Numerical Simulation Of Particle Settlement In Viscoelastic Fluid With Lattice Boltzmann Method

The sedimentation of particles in viscoelastic fluid is a relatively common two-phase flow problem in actual industrial,such as:high polymer molding processes.During the process of simulating such two-phase flow,the traditional CFD method still has problems when dealing with complex boundary problems,while the lattice Boltzmann method(LBM)can easily deal with this problem,and its program is simple and its parallelism is good,providing new solutions and ideas.This paper uses LBM to study the flow of viscoelastic fluid around column and the settlement of particles in the flow channel of viscoelastic fluid.Specific research contents are as follows:First,the effects of particle relative mass M and initial position Y,Reynolds number Re and Weissenberg number Wi on particle sedimentation in the viscoelastic fluid channel are analyzed based on the point source particle LBE method.The results show that the falling point of particle sedimentation is getting farther and farther with the decrease of M and the increase of Re and Y,while Wi does not affect the particle sedimentation.In addition,due to the existence of vortices in the shrinkage tube,the particle trajectory will decline first,then rise and then fall.Then,in the two-dimensional flow problem of viscoelastic fluids around column,the Oldroyd-B viscoelastic fluid is solved by coupling of double distribution function,and the particle boundary is treated by the smooth profile method(SPM)to verify the possibility of SPM in the flow around a cylinder.The method is extended to the flow around an elliptical cylinder,and the influence of the geometric size of an elliptical cylinder a on the flow is discussed.Finally,the flow around the double cylinder is analyzed,and the influence of the spacing S and the shape of the cylinder on the flow are discussed.The results show that the simulation results of the method are good agreement with the previous ones in the flow around the cylinder when 0.1?Wi?1.2.Finally,the particle boundary is treated with SPM,and the effect of the above parameters on the settlement of particles in the viscoelastic fluid flow channel is analyzed based on the LBE method with a finite volume of particles,which compared with the consequences of the method of point source.At last,motion of particle and flow conditions in the flow field which compared with the results of flow around a single cylinder are analyzed.The results show that the effects of the above four parameters on particle sedimentation are basically the same,which compared with the method of point source.In addition,the rotation of particles will affect the flow field distribution on the left and right sides of the particles.