Time-Domain Higher-Order Boundary Element Method for Simulating High Forward-Speed Ship Motions in Waves

The hydrodynamic performance of a high forward-speed ship in obliquely propagating waves is numerically examined to assess both free motions and wave field in comparison with a low forward-speed ship. This numerical model is based on the time-domain potential flow theory and higher-order boundary element method, where an analytical expression is completely expanded to determine the base-unsteady coupling flow imposed on the moving condition of the ship. The ship in the numerical model may possess different advancing speeds, i.e. stationary, low speed, and high speed. The role of the water depth, wave height, wave period, and incident wave angle is analyzed by means of the accurate numerical model. It is found that the resonant motions of the high forward-speed ship are triggered by comparison with the stationary one. More specifically, a higher forward speed generates a V-shaped wave region with a larger elevation, which induces stronger resonant motions corresponding to larger wave periods. The shoaling effect is adverse to the motion of the low-speed ship, but is beneficial to the resonant motion of the high-speed ship. When waves obliquely propagate toward the ship, the V-shaped wave region would be broken due to the coupling effect between roll and pitch motions. It is also demonstrated that the maximum heave motion occurs in beam seas for stationary cases but occurs in head waves for high speeds. However, the variation of the pitch motion with period is hardly affected by wave incident angles.