Numerical Simulation Research On Stepped Spillway Of Gangqu River Primary Hydropower Station

Stepped spillway has been widely used in water conservancy engineering.Based on the previous analysis,it is very important for theory and engineering practice to continue to analyze its hydraulic characteristics.It can promote the development of stepped spillway.In this paper,based on the hydraulic characteristic data of stepped spillway test of Gangqu River Primary Hydropower Station,combined with numerical simulation method,the VOF method are used.And standard k-? two-equation turbulence model and Open channel flow method are used to simulate the stepped spillway of the Gangqu River Primary Hydropower Station.Compared by simulation values with the measured values of test,the results show that the coincidence between the two methods is good.Finally,on the basis of the numerical simulation,it is found that the two methods are in good agreement with each other.The friction velocity and other hydraulic characteristics of the stepped spillway of the Gangqu River Primary Hydropower Station is studied.The main conclusions as follows:(1)The water depth of stepped spillway inlet gradually shrinks,and gradually keeps steady further downstream.The water surface line is close to that of the bottom slope.The velocity increases from the position of the steps to the surface of the flow gradually.The velocity which close to water surface,is maximum,and it maintans a good linear positive correlation with the discharge.The direction of velocity at main flow area is almost parallel to the bottom slope.In the steps interior,the water flow occurs clockwise vortex.(2)In the area of water depth stability of stepped spillway downstream,the pressure isoline of each step in the step overflow section is basically same.In terms of the step pressure,the horizontal plane is larger than the vertical plane.The maximum position is located to the lobe in the middle of the step horizontal plane.(3)The wall shear stress of vertical plane increases first from bottom to top and then decreases,while the wall shear stress of horizontal plane increases first from inside to outside,then decreases and it rapidly increases finally,both of which increase with the increase of discharge.And gradually stabilized downstream.The direction of wall shear stress at step angle is parallel to the connecting line of step angle,and it maintans a good linear positive correlation with the flow length and the discharge.And it gradually keeps steady in the downstream.(4)The friction velocity of stepped spillway maintans a good linear positive correlationwith the flow length and the discharge.Compared with the velocity,it is smaller.In the stepped spillway,there is also a good linear positive correlation between the section mean velocity at the step angle and the friction velocity,which is advantageous for analysis and application.(5)The friction velocity obtained by the two methods is basically close to that calculated by wall shear stress.This further shows that it is feasible to calculate the friction velocity by using the velocity and the wall shear stress obtained by numerical simulation.The formula of the relationship between the wall shear stress and the friction velocity in the open channel is also applicable to the calculation of the friction velocity at the step angle of the stepped spillway,which gives a idea for the research of stepped spillway.(6)The variation of the relative friction velocity along the flow length has a good linear positive correlation,which is advantageous for analysis and application.The relative friction velocity is negatively correlated with the discharge.It indicates that under the same conditions,the friction velocity maintans a good linear positive correlation with the discharge,but the relative friction velocity decreases gradually,which shows that increasing the discharge is disadvantageous to the step energy dissipation.