Three Dimensional Large Eddy Simulation Of Waves And Its Dynamic Response To Structures

This dissertation discusses the interaction between waves and structures ,gives a comprehensive analysis to numerical wave models in the coastal engineering. Based on the vertical two-dimensional RANS equation and three-dimensional LES equation, a 2DRANS-VOF model and a 3DLES-VOF model ,which have a wide application field, are established respectively by using the wave surface tracking of the Lagrangian-Eulerian slant-line VOF method. And examples of the wave deformation and its interaction with structures under different situations are analyzed. The main results are as follows: 1.A high precision mathematical theory and its application based on the of the Lagrangian-Eulerian slant-line VOF method has been proposed. The PLIC method is used to give the slant-plane of the Donor cell, move the unit cell volume at the local surface Lagrangian rate of each unit cell, replace the original Eulerian unit cell with the new volume, reconstitute the free surface, and apportion the volume of the flowing unit cell to the new acceptor grid. 2.A vertical two-dimensional mathematical wave model (2DRANS-VOF) has been established. The k-εmodel is applied to close the two-dimensional turbulent control equations, the spatial discretization in the finite difference is carried out based on the two-step projection method, a new VOF method is used to trace the free surface. The boundary condition of the absorpting wave-maker is taken as the incident condition, the Sommerfield radiation condition and the sponge layer absorption is taken as the out flow condition. 3.The wave deformation caused by the submerged trapezoidal shelf under different wave conditions is calculated by the two-dimensional numerical wave tank 2DRANS-VOF, and the reliability of the numerical model is testified by the typical test data. The wave process and the wave force near the vertical breakwater on the wave –penetration foundation is simulated, which indicates that the 2DRANS-VOF model could give a well result to the nonlinear wave deformation in the nearshore area, and to the calculation of the interaction between waves and vertical two-dimensional structures. 4.Coastal dynamics and structure dynamics are of the same nature, a re-development is made to the current structure program ANSYS, and for the first time, the 2DRANS-VOF model and ANSYS are combined to study the dynamic response characteristics of the vertical breakwater under waves. 5.The splitter operator method is adopted in the three-dimensional LES of waves to split the control equation into 3 parts-----advection, diffusion and generation .The QBC difference scheme is successfully used in the advection part, which saves the calculation period and avoids the numerical dissipation and oscillation. 6.Based on a new VOF method and LES , a three-dimensional mathematical wave model (3DLES-VOF) is established. According to the LES equations, the three-dimensional LES turbulent control equations are closed by the k-1 model. The three-dimensional VOF method is used to locate the free surface and the SOR method is used in the Poisson equation to give the pressure of each point in the water. The numerical tests show that the established numerical wave tank has suitable wave characteristics, therefore, an improved and stable coastal dynamics software system is expected to be accomplished in the near future. 7.The three-dimensional LES model of waves is extended to the engineering application. Based on this model, firstly, the wave transformation and breaking process on a slope are simulated, secondly, the three-dimensional LES model of waves simulates the turbulent wave field and the pressure field of the vertical square post and circular post, dynamically showing the turbulence processing and the wave actions on the vertical post when the post is out of water, half in the water and submerged in the water, respectively.