Numerical Simulation Method And Application Of Drainage Process In Urban Pipe Network

In recent years,with the increasing frequency of extreme rainstorms,urban inundation is now becoming a frequently disasters around the world,which caused huge social,economic,life and property losses.As the raising of rainfall intensity and the concentration of rainfall time,combined with underlying surface changes condition in urban areas,the city’s natural water storage area has continuously reduced that can be accommodated,which increases the pressures on urban flood control and disaster mitigation.The urban drainage pipe network must be used to relieve the drainage pressure.Therefore,is of great significance for improving the early warning and management of urban inundation disasters by mastering the process of rainwater confluence on the surface and the drainage process of urban pipe networks through the numerical simulation of urban floods.Indeed,it is also important for the construction and optimization of urban drainage pipe networks,and reducing the losses caused by urban inundation.In this research,combining with previous related research,a coupled model with one-dimensional pipe network hydrodynamic model and two-dimensional surface hydrodynamic model(GAST)is established,,for which the model can fully consider the rainfall generation and confluence and the drainage process of the urban pipe network.The two-dimensional surface hydrodynamic model uses the Godunov format finite volume method to solve the two-dimensional shallow water equation to calculate the surface rainwater confluence process.At the same time,the GPU acceleration techniques are used to improve the calculation efficiency without reducing the simulation accuracy.The one-dimensional pipe network hydrodynamic model uses the finite difference method to solve the diffusion wave equations to calculate the drainage process of rainwater in the pipe network.Between the one-dimensional and two-dimensional models,the weir formula and the principle of water balance are used to calculate the water exchange between the ground surface and the pipe network.By simulating the rainfall runoff process under rainfall conditions,calculating the surface water area,water depth,water duration and various hydraulic elements in the pipe network,that can provide technical tools for flood prevention and disaster reduction.After building the model,the reliability and stability of the model are verified from different angles through 6 calculation examples.In the tree-shaped and ring-shaped pipe network calculation examples,the simulation solution and theoretical solution of the model in this paper are compared and analyzed.The results show that the two results are in good agreement,which proves that the model can handle the tree-shaped and ring-shaped pipe network.Drainage process,including open channel flow,pressurized flow and open full flow and other water flow patterns.In the case of Morpeth Town,the simulation results of the model constructed in this paper are compared with the measured data,which proves that the model can handle the rainfall runoff process under complex underlying surface conditions and has good accuracy.Then the coupling model is verified by two examples of ideal pipe network and actual pipe network,and compared with the SWMM model under the same conditions.The results show that the two models are in good agreement with the measured data,and the accuracy of the constructed model also has been improved.Finally,the model was applied to the torrential rain and flood simulation in Xixian New District,and the simulation results were consistent with the measured data,which proved that the coupled model constructed in this paper can simulate the surface flow generation and drainage process under real terrain and has the ability to deal with practical problems.It can be better used in the calculate of numerical simulation of urban inundation.