Water-hammer control in an actual branched cast iron network by means of polymeric pipes

The purpose of this paper is to numerically investigate the impact of replacing existing cast iron pipes of an actual branched network with High-Density Polyethylene HDPE pipes on damping and dispersing pressure waves created by water hammer phenomenon. A transient solver based on the Kelvin-Voigt formulations was developed. The numerical model takes into consideration the pipe wall viscoelastic behavior of polymeric pipes. The numerical resolution method of characteristics MOC with specified time intervals was adopted to solve the nonlinear, hyperbolic, partial differential equations that govern the unsteady flow generated in the network. The reliability of the numerical model was validated with experimental results from the literature. Flow disturbances in the branched network were generated due to the simultaneous fast closure of both downstream valves. Three different configurations of control strategies were suggested. The proposed strategies were based on implementing one or two high-density polyethylene (HDPE) pipes in the sensitive regions where the highest pressure perturbations took place. A comparison between the performances of the different control strategies was performed. Obtained results showed that even with one HDPE pipe implemented in the network, the positive and negative pressure peaks were reduced remarkable. Furthermore, the results have also shown that the risk of cavitation has been completely avoided using the control strategies.