Elastic Water Column Model for Hydraulic Transient Analysis of Pipe Networks

The transient behavior of pipe systems is typically simulated using water hammer models [such as the method of characteristics (MOC)], or rigid water column (RWC) models depending on whether the hydraulic transition is fast or gradual. In this paper, an elastic water column (EWC) model for analyzing hydraulic transients in pipe networks is formulated using a novel graph-theoretic approach. The new method of modeling a network with a state-space representation inherits the advantages of the RWC model, such as its high computational efficiency and potential to integrate with modern control theory and signal analysis algorithms. Meanwhile, the proposed method incorporates water compressibility and is therefore significantly more accurate than the standard RWC models, and is shown to be equivalent to MOC models below a critical frequency. Another advantage of the new model is its elegantly simple formulation for an arbitrarily configured pipe network. The accuracy of the model was validated numerically on 6- and 51-pipe networks. The simulated results of the 51-pipe network demonstrate that the transient pressures in a large-scale pipe network dominate in the low-frequency range where the EWC model has high accuracy. These results demonstrate the utility of the proposed method to provide a flexible solution to optimize accuracy and efficiency for simulating hydraulic transient events in pipeline networks. The EWC model has great potential to be combined with other control and signal analysis techniques because of its state-space representation of a water network.