This research work focuses on the analysis of hydraulic transients in polyvinyl chloride (PVC) pipes, which are characterized by a viscoelastic rheological behavior. Transient pressure data were collected in a pipe rig consisting of a set of PVC pipes. The creep function of the PVC pipes was determined by using an inverse transient model based on collected transient pressure data and compared with that obtained by carrying out mechanical tensile tests of PVC pipe specimens. The numerical results obtained from the transient solver have shown that the attenuation, dispersion, and shape of transient pressures were well described. The incorporation of the viscoelastic mechanical behavior in the hydraulic transient model has provided an excellent fitting between numerical results and observed data. Calibrated creep function based on inverse analysis fit the one determined by mechanical tests well, which emphasized the importance of pipe-wall viscoelasticity in hydraulic transients in PVC pipes.

Leakage reduction in water supply systems and distribution networks has been an increasingly important issue in the water industry since leaks and ruptures result in major physical and economic losses. Hydraulic transient solvers can be used in the system operational diagnosis, namely for leak detection purposes, due to their capability to describe the dynamic behaviour of the systems and to provide substantial amounts of data. In this research work, the association of hydraulic transient analysis with an optimisation model, through inverse transient analysis (ITA), has been used for leak detection and its location in an experimental facility containing PVC pipes. Observed transient pressure data have been used for testing ITA. A key factor for the success of the leak detection technique used is the accurate calibration of the transient solver, namely adequate boundary conditions and the description of energy dissipation effects since PVC pipes are characterised by a viscoelastic mechanical response. Results have shown that leaks were located with an accuracy between 4–15% of the total length of the pipeline, depending on the discretisation of the system model.

The research focuses on the analysis of transient cavitating flow in polyethylene pipes, which are characterized by a viscoelastic–rheological behaviour. A hydraulic transient solver incorporating the description of the rheological–mechanical behaviour of these pipes and the cavitating pipe flow has been developed. Both the discrete vapour cavity model and the discrete gas cavity model have been used to describe transient cavitating flow. These assume that discrete air cavities are formed at fixed pipe sections and consider a constant wave speed in the pipe reaches between the cavities. An experimental programme was conducted in a pipe-rig composed of a high-density polyethylene (HDPE) pipeline. Numerical results have been compared with collected data resulting in a good agreement. Effects related to the viscoelasticity of HDPE pipes and to the occurrence of vapour pressures during the transient events are also discussed.

The current paper aims at the experimental and numerical analysis of the cavitating pipe flow during the occurrence of hydraulic transients in a quasi-horizontal straight copper pipe rig. Transient events were simulated by the quasi-instantaneous closure of a pneumatically actuated ball valve located at the downstream end of the pipe. A hydraulic transient model has been developed for describing cavitating pipe flow by means of two approaches – the discrete vapour cavity model (DVCM) and the discrete gas cavity model (DGCM). Firstly, the model has been calibrated by using transient data without cavitation. Numerical results have been compared with collected data and a good agreement has been observed as long as the unsteady friction losses are considered. Secondly, DVCM and DGCM have been used to describe cavitating flows. Results of both models have been compared, and the DGCM model has shown to better describe transient events with cavitation

This research focuses on the analysis of transient cavitating flow in a horizontal copper pipe. Experiments have been conducted in a reservoir-pipe-valve copper pipe-rig to collect transient pressure data with and without cavitation. A hydraulic transient solver incorporating unsteady friction losses and distributed cavitation flow (discrete gas cavity model) has been developed. The system behaviour and the obtained transient pressure signal have been compared with the experimental results for sloping pipes reported in previous studies and a good agreement has been observed. Numerical results are compared with collected data and effects related to the unsteady friction losses and to the occurrence of transient vapour pressures are discussed.