Simultaneous Layout and Size Optimization of Water Distribution Networks: Engineering Approach

A heuristic method is presented for the simultaneous layout and component size optimization of water distribution networks. The method is based on the engineering concept of reliability in which the number of independent paths from source nodes to each of the consumption nodes is considered as a measure of reliability. The method starts with a predefined maximum layout which includes all possible and useful connections. An iterative design-float procedure is then used to move from the current to a cheaper layout satisfying a predetermined reliability set by the user. This is achieved via identifying the hydraulically least important pipes and floating the one which would lead to the cheapest layout. A pipe is floated by relaxing its minimum diameter constraint requirement so that the optimization process could eliminate the pipe from the layout by assigning a zero value to its diameter if required. An iterative penalty method is used for design purpose at each iteration. Three different floating procedures are developed and their efficiencies are tested. A heuristic method is also developed to convert the continuous pipe size solution to a set of discrete solutions. The performance of the method for layout optimization of pipe networks is tested against the benchmark example in the literature and the results are presented.