Transient flow in water distribution system.

摘要

Transient flow in a piping network was studied using both experimental and computer models. In the present study, three different numerical methods, the method of characteristics, the two-dimensional method, and the implicit method, are presented and discussed. Experiments for transient flow in a piping system has also been conducted to verify the computer model.; The method of characteristics was developed using two traditional governing equations namely the continuity and the dynamic equation. The two-dimensional method was developed using cylindrical coordinates with transient computation employing an explicit scheme. Logarithmic velocity profiles are used in the cross section of a pipe and the hydraulic head as a function of space and time are computed. The implicit method was also developed using the same governing equations as that used in the method of characteristics with the implicit scheme for the finite difference analysis. Experimental investigations were conducted in order to measure the pressure time history for transient flow. Both frictional head loss and various minor losses in the piping system were measured experimentally. The equivalent head loss coefficient C L has been introduced in this study for both the method of characteristics and the implicit method. After conducting several experiments, the equivalent head loss coefficient CL for the experimental piping system in the present study was determined. All of the numerical methods were compared with the experimental data. The results of different methods of computation developed in the present study agree well with the experimental data. Six cases of numerical simulation for transient flow in distribution system were considered to demonstrate the transient effects in a distribution system. These cases are the simple looped network, small city model, small city model with backflow prevention assembly, small city with surge tank, medium sized city model, and the large sized city model. Each case was simulated with specified scenarios.; The numerical methods developed in this study have been found to be a promising simulation tools for the solution of transient flow in a distribution system. These numerical methods can be used for the design of distribution system subject to transient flow. Moreover, it can be used as operational tools to protect the distribution system from the excessively high pressure, column separation due to excessive negative pressure, or any undesirable incidents in a distribution system.