Study On The Coupled Model Of Ship-ice-water Interaction And The Prediction Method Of Ice Resistance

Ice resistance performance is the basis of the study for polar ships.It is also the important criterion for calculating main motor power and optimizing ship hull form.Ice resistance performance directly affects the icebreaking capacity and icebreaking speed.At present,the main research method for ice resistance is to simulate ship-ice interaction process by numerical methods from a macroscopic angle.And the fluid portion is simplified as Winkler elastic foundation which leads to the low calculation accuracy.In order to simulation the real-time icebreaking process and predict ice resistance performance,in the form of programming,smoothed particle hydrodynamics method has been used to simulate icebreaking process.Smoothed particle hydrodynamics method is a Lagrangian mesh-free algorithm which is not constrained by the grid.The physical quantities of each material point can be effectively displayed and tracked.At the same time,it is easy to embed many kinds of material models.There are obvious advantages in solving the multi-media coupling problem.However,icebreaking is a sophyscated problem which contains the problem of lower impact velocity,the problem of small deformation,the problem of fracture and the problem of multi-media coupling.To use SPH to solve the icebreaking problem,there must be a corresponding improvement.Therefore,the basic theory of traditional SPH method,some related numerical methods and correction methods have been studied deeply.On the basis of that,corrected SPH method has been used to solve the problem of cantilever motion under the harmonic external excitation and the problem of 3-point bending.The research results verify the effectiveness of the method in solving small deformation problem.At the same time,the shortcomings of the method in dealing with the problem of low-speed fracture are clarified.Then,according to the microscopic fracture mechanism of elastic brittle ice material,a complete set of methods is established which is suitable for SPH to solve low-impact speed fracture problem.The treatment method of fracture surface is presented.Based on this,the interaction between particles is redefined.And the stress damage model is proposed.And the expression of the contact force which is produced by collision is also proposed.At the end,by comparing with the ice bending experiment results,the fracture model and contact force model can be verified.By combining the fracture model,SPH method and CSPM method,the mechanism of icebreaking is studied.The treatment of fluid boundary has two forms,which is the elastic foundation based the Ventilation phenomenon and the fluid-structure interaction condition.Under each boundary condition,the breaking ice resistance and submersion resistance can be predicted separately.Through the comparison with the analytical solution and experimental results,the effectivemess of the method to solve ice fragmentation in this paper can be verified.Finally,based on improved CSPM method,the preliminary studies on the icebreaking problem for polar ships are carried out.A method of hull boundary recognition and mirror particles generation is proposed.Based on improved CSPM method,the 3D calculation model for ship hydrodynamic,the 3D calculation model for ship-ice interaction and the 3D calculation model for ship-ice-water interaction have been built.Under the coupling interaction of ice-water-ship,the ice sheet damage form and fluid velocity distribution will be predicted.Then,the characteristics of ice resistance and water resistance are compared.Finally,a complete ice resistance prediction analysis method based on improved CSPM method is established.The numerical results show that the improved CSPM method can not only simulate icebreaking process realistically,but also deal with the fluid-structure interaction problem and can predict ice resistance effectively.