The Ro-Ro passenger ship "Estonia"sank in 1994 because of large amount of flooding water on vehicle deck. To prevent such kinds of disasters, safety of damaged Ro-Ro passenger ships has been discussed in IMO (International Maritime Organization). This paper investigates validity of a time domain simulation method of rolling motion of a Ro- Ro passenger ship with flooded water on vehicle deck expressed by 2- dimensional lump mass concept. Model experiments with different amounts of water on the deck were carried out to confirm effectiveness of the method in regular beam waves. As a result, the simulation method on rolling motion shows reduction of roll response caused by moving water on deck and roll amplitudes obtained from the simulation are good agreement with experimental ones. The present method shows possibility of assessing the safety of Ro-Ro passenger ships with damaged holes and flooding water on deck.
After the disaster of the Ro-Ro passenger ship "Estonia" in 1994, safety of damaged Ro-Ro passenger ships in severe sea condition has been examined in IMO. Since a Ro-Ro passenger ship has large flat vehicle decks, the condition, which large amount water came into from damaged holes exists on the deck, may cause the ship to capsize. Many experimental researches on Ro-Ro passenger ships with flooding water have been conducted until now (Ishida, 1996; Hamano, 1997; Haraguchi, 1998; Vassalos, 2000 etc.). It is, however, difficult to capture all dangerous conditions of the ship with flooding water under a limit of sample ships and experimental conditions. Although calculation methods on motion of ships have been presented to predict capsize of the ships (Papanikolaou, 2000; Zaraphonitis, 1997; Hasegawa, 2000), there are many points which are uncertain on application range of them at this stage.