Time Simulation of the Behaviour of Damaged Ships in Waves

Licentiate thesis, 2005

The cause of event and ability for ship survival after damage are in many cases poorly described by pure static considerations. The dynamic properties of the ship and environment will be significant in the assessment of the damage scenario. Physical theories describing these properties have been developed since many decades. It is only in the last few decades though, that computing capacity has made it possible to develop practical tools for assessing a damage event for a ship at sea. The present thesis contains a description of the numerical simulation program SIMCAP that has been developed at the Department of Shipping and Marine Technology, Chalmers University of Technology. Simulation results and validation tests are also presented and discussed. The objective of this work has been to develop a numerical tool that can be used to evaluate and test ship designs as to increase the survivability of a damaged ship. The tool should be able to describe the dynamic course of events regarding water inflow and the behaviour of the ship in waves. Validation shows that SIMCAP is well advanced in predicting damaged ship behaviour in waves compared to similar existing programs. Validation also shows total agreement with commercial static stability software, in both intact and damaged conditions, for all general static stability properties. A time simulation model with coupled equations is employed. The modelling of radiation and diffraction forces is based on linear strip theory, while the Froude-Krylov forces are treated in a non-linear fashion by integrating the incident wave pressure over the momentarily wetted hull surface. The water inflow and floodwater forces are based on quasi-static assumptions.