NUMERICAL SIMULATION OF FLOWS AND MOTIONS OF SEMI-SUBMERGIBLE HIGH SPEED SHIP WITH WINGS

Flow fields and motions of a semi-submersible high-speed ship with wings (HSV) were studied by numerical simulation. Using the boundary element method computations of lifting force and resistance were carried out, together with the flow fields for various cases where the submergence depth, the position of wing and the angle of attack are systematically changed. It was confirmed that the depth of submergence is important both for the resistance and lifting force. It is a well-known fact that the shallower submergence depth requires more resistance, but it may be an important finding that the lifting force is large when the submergence depth is less. This nature is beneficial for HSV for which much lifting force is required during its shallower submergence. On the other hand, the position of the wing has little effect. The resistance remains unchanged even if the attack angle is changed. Non-zero attack angle of the main wing can be designed to reduce the frictional resistance. The motion of HSV was numerically simulated by solving the motion equation. All the forces, including the damping force are provided by experiments or simple estimation. The cases with and without control are compared under various situations to conclude that the control is essential for any cases, although it is a primitive PD method. It was also found that the negative dihedral angle of the main wing is not so effective to control the rolling motion as expected. It is concluded that such simulations of flow fields or motions of unexperienced vehicles like HSV are very useful when they are carried out in advance of the experiments.