Evaluation of Wave-Diffraction Forces on a Submerged Sphere Using a Hybrid BE-FE Method

Computational methods for predicting wave effects are important in the design and operation of offshore structures. Structures with rather large dimensions in comparison to the wavelength must be analyzed considering the diffraction theory. In this research, a frequency domain Boundary Element Method (BEM) is presented for 3D diffraction phenomenon by which, wave effects on rigid structures could be evaluated. To verify the present methodology, a submerged sphere, affected by sea waves, has been modeled by a BEM code. By means of the code, the sphere surface is discretized by a consistent mesh, and the point collocation method is applied to solve the system of linear algebraic equations for the nodal potentials. In order to employ the advantages of hybrid methods, the BEM results (in form of hydrodynamic pressures on nodes) are coupled with Finite Element Method (FEM) analysis of the sphere modeled in ANSYS, for its high reliability in analysis and ability to link with available geometry sources by APDL programming. Numerical results show a promising performance of proposed method in comparison to the Froude-Krylov theory.