Application of the IMO maneuvering criteria for pod-driven ships

The fundamental objective of this paper is to make qualified assessment of the validity of the International Maritime Organization (IMO) maneuvering criteria "Resolution MSC.137(76)," when applied to pod-driven ships. The performance limits given by the criteria provide an adequate benchmark to compare all ships, regardless of propulsion type. However, the application of specific helm angle is less well defined as azimuthing pod drives, like any vectoring thrusters, can be turned to any helm angle, with no specific definition for the angle of maximum force. To address this problem, new methods for modeling the hydrodynamic reaction for both the ship hull and pod drive are identified. Then, a dedicated numerical tool is developed and simulation study conducted exploring systematic variation of applied helm angles with comparison of time- and frequency-domain responses. The study reaches the definitive conclusion that the criteria provides equivalent information about the maneuvering response of pod-driven ships as for conventionally propelled ships and can thus be applied directly.