainwater pipe network optimization model,and by increasing the objective function to achieve the optimization goal of saving investment and greatly improving the drainage capacity of the rainwater pipe network,so as to avoid the rainwater pipe caused by the designer’s subjective influence or the single-objective optimization method.The single shortcoming of the network optimization plan finally makes the rainwater pipe network meet the city’s demand for drainage and waterlogging prevention.This paper studies the optimization model of rainwater pipe network from the following aspects:Based on the existing pipe network data on site,the rainwater pipe network model was established using SWMM software,and by learning the principles and applications of SWMM,the various visualization modules built in SWMM were used to dynamically simulate and analyze the pipe network operation to optimize the rainwater pipe network.Prepare for the comparative analysis of the before and after results.In addition,the core algorithm used in the optimization model of rainwater pipe network in this paper-fast non-dominant sorting genetic algorithm(NSGA-Ⅱ)has been studied in depth.Corresponding calculation programs are written through Matlab to lay the foundation for the model’s algorithm structure,optimized route and parameter settings basis.This study uses pipe diameter as a variable to optimize,takes pipe diameter,slope,flow velocity,and buried depth as constraints.On the basis of saving cost,adds an objective function to improve drainage capacity,and compiles a rainwater pipe network optimization model through Matlab.NSGA-Ⅱ is used as the core algorithm of the rainwater pipe network optimization model in this study to obtain the best design pipe diameter combination.At the same time,Matlab is used to realize the optimization model to independently call SWMM for simulation operation,so that the optimization algorithm and hydraulic simulation software are combined to optimize,reduce the error and time consumption caused by manual operation,and improve the accuracy and efficiency of calculation.The created rainwater pipe network optimization model is applied to the old city west area of Pengshan District,Meishan City(Limi Avenue,Zhanggang Road,and Pengzu Avenue surrounding plots).The results show that the total overflow flow of the pipeline network in the study area before optimization is 2299,and the total pipeline network after optimization The overflow rate was reduced to 627,the road area water volume was reduced by 73%,and the drainage capacity of the pipe network was improved.In addition,under the pipe diameter combination when the total overflow at the node is 627,the cost of pipe network transformation given by the economic function is about 125 million yuan,and the result is in line with the Pareto curve under the two optimization goals.Through the optimization of the optimization model of the existing rainwater pipe network,the drainage performance of the pipe network has been improved,and the road area water volume has been reduced.This result meets the economical and greatly improved optimization goal of drainage performance and the original intention of constructing the rainwater pipe network optimization model.This paper optimizes the cost and improves the drainage performance of the rainwater pipe network,creates a rainwater pipe network optimization model,and optimizes the optimization algorithm and hydraulic simulation software to reduce the error and time consumption caused by manual operation,and improve the accuracy and efficiency of the calculation.It is hoped that it will have a certain value in the optimization design of urban rainwater pipe network and the prevention and control of waterlogging disasters.