Time-domain computations of ship motion with forward speed using finite element method

Abstract

The motion of ocean-going ship with constant forward speed is considered in time domain. The double-body linearization is adopted for ship motion calculations. The finite element method (FEM) based on variational principle is applied to solve the linearized boundary value problem. Time integration of free-surface boundary condition is carried out by 4th order Adams-Bashforth-Moultn method. In order to remove reflected waves at the truncated boundary, numerical damping zone is utilized. At every few steps, five-point Chebyshev filtering scheme is applied to smooth out unwanted saw-tooth waves. To include body nonlinear effect, nonlinear restoring and Froude-Kylov forces are additionaly calculated by considering incident wave elevation and relative ship position. For the validation of developed code, responses of three different ship models, wigley III, series60 and s175 container, are compared with existing experimental results or other computations. Nonlinear effects on motion RAO and structural load are also observed in detail. Copyright ？ 2009 by The International Society of Offshore and Polar Engineers (ISOPE).