ABSTRACT
The outcome of a ship collision can be analysed considering both ships internal mechanics and external dynamics. Internal mechanics is related to the structure strength and gives information about the damage of the ship structure, while external dynamics consider the global motions of the involved ships. External dynamic depends on ship hydrodynamic properties and the effect of the surrounding water in ship collision shall be considered. There are several ways to consider the external dynamics of ships involved in a collision. For the users of LS-DYNA software, a very convenient MCOL boundary condition is available, where hydrodynamic forces are calculated, and ship motions updated in selected time steps. Another option is modelling fluid-structure interaction directly using the Arbitrary-Lagrangian-Eulerian method. In this paper, a novel method is considered. A user-defined load (LOADUD) LS-DYNA subroutine is used to implement the Abkowitz manoeuvrability model, calculate hydrodynamic forces and apply them to the ship’s centre of gravity in each time step of ship collision calculation. This approach is compared with the other three methods, on two predefined collision study cases: one with an acute angle and one with an oblique angle. The main scope of the paper is, therefore, the evaluation of the accuracy and efficiency of the proposed new method, as well as to examine its drawbacks. This research is in part connected to the interdisciplinary Croatian Science Foundation project NEREAS, studying ancient ship collisions and groundings, as well as flooding and sinking of ships.
