محمد واقفی

This paper investigates the transient behavior and the water hammer in pipelines due to rapid changes in the operation of the group of parallel pumps. After a brief introduction of the water hammer and the boundary conditions related to the transient characteristics of a group of pumps with a parallel arrangement, a time marching second-order finite difference scheme based on the MacCormack method is used to discretize and solve the governing equations. The excellent validity of the present model is evaluated by comparing the obtained results with another well-known solution from previous studies. For example, in case No. 1, which considers the transient behavior of a pumping station with parallel pumps, the maximum absolute difference of the energy head from the proposed model results compared with the benchmark solution is 0.79%. Besides, two other examples are considered, using the present model to investigate the water hammer caused by different scenarios of changing in the operation of the parallel pumps. The results show that the transient characteristics of the system entirely depend on the shutdown and the start-up pattern of the group of pumps. So, variations in the trip and startup times result in a significant change in the pressure increase caused by the water hammer.