| Summary: | This thesis studies the response of the ship and the floodwater motions in the transient stage of flooding. At the transient stage, i.e. immediately after the accident, when the water rushes into the ship, the ship may experience high roll angles or even capsize. The motions of the ship and the floodwater are coupled. A fast method for predicting the transient response of the motion of the ship in an abrupt flooding case was developed within this thesis. In the abrupt inflooding the initial flow through the opening on the side of the ship resembles dam-breaking type jet. The ship motion response, mainly roll, together with the inflooding jet excites the sloshing of the floodwater. Furthermore, the obstructions and openings inside the ship complicate the modeling of the flooding process. Previous studies on sloshing concentrate mainly on sloshing with a fixed amount of water around the equilibrium, i.e an even keel, position. In the flooding accident, the amount of water varies, water ingress can be violent and the motions can take place around a heel angle far from the even keel, zero angle. The simulation method for the flooding process needs to be capable of taking into account the variation in the amount of the floodwater, ingress jet and motions around an arbitrary angle. This thesis shows that the transient stage of the flooding can be modeled with a computationally efficient and simple method (lumped mass method with a moving free surface), provided the inflow momentum flux is taken into account. This is particularly important when a wide compartment free of obstructions is flooded. The traditional approach of a quasi-static or lumped mass method with a moving free surface without the inflow momentum flux can estimate the motion response of the ship to an abrupt flooding only for divided compartments where the openings in the dividing obstructions are small. When the opening size is increased, i.e. the obstructions are reduced, the results of the presented method and the traditional methods start to ...
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