Lattice-Boltzman Simulation Of Non-uniform Flow Structures And Interactions In Fluid-particle Sedimentations

Particle clustering is an important characteristic of dense–solid flow. Particle cluster is common in many industrial processes, such as drug manufacturing, coal combustion etc. Research on particle cluster has a very significant academic and engineering value.In recent years, some scholars have simulated the cluster process of dense gas-particle flow. And conclusions of judging criteria, factors, accumulation of particles size prediction are got. But due to cluster formation mechanism is very complicated, affected by many factors,the study does not take into account all information. Overall, the study on the effect of particle properties on particle is not enough. So this article is mainly considering the effects of particle properties. Particle properties refer to the particle size, surface viscous and elastic coefficient of restitution. There is another properties-density ratio, always ignored by people. Therefore, this article will consider the influence of density ratio and analyses the velocity, drag force and structure factor parameters etc.Lattice-Boltzman Method(LBM) is based on lattice gas automata, kinetic theory and statistical physics theory. Considering the time and cost of calculation, based on Lattice-Boltzman method, this article will construct a three dimensional settlement system with density ratio from 2 to 4, and 1000, 1250. Archimedes numbers is 71.03 and 1432 at volume fractions of as high as 0.4. In this way, the simulation of this article will cover fluid-particle and gas-particle flow.Research shows that in low density ratio, particles distribute uniformly over the entire domain under different volume fractions, and there is no obvious non-uniform structure. But under high density ratio, there is dense part and dilute part within the entire field, and with the increase of solid volume fraction, this non-uniform phenomenon is more apparent. With the volume fraction of particles increasing, dimensionless drag force and drag coefficient also increase. Under high density ratio, dimensionless drag force and drag coefficient is bigger than what under low density ratio values. In dense structures, dimensionless drag force and drag coefficient is larger than the time-averaged value with different density ratio.When the volume fraction of particles is low, the dimensionless drag and the drag coefficient in dense structure is almost same no matter what the density ratio is. So a conclusion can be given that when the volume fraction of particles is low, non-uniform structure can be ignored. On the contrary, when the value is high, non-uniform structure and density ratio should be considered.Under conditions of Archimede=1432,density ratio=1000, the dimensionless drag force and drag coefficient of non-uniform structure increase with volume fraction increasing. Meanwhile, drag force and drag coefficient of particles at the interface of dense and dilute zone is determined by particles’ state.