Wave groupiness is an important characteristic of ocean waves, and waves in quick succession are regarded as wave groups, which affects the behavior of a moored ship system directly. As a need for understanding the interaction between groupiness and the motion behavior of a moored ship, a mathematical model of a moored ship under the action of waves with the same wave parameters, such as significant wave height and period, but with different groupiness factors of height GFH is established and presented in this paper. The numerical results show that the motion behavior of a moored ship is greatly affected by the wave groups compared with random waves with same energy. The sway motions increase with an increase in GFH, in contrast to the influence of wave groups on the motion of heave is weak. Under the action of wave groups, the surge motion spectrum peak frequency is so close to the natural frequency that it may lead to the moored ship larger motion responses.
For the stability of wharf structure, vessel and cargo handling, it is significant to determine accurately the motion of a moored ship exposed to the action of waves. Wave is the key factor of governing the motion responses of moored ship and mooring line forces. Zou etc. (1995) studied the nonlinear features of moored ship motion in harbor in resonance. Xiang etc. (2001) derive of static equilibrium equations for a moored ship subjected to wind, current and waves and solved the mooring equations with Monte Carlo method, without considering the nonlinear mooring line strain. Wang etc. (2007) simulated the nonlinear wave forces on a fixed ship by developing a coupled model, in which the outer domain was expressed by the Boussinesq equations and inner domain was described by the Laplace equation.
