Abstract

Parametric roll is a nonlinear phenomenon that can result in large roll angles coupled with significant pitch motions. These motions might induce large loads on the ship structure, and compromise the safety of the crew and the cargo. The severity of the motions might reach to such levels that capsizing might occur. In this study sensitivity analysis in parametric rolling of a modern cruise ship is investigated using numerical simulations. Several parameters were considered as sources of uncertainty such as the combined effect of GM and roll radius of gyration, roll damping, ship speed, and fin characteristics. In terms of fin characteristics, fin angle rate and maximum angle, fin area and aspect ratio, and fin gains were investigated. Additionally, the non-ergodicity of parametric roll was studied as well as the effect of simulation duration on the statistics of parametric roll. The simulations were carried out with a hybrid time-domain seakeeping and manoeuvring code. The time-domain code was used in combination with a strip-theory based frequency-domain program in order to calculate diffraction and radiation forces as well as added-mass. The time-domain code was able simulate the dynamic behavior of a steered ship in 6-DOF, where the motions can be large up to the moment of capsize.

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