Numerical Study Of Ship-layer Ice And Ship-Iceberg Collisions

In recent years,the rise of global temperature has reduced coverage ice area in the polar region and northern route navigation has become a reality.Considering the strategic position,rich natural gas and oil resources,the Arctic region is becoming so important that many countries scramble it hardly.When ships navigate and carry out various mining activities,they can not avoid contacting with sea ice.If the ship is damaged during the collision with sea ice,it will not only harm the life safety of the ship,but also cause oil and gas leakage,which seriously pollutes the marine environment and makes huge property economic losses.The research on collision between ships and sea ice has become a hotspot in recent years.For the above reasons,based on the nonlinear finite element program LS-DYNA,the collision problem between ship and sea ice is studied in this work.The paper gives examples of the disaster accidents in the polar navigation first and emphasizes the importance of studying the ice load to the safety of the ship.Besides,it summarizes the main study methods and present situation of the ice load research and gives a detail introduction of the full text work.The whole works are divided into ship-layer ice and ship-iceberg collision research.In the study of ship-ice layer collision,the author uses the cohesive element method which has just emerged in recent years.Paper focuses on the advantages of method in the study of layer ice,and explores the idea of constructing the layer ice model using the cohesive element.At the same time,the ice resistance changing law at different speed of ship is studied.When ice interacts with ship or structures,it has behaviors of accumulation and climbing which leads to a big difficulty for the previous research methods.By simplifying the buoyancy of sea ice approximately,the paper uses the cohesive element method to simulate the ice accumulation and climbing behaviors successfully.Besides,the effect of the fracture energy of the cohesive element to the collision force is considered.This study provides a new idea for the prediction of the ship’s ice resistance.The numerical results are in good agreement with the empirical formula,which verifies the accuracy and feasibility of this present method to predict the ice breaking resistance.In the study of ship-iceberg collision,the fluid-structure interaction method and the Arbitrary Lagrangian-Eulerian(ALE)algorithm are applied to study the collision between the shipside and spherical iceberg as well as that between whole scale ship and hexahedral iceberg.In the research,buoyancy is first simulated by hydrostatic pressure,then studies about collision problems studies are carried out.In the study of the shipside-spherical iceberg collision problem,the method used in the laboratory for ice-structure collision problem is adopted to explore the impact force characteristics when the iceberg sails to the shipside by different collision angles.At the same time,the collision phenomena in the whole process are explained reasonably.The results show that the collision angle and the material strength of the iceberg affect the collision force simultaneously.The full scale collision research can study the effect of the ship navigation to the displacement of the floating iceberg.After the convergence analysis of the collision time history force curves of the iceberg under different size grids,the optimum size of the floating ice grid is determined.In order to study the effect of fluid in the whole collision process,the author also carried out the collision simulations without considering the fluid.The results show that the fluid plays an obvious role in the whole collision process,which not only affects the peak value of the collision force,but also has a significant impact on the collision time.