The gas-solid flows in two-dimensional downer were simulated by using a CFD-DEM method.The simulation results showed the typical flow structures in the dower.Along the flow direction

there existed the entrance region

the transition region

and the (fully) developed region

in which the clusters started to form in the transition region instead of the entrance region with a denser particle concentration.With the flow development

the clusters grew in size and increased in number.Particles inside each cluster were loosely collected

flowing in the same direction as the bulk flow.The lateral distribution of solids fraction in the fully developed region was non-uniform

with a denser ring near the wall.These results agreed well with the experimental results reported in the literature.The influence of the physical properties of the wall and particles on the global solids flow structure was investigated.The ideally elastic particles with no friction during collisions dispersed very rapidly and uniformly at the entrance.The influence of the collision parameters between particles on the lateral flow structure was not obvious in this work.