Water hammer transient pressure response during coordinated multi-valve closure in a self-pressurized irrigation pipe network

Coordinated multi valve closure can generate interacting water hammer waves in self-pressurized irrigation networks. However, the effects of valve closure duration and starting sequence on transient pressure responses remain insufficiently understood. This study investigated water hammer characteristics in an experimental self-pressurized irrigation network comprising one main pipe and three parallel sub main pipes at Shihezi University, China. Three closure durations (3, 5, and 7 s, where s denotes seconds) and three closure modes (simultaneous, upstream to downstream sequential, and downstream to upstream reverse closure) were examined, with transient pressures recorded synchronously at nine measurement points. Under simultaneous closure, the system wide mean peak pressure decreased from 0.0807 MPa at 3 s to 0.0577 MPa at 5 s and 0.0495 MPa at 7 s, indicating diminishing benefits from longer closure durations. At a closure duration of 5 s, sequential closure produced a peak pressure of 0.0964 MPa at the near valve measurement point on the most distal sub main pipe, compared with 0.0650 MPa under simultaneous closure. The empirical pressure increment amplification indices were 2.84, 2.25, and 1.81 for sequential, reverse, and simultaneous closure, respectively. These findings demonstrate that valve starting sequence substantially affects pressure amplification and that the distal near valve region is particularly vulnerable. Upstream to downstream sequential closure generated the highest water hammer risk, whereas simultaneous closure yielded a more stable transient response. Coordinated valve operation and targeted protection of vulnerable pipe sections are therefore recommended.