Numerical simulation of Sewol ferry capsize

Abstract

In this study, numerical simulations are conducted in order to analyze the capsizing of roll-on/roll-off passenger ship, Sewol, which occurred on 16 April 2014. Since little is known about the reason of ship capsize, numerical simulation aims to the finding of possible scenarios which can cause this tragic accident. To this end, 4-degree-of-freedom (surge, sway, yaw, and roll motions) maneuvering equations are solved. The hydrodynamic coefficients obtained from a similar ship are applied and the WISH-Maneuver program of Seoul National University is used to perform the numerical simulation. The present analysis utilizes the probabilistic approach, which considers various physical variables and involves the simulation of a large number of cases using different combinations of the variables. The total number of simulation cases is over 70 millions, and the simulation results that are close to the conditions of the actual accident situation are selected. Through this process, the effects of the simulation variables are investigated and the potential causes of the accident are identified. The results show the hydrostatic instability of the ship in the operational condition owing to cargo overload and insufficient ballast water, which raised the vertical center of gravity. The reduced stability combined with large starboard steering angle and cargo movement during large heel may have been the decisive reason of capsizing.