Study On Hydrodynamic Effects On Ice-structure Interaction

The opening and utilization of the Arctic Routes is of great strategic significance to China.On one hand,the routes provide guarantee for China’s resource supplies,and on the other hand,they improve the economics of the carriage of goods by sea.In recent years,with the global warming,the melting rate of sea ice is accelerating.Ships will inevitably interact with broken ice floes when sailing in the polar regions.When ice collides with a structure,the influence of hydrodynamic force is of great importance.Therefore,in this paper,the ice and structure collision scenes are numerically studied using LS-DYNA software to reveal the mechanism of structure-ice-fluid interaction.The main results of this thesis are listed as follows:1.The research background and research significance of the ship-ice collision problem are described,and the state of art of ice research results are summarized.2.In this thesis the basic methods of LS-DYNA are described,including the principles of the nonlinear explicit finite element algorithms,ALE fluid-structure interaction method and contact collision algorithm used in the simulation of collision problems.3.The pressure-contact area curve of the material model used in this paper is compared with the specification curve proposed by the International Association Classification Societies,which verifies the reliability of the ice material.The added mass of the fluid when the rigid body moves underwater is obtained from theoretical calculation and numerical simulation respectively to verify the rationality of numerical results.Convergence analysis of the element size of the numerical test model was performed to determine the optimal ice element size and fluid element size.4.Numerical test is conducted on the collision of ice and plate.The collision process of rigid ice,elastic ice and elastoplastic ice with rigid plate and elastic plate in air,on the water surface and under water is simulated respectively.Through the comparative analysis of the relationship between momentum and impulse in the process of collision,the action mechanism of the fluid when the ice collides with the plate is obtained.The results show that hydrodynamic influences are not important for rigid body modes of the ice,but important for elastic modes of sea ice.This is useful for ice-structure modeling.5.The above normal-impact study is extended to oblique impact.The effects of collision velocity and collision angle on the structure-ice-fluid interaction process were studied by numerical simulation under each collision condition.The results show that oblique impacts share the same behaviors with normal impacts.The differences are reflected in numerical values only.