Numerical Simulation Study Of Particle Sedimentation And Flow Based On IBM-LBM

Liquid-solid two-phase flow is an important part of multiphase flow,which is widely used in industrial production,medical and health,monitoring and prevention of natural disasters and so on.Because the liquid-solid two-phase flow involves complex fluid-solid interaction,it is difficult to obtain the particle characteristics and the microstructure of the fluid through experiments,meanwhile the numerical simulation method plays an alternative role because of its unique advantages.The Lattice Boltzmann Method is widely used in multiphase flow research due to its clear particle motion image and its good parallelism,which makes the processing of fluid-structure coupling very intuitive.This paper studied the sedimentation and flow of particles using IBM-LBM.Firstly,the paper calculated and analyzed the sedimentations of single particle and two particles in compressible fluid and incompressible fluid based on the LBGK model for compressible fluid and D2G9 model for incompressible fluid,and compared the simulated differences of various boundary conditions and particle-particle collision models.Then we examined the settlement characteristics of three particles in incompressible fluid when being initially distributed in "inverted triangle" and "positive triangle".It is found that the variation range of horizontal fluid force of single particle in incompressible fluid is smaller than that in compressible fluid.The DKT phenomenon appear both in incompressible fluid and in compressible fluid,but in incompressible fluids,the kissing phase takes less time.The phenomenon of crossing the interval between particles will occur when the density,particle size and spacing of the three particles change.Secondly,the paper simulated the sedimentation of particles in compressible fluid and incompressible fluid.We explored the motion characteristics of particle cluster and the change laws of velocity field and pressure field of the fluid respectively at different initial distance of particles,overall density,arrangement mode,and density distribution in a closed square cavity filled with incompressible fluid.Then,this paper investigated the particles in the lid driven flow,and attained the motion characteristics of the particles under different Re,initial particle spacing,density distribution and particle size distribution,as well as the pressure variation and streamline distribution of the fluid.Finally,this paper analyzed the motions of particle cluster in vertical channels with or without obstacles at different Re.It is found that the dispersion degree of particles in the channel increases at first and then decreases with the increment of Re during the motion.If there are obstacles in the channel,the smaller the porosity,the lower the transport efficiency of particles and the longer the retention time in the channel.When the porosity is constant,the larger the Re,the lower the retention rate of particles and the larger the range of horizontal movement.