Straightforward transient-based approach for the creep function determination in viscoelastic pipes

This work introduces a simple and straightforward approach for the creep function determination in viscoelastic pipes on the basis of transient flow analysis. The governing equations are expanded and analytically solved for the first half period of the transient. This solution results in a direct formula for the viscoelastic Joukowsky pressure head as a function of the creep function coefficients which are a priori unknown. Utilizing the measured data, only in the first half water hammer period and the proposed viscoelastic Joukowsky formula, the problem unknowns are determined. To investigate the method's merits and limitations, two experimental polyethylene pipes are taken into account from the literature. The results show that the proposed approach works very well for long enough pipelines which are completely crept in the half period of the transient flow. The method is found to be computationally efficient and easy to implement in comparison with traditional inverse transient analysis techniques.