Numerical Simulation Of Free Surface Based On Level Set Method

The investigation of moving interfaces has great theoretical and realistic significance. Nowadays, level set methods are more and more widely used to solve the fluid problems involving moving interfaces.In this paper, the main study are simulation of free surface which is between water and air based on a single phase level set method, which is incorporated with an incompressible viscous RANS flow solver on structured meshes, and the influence of navigational surrounding of surface ship after introducing a simplified polydisperse model for bubbly two-phase flow. The incompressible viscous flow solver is adopted pressure implicit with splitting of operators method and pressure Poisson equation. The dynamic free-surface boundary condition model is used for interface capturing. The standard k ?εmodel and a low Reynolds number k ?εmodel are used. The discretisation of equations is betaken finite difference method. For temporal discretization of equations is used first-order Euler backward method. For spatial discretization of equations are used second-order upwind format in convective terms and second-order central format in diffusive terms. Finite difference equations are using the alternating direction implicit technique and relaxation method to solve. In the bubbly two-phase flow model, the liquid momentum equations are discretized using the finite-analytic method and the liquid continuity equation is discretized using a control volume approach. The gas momentum equations are solved using a full upwind approach, and the gas continuity equation and the group number density equations using a control volume approach with a TVD flux limiter which can minimize the numerical diffusion. Lastly, using NACA0024 airfoil model and Wigley Hull model as test cases to demonstrate all methods are feasible and correct.The main researches in this thesis are as followings: (1) Analyzing and applying the Reynolds-averaged Navier-Stokes (RANS) equation solver in the incompressible viscous fluid field basing on finite difference method. (2) Programming a code based the single-phase level set method with finite difference method, and making sure that it runs successfully after coupling with fluid field solver. (3) Adding turbulence models: the standard k ?εmodel and a low Reynolds number k ?εmodel were introduced. (4) Introducing a simplified three dimensional polydisperse model for bubbly two-phase flow around a surface ship, then, making it coupled with the flow field solver. NACA 0024 model and Wigley Hull model in typical conditions were simulated, and the results were compared with experimental data. (5) The work was summarized in this thesis and the future work was presented.