Hydrodynamic performance of a novel semi-submersible platform with nonsymmetrical pontoons

The hydrodynamic performance of a novel semi-submersible platform (SEMI) was investigated in the present study. This new type of SEMI, which features two nonsymmetrical pontoons and no horizontal connection braces, can serve as a semi-submersible crane vessel. For a comparative study, two conventional SEMI models, i.e., one SEMI having both twin symmetric pontoons and horizontal braces and the other SEMI having twin symmetric pontoons with no horizontal braces, were established. The hydrodynamic characteristics were first investigated and compared with a special focus on the heave, roll and pitch motions. Furthermore, the motion response of the novel SEMI was studied under normal operation in eight different wave directions. The numerical results demonstrate that there exists significant heave-roll/heave-pitch coupling effects in the novel SEMI due to the nonsymmetrical pontoon shapes. These coupling effects require that more attention be paid to long waves whose periods are close to the heave resonance period. The motion responses of the novel SEMI are generally satisfactory for a typical normal sea state.