A practical approach for simplified operational guidance to avoid parametric roll resonance

• Practical approach for polar charts on parametric roll risk has been developed. • Dynamic roll motion equation with quasi-static pitch and heave is applied. • Concept of Grim’s effective wave in oblique seas is utilized. • Results are compared against public model tests and dedicated 6-DOF simulations. • Simplified method is found to provide good results for practical applications. Parametric roll resonance is known to have caused several accidents with significant loss of containers over the past decades. International Maritime Organization has introduced interim guidelines for the Second Generation Intact Stability Criteria (SGISC) that consider also parametric roll with a multi-tier approach. In this study, a new practical approach for preparing ship-specific simplified operational guidance for avoiding parametric roll, in the context of the SGISC framework, is described, with focus on large ocean-going ships. The method is based on time-domain solution of non-linear roll equation in regular longitudinal waves, with quasi-static calculation of pitch and heave motions. The concept of longitudinally moving Grim’s effective wave, with an extension to oblique seas, is utilized. The method is validated against model test experiments, and comparative direct stability assessment simulations have also been conducted. A case study with a very large container ship design, replicating the conditions of a well-documented accident, is presented to demonstrate that the parametric rolling in stern quartering seas is properly captured. The results indicate that this kind of ship-specific simplified operational guidance can identify dangerous conditions, and therefore, this approach has potential use in planning operation of ships to reduce the risk of parametric roll resonance.