Numerical Analysis Of Interaction Between Wave And Porous Structure

The development and utilization of marine resources can't be separated from offshore buildings,but the impact of waves has caused serious damage to offshore buildings and huge economic losses.In order to reduce the wave forces,it is necessary to build matching marine engineering facilities.It is found that porous media structure has the advantage of reducing the wave force of the structure and reducing the wave reflection before the structure through theoretical and experimental studies.So the porous media structure has good application prospects in practical engineering.In this paper,the scaled boundary finite element method(SBFEM)has applied to the interaction between the wave and porous structure.The SBFEM is a new semi-analytical numerical method,which combines the advantages of the finite element and the boundary element methods.Since only the boundary of computational domain needs to be discretized as the same as the boundary element method,the spatial dimensions can be reduced by one and the computation is reduced greatly.The solution in the radial direction is analytical,which improves the precision of the computation.In addition,the SBFEM does not need the basic solution,and there is no problem of integral singularity.Another advantage of this method is that the radiation condition at infinity can be satisfied rigorously.The scaled boundary finite element method was originally developed for solving problems of fracture mechanics,fluid-solid coupling,structure-infinite foundation interaction,dam-water interaction,etc.In this paper,the cylindrical structure of porous media is studied emphatically.There are four mathematical models of interaction between the wave and different types of porous structures,involving the cylindrical porous media with filled structure,annular cylindrical porous media with filled structure,annular cylindrical porous media inscribed impermeable cylindrical structure and annular cylindrical porous media circumscribed porous cylindrical structure.Porous media filled with gravel have permeability which can be described by three filling parameters: resistance coefficient f,inertia coefficient s and porosity ?.For the interaction between cylinder structure and wave,the Laplace equation is taken as the basic governing equation,and its influence in the vertical direction is expressed by the characteristic function.By further improving the scaled coordinate system,the SBFEM governing equation,which is a Bessel equation,and the corresponding internal and external boundary conditions are derived by variational principle.For different structural models,the computational domain is divided into multiple finite domains and one infinite domain.Furthermore,the Bessel function and the Hankel function are introduced as the basis of the finite domains and the infinite domain,respectively.Through the coupled boundary conditions of the interaction between the wave and the porous medium structure,the undetermined coefficient matrix can be calculated,and the velocity potential of each point in the domain,the wave force,wave climb and amplitude distribution of the structure are further calculated.Comparing the numerical simulation results with the analytical solutions,it is found that only a few units can fit the analytical solution when using this method,which proves the accuracy and efficiency of the proposed method.In this paper,the effects of relative wavenumber,filling radius,filling factor(porosity,linear resistance coefficient)and wave parameters on the interaction between porous structure and wave are further studied.The present results are of practical significance to the hydrodynamic analysis and design for the interaction between wave and porous media structure.