Simulation Of Movement Of Suspended Particles With Thermal Convection Using The Lattice Boltzmann Method

The motion of the suspended particles is a typical issue of the solid-fluid two-phaseflow,and it appears in many nature and industrial process,for example,the deposit ofsediment in river and the increasingly serious sandstorms in nature, the treatment of solidimpurities in the wastewater, the motion of coal particles in fluidize bed and the dustremoval system of flue gas etc. in industry, so it’s important to study the way how theparticles move in fluid and the role of interaction between the particle and fluid. With therapid development of computer technology, the numerical simulation methods has becomean important means in studying the motion of the suspended particles, while the traditionalcomputational fluid dynamics methods have the defects of computationally intensive andthe complex boundary treatment;however, the commonly used PIV(particle imagevelocimetry) and PDA(particle dynamics analyzer) in experimental methods aresignificantly limited because they cannot give the force between particles. As a newtechnology of computational fluid dynamics, the Lattice Boltzmann Method(LBM) hasbecome an important tool to study the solid-fluid two-phase flow because of the smallcomputation and the simple boundary treatment.The solid and fluid two-phase boundary coupling is critical when studying themotion of the suspended particles using LBM, and the different treatment lead to thedifferent accuracy and computation. Firstly, we use three different boundary treatment(thenon-equilibrium extrapolation method of the curved edge, the Ladd’s method, the immersedboundary method) to simulate the process of the sedimentation of one circular particle, thesedimentation of one elliptical particle and the sedimentation of two circular particles. Wecompared the advantages and disadvantages of the three method and the result shows thatthe Ladd’s method gives the more accurate result and has less computation. Secondly, basedon the study of sedimentation of isothermal particle, we carefully researched the motion ofone circular particle, the motion of one elliptical particle, the motion of one neutrallybuoyant particle, the motion of two particles with same temperature, and the motion of twoparticles with different temperature with thermal convection. The simulation results of onecircular particle verified the accuracy of the calculation method; the simulation results of one elliptical particle shows that the settlement trajectory of the elliptical particle aredifferent when Grashof number changes; the simulation results of the neutrally buoyantparticle shows that the final balanced position is different if we set the particle in thedifferent position of the pipe when Gr number is small while the final balanced position ifsame when Gr is big, and we computed the limit distance from the pipe wall the particlecan approach; and the simulation results of two particles shows that the dynamics of thetwo particles with the same temperature is closely related to the Re number and the Grnumber, while the process of two particles with different temperature are distinct from thattwo particles with same temperature, the cold particle will eventually descend the hotparticle, and the drafting and kissing phenomenon occurs as Re is large, while the coldparticle falls away from the hot one as Re is small.