A more realistic approach to the "extended period simulation" of water distribution networks

This paper deals with the problem of extending several readily available packages, originally developed for the analysis of looped water distribution systems, such as for instance EPANET2, to perform more realistic "extended period simulations" (EPS). The EPS problem can be solved by introducing a pressure-demand relationship at the nodes, as proposed by several authors, but this tends to reduce convergence. The purpose of this paper is to show that there is no need of defining and introducing such a pressure-demand relationship. Based upon the minimization properties of constrained convex functions and some logical reasoning, a three steps technique is here introduced as a simple alternative to allow most of the available packages to perform a more realistic EPS. The performances of the new approach will be demonstrated with a numerical example for which a clearly incorrect solution is obtained using EPANET2 with "emitters".