Numerical Simulation Of Water Hammer Pressure In A Long Distance Water Gravitational Transportation Pipeline

The long distance water gravitational transportation pipeline has many branchesand large water head. It will produce severe destructive water hammer pressure whenthe valves of the waterworks are suddenly turned off. The analysis of hammercharacteristics and taking necessary prevention measures are of great importance. Itwill ensure the reliability of water transportation project and reduce the cost.The numerical model of water hammer pressure is proposed. The watertransportation pipeline is taken as a case. The pressure variation caused by the suddenclosure of the terminal value is analyzed. The maximum pressure and its occurrenceposition are determined. According to the research on different conditions withdifferent numbers of the closed valves, the condition that all of the valves along thepipeline are closed simultaneously is identified as the worst condition. Based on thenumerical simulation results of that all the valves are closed simultaneously withoutany protective measures, air valves and over-pressure relief valves are considered asthe water hammer protection measures of the water transportation pipeline.Furthermore, with the condition that all the valves are closed, the effect of the valveclosure time and valve closure style on the water hammer pressure in the pipeline isstudied.(1)Numerical simulation of the endmost valve-closure without protective measureBased on the layout schemes of the water transportation pipeline, study on thevarious working conditions with the water hammer phenomenon is made. Theendmost valve-closure is taken as the main research object. Under the condition thatdifferent numbers of valves are closed simultaneously, the water hammer pressure iscalculated. The pressure change rules are analyzed. The maximum water hammerpressure and its occurrence position are determined by the analyzing the waterhammer pressure of typical sections.(2) Research on the water hammer protection of the water transportation pipelineThe worst condition is that all the valves are closed simultaneously without anywater hammer protection measures. According to the numerical simulation results ofthe worst condition, protection measures are put forward. The number of theover-pressure relief valves and the parameters of the boundary pressure are optimized.The final water hammer protection plan is selected. (3) Research on the influence of the valve–closure time on the water hammerpressure when Endmost valve are closed at the same timeAll the endmost values are closed at the same time with any protective measures.When the valve-closure time is900s with the linear closure style, the maximumpressure is small, and there is no negative pressure along the pipeline.(4) Research of the effect of the endmost valve closing sequence on the waterhammer pressureWhen eight valves of the water plants are turned off from downstream toupstream in turn, the pipeline’s water hammer pressure is less than that from upstreamto downstream. Comparing the results of the conditions that eight valves are closedsimultaneously or in turn, the maximum pressure along the pipeline is lower when thevalves are closed in turn. If the valve-closure time is staggered, it is recommended touse the sequence that from downstream to upstream in turn. The valves-closure timeis300s. The closing valve interval is100s.