An Investigation On The Effects Of Pitching Reduction Of Ships Equipped With Anti-Pitching Rudders In Waves

When the ship is moving in the ocean, there are six directions of motions. Among these, pitch sometimes will reach a large angle, which has a big influence on the navigability of the ship, the accuracy of the weapons and the life of the staff on the naval vessels. And if the pitch is too strong, it will have severe fore slapping and green water, even cause the ship capsize. But till now, there is not any equipment, which can reduce the ship's pitch effectively.In this paper, the concept of anti-pitching rudder is raised. The new strip theory (STF method) and spectrum analysis theory are introduced at the beginning. And then how to design an anti-pitching rudder and the hydrodynamic mechanism of it are discussed. Based on all of these theories above, the anti-pitching rudder is applied to different types of ships, and different design styles are given. According to different types of anti-pitching rudders, and after numerical calculations to each other in a series of ship's velocities and incident wave angles, the amplitude of pitch and heave in regular wave are selected to compare to see which design is more effective to decrease the amplitude of ship's pitch and heave. While in irregular wave, besides the amplitude of pitch and heave, the fore and aft accelerations, green water occurrence and the minimum topside are also selected to investigate the effectiveness of different types of the anti-pitching rudders. The result of this paper's research manifests that the anti-pitching rudder is effective in reducing the amplitude of ship's pitch, and it is of great significance in applications to the naval vessels in the future.