Numerical Study of the Collision Structure Damage of Double Shell Tanker and the Cargo Leakage Analysis
|School||Dalian Maritime University|
|Keywords||Ship-ship collisions Collision parameters Critical speed Liqudileakage Spoll oil mass|
Ship-ship collision is refered to the damaging accidents caused by ships contacting each other at navigable waters adjacent thereto, and its consequences are often disastrous. At present, researchers in many countries are trying to find methods which can avoid ship-ship collision accidents occurred. In recent years, the main reason of causing ship-ship collision happening continuously is the inevitability of human factors. From the point of the ship’s structure, based on the safety consideration of ship-ship collision, there are much leeway of improvement and innovation in ship structures, but changing the ship structures needs a lot of simulation experiments and prototype verifications, which not only requires a long time but also costs a lot of manpower, material resources and money. Therefore, in order to avoid ship-ship collision, this paper considers exploring methods of avoiding or reducing consequences in ship-ship collision by controlling the ship speed.Therefore, this paper demonstrates a comparative study on the influences of collision parameters (collision angle, position, initial velocity, etc) by applying numerical simulation methods, and the damage model and energy absorption characteristics of components are analyzed in detail, what’s more, curves with displacement change of side structure collision force, structure energy absorption and damage deformation, which give the general conclusion having a guiding significance: the damage on the struck ship caused by bulb outstanding ship stem is very serious; the bigger of the collided ships’tonnage, initial velocity and kinetic energy of collision, the neavier of the damage of the struck ship; Angles of collision cannot compete with vertical collision in damaging to the stuck ship; In addition to the above, tiny change of collision position will lead to the obvious change of broken failure time of the struck ships’whole side structure.After the ship’s type of collisions are determined, based on the effect of collision parameters to ship-ship collision, this paper talks about lots of numerical experiments between double shell oil tanker and bulk cargo ship with different tonnage from angle of quantitative consideration, the research shows that:the greater of the collision angle and the collided ship’s tonnage, the smaller of the needed struck ship’s critical velocity which leads to broken of inner shell and outer shell, moreover, the critical velocity calculation formula of the striking ship which makes the inner shell and outer shell of struck double shell oil tanker broken is put forward through the analysis of the test results research finally.Once the ship’s speed lose control, the inner shell of double shell oil tanker will rupture, which can cause liquid leakage. The VOF model from Fluent and PISO algorithm of pressure speed coupled are adopted in this paper to simulate the unsteady flow dynamic with free surface, no miscibility, oil-water-gas three-phase incompressible in the conditions of three dimensional.For the better description of liquid leakage process in the double hull oil tanker, firstly, based on the factors of the oil surface, water surface and height to the split, etc, through the physical experiment, the liquid leakage process is observed and studies in this paper, then putting the physical design of experiment into three groups of numerical experiments, and contrasting the processes and results in two experiments, by the contrast, the liquid leakage process, leakage time, height of water which goes into the cargo oil tank and the experimental results are consistent with the results obtained in numerical calculation, it shows that the numerical calculation of leakage process in double shell oil tanker at clam sea by Fluent is feasible and credible, which could be used in further research. After that, by applying the numerical calculation of leakage process in double shell oil tanker at clam sea by Fluent, and doing detail description, the amount of leakage in double shell oil tanker can be decided by split height of inner and outer shell and the geometry size of cargo oil tank, that is the amount of leakage=length of tank carbinxwidth of tankxvertical distance from inner split bottom of tankxdensity of liquid, which can be found in the contrast of results. Based on the analysis above, the numerical experiment of liquid leakage influenced by the physical parameters (oil density, split height, level difference) are conducted and researched in this paper, the research shows that the changes of other physical parameter have influence on both leakage time and the amount of leakage, besides of the split shape and area change which influence the time of leakage mainly.