Experimental investigation of the hydrodynamic characteristics of a novel column design for semi-submersible platforms

Hydrodynamic features of a novel column design for semi-submersible platforms have been investigated. Each column consists of a cylinder with a special pontoon design at the lower end called "damper". Each of these dampers is aimed at producing increased resistance for heave, roll and pitch motions by the combined action of curved upper and lower surfaces and a passive jet system. The hydrodynamic performance of the concept has been investigated analytically, numerically and experimentally. A testing procedure was established to efficiently carry out 848 forced-oscillation tests within 4 days. A systematic processing of time series provided values of added-mass and drag coefficients for the different configurations, amplitudes and periods considered. Linear damping due to radiated waves was observed to be small. Hence the main source of damping was found to be quadratic damping. Conclusions about the behavior of the concept have been drawn.