Two-dimensional features of viscoelastic models of pipe transients

Transients in pressurized pipes are analyzed by means of a 2D Kelvin-Voigt viscoelastic model, calibrated by means of micro-genetic algorithm on the basis of pressure traces. The reliability of the proposed model is then tested by comparing numerical and experimental profiles of the axial component of the local velocity, the latter measured by means of an ultrasonic Doppler velocimeter. Differences between transients in viscoelastic and elastic pipes are pointed out by considering a 2D model in which an elastic behavior is assumed for pipe material. The comparison between the two 2D models allows to attribute the faster decay of pressure oscillations and velocity profiles to viscoelasticity, because of the time-shift between pressure oscillation and circumferential strain. The 2D analysis puts into evidence that the viscoelastic model generally presents flatter velocity profiles with respect to the elastic model.