Infinite Elements for 3-Dimensional Wave-Structure Interaction Problems

Abstract

The finite element technique incorporating infinite elements is applied to analysing the general three-dimensional wave-structure interaction problems within the limits of linear wave theory. The hydrodynamic forces are assumed to be inertially dominated, and viscous effects are neglected. In order to analyse the corresponding boundary value problems, efficiently, two types of elements are developed. One is the infinite element for modelling the radiation condition at infinity, and the other is the fictitious bottom boundary element for the case of deep water. The shape functions for infinite elements in the radial direction are derived from the asymptotic expressions for the progressive wave and the first evanescent wave components in the analytical boundary series solutions. To validate the infinite and the fictitious bottom boundary elements, numerical analyses are performed for several floating structures. Comparisons with the results from other available solution methods show that the present method incorporating the infinite and the fictitious bottom boundary elements gives good results.