Effects of tidal bore on hydraulic transients in low-head pressurized water conveyance systems

Abstract In low-head pressurized water conveyance systems affected by tidal bore, the influence of tidal bore on the stability of the system is significant. This study focuses on a pumping station located on the Qiantang River to investigate the impact of tidal bore under extreme conditions on hydraulic transients in low-head pressurized water conveyance systems. Tidal bore height and maximum tidal bore velocity are considered as key parameters, and their effects are modelled under extreme conditions in hydraulic transient analysis. Two operational scenarios, including normal operation and pumps shutdown, are simulated. The results indicate that, during normal pump operation, increases in tidal bore height and maximum velocity lead to greater fluctuations in surge tank water level, pump flow fluctuations, and pressure pulsations in the pipeline. In scenarios involving pumps shutdown and gates closure, increases in tidal bore height and maximum velocity result in larger fluctuations in surge tank water level. Additionally, since the gates are closed when pumps shutdown, tidal bore effects have minimal influence on pump flow rates. Therefore, the maximum pressure in the middle section of pipeline is primarily controlled by the tidal bore height and maximum flow rate. When tidal bore height is relatively high, maximum pressure occurs rapidly, whereas when maximum tidal bore velocity is high, the increase in maximum pressure occurs slower. This study introduces a method for incorporating tidal bore effects into hydraulic transient calculations, providing valuable insights for project design and construction. It serves as a reference for transient flow analysis in similar low-head pressurized water conveyance systems affected by tidal bore.