Coupled vessel-dry-granular-cargo roll dynamics in regular beam seas

The behaviour of granular cargos transported by sea has not been sufficiently investigated yet from a theoretical perspective. International regulations controlling the loading and stowage of bulky cargos, despite some updating and improvement, remain empirical, lacking a solid theoretical foundation. In the paper is investigated the inception of roll instability for a vessel containing a rectangular hold partially filled with dry granular material, by applying a simulation approach based on coupled micro-scale modelling of particles with vessel motion. The method of molecular dynamics is employed, combined with a rudimentary model of vessel motion in beam seas. The key assumptions behind the modelling of cargo's movement are that, the granular material is dry, all particles are spherical and adjacent particles interact through non-linear elastic and frictional forces. Characteristic simulation results, including comparisons against cases of rigid cargo, are presented, pointing out cases where the agility of the cargo may have a positive or a negative effect on vessel's stability.