A New Indicator for Unsteady Flow Analysis in Pressurized Irrigation Systems

Pressurized irrigation systems operating on-demand offer large flexibility to farmers for managing their irrigation practices. Within these systems, the fast moving water and the sudden closing of hydrants generates unsteady flow and may create a significant pressure variation in the pipes causing noise, vibration and, sometimes, also pipes’ collapse. The present study describes a simulation tool that was developed for the analysis of unsteady flow effects. A large number of configurations of hydrants simultaneously open has been used to reflect farmers’ behaviour. A new indicator, called Relative Pressure Variation (RPV), was proposed to evaluate the pressure variation occurring into the system in respect to the steady-state pressure. This is very relevant and can be used to identify pipes with potential risk of failure. In addition, an analysis with different gate-valves’ closing time was carried out. It demonstrated that closing time shorter than Tc = 3 s may create dangerous pressures for the pipes.