Global motion and airgap computations for semi-submersible floating production unit in waves

Extensive parametric studies have been performed to examine the dependence of the motion responses and the other key design criteria on the principal dimensions including hull draft, column width, column spacing, column corner radius, pontoon height, pontoon width, and the size of cakepiece. By comprehensive and systematic hydrodynamic computations and analyses, it is revealed that the combined vertical motion at the worst airgap location is almost in phase with the wave elevation in extreme wave condition with a peak wave period around 14-15 s. Moreover, it is found that the most efficient way to reduce the motion is to increase the hull draft, though the airgap may also decrease. Besides, reducing the pontoon height can achieve better motion performance and larger airgap simultaneously. This paper aims to provide a benchmark for future studies on automatic hull form optimization.