Water Hammer in Polyethylene Pipes

This research aims to model the dynamic viscoelastic effects of polyethylene pipes under waterhammerpressures. As known, following the water hammer event, a cyclic loading and unloading dueto the pressure fluctuations occurs. Loading on polymeric materials results in deformations that unlikethe elastic materials do not immediately return after unloading. This retarded behaviour graduallyreduces the wave speed causing to a different transient response. Herein, the viscoelastic effects ofpolyethylene pipes on the transient flow is numerically simulated and studied using the Kelvin-Voigtmodel. The developed model is then verified using some experimental data from the literature.Afterwards, a simple hypothetical reservoir-pipe-valve system is defined to investigate several aspectsof viscoelasticity. It is concluded that in a standard water hammer caused by valve closure, theminimum pressure head is more affected by viscoelasticity than the maximum one. Furthermore, withthe increase of initial flow, viscoelasticity takes part more to damp out the destructive dynamic effectsof water hammer. This makes the viscoelastic properties of polyethylene pipes to be figured out as anadaptive procedure to automatically alleviate the water hammer issues in water supply systems.