Application of Genetic Algorithm for Determining the Existent Friction Coefficients in the Real-life Pipe Networks as an Inverse Problem

An integrated approach for determining the existent friction coefficients in water networks is proposed. As pressurized systems age, the carrying capacity of network decreases because the internal roughness increases with the aging of pipes. This can lead to loss of satisfactory performance and uneconomic operation. Therefore, rehabilitation of an existing network becomes very important problem in water industry. Determining the real physical characteristics of pipes for network analysis is a regular component of the rehabilitation process. Pipe friction coefficients cannot be determined explicitly by direct measurement, they are determined implicitly, as an inverse problem, from measured model outputs (pressures). Values of friction coefficients are determined in a way that they should yield a reasonable match between measured and predicated pressures in the network. One problem associated with the Re-calibration of real-life pipe networks is the lack of field measurements, which can sometimes, lead to the formulation of an ill-posed inverse problem. In this study certain methods have been utilized to tackle this problem. The hydraulic analysis of steady and quasi-steady flow and optimization process are combined to develop a program. By selecting a proper optimization method (Genetic Algorithm) the inverse model was developed and verified successfully in a case study.