Numerical Simulation Of Transient Flow Of Free Water Surface In The Surge Tank With Long Upper-Chamber

With the rapid development of modern computer technology and the Computational Fluid Dynamics(CFD) in the related fields, the numerical simulation method of CFD has been achieved a wide application and become a very important method in the area of various fluid flow research. The problem of complicated free surface widely exists in the hydraulic engineering. If this kind of problem can be solved by means of numerical simulation, it not only can do some research on those flow rules, but also can save manpower, budget and time. The paper takes the tailrace surge tank with long upper-chamber in a pumped-storage power station for instance, and the application of CFD method in the area of numerical simulation of transient flow of the water surface has been discussed.The water level in surge tank is unsteady,which,needs the unsteady boundary conditions while computing. In this paper, the coefficients of head loss of surge tank have been calculated by means of CFD and then applied in the computation of transient process in hydropower station. According to that, the boundary condition varying with time at the bottom of surge tank can be achieved. The main contents are as follows:1. It has introduced briefly the basic principles of CFD and its numerical methods, and the recent research on solving the problem of free surface has been summarized.2. The coefficients of head loss of surge tank have been calculated by means of CFD, and then the calculated results are compared with the hydraulic model test data. By comparision, it shows the calculated results are reasonable.3. The computation of transient flow in hydropower station has been done on the basis of the coefficients of head loss of surge tank with long upper-chamber which have been calculated by means of CFD, and then the discharge at the bottom of surge tank which varies with time can be obtained.4. By taking the discharge calculated above as the transient boundary condition, numerical simulation of the transient flow of the water surface in surge tank has been done using two dimension Realizable k—εturbulent model, VOF method which tracks the free surface. The specific water surface of the surge tank at different time was given. According to the calculations, the transient flow of surge tank water surface was simulated.