專技◆驗船師◆專業英文題庫

Slamming Loads. When a ship operates at high speeds, especially in head seas, the bow may occasionally emerge from one wave and re-enter the next wave with a heavy impact or slam as the bottom forward comes in contact with the water. Related phenomena are associated with the impact of large waves on the bow topsides having pronounced flare and with green water on deck coming in contact with the front of a deckhouse or superstructure. In each case the phenomenon involves the impact at high relative velocity between the free surface of the nearly incompressible water and a portion of the ship’s structure.

Two noticeable effects may be caused by bottom slamming. There may be localized structural damage in the area of the bottom that experiences the highest impact pressure. This may include set up plating and buckled internal frames, floors and bulkheads. A second effect of slamming is a transient vibration of the entire hull in which the principal contribution comes from the fundamental two-noded vertical mode. This slam-induced vibration is termed whipping, and it may result in vibratory stress intensities that are equal in magnitude to the wave-induced low-frequency bending stresses.