Numerical Study of Water Hammer in a Non-homogeneous Hydraulic System: Effect of Maneuvering Time and Material Behavior on the Wave Propagation

This research work is dedicated to the analysis of pressure wave propagation in a non homogenous piping system. The considered system is composed of three pipes; one metallic (elastic) placed between two viscoelastic pipes. The hydraulic system is fed from a water tank and at its downstream side a valve is mounted. The study of the system is based on a mathematical development in which the viscoelastic behaviors of pipe walls are based on the Kelvin-Voigt model. For the numerical modeling, the set of partial differential equations governing the water hammer phenomenon is solved through discretization following the method of characteristics. The propagation of the water hammer wave induced by the closure of the downstream valve is followed up. To illustrate the impact of closing times ranging from fast to slow maneuvers, the temporal evolution of the hydraulic transient simulated at the downstream end of the hydraulic system is investigated for different closing times. Additionally, the effects of the hydraulic characteristics of the system on the wave propagation are studied. Through obtained results, it was found out that the attenuation of the wave is influenced mainly by the mechanical characteristics of the pipe material, its dimensions and the operating time.