Modeling of nonlinear viscoelastic creep of a polyethylene pipeline during water hammer

In this research, the nonlinear behavior of a viscoelastic pipe during water hammer is investigated. To this end, the creep coefficients of the multiple element Kelvin–Voigt model have been determined for different flow rates and then they are incorporated to derive a holistic relation for the creep compliance. A linear interpolation scheme has been adopted to arrive at the holistic generalized Kelvin–Voigt model as a function of flow rates. The proposed relation is then applied in the established mathematical model and corresponding numerical solution to predict pressure fluctuations. The proposed approach in the application of the creep functions could capture the nonlinear material behavior during transients. Specifically, it revealed a higher creep behavior for higher loading rates (Joukowsky pressures) which was consistent with the experimental observations. Several numerical and experimental results were analyzed and investigated and to demonstrate the performance of the proposed approach.