Interaction Of Water Waves By Infinite Horizontal Structures Using Boundary Element Method

The study on the mechanism and method of interaction between ocean structures and waves provides a theoretical basis for the design,deployment and application of ocean structures such as wave power generation,ship engineering,marine aquaculture,ocean communication and coastal protection.The common analytical methods have high accuracy and fast solution speed,but the solving conditions are harsh and can only be applied to the solution of regular-shaped structures.The numerical method can be used to solve the interaction between irregular shape structures and waves,which is universal.However,most common numerical methods such as finite element method(FEM)use discretization of the whole solution domain to solve the problem.However,the boundary element method(BEM)can solve the same problem with reduced dimension,less computation and high accuracy.Therefore,The parametric element boundary element method(BEM)is proposed in this paper in order to solve this kind of problem.This method has theoretical guiding significance and engineering application value for the analysis and solution of the interaction between ocean structures and waves.The main research contents of this paper are as follows:Firstly,on the basis of introducing the theoretical equation of potential flow,according to the integral equation,the parametric element boundary element method is used to solve the potential flow problem,and the velocity potential of the flow field is obtained.The classical examples are calculated numerically,compared with the analytical solutions,and the error analysis is carried out.In solving two-dimensional problems,discontinuous parameterized element and parameterized element boundary element method are used to solve the potential flow velocity field,and in solving three-dimensional problems,the parameterized constant element is used to solve the flow around a cylinder through coordinate transformation.Then,a parameterized element boundary element method(BEM)is proposed to solve the potential flow field of wave interaction with a single rectangular floating body.In dealing with the radiation condition at infinite distance,the radiation condition is set as far as possible from the floating body,and the radiation surface is 3-5 times water depth from the floating body end.The correctness of the method is verified,and the influence of different geometric parameters of the model on the hydrodynamic coefficient of the heave is analyzedThirdly,in view of the limitations of the parametric element boundary element method in solving the potential flow field of wave-to-single rectangular floating body interaction,a method of coupling the eigen-function expansion method(EEM)with the parametric constant element boundary element method(PCBEM)is proposed This method not only retains the advantages of fast solving speed of the characteristic function expansion method,but also has the advantages of easy realization and advantages of the interaction between regular-shaped floating bodies and waves.The effects of different geometric parameters of floating body on the hydrodynamic coefficients of heave,surge and pitch are also studied.Finally,the improved method is extended to solve the interaction between double floating bodies and waves,and the hydrodynamic coefficients of double floating bodies are solved and analyzed.The results are in good agreement with those of EEM,which further proves the accuracy and reliability of the proposed method.