Influence of trapped air on the slamming of a ship

We describe a theoretical approach to a distorted plate penetrating calm water surface as a flow model of the water impact in rough seas. Further simplifications are employed so that the structure of ship is modeled by a tandem mass and spring system and a sequence of circular hollows is used as a bottom shape of the body instead of the surface shape of short crested waves. The results show that the model-scale ship experiences much larger stress at the local structure because of the influence of trapped air. Some results for the full-scale ship show that the three-dimensional effect, that is, the shape of sea surface deformation, is dominant for the cushioning of the impact force, and the trapped air affects some of this effect according to the magnitude of β and the natural period of the local structure.