Failure Mechanism Of Leakage-resistance Of Double Hull Structure And Characteristics Of Crude Oil Leakage From Sloshing Damaged Tanker

A 3D full scale numerical model was developed to simulate crude oil leakage from damaged tank of VLCC due to grounding accidents.The methods of theoretical analysis and numerical simulation have been applied to investigate the failure mechanism of leakage-resistance of double hull structure and dynamic characteristics of crude oil leakage from sloshing damaged tanker.The main content of this paper are as follows:Firstly,based on theoretical analysis of crude oil leakage from sloshing damaged tank,the sloshing types of tanker,sloshing factors and properties of crude oil have been defined,and the domain powers of crude oil leakage were analyzed.Secondly,considering multiphase flow of crude oil leakage from sloshing damaged tank,the VOF three-phase model was adopted to track the free surface.The dynamic mesh technique was applied to solve the motion of damaged tank;the N–S equations and continuity equation were used for the governing equations and solved with finite volume method;the k-? turbulence equation was employed to solve the viscous effect and turbulence effect.Thirdly,according to selected mathematical model,the non-coupled implicit algorithm based on pressure and the PISO algorithm based on coupling of pressure and velocity were adopted to solve a series of flow equations of crude oil leakage.The numerical methods of crude oil leakage were validated by model experiments of liquid sloshing in a rectangle tank and oil leakage from static damaged tank,respectively.Further,the numerical investigations on crude oil leakage from full scale sloshing damaged tank and static damaged tank were carried out,respectively.Fourth,the limitations of resistance-leakage of double hull structure and the difference between crude oil leakage from static damaged tank and sloshing damaged tank were proved by numerical results.Considering the effects of gravity,viscosity and fluctuation pressure induced by tanker sloshing,the process of crude oil leakage from sloshing damaged tank was divided into gravity flow stage,transition flow stage and sloshing flow stage.Failure mechanism of resistance-leakage of double hull structure(DHS)was explored and failure mechanism model of DHS was presented.Fifth,the characteristics of crude oil leakage from sloshing damaged tank were captured by exploring characteristics of crude oil and water,free surface deformation and microcosmic flow field.The effects of sloshing amplitudes and periods on crude oil leakage were exploited by estimating volume of crude oil leakage and the importance of different leakage stage was claimed,which provide a theoretical basis for control of crude oil leakage from damaged tanker in actual sea condition.