Analysis of 2nd-Order Wave Force on Floating Bodies Using FEM in Time Domain

Abstract

The wave effect on hydrodynamic forces acting on offshore structures is numerically investigated with a focus on multibody hydrodynamic interactions by using the finite element method (FEM) in time domain. Boundary value problems were formulated up to the 2nd order, according to Stokes' perturbation expansion. The Laplace equation with boundary conditions was solved by the classical FEM based on weak formulation. The wave damping zone was employed to implement the radiation condition numerically. The time integration of the free-surface condition was conducted by the 4th-order Adams-Bashforth-Moulton method. Hydrodynamic forces on bottom-mounted and truncated cylinders up to the 2nd order were investigated as a validation study. Second-order forces such as drift force and diffraction force on bodies arranged side by side were analyzed and compared with model test data. The agreement between present computations and other results was fairly good.