ABSTRACT:In this paper, the effects of using ribs on the flow pattern and performance of cyclone separators are investigated using CFD techniques. The Reynolds averaged Navier-Stokes equations with Reynolds Stress Turbulence Model (RSTM) are solved by use of the finite volume method based on the SIMPLE pressure correction algorithm in the computational domain. The Eulerian-Lagrangian computational procedure is used to predict particles tracks in cyclones with different rib pitch to cyclone diameter (P/D) ratios. The velocity fluctuations are simulated using Discrete Random Walk (DRW). The results show that using ribs in cyclones leads to higher collection efficiency but higher pressure drop and the cyclone with P/D equal to 1 has the maximum collection efficiency among the ribbed cyclones and the cyclone without ribs has the least pressure drop.