Solute Mixing Model Of Joints For Urban Water Distribution Networks

Soluet mixing model of joints in water distribution networks has important impact on the result of water quality simulation. For the defect of the "perfect" mixing assumption which is widely used, this paper presented a systematically study on a typical node type:1. This paper defined the mixing index d*and D*for the joints based on the basic hydraulic and quality equation, which improves the index used now. Results by typical scenario had shown that:the new index is more reasonable and can reflect better on the degree of mixing by each condition.2. Used orthogonal experiment method and FLUENT simulation software to analyze the impact of the factors on the joint mixing and achieved good results:the design of orthogonal experiment greatly improved the efficiency of the test by selecting some representative ones from a large amount of tests; FLUENT simulation software has good convergence speed and solution accuracy, and is suitable for the qualitative simulation for the joints mixing. The results show that the ratio of Reynolds numbers of inlets and outlets (Res/W and RcE/N) and the ratio of pipe diameter of inlets (DS/W) have more impacts on the mixing at the joints.3. This paper accomplished the experimental study of solute mixing at cross joints by using high water head tank and valve based on improving the mode of pressure boost. Entrance pressure data shows that the pressure of the system was stable during each experiment scenario; The percentage mass fraction error of the experimental data shows that each parameter of the experiment was controlled well and the error of the experimental data was insignificant; Comparative analysis of experimental data indicates that:the curves obtained by this experiment and other scholars match well.4. A mixing model of joints based on improved PSO algorithm has been proposed. A search factor is added into the movement of the particle to develop basic PSO algorithm and results manifest that the developed algorithm has stronger global optimizing ability and better search accuracy; The objective function has been built based on the method of the least square, which is used to minimum the sum of the errors between experimental data and simulated data. Then, the mixing models have been fitted by improved PSO algorithm; the water quality simulation of EPANET software is utilized for improving the practicality by using the mixing models in the process of the mixing reaction of the fluid element and the generation of new element.5. In order to detect a random external input of water pollution, this paper built a model that can optimize the layout of the monitoring stations for the city water supply system. The model is based on defining of the concept of shortest flow-time matrix and pollution coverage matrix. To resolve the computational complexity in shortest flow-time matrix for complicated water distribution systems, the method of using dynamic programming to obtain the pollution coverage matrix under a given monitor level. Genetic algorithm is adopted to optimally allocate the monitoring stations. The method maximizes the monitoring coverage considering the duplication of coverage. The results show that the shortest flow-time matrix of complicated networks can be efficiently obtained by using dynamic programming, which can be coded easily; genetic algorithm can find the optimal layout of monitoring stations rapidly, which can monitor the accidental contaminations of the whole network by the greatest degree in a given monitor level.6. The developed EPANET program has been used in a realistic network, the result contrasted to basic EPANET software indicates that:the mixing models have a certain impact on the concentration distribution in the pipes and the concentration change trend at monitoring stations.