Research On The Pure Loss Of Stability And The Turning Security Of The Ro-Ro Passenger Ship

The passenger ships'steady angle of heel on account of turning must be checked in order to meeting the requirements of the 2008 IS Code at present. However, the values which were calculated based on the formula of the 2008 IS Code are smaller than the reals, and the differences are very large. It's bad for the navigation security. This article mainly establishes a passenger ro-ro ship model using COMPASS software,subdivision,loading, simulate the actual loading conditions, research the stability when turning. At the same time, the formula used for calculations of this criterion can be revised through the data which acquired from the COMPASS calculation results and the actual maneuverability trials, the turning coefficient is changed from 0.2 to 0.35.Then, the calculated steady turning angle is more closed to the measured value and it's positive to the navigation security.Moreover, the maneuverability tests cost so much money and time. At the same time, the turning parameters such as the steady turning diameter,the heading angle,the ship maneuvering index K and T play an very important role in the navigation security. This paper adopts MMG model,derives the linear responsive model formula and establishes the motion model of a passenger ro-ro ship using simulink software,then, describe the ship's turning characteristics as well as explaining the affect of those parameters on the navigation security. The turning diameter is about 9 times as long as the Lpp when turning with full speed ahead and full rudder under the light Load condition of the passenger ro-ro ship. At the same time,the turning ability index K=0.02215,the turning lag indexT= 60.44, These parameters can predict the ship's turning and following abilities.The ship is inevitable to encounter with the following waves or tail oblique waves throughout the entire life cycle. However,many facts indicate that the stability in still water is different from that in waves, the stability criterion of water based on static condition can not ensure the safety of ships in waves. The pure loss of stability which is one of the failure modes of the second generation intact stability describes the righting lever changes versus the waves position changes when the ship navigating in following waves or tail oblique waves. The container ships and the passenger ships are easy to occur the pure loss of stability. Thus, in this paper,the criterias of the first layer and the second layer are calculated which are based on some of a passenger ro-ro ship's selected loading conditions. According to the calculation results, this ship may occur pure loss of stability phenomenon when sailing in following waves or tail oblique waves. Meanwhile, the effect of the height of the center of gravity on the loss of pure stability is explored when compared the calculation results of this passenger ro-ro ship with the sister ship-the passenger ro-ro ship 2. We can conclude that reducing the ship's center of gravity can effectively decrease the occurrences of the pure loss of stability phenomena.