Second Generation Intact Stability Criteria: on the validation of codes for direct stability assessment in the framework of an example application

The Sub-Committee on Stability and Load Lines and on Fishing Vessels Safety (SLF) of the International Maritime Organization (IMO) has undertaken the development of so-called "Second Generation Intact Stability Criteria" (SGISC) with the intention of providing a new set of rules covering those phenomena which are not properly covered by present, mostly semi-empirical, requirements. The first two levels of the envisioned 3 + 1 tiers structure of SGISC are so-called "vulnerability assessment" levels: most of the discussion has so far been dedicated to these levels. At the highest level there is the so-called "Direct Stability Assessment", which is also strictly linked with the development of ship-specific "Operational Guidance". Recent discussion on the topic of "Direct Stability Assessment" (DSA) has touched the issue of "validation" of numerical codes to be employed at this level. Stimulated by, and in view of, the ongoing IMO discussion, this paper presents the results of a recent series of experiments in beam waves (mono-/bi-chromatic, irregular) and associated simulations based on a 6-DOF blended code. Nonlinear harmonic and sub-harmonic resonances are observed and simulated.