Three-dimensional slamming of a distorted plate

A theoretical and numerical approach to the distorted plate penetrating the calm water surface is investigated as a flow model of a blunt body slamming in rough seas and the effect of air trapping is also investigated in this paper. This theory is based on the variational formulation in which the displacement potential is obtained instead of the velocity potential. Numerical results show that the maximum impact force becomes smaller and smaller as the steepness of distortion increases, and the duration of the impact becomes longer as the steepness increases. In order to clarify the reduction effect of the roughness of water surface, a diagram of the maximum impact force with variation of the deadrise angle of the wedge is depicted. This diagram shows that the reduction effect seems significant in the region of small deadrise angle. Other numerical results show that the trapped air makes the impact force stronger and the reduction of the maximum impact force is mainly brought about by the three-dimensional effect of the roughness of water surface when the water surface is rough enough to guarantee the formation of a cavity in advance. It is considered that the effect of the trapped air becomes dominant for the reduction of the maximum impact force as the steepness of surface waves decrease. Summarizing the numerical results, a new scenario is implied in that the reduction effect of the maximum impact force acting on a blunt body is mainly brought about by the three-dimensional effect of the roughness of water surface when the body falls into rough seas, and when the water surface is calm the effect of the trapped air becomes dominant as indicated in previous experimental works.