Research On Surface-Surface SPH Contact Algorithm Based On Reconstructed Surface

Smoothed particle fluid dynamics(SPH)is a meshless method with Lagrangian properties.Compared with the numerical method based on grid,there is no mesh distortion and distortion when dealing with large deformation and material breakage problems,so it has been widely used in various engineering fields in recent years.However,the traditional SPH method has some shortcomings,such as tensile instability,boundary defects and difficult to apply boundary conditions.These problems lead to lower calculation accuracy,efficiency and stability of SPH method compared with grid method.Therefore,it is of great significance to put forward a reasonable improvement method to solve the current defects of SPH method for further expanding the application range of SPH.The implementation process of SPH method is to solve various problems through interpolation calculation of a group of discrete particles with material properties such as density,velocity and energy.The lack of connection between particles makes it difficult for SPH method to deal with contact correctly.At present,particle-particle contact algorithm is often used to deal with contact in SPH simulation.However,this contact algorithm needs to estimate the size and normal vector of boundary particles,which may seriously affect the accuracy and stability of the calculation.In this paper,some improvements are made to the previous contact algorithms.A new surface-surface SPH contact algorithm based on penalty function method is proposed,and the numerical simulation of high-speed impact and friction problems is carried out by using this algorithm.After verifying the accuracy and stability of the algorithm,the algorithm is further applied to the interaction between fluid and solid.The specific work carried out and completed in this paper is as follows:First,a face-surface SPH contact algorithm based on reconstructed surface is proposed.The basic idea of the algorithm is as follows: in the calculation process,α-shape method is used to dynamically reconstruct the surface of the object represented by discrete particles;According to the reconstructed object surface,the contact detection is realized by using the search strategy of box test and crossed test.Contact conditions are applied to the detected contact pairs by penalty function method.The proposed contact algorithm is applied to a series of solid mechanics problems.The influence of parameters on the accuracy of the contact algorithm is analyzed and compared with the results of the particle-particle contact algorithm.Numerical results show that the proposed contact algorithm has good precision in friction-free and frictional problems,and can handle high speed collisions involving great deformation and material breakage.The performance of the proposed contact algorithm is better than that of the particle-particle contact algorithm.Second,simulation of fluid-structure coupling problem based on surface-surface contact algorithm.In the simulation,the interaction between the fluid and the solid is treated by the reconstructed surface.In order to normalize the distribution of particles,the particle shift technique and XSPH method are introduced,and the influence of the parameters of the two methods on the algorithm is explored.Three typical examples of water column collapse,water column collapse against rigid obstacle and elastic obstacle involving violent free surface flow and interaction between fluid and solid are simulated.The results show that the proposed contact algorithm can naturally simulate the motion of water column under the action of gravity,and the surface of the fluid can be reconstructed accurately when it collides with obstacles and flies away.When simulating the impact of water column collapse on the elastic plate obstacle,the displacement of the elastic plate with time is analyzed.The obtained results are consistent with the experimental results,which verifies that the algorithm proposed in this paper has good stability and accuracy in dealing with the fluid-structure interaction problem.Third,the 2D face-surface contact algorithm is extended to 3D,the realization process of3 D face-surface contact algorithm is studied,and its application in practical engineering is expanded.Two examples are given to verify the accuracy and effectiveness of the proposed algorithm.The calculation results show that this contact algorithm has high accuracy and can deal with various contact problems,including frictionless and frictional problems,small deformation and large deformation problems.