Research Of Fluid-structure Interaction And Impact Failure Problems Using Moving Particle Semi-implicite Method With Large Eddy Simulation

Fluid-structure interaction problems exist in many engineering fields,it is necessary to analysis fluid-structure interaction on the problems such as dam breaks,tank sloshing,and water impacting.The existing fluid-structure interaction analysis methods are mostly based on grid information.When dealing with the problems of large deformation of free surface,the large deformation of the elastic structure and the failure of the structure,the serious distortion of the grid element will occur,and the precision of calculation will be reduced or even unable to converge.The MPS Method is a new kind of Lagrange particle method.This method is not constrained by the grid and uses particles to express the solution domain.It will not meet the problem of excessive deformation of the grid,so it is very suitable for solving the large deformation problem in the fluid-structure interaction calculation.During the period of the early development of the MPS method,the research fields ware mainly on fluid mechanic instead of research on fluid-structure interaction simulation.Nowadays,Considering the advantages of the MPS method in the computation of fluid solid interaction problems,This method has gradually attracted wide attention from the scientific community.The MPS method has been used to do preliminary research on the computational fluid-structure interaction problems.The free surface of the liquid is usually turbulent flow.So large eddy simulation(LES)is a very important numerical method for studying turbulent problems.Because there is no grid in the Particle method,according to the subgrid stress model of the grid method,in this paper the filtered equation is discrete by particle method.On the basis of continuity of the moving particles semi-implicit method(MPS)kernel function,uniform MPS particles are used to separate the macroscopic fluid and the solid in a certain form.Also,because the discrete methods of the fluid and the solid are the same,the coordination problems in fluid-structure interaction are solved correctly.Based on the characteristics of the MPS method,a new fluid solid coupling calculation process is adopted.This method identifies fluids and solid particles by means of separate assignments.It is not necessary to deal with the interfaces,so it can simplify the calculation steps.A new pressure mitigation method was proposed to reduction pressure oscillation in the fluid-structure interaction problems of the MPS algorithm.The divergence free condition was added to the Poisson equation to relieve the oscillation of pressure,and then the area-time average is carried out after the calculation is completed.The method can reduce this phenomenon.Due to the Lagrange nature of MPS particles,fluid particles may cross solids when calculating fluid-structure interaction problems.It may affect the whole simulation when particle traversal occurs.The collision and crossing phenomenon between particles in the simulation of MPS method is discussed,and an artificial additional correction step is used to eliminate the phenomenon of the particle crossing the boundary.Dam break models are chosen for validation of most meshless methods.The dam break problem is a typical example.The model is relatively simple and has some universality and representativeness.It is very suitable for the feasibility of meshless algorithm validation.This paper combined the MPS method and large eddy simulation to simulate the most typical dam-break fluid-structure interaction problems.By setting the elastic baffle to simulate the most typical dam break fluid solid coupling problem,the convergence of the numerical results obtained by the MPS method are verified.Compared with thI calculation results of ideal fluid and viscous laminar flow,it is more accurate by using LES.The fluid-structure interaction problems of the large deformation of the elastic baffle under the liquid sloshing have been an extremely important issue in naval architecture and ocean engineering.It is a very effective method for reducing the sloshing to install the elastic damping baffle.We know that the phenomenon of elastic structure deforms only occurs under the impact of water flow in the dam-break problems,but when it comes to the problems of sloshing,we will know that the liquid tank and the elastic baffle plate are forced to slosh due to the harmonic rolling motion,and the fluid-structure interaction boundary will change over time.Comparing with the fixed elastic baffle in the dam-break problems,the problems of tank sloshing at the coupling plane is more complicated.This paper used the MPS-LES-FSI method to analyze the fluid-structure interaction of tank sloshing.The results show that the baffle can damp the liquid,and it can reduce the impact the pressure of liquid on the bulkhead.When a ship is sailing in storms and waves,the hull will emerge a large slamming load with the wave surface.The water entry of ship slamming is a very complicated transient process,which is caused by the non-continuous,the nonlinear phenomena on the free surface such as splashing in the water entering process.Moreover,the slamming of water entry involves some difficult problems,such as large deformation,high strain and even failure.It is difficult for traditional numerical methods to calculate the fluid solid coupling problem of slamming into water.In this paper,using the advantage of MPS method without grid constraints,The failure process is simulated by the MPS method of elastic structure under water flow impact problem of fluid solid coupling and structure.The calculation results of water entry slamming under different parameters are comprehensively analyzed.In this paper,some internal ribs are set in the box structure to reduce the structural deformation and improve the safety of the plate.It can be seen from the calculation results that the rib has no significant effect on the impact pressure of water,but it can obviously reduce the structural deformation.In this paper,the fluid and the solid discretized on the basis of the MPS method,And then,a new MPS-LES-FSI meshless algorithm was proposed by combining the large eddy simulation with the MPS method.Through a large number of numerical simulations,it is proved that this method has strong generality and stability for the large deformation problem of fluid-structure interaction.Therefore,this method can be used as a new technical means for analyzing large deformation problems with fluid-structure interaction.