Impact of Valve Maneuver Pattern and Operation Time in Course of Water Hammer: An Analysis based on Numerical Simulation of Hydraulic Transient

Abstract

The information of transient flow in pressure pipelines is exceptionally imperative for the planning, designing, and depiction of pressure networks. During the transient phenomenon, kinetic energy is transformed into pressure energy which is transmitted as a pressure wave and can lead to serious problems in the operation and management of the pressure networks. The phenomenon is complex , and a number of different factors influence its course. Within the case of a water hammer caused by valve operation, the mechanism of the guide vane operation is one of the key factors. Nevertheless, there is only limited research on this factor. In this research, numerical simulation of hydraulic transients in a pressure pipeline using Method of Characteristics (MOC) was carried out and the analysis of the water hammer pressure along the pipe and the mass oscillation in the surge tank were performed. The effects of different valve maneuver patterns and times were analyzed. For each operation pattern, characteristics of pressure change, the maximum water hammer pressure, and the maximum upsurge and the minimum downsurge levels in the surge tank were examined and recorded and a comparison was done. The comparison reveals a significant impact on the water hammer pressure with the change of the valve operation pattern and time while the impact on the mass oscillation is negligible. Among the different operation mechanisms considering the same operation time, linear valve operation resulted in the least extreme values of water hammer pressure and has been concluded as the most suitable operation mechanism to be used for the hydropower project under consideration. The analysis with the linear valve operation at 10 seconds shows that the maximum pressure rise is 42.2% of the steady head at the pipe end for load rejection and the maximum pressure drop of 44% for load acceptance.