Heeling moment in the alternative assessment of the Weather Criterion: direct experiments and numerical simulations

It is well known that the restoring moment in intact condition is one of the most important characteristics of a ship and it represents an essential contribution to the overall ship safety. Minimum intact ship stability requirements for ships in international voyages are governed by IMO rules and it is therefore evident that any change in IMO regulations for what concerns intact stability has a direct impact on the overall ship safety. Recent amendments to the well known Weather Criterion allow the use of an experimental alternative as specified in MSC.1/Circ.1200 "Interim Guidelines for the Alternative Assessment of the Weather Criterion", while relevant explanatory notes have been issued as MSC.1/Cirs.1227. This paper reports some results of ongoing experimental and numerical investigations carried at the University of Trieste and at Fincantieri SpA, aimed at determining the potential impact of the alternative experimental assessment of Weather Criterion. In particular, the interest of the paper is on lateral drift in calm water and wind effects, i.e. the two ingredients for the determination of the heeling moment due to the wind action. The paper shows results from experiments, simulations and an example application assessing the potential impact of the experimental approach on the wind heeling lever to be taken into account in the assessment of the Weather Criterion for a small RoRo. For what concerns simulations of wind effects, some considerations are given from the experience gained in the initial phase of an ongoing research activity.