Transient vaporous cavitation in viscoelastic pipes

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.