The Laws Of Water Quality Of Mixing At Junctions Of Urban Water Distribution Network

With the rapid development and urbanization of China’s economy, drinking water safety issues received more and more attention.The phenomenon that drinking water resources quality is often standdard,However,the water users drinking isn’t up to standard in most cases. In addition, the current urban water distribution network for water quality modeling of water quality based on node instantaneous complete mixing assumption,resulting in the model results and the actual value are quite differences. The purpose of this paper is to discovery node water quality mixing law, establish node water quality mixed mathematical empirical formula, improve the existing node water quality hybrid model to accurately predict the city for water distribution network in the concentration of pollutants in the space-time and the total amount of the distribution by reserching the mixing mechanism in the junctions of city’s water distribution system.The research has a important practical significance to accurately locate the pipe network of water quality monitoring sites, predict water quality of early warning systems, identify multi-source water supply water pollution sources and risk assessment.The paper is researching the double –T and H junctions in the urban water supply and distribution network. Frist, the paper defined the mixing index f* to quantitatively describe the degree of mixing node water quality. Used FLUENT simulation software to analysys the impact of factors such as the ratio of Reynolds numbers of inlets and outlets and diameter and the distance between the inflow and outflow on the joints mixing results. The results demonstrated that the diameter D of the two nodes has little influence on water quality level of mixing and the ratio of Reynolds numbers of inlets and outlets and the distance between the inflow and outflow on the joints significantly important to joints mixing results. The reserach also use FLUENT simulation software to simulate the mixing in the 3 × 3 small pipe network,analysising the water quality condations at different spatial distribution in the pipe network.Then create a water supply network mixing experimental platfprm in the laboratory for the actual operation simulation to verify CFD numerical simulation results as well as laid empirical data base for the building of water quality mixed node mathematical formula. The paper set pipe diameter of the node connection as an auxiliary study and mainly focused on the ratio of Reynolds numbers of inlets and outlets and diameter and the distance between the inflow and outflow. Experimental simulation effectively verify the numerical simulation results, also found that the distance between the inflow and outflow is larger the degree of mixing node water quality is more adequatly. when it reaches a certain level, the node water quality is almost close to instantaneously mixing thoroughly. Build a 3 × 3 small pipe network test platform. By controlling the flow of two different in flows to analysis the water quality in spatial distribution and compared the results of experienment simulation and CFD simulation and EPANET simulaion which clarify that the actual water mixing in the network is more closer to incomplete mixing with CFD simulation results converge and there is a big difference in the quality of the existing nodes EPANET hybrid model simulation results.Build quality network node mixed empirical mathematical formula based on large number of water quality mixing experiments data by regression analysis to form a the city water distribution network node quality Hybrid Theory guiding the actual project.Used the building mixed mathematical formula to improve EPANET water quality modle.