The Influence Of Unconventional Free Surface On Ship Stability

According to statistics,the proportion of fire accidents in ship accidents at home and abroad is increasing.When the ship fire occurs,water is used to extinguish the fire,and free surface is easily formed in the cargo tank.The free surface will lead to the ship stability be insufficient or disappear,eventually the ship sank.It is worth noting that the free surface formed in the cargo tank caused by the ship fire extinguishing is different from free surface formed produced by the pure liquid in the conventional liquid tank.Because of the division of the cargo in the tank the free surface is not complete,and the effect on the ship stability is quite different Moreover,the density of liquid in some tanks is also changing.Therefore,this paper will study the influence of unconventional free surface on ship stability due to surface breakage and the density of liquid changing.In this paper,the influence of unconventional free surface on ship stability is studied,including the following aspects:1)In this paper,the approximate algorithm of the area moment of inertia of the broken free surface is summarized,and the precise algorithm for calculating the moment of inertia of free surface is put forward.Then the calculation formula of the moment of inertia of the free surface under different positions of the liquid surface of the container ship,the wood ship and the general cargo ship is summarized.2)The influence on ship stability of free surface is summarized,when the variable density of two kinds of liquid stratified at the full cabin and the not full cabin.And the calculation formula of the influence on the ship stability is deduced where the goods through the interface of the stratified free surface.Then the calculation formula of the influence on the ship stability is derived where the density of the free surface is uniform increasing from top to bottom.By deducing the calculation formula of the unconventional free surface on the influence of the ship stability,in can provide the theoretical basis for the crew to take measures when they meet the unconventional free surface and reduce or avoid the risk caused by the unconventional free surface.