| The riverside multi-well water source system is an important form of groundwater exploitation,which has the characteristics of close connection with surface water,large water output and excellent water quality.The water hammer phenomenon seriously threatens the safety of water supply pipelines.In order to meet the increasing demand for water resources,promote the scientific and rational development and utilization of groundwater,and ensure the safe and stable operation of the water supply system,this paper focuses on the simulation calculation of steady-state operation and hydraulic transition process for the riverside multi-well water source system.First,for the problems that the water column separation conditions of the traditional water hammer calculation model are more sensitive and the water hammer pressure oscillation convergence rate is slower,the constant friction model,the quasi-constant friction model and the non-constant friction model are compared and analyzed through the experimental pipeline system.In the application of water hammer simulation calculation,the traditional water hammer calculation model is optimized according to the elastic characteristics of the water body and pipeline and the Brunone non-constant friction model.The water hammer calculation results after model optimization are in good agreement with the experimental data in terms of maximum pressure,water column separation and water hammer pressure oscillation convergence,and the calculation results are in good agreement with the actual experimental conditions.It provides a reliable theoretical basis and guidance for the calculation research of the hydraulic transition process in this paper.Secondly,based on the treatment of the river recharge boundary based on the mirror image method,based on the principle of potential flow superposition and the theory of virtual ring adjustment,the hydraulic calculation and analysis of the steady-state operating conditions of the riverside multi-well water source system are carried out.When the system is running in a steady state,the difference in water level depth,water output and pump operating conditions of each water source well is large,but the impact on the groundwater level is small,and the average water level depth of the water source well is only 15.82m.It has laid a foundation for the calculation research of the system hydraulic transition process.Thirdly,through the calculation and analysis of the hydraulic transition process of each water source well in the riverside multi-well water source system,the accidental pump stop condition,the 1/2 water source well simultaneous pump stop condition and all the water source wells simultaneous pump stop conditions.It is found that when the system stops the pump accidentally,the downstream of slow closing check valve of accident pump is more likely to cause water hammer of cavities collapsing.The water hammer has a larger pressure increase.The water hammer phenomenon on the upstream of the main pipe as a whole is more significant than the downstream,and the pressure increase is greater.The closer the water source well that stopped the pump to the upstream of the main pipe,the water hammer phenomenon generated on the main pipe and the entire riverside multi-well water system.Conversely,the closer to the downstream,the smaller the impact.In addition,the larger diameter of the main pipe has a buffer reduction effect on the water hammer boost generated in the small-diameter connecting pipe.Finally,according to the analysis of the water hammer calculation and protection of the engineering example,it was found that under the most unfavorable working conditions of all water source wells stopping pumps at the same time,the maximum pipeline pressures of the main pipe and the water source well connecting pipe were 233.27m H2O and 310.01m H2O,respectively.The hammer has a large pressure increase and the pipeline overpressure is serious.After adopting the water hammer protection scheme of"box-type two-way surge tank+inlet and exhaust valve",the water hammer boosting pressure can be effectively controlled below the pressure value of the pipeline to ensure the safe operation of the pipeline. |
