The present paper is based on CFD modelling of gas-solid flow in cyclone separators with different dust outlet geometries (with and without down-comer tubes at the cyclone bottom) to analyse the flow characteristics and the cyclone performance. Numerically obtained cyclone performance parameters, collection efficiency, and pressure drop were compared with experimental results. Changes in the particle trajectories due to the variation of the flow field inside the cyclone separators with the effect of the dust outlet section were also analysed in detail. The simulation results largely agreed with the experimental results, and discrepancies were caused by modelling limitations and inconsistencies of the particle tracking model with the real gas-solid flow. However, comparable to the experiments, the CFD simulations also predicted the increments in collection efficiencies by dust outlet geometries modified with down-corners within acceptable pressure drops. (C) 2015 Elsevier B.V. All rights reserved.