A Study On Ship-iceberg Collision Based On Fluid-structure Interaction And Ultimate Strength

As the global climate warms,the Arctic sea ice area is rapidly decreasing,which makes it possible for ships to sail in the Arctic waterways.Data from the U.S.Geological Survey shows that more than one-tenth of unproved oil reserves and about one-third of unproven natural gas reserves are stored in the Arctic.Floating Production Storage and Offloading(FPSO)is needed to exploit these abundant resources.However,relevant studies show that there will still be a large number of icebergs in the Arctic region before the middle of the 21 st century.In this context,once the collision between FPSO and icebergs occurs,it will not only cause serious damage to the ship’s own structure,but also cause environmental pollution in the Arctic region and even threaten the life safety of the crew.Therefore,it is necessary to carry out relevant research on ship ice collision.In addition,the related collision accidents show that when rescuing ship ice after collision,it may cause secondary damage due to the insufficient bearing capacity of its structure and bring huge economic loss.Therefore,it is significant to study the ultimate strength of ships after collision,which can provide some valuable references for the construction of floating production,storage and unloading devices in polar regions as well as rescue plans after accidents.In terms of ship ice collision,the nonlinear finite element software LS-DYNA and LS-Prepost are used for solving and post-processing.Firstly,in this thesis,the constant additional mass method and the fluid-solid coupling method are used to simulate the small scale collision model,and the results are compared with the experimental results.The accuracy of the calculation results of the two methods is compared,and the application range of the two methods is determined and the reasons for the difference are analyzed.Secondly,taking a certain FPSO oil tank as the hitting object,the fluid-solid coupling method is used to calculate the deformation and failure of the side structure and iceberg after the iceberg hits the FPSO at different speeds and angles,or the iceberg of different shapes and different masses collides with the FPSO as well as the magnitude of the collision force and the energy absorption of each component.The variation trend of the collision force with velocity and angle is studied,and the more dangerous working conditions are determined,which lays a foundation for the development of oil and gas in the polar area.In terms of ultimate strength,this thesis uses the finite element software ANSYS and uses the nonlinear finite element method to calculate.Firstly,the Nishihara box beam is used as the simulation object,and its ultimate strength is calculated and compared with the experiment and related literature to ensure the accuracy of the method.Secondly,nonlinear finite element method is used to calculate the ultimate strength of the FPSO cabin model in order to obtain the ultimate bending moment of the intact cabin under the sagging state of the arch.This result is used as the basis for the subsequent comparison of the ultimate strength before and changes after the collision.Finally,in order to ensure the accuracy of the ultimate strength calculation results after ship damage,this thesis uses LS-DYNA to calculate the deformation results of the model after the collision.After processing some elements in the collision area in LS-Prepost,the relevant node element information is imported into ANSYS,The real collision model is applied to calculate the ultimate strength of the damaged ship,and the result is compared with the result before the collision to get the ultimate strength change after the collision,which provides a reference for the rescue of the ship after the collision.