Study On Numerical Analysis Method Of Solid To Solid Collision Coupling With Fluid

Many engineering structures are affected by the environment fluid,which can produce large unsteady force,so that the safety of the structure has a great hidden danger.In particular,the collision between solids in the fluid will cause more complex damage to the structure and directly threaten the safe operation of the structure.The collision between solids in fluid involves the problems of fluid dynamics and nonlinear collision in solid mechanics,which makes the contradiction between solution scale and efficiency more prominent and difficult to be applied in engineering.Therefore,study on numerical analysis method of solid to solid collision coupling with fluid not only has strong academic value,but also has obvious engineering application prospect.This dissertation aims to establish an effective numerical analysis method to describe the collision between solids coupling with fluid,which can provide theoretical support and technical means for safety operation evaluation and optimization design of such engineering structures.Based on the finite volume method,the wall function method and SST-DES turbulence model were introduced to establish an improved sharp interface immersed boundary method suitable for turbulence dynamics numerical analysis.The improved immersed boundary method reduces the requirement of mesh resolution for high Reynolds number turbulent boundary layer and improves the computational efficiency of turbulent flow numerical simulation.The turbulence variable can be adjusted automatically according to the flow state of the near-wall node so it has high robustness.Numerical simulation of turbulent flow on stationary and dynamic boundary shows that the results are consistent with the experimental data and the numerical results of boundary-fitting method,which indicates that the improved immersed boundary method is accurate and reliable for the numerical simulation of turbulent flow.In fluid-solid coupling numerical simulation,the improved immersed boundary method is used to simulate the fluid dynamic boundary,which avoids the problem of heavy computation when the grid is reconstructed repeatedly in fluid domain.The structural dynamics is solved by finite element method.According to displacement and velocity coordination conditions and load balance conditions on the coupling interface,the transfer formulas of fluid-solid coupling interface displacement,velocity and load information arederived.The convergence criterion of coupling interface physical quantity is put forward,the iterative calculation flow in partitioned coupling solution is given,and the numerical method of fully coupled approach in partitioned coupling is established.The numerical simulation of the single cylinder vortex-induced vibration with low Reynolds number is carried out,and the results are consistent with the variation trend of the maximum displacement of the cylinder with the reduced velocity obtained by the boundary-fitting method and the immersed boundary method.Then the validity of the proposed method is verified.By numerical simulation of free sedimentation movement of a single spherical particle,the maximum error between the ultimate sedimentation velocity and the Reynolds number and the experimental data is 2.68%,which verifies that the proposed method is also applicable to fluid-solid coupling analysis under high Reynolds number.In the fluid domain,when an solid collides with another solid(wall),the fluid grid resolution between the immersed boundaries is lacking due to the existence of multiple immersed boundaries.For this reason,this dissertation establishes a lubrication model with high Reynolds number for two cylinders with no background velocity and with background velocity by means of data regression method,which is used to modify the force of fluid acting on solid boundary.The finite element method of penalty function is used to solve the structural collision.Finally,numerical analysis method of solid to solid collision coupling with fluid is established.The numerical simulation of the normal collision and oblique collision between spherical particles and wall surface is carried out,and the results are consistent with the trend of experimental data.It is shown that the proposed method is fully applicable to the numerical simulation of the collision between movement and stationary solids in a fluid.By simulating the collision between two cylindrical particles,the DKT phenomenon is obtained.It is shown that the proposed method is also applicable to numerical simulation of collision between moving solids.Through the numerical analysis method of solid to solid collision coupling with fluid,the vortex-induced collisions of two side-by-side cylinders are are studied.The change rules and mechanisms of fluid force,velocity and flow field are obtained.The free settlement and impact of falling objects on submarine pipelines are simulated.The effects of current velocity on falling object velocity,angle and pipe sag are obtained.The law of flow-induced vibration of riser with small gap ratio is analyzed.The changing rules of collision velocity,collision force and collision stress are obtained,which can be used for safety evaluation and optimization design of such engineering structures.The method established in this dissertation can also be applied to the erosion of fracturing fluid containing sand on pipelines,the impact of solid particles on turbine blades in fluid machinery and other engineering problems,which has a broad application prospect.