Operational guidance to avoid parametric roll

In October 1998, a post-Panamax, Cll class containership encountered extreme weather and sustained extensive loss and damage to deck stowed containers. The motions of the vessel during this storm event were investigated through a series of model tests and numerical analysis. This confirmed that parametric roll was the most likely cause of the accident. The results of this study were presented in a technical paper in 2003 [1]. The conclusion of the study confirmed the fact that any large container vessels given the right conditions (hull form, loading condition, speed, wave heading and wave condition) can encounter very large roll angles due to parametric roll. The master at that time was not aware of the parametric roll phenomenon and did not know how to correctly react in order to decrease or avoid the large motions. In this paper we will discuss the tools which can be used to predict the parametric roll phenomenon. A comparison between numerical results and model tests will be made and attention will be paid to the validity of the numerical results and the consequences of the validity. By making many simulations where loading condition, speed and wave condition are varied polar diagrams will be presented which could be very valuable for a master of a container vessel to avoid a situation in which it is likely that parametric roll will occur.