A Model for Simulating Transients in Looped Viscoelastic Pipe Systems. Preliminary Results

Because of their mechanical characteristics and durability, polymeric pipes use has grown, significantly, in Water Distribution Systems replacing elastic pipes (Steel, Concrete, …). In this paper, the study of transient flows in a polymeric looped network exhibiting a specific rheological behaviour compared to elastic pipes has been carried out. The transient flow is governed by a set of two hyperbolic partial derivative equations. The numerical simulation was conducted by solving continuity and momentum equations for uni-dimensional flow using the Method of Characteristic (MOC) for specified time intervals taking into account the viscoelastic behaviour of the pipe wall material. The numerically obtained results have been compared to the experiments carried out in a 6-loops network made of 19 high-density polyethene pipes of, relatively, small system-scale. The transient flow was generated by a valve closure. The manoeuver was simulated based on a linear closure law as the downstream boundary condition. The experimental setup was fed by a constant level reservoir. The results have proven the efficiency of the MOC for transient simulations even in complex networks. However, the accuracy of the MOC-based model depends on the calibration of the viscoelastic parameters describing the behaviour of the pipe wall during the hydraulic transients.