Fin Effect on Pitch Motion and the Avoidance of Initiation of Parametric Roll

Abstract

Container ships are prone to move at a greater speed compared to that of other merchant ships. The slenderness of the hull of container vessel is for better speed, but it leads to unfavorable motions especially while rolling. Such a slender hull when get twisted due to relative wave positions both port and starboard sides cause torsion and warping on the hull. The pitch and roll are related and sometimes the vessel might be forced to parametric roll condition which is very dangerous. A fin attached to the ship hull proves to be more efficient in controlling the ship motions particularly pitch. The fin is fitted at a lowest possible location of the hull surface and it is at the bow part of the ship. Computer simulation is done using proved software package ANSYS AQWA and the results are compared. Simulation is done for both regular and irregular sea and the effect of fin on ship motion is studied. The fin proves to be less effective at higher frequency range in controlling the ship motion. Although the ultimate aim in this paper is to avoid the situation leading to parametric roll, immediate attention is to modify pitch performance of the moving ship. Such situations of ship motion combined with the slender hull deformation cause the failure of lashing arrangements leading to cargo stack disorder and imbalance.