Study On Numerical Simulation For Ice Resistance Of Ice-going Ships In Crushed Ice And Level Ice Conditions

With the global warming,the exploration and development of oil and gas in the Arctic region and the increase of ship transportation,the operation and navigation activities of ships in the ice region in the polar waters have increased significantly.For ice-going ship,on the premise of ensuring safety and economy,it is necessary to maintain reasonable speed in a certain thickness of flat ice or a certain density of crushed ice area,and to ensure navigation in higher ice conditions.In the design stage,it is very important to evaluate the performance of ships in ice area and estimate the ice resistance reasonably.On the basis of summing up predecessors,combined with model test and numerical simulation,this paper improves the numerical method,realizes the prediction of ship performance in ice area,and completes the analysis and research of the ship with crashed ice,ship with level ice interaction.The model test and numerical simulation study on the key issues of the navigation performance of the ship in the ice-breaking area are completed.The paraffin model ice is used to simulate the polar ice-crushing environment,and the resistance measurement and phenomenon observation of 6 speeds and 3 kinds of density(60%,80%,90%)were completed.At the same time,the finite element software LSDYNA is used to simulate the navigation performance of the ship under the condition of crushed ice,and the buoyancy effect of water is considered.The coupling calculation of ship-ice-water-air is realized by ALE method.Both results show that the collision between ship and crushed ice causes the accumulation,rolling,slipping and distribution of crushed ice in ship wake,and the severity is affected by the different speeds and crushing ice density.At the same time,the ship model resistance As the density of crushed ice encountered and the speed of the ship's model increase,the effect between the ship's ice is more severe;the collision between the ship's model and the crushed ice is mainly concentrated in the ship's stern,and the ice load in the navigation direction is the largest;Both simulation and model tests can well predict the navigation performance of ships under crushed ice conditions,and provide technical reference for the design of ice transport vessels.The finite element numerical simulation of the icebreaker sailing process under the condition of level ice area is carried out.The ALE method of LSDYNA software,erosion contact algorithm and penalty function method are used,and paper focuses on the buoyancy of water,HJC ice material model selection and material yield criterion.The numerical simulation analysis of the model ice thickness of 37.5mm(actual ice thickness 1.5m)and four ship model speeds.The results of numerical simulation and the results of the ship model ice resistance test completed by the Ice Engineering Laboratory of Tianjin University show that the ship model resistance increases with the increase of the speed under the condition of flat ice,and the ice damage mode is different under different ice breaking speeds.The ice-breaking ship-level ice interaction process is analyzed,and the crack propagation pattern of the flat ice is obtained by the stress propagation law of the flat ice.At the same time,Fourier analysis of the ice load on the hull in three directions can be used as a reference for ice-induced vibration and hull design.The finite element numerical method can accurately simulate the failure mode of the flat ice and realize the navigation performance prediction of the icebreaker under the condition of flat iceIn this paper,The empirical research on the ship's resistance component proposed by foreign scholars is carried out.At the same time,the resistance tests of two different ship types under crushed ice conditions are analyzed.The ratio of the resistance component of the crushed ice to the total resistance is analyzed,which indicates that the ship's wave can help reduce the ice resistance component.