Uncertainties in Hydraulic Transient Modelling in Raising Pipe Systems: Laboratory Case Studies

Abstract

The current paper aims to discuss the main uncertainties associated with the hydraulic transient modelling of raising pipe systems with and without surge protection. A one-dimensional hydraulic transient solver was developed based on the classic water hammer theory and solved by the Method of Characteristics (MOC). The solver incorporates the pump-element described by Suter parameters, a pressurised surge tank (hydropneumatic vessel, HPV) and Vitkovsky's (2000) formula for unsteady friction description. The model was tested using transient pressure data and steady-state flow data from two hydraulic circuits installed at the Hydraulics Laboratory of the Civil Engineering Department, in Instituto Superior Técnico (Lisbon, Portugal). Pressure data were obtained at two/three locations (at the upstream end, at a middle section and at the downstream end). Transient tests with and without the HPV connected to the system were carried out for different flow rates. Transients were generated by the sudden stoppage of the pump. Collected data were compared with the results of the numerical modelling and used to calibrate model parameters. Good agreement between data and numerical results was obtained. Some tests with the HPV connected lead to higher pressure surges than when there was no protection in the system. These analyses are important to develop more solid and reliable numerical models as well to create awareness of the main uncertainties of developed models.