Scaled boundary FEM :methodology development and applications for offshore wave diffraction

Abstract

Many offshore structures have been installed to harvest resources in the ocean. These large structures undergo several experimental and numerical tests before they are constructed. A reliable and efficient analysis tool is therefore crucial to this industry. Many methods have been introduced; each offering different advantages while providing the solution, as well as suffering from certain limitations. The scaled boundary finite element method (SBFEM) was developed to solve engineering problems. This particular method combines the advantages of two commonly used methods in the offshore industry, the Finite Element Method (FEM) and the Boundary Element Method (BEM), making it a suitable semi-analytical approach that requires less computational time while satisfying the boundary condition at infinity. Several attempts at using this method to solve the hydrodynamic problem have been executed with great success. However, there is still much room for further development. The first part of this thesis discusses further application of the two-dimensional SBFEM, using the proposed advantages by manipulating the position of the scaling centre to solve for more complex geometry. This methodology has also been extended with an integrated model to evaluate the wave-structure-soil interaction examining offshore monopile deflection. The second part of this thesis develops a three-dimensional (3D) SBFEM model. General formulations in the Scaled Boundary coordinates for the 3D SBFEM model have been developed and are presented in detail. Case studies have been carried out demonstrating the validity and efficiency of the 3D model. These developments are important in allowing extended usage of the methodology to solve more complex problems such as wave interaction with floating offshore structures. Due to its clear advantages in computational efficiency and accuracy, the extended SBFEM model can be applied to engineering problems in hydrodynamic analysis for more complex wave-structure interaction in the offshore industry.