| As the reduction of ice cover,people are more and more interested in shipping activities in the Arctic,which will also increase the demand for ships sailing in these waters.Compared with ordinary sea areas,the biggest difference in polar areas is the existence of ice,which is one of the factors that pose the greatest threat to the safety performance of polar offshore engineering structures.In this paper,the progress of numerical research on ice mechanics characteristics and application in offshore engineering is reviewed.It is found that the ice structure interaction process can be classified into three main research questions:1)the mechanical properties of ice;2)Contact between ice and structure;3)Ice water coupling.Correspondingly,the numerical simulation of ice structure interaction process has three basic requirements:1)simulating the failure initiation and crack propagation of materials;2)Simulate the interaction of crushed ice,structure and intact ice;3)Simulate ice water coupling.In order to meet these three basic requirements,the peridynamics method is used to study the mechanical properties of ice,ice structure contact model and ice water coupling model.As a new nonlocal method,peridynamics has been widely used in the dynamic mechanical analysis and static and dynamic crack propagation of solid materials,especially in the simulation of brittle material failure.However,there are still some shortcomings in the existing peridynamics models.Bond based peridynamics model is suitable for studying elastic brittle ice,but it is limited by Poisson’s ratio;The peridynamics model of unconventional basis is related to the constitutive model of classical continuum mechanics,but the deformation gradient needs special numerical treatment in simulating crack propagation,so human factors are introduced.The numerical algorithm of peridynamics adopts nonlocal numerical discretization,which requires high computing platform in particle search and computing cycle.It is of great significance to study the parallel algorithm suitable for peridynamics model;At present,the deformation of peridynamics bonds adopts the first-order form,which can not simulate the gradual softening of bonds;The full-scale model is adopted in the numerical model of ice,and there is no research on the scale model ice.The scale model ice corresponds to the scale ship model test in the ice pool.Therefore,the research on the numerical model of scale model ice will be more beneficial to make full use of the model test;Because peridynamics is a nonlocal theory,the choice of near-field size has a significant impact on the simulation results.At present,there is no relevant research on dimensionless analysis of near-field;There is no relevant research on ice water coupling based on peridynamics,and there is no updated Lagrangian particle hydrodynamics to simulate three-dimensional fluid problems.Aiming at the above problems,this paper establishes an improved ice scale model of peridynamics based on the research of ice numerical model,studies the efficient parallel code suitable for peridynamics algorithm based on OpenMP framework,studies the contact model suitable for peridynamics,proposes a nonlocal contact model,and finally studies the ice water coupling algorithm,as follows:In Chapter 2,the theory of peridynamics is introduced from the two aspects of peridynamics motion equation and constitutive model.The nonlocal theory is compared with the local theory in the traditional mechanical model.The deformation,force density,strain energy density and Lagrangian motion equation are discussed,and the bond based peridynamics is deduced,The relationship between the peridynamics of conventional state basis and the peridynamics of unconventional state basis.In order to improve the computational efficiency,Chapter 2 studies the high-performance parallel algorithm based on OpenMP framework,develops the FORTRAN language peridynamics parallel algorithm based on OpenMP,and quantitatively analyzes the performance of the current parallel algorithm from two aspects of relative speedup and parallel efficiency.In Chapter 3,the second-order measurement of bond deformation is introduced to improve the peridynamics theory.Based on this,the ice scale numerical model is studied,and the ability of the improved peridynamics model to simulate cracks and ice mechanics problems are systematically studied.In order to study the ability of the current model in simulating crack formation and propagation,the problems of mode Ⅰ,mode Ⅱ and mode Ⅲ crack propagation are studied in Chapter 4.Then,the classical three-point bending failure characteristics in ice mechanics are studied.Then,the mechanical characteristics of scaled model ice are studied,and the influence of nonlocal parameters of peridynamics on the simulation results is studied.At the same time,in Chapter 4,the numerical stability and convergence of different scale factors are studied,the influence of nonlocal parameters on the calculation results is analyzed by dimensionless method,and the M convergence of scale model ice under different scale factors is studied δ Convergence and bending strength,analysis of relative near-field radius δ/Analysis of the influence of L on bending strength.In Chapter 5,the contact model used in the peridynamics model is given,and a nonlocal contact model is proposed to analyze the influence of different parameters on the contact results,and the influence of local and nonlocal contact on the collision results is compared and analyzed.The effectiveness of the current contact algorithm is verified by numerical simulation of Taylor rod impact test,the radial expansion profile of the impact end of the rod is compared and analyzed,and the reasons for the differences between the existing models and other results are analyzed.In the analysis of crack propagation characteristics of ice plate impacted by a small ball with elastic support,the effects of loading rate on the characteristics,number and initiation of circumferential and radial cracks are studied.Finally,in Chapter 6,an ice water coupling model coupled with updated Lagrangian fluid particle method and peridynamics method is studied.On the basis of previous work,a threedimensional updated Lagrangian particle hydrodynamics model for solving Navier Stokes equation based on three-dimensional nonlocal gradient operator and divergence operator is derived based on unconventional basis peridynamics.A coupling model of peridynamics and updated Lagrangian particle hydrodynamics is proposed to simulate the water entry of wedge and three-dimensional rigid cylinder,compare it with the existing data in the literature,discuss and analyze the failure form of ice and the pressure on the fluid,and verify the effectiveness of the coupling method.Near field dynamics is used to simulate the breaking and fracture of ice plate under impact load,ice water coupling and other complex behaviors. |
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