Temperature Modeling For Stormwater Runoff In Urban Surface And Conduit Network

With the development of urbanization,the influence of runoff heat pollution in urban surface and underground conduit network on water ecological environment is becoming more and more prominent.At present,relevant researches have been carried out to solve this problem,but most of them lack theoretical support and experimental exploration.There are many variables and factors that affect the runoff temperature,resulting in the physical mechanism system of rainfall runoff temperature simulation in urban surface and underground condiut network is incomplete,which brings a lot of uncertainties to the simulation of runoff temperature.Based on previous studies,using the principles of energy balance,mass conservation and heat transfer to analyze the physical change process of temperature for rainfall runoff in urban surface and underground conduit network in this paper,and the temperature model of rainfall runoff for typical urban watershed(SWMM-T)is constructed.The SWMM-T model is applied to a typical urban watershed,and the measured results and simulation results are compared and analyzed to verify the rationality and feasibility of the SWMM-T model.In order to facilitate the application and promotion of SWMM-T model,the integration platform of SWMM-T model is also realized in this paper.The specific study contents and conclusions are as follows:(1)In this paper,typical urban watershed is generalized into two types: urban surface and underground conduit.Based on the principle of thermal energy balance,the thermal energy balance formulas of urban overland flow and underground conduit flow under short-duration rainfall in summer is defined through reasonable assumptions and simplification,and the calculation method of heat exchange coefficient in the formula is revised.The revised calculation method of heat exchange coefficient is not only concise,but also takes into account the "striking" or "erosion" force of raindrops on the surface,and introduces the kinetic energy of raindrops to quantify the effect of rainfall intensity on heat exchange between runoff and surface.Therefore,it is more physical significant for the modified heat exchange coefficient.(2)Based on hydrodynamic model which established by SWMM,the SWMM-T model is finally constructed according to the heat energy balance formulas of urban overland flow and underground conduit flow.Three types of urban surface are mainly considered for the SWMM-T model: permeable artificially hardened surface,impermeable artificially hardened surface and saturated artificially afforested surface.The SWMM-T model is applied to a typical urban watershed,and the rationality and feasibility of the SWMM-T model are verified by comparing the simulation results with the measured results.(3)The simulation results show that the heat exchange coefficient between runoff and surface is positively correlated with rainfall intensity,so the smaller the runoff flow,the lower the temperature of runoff.In addition,compared with the artificially hardened surface,the soil surface not only has the function of relieving urban rainstorm and flood,but also can relieve the "heat load" brought by urbanization to runoff.(4)Based on the SWMM which is free and open-source,the calculation integration platform of SWMM-T model is realized.SWMM-T＿1.0 with concise interface is easy for users to learn and operate quickly.It can provide prediction data of runoff temperature for municipal management planning and supply some reference for planning,design and management of urban environment when using this integrated platform to simulate the temperature of urban runoff.Therefore,it is certain engineering significant for the integration platform of SWMM-T model.