针对某大(1)型水电站泄洪时表孔闸前出现立轴漩涡现象,利用VOF(volume of fluid)方法对进口漩涡等水力特性进行了数值模拟计算,据此分析了坝前漩涡出现的原因、变化趋势等,初步探讨了漩涡对坝体泄洪结构的影响,提出了减弱表孔门槽及闸...针对某大(1)型水电站泄洪时表孔闸前出现立轴漩涡现象,利用VOF(volume of fluid)方法对进口漩涡等水力特性进行了数值模拟计算,据此分析了坝前漩涡出现的原因、变化趋势等,初步探讨了漩涡对坝体泄洪结构的影响,提出了减弱表孔门槽及闸首部位出现有害漩涡的调度方案。展开更多
The siphon-shaped overflow tower is a new type of pressure-suppressing structure used in long water conveyance systems,and it plays a crucial role in guaranteeing the system＇s stability and safety during hydraulic tr...The siphon-shaped overflow tower is a new type of pressure-suppressing structure used in long water conveyance systems,and it plays a crucial role in guaranteeing the system＇s stability and safety during hydraulic transient processes.The flow in the tower is characteristic of weir flow in a closed duct,and is thus a complex air-water two-phase flow.Intensive studies of the flow patterns,the pressure pulsations,and the discharge capacity are necessary for better understanding of the flow processes and for the purpose of design.In this paper,we simulate the flow in a siphon-shaped overflow tower under both steady and unsteady flow conditions.Through a steady-flow field simulation,the relationship between the overflow discharge and the pressure in the connected pipeline is analyzed and an empirical formula for evaluating the discharge capacity is provided.Through a transient-flow field simulation,the negative-pressure distributions on the weir crest,the pressure pulsations on the crest and in the falling pond,and the transformation of the air-water two-phase flow in the downstream outlet pipe are analyzed.Moreover,the major influencing factors of the flow patterns,especially,the sectional area of the air vents,are clarified.It is indicated that the siphon-shaped overflow tower can regulate the pressure surge during hydraulic transients and guarantee the safety and stability of the pipeline system,if the shape and the vents are properly designed.展开更多
基金supported by the National Natural Science Foun-dation of China(Grant Nos.51039005,50909076 and 51579187)
文摘The siphon-shaped overflow tower is a new type of pressure-suppressing structure used in long water conveyance systems,and it plays a crucial role in guaranteeing the system＇s stability and safety during hydraulic transient processes.The flow in the tower is characteristic of weir flow in a closed duct,and is thus a complex air-water two-phase flow.Intensive studies of the flow patterns,the pressure pulsations,and the discharge capacity are necessary for better understanding of the flow processes and for the purpose of design.In this paper,we simulate the flow in a siphon-shaped overflow tower under both steady and unsteady flow conditions.Through a steady-flow field simulation,the relationship between the overflow discharge and the pressure in the connected pipeline is analyzed and an empirical formula for evaluating the discharge capacity is provided.Through a transient-flow field simulation,the negative-pressure distributions on the weir crest,the pressure pulsations on the crest and in the falling pond,and the transformation of the air-water two-phase flow in the downstream outlet pipe are analyzed.Moreover,the major influencing factors of the flow patterns,especially,the sectional area of the air vents,are clarified.It is indicated that the siphon-shaped overflow tower can regulate the pressure surge during hydraulic transients and guarantee the safety and stability of the pipeline system,if the shape and the vents are properly designed.
