Comprehensive calculation and safety assessment of parametric roll of very large container ship

Abstract

As the significant variation of GM in waves for very large container ships, strict demands are raised for this ship type in the evaluation and safety assessment of parametric roll. Targeting a 10 000 TEU container ship sailing in head sea, this study conducts a series of calculations and evaluations on parametric roll motion in which each loading condition is calculated step-by-step. Direct calculation is conducted if neither Level 1 nor Level 2 is satisfied. In this paper, an independently developed time-domain simulation is conducted for loading conditions that fail to match the Level 2 criteria, which is based on a typical 3-DOF weakly nonlinear numerical model. Ship velocity and wave conditions are taken into consideration to explore sensible conditions concerning parametric roll. Finally, according to the results, corresponding safety assessments and several avoidance measures are proposed, such as reducing the height of the center of gravity and raising the speed moderately. In addition, if wave predictions can be detected in advance, the circumstance of the natural rolling period being twice as great as the encountering period should be avoided, which is the most sensible factor for inducing parametric roll. Comprehensive calculation and checking for the 10 000 TEU ship can instruct the general design and improve safety for very large container ships; as a result, remarkable engineering applications and reference value can be recognized.