Construction And Application Of Water Quality Model Of Mixing At Junctions Of Urban Water Distribution Network

As water utilities evolve from having the single mission of supplying high quality water to consumers to also ensuring water security, accurate modeling of water quality has become an increasingly significant issue in prediction of disinfectant residuals and prediction models for early warning systems. Water quality model EPANET is based on that perfect and instantaneous mixing of incoming water occurs at all intersections. However, this years many researchers proposed that among several other concerns about water quality modeling, the assumption of perfect mixing was regarded as a potentially significant cause of discrepancies between model predictions and actual measurements. Therefore, the purpose of this paper is mechanism study of mixing in water supply pipe network junctions and to build a empiric mixing model, in order to improve EPANET water quality model.Firstly, used orthogonal experiment method to make CFD numerical simulation. Orthogonal experiment results show that the ratio of inflow and outflow Reynolds affected three types of junctions mixing sign ificantly, in addition, the distance between the double-T also have a significant impact on double-T junction. Therefore, choose the above factors to make the full CFD simulation, and take the new definition of the degree of junctions mixing index C*as the evaluation index. CFD numerical simulation results were collated and done regression analysis, got the water supply network junctions mixing numerical models.Then create a water supply network junctions mixing experimental platform. Choose above factors to do laboratory simulation. Take NaCl as a tracer, and analy dimensionless concentration of sodium chloride and sodium chloride mass percentage in the East exit, research the junctions mixing mechanism. Take the new definition of the degree of junctions mixing index C*as the evaluation index. Laboratory simulation results were collated and done regression analysis, got the water supply network junctions mixing experimental models.There are some errors in water supply network junctions mixing numerical model and experimental models, as former is too idealistic, while the latter has errors. So in this paper, the water supply network junctions mixing numerical model and the experimental model were manually fitted to form the water supply network junctions empiric model.On this basis, the paper combined with water supply network of Southern City, then proposed ideas and methods to improve EPANET water quality model. After comparing the measured values, indicating that the empirical model improves the accuracy of the water quality model. In addition, using EPANET software and improved EPANET program to do water quality simulation for pipe and nodes of the city’s water distribution network, and water quality simulation results were compared with the measured results. The results show that the improved EPANET program is with higher accuracy.