Implication And Research Of The Fractional Volume Of Fluid Method In Water Conservancy And Hydropower Engineering

Surface tracking in numerical modeling of two phase and multi phase is important and difficult. How to define pressure and velocity condition is decided by interface tracking and reconstruction between phase in two and multi phase flow. Numerical modeling results depend on pressure and velocity. In that, interface tracking method with N-S equation and continuous equation models must be researched.In this thesis, surface tracking problems often met in water conservancy and hydropower engineering have been studied and discussed with YOUNGS-VOF methods, viscous incompressible fluid control equation included. Numerical simulation in 2D broken dam flood and transient of two phases with air and water in long water conveyance pipe system have been researched as well. The main points and ideas are introduced below.1. Advance of interface tracking method in multi phase.Exited references show that study in two phases and multi phases has been in many years. Interface problems such as broken dam flood, two phase transients with air-liquid phase, urban underground drainage system, and so on are often encountered in water conservancy and hydropower engineering. Methods of interface tracking between viscous incompressible fluids have been introduced below. MAC method, in which Lagrangian marker particles have been tracked with the local velocity; VOF method, in which free surface can be captured and reconstructed by use of the volume fraction of a calculation cell and its neighboring cells; FRONT TRACKING method; LEVEL SET method, in which interface between two-phase are simulated by use of the some function φ whose value is zero; PHASE-FIELD method, and so on. In those methods, VOF method has developed rapidly because the theory is not only simple but also powerful and numerical store information is reduced.2. Advance of VOF method in multi phase.VOF method has been improved in volume transport algorithm, interface reconstruction techniques and numerical methods of discrete for improving accuracy and correction of interface simulation since HIRT first described it. Interface problem between immiscible multi fluids can be resolved by this method. It can be used in rectangular grids, regular cubic grids, arbitrary meshes, and so on. In this paper, basedon YOUNGS-VOF method, parameters of the straight line equation of free surface in the rectangular cell can be solved by the dichomizing method.3. Research on broken dam flow2D broken dam flood are numerically simulated with YOUNGS-VOF method, momentum equation and mass conservation equation in staggered included. Numerical results are consistent with the experiment data by MATRIN, even better than numerical results by the use of HIRT-VOF method. Based on the method, mass error is described and depends on numerical algorithm and VOF techniques.4. Research on flow rush to interception air-mass in long water conveyance pipe systemYOUNGS-VOF method is employed to solve problem of transients of two phases with air and water in long water conveyance pipe system. Compared with the characteristic method, the results with VOF method is less and consistent with the experimental results. Free surface tracked with VOF method is better than that with characteristic method, while the former is more accurate. Parameters in system have been studied, which influences the interface, pressure, and so on.