Research Of Ship Navigation Safety Based On Draft Criteria Of Parametric Roll And Pure Loss Of Stability

Stability is an important and complicated subject in ship industry all the time. It is also one of the main performances that make sure the safety of ship’s sailing and offshore floating body’s working. At the same time, ship stability is one of the tasks of ship inspection. At present, the intact stability criteria established by countries in the world are based on hydrostatic theories and experience. However, many accidents occurring due to loss of stability in recent years demonstrate that even though a ship meets the requirements of intact stability criteria completely, it doesn’t means absolute safety for intact stability. On the other hand, the intact stability criteria at present refer to little about stability in waves. Nevertheless, most accidents about stability occur in waves, such as the typical accident of C11container ship. As a result, the intact stability criteria at present haven’t satisfied the requirements of development of ships. And the task of developing new generation intact stability criteria based on performances is pressing. Pure loss of stability and parametric roll are two important failure modes in Second Generation Intact Stability Criteria that is establishing now, the research on the draft criteria of them can provide a basis for the final establishment of Second Generation Intact Stability Criteria.The work of the article is to research stability in waves based on draft criteria of parametric roll and pure loss of stability, and operation guidance for ship when sailing in seas is presented combined with sample calculation to improve navigation safety for ships. The main contents are as follows:(1) GZ calculation and its change low:The instantaneous attitude of ship in waves is ascertained based on static balance in sinkage and trim on waves, and then GZ in waves is calculate according to the righting arm formula based on Froude-Krylov assumption. Then righting arms are analyzed to study the change law of them;(2) Draft criteria of parametric roll and pure loss of stability and its program development:The article analyses the reasons why pure loss of stability and parametric roll occur based on the change low of GZ. Then the simplified version of Ikeda’s semi-empirical formula is applied to calculating roll damping coefficients. And restoring force coefficients are solved by using multiple linear regression method. Then parametric roll amplitude is calculated by solving the uncoupled roll model. In order to realize hybrid programming of Visual Basic and MATLAB, Dynamic Linking Library(DLL) technique is applied and corresponding computational codes are developed that can realize the function above. Then C11container ship is taken as an example to verify and analyze the system. (3) Research on navigation safety for ships:NO.1and NO.3fishery administer ship are taken as examples to calculate their stability conditions based on draft criteria of pure loss of stability. In order to research parametric roll in head seas, NO.1fishery administer ship is taken as an example. And then the influence on parametric roll by the variation of roll damping and load conditions is analyzed. Possible area of parametric roll occurring when ship sails in waves is figured according to the calculation results. At last, operation guidance is presented combined with the figure corresponding to actual situation when ship sailing in seas, which can improve the navigation safety for ships when sailing in seas.