2D And 3D Fluid Numerical Simulation Of Water Diversion Structure Under Complex Boundary Condition

It is an economical and effective way to divert water from water-affluent area to water shortage area by water diversion structure, which plays an important role in the world. The fundamentals and methods of 2D and 3D fluid numerical simulation are reviewed and analyzed, and some significant factors concerning water numerical simulation under complex boundary conditions of the water diversion structure are discussed.In this research, the plane 2D mathematical model under Cartesian coordinate system and the 3D turbulence mathematical model under body-fitted coordinate system are established, the discrete format of control equations, the solutions of algebraic equations, initial conditions, boundary conditions and moving boundary problems are studied, then the corresponding computational programs are compiled. On the base of above preparations, the coupling model of 2D and 3D is established, its coupling condition, initial condition and boundary condition are introduced. Then the coupling model is verified properly by some cases.A modified method based on 2D mathematical model is proposed to simulate complex 3D free-surface flow, which is applied and verified by an engineering case, showing the computational results are in agreement with model test flow fields properly.The head losses of serial sudden expansions pipe flow and tunnel flow with the concave-convex boundary are studied by the mathematical model respectively, and the least head loss scheme of serial sudden expansions pipe flow and the head loss variation rule of tunnel flow caused by the concave-convex varying at individual direction are reached.The VOF method based on local refined grid is proposed to simulate the free-surface flow on the base of FLUENT software, which is applied to simualte 2D turbulence and complex 3D turbulence respectively. The results indicate that it is economical and reliable to treat free surface flow, comparing with the VOF method based on coarse grid and the VOF method based on refined grid.The 2D flow and complex 3D turbulence cases under complex boundary conditions are simulated respectively under some typical working conditions by the mathematical models, and the distributions of hydraulic factors including velocity, pressure(or water depth),turbulence kinetic energy and turbulence dissipation rate are obtained, which can serve to the decision-making, design, construction and management of water diversion structures.