Research On The Law Of Fluid-solid Coupling Water Hammer Of Pressure Steel Bifurcated Pipes In Hydropower Stations

As a common water conveyance equipment in hydraulic engineering,the working environment of pressurized pipeline is very complex.Especially the pressurized water conveyance pipe in hydropower station,which bears almost all water heads of hydropower station,the upstream of pipeline that connect to the reservoir,is affected by water level change,the downstream that connect to the unit of machine,is affected by unit and control equipment that result in the complex flow pattern.During the operation of hydropower station,the quick opening and closing of valves often occurs,which will induce water hammer in the pressurized steel pipe.Because the water conveyance equipment of hydropower station needs strong overflow capacity,the flow velocity of pressurized steel pipe is often very high,which leads to the high water hammer pressure induced by the quick opening and closing of valves.If not paid attention to and prevented,it will affect the safety of pressure pipelines.In serious cases,it will even cause damage to water control hubs.Therefore,the study of water hammer in the pressurized water conveyance pipeline of hydropower station has become a research hot-spot in recent years.There are two main measures in the study of water hammer: classical water hammer theory and fluid-structure-interaction(FSI)water hammer theory.The phenomenon of water hammer was discovered long ago and the classical theory of water hammer was put forward.However,due to the limitation of scientific and technological conditions at that time,the classical theory of water hammer was deduced on the basis of a great deal of simplification,the most obvious point is that the influence of dynamic characteristics of pipelines on fluid motion was neglected.Although the classical water hammer theory has some defects,it has been widely used in guiding actual industrial production because of its simplicity and practicability.With the deepening of the research on water hammer,many scholars have found the shortcomings of the classical water hammer theory,improved and expanded it,and obtained the fluid-structure-interaction water hammer theory which make a consideration of the dynamic characteristics of pipelines and the interaction between fluids and pipe.FSI water hammer theory has been widely applied in many industrial fields such as water conservancy and Hydropower engineering,civil engineering,petroleumengineering and nuclear power engineering and so on.After decades of development,the research on FSI water hammer in pressure pipeline of hydropower station has made remarkable achievements.For large-scale pipelines,it is difficult to establish experimental model for water hammer experiments,so numerical simulation method is often used to analyze it.In the past,most of the numerical simulation of water hammer is aimed at thin-walled pipelines with small diameter and simple shape.For large-scale complex pipelines,simulation calculation is rare.Therefore,this paper takes the large diameter steel crescent-rib reinforced branch pipe of a pumped storage power station as the prototype,establishes a numerical model,simulates the quick opening and closing of the valve through the calculation software,and analyses the water hammer phenomenon in the pipe.