DEVELOPMENT OF SAFER SHIPS BY DETERMINISTIC ANALYSIS OF EXTREME ROLL MOTIONS IN HARSH SEAS

For modern ship design — as confirmed by many examples of ship design and operation — the current intact stability code (IMO (2002)) does not provide a reliable basis for the assess-ment of ship safety in rough seas. In ship design the applica-tion of the IS-Code is not supporting design decisions towards increased safety in rough seas (Cramer and Krüger (2001)), and ship operators find their cargo and/or vessels endangered by large roll angles and accelerations (France et al. (2001)). Thus, there is a great need for procedures to analyze ship safety in rough seas. This paper presents innovative deterministic seakeeping test procedures which are used to identify the physical mechanism endangering intact ships by evaluating cause-reaction relations of wave/structure interaction. Rogue wave sequences are embedded in severe seas for computer controlled capsizing tests of different vessels at the Hamburg Ship Model Basin. The model test results are used as a basis for the development of non-linear numerical methods to simulate ship motions in extreme seas with the target to design safer ships with reduced capsizing risk. Polar plots following from the non-linear simulations allow the evaluation of ship safety in severe seas with reference to course, speed and trim. NOMENCLATURE |F(ω) | Fourier spectrum GM metacentric height Hmax maximum wave height Hs significant wave height Tp peak period TR period of roll resonance T0 zero-upcrossing period d water depth t time v velocity x,y coordinates in space α1 main board angle α2 upper flap angle ζ(t,x) surface elevation ϑ pitch µ course ϕ roll ω circular frequenc