Lagrangian approach is usually used in previous CFD (Computational Fluid Dynamics) studies of gas-solid system in a Cyclone separator. By using this approach the gas is treated as a continuum while the dispersed phase is solved by tracking the catalyst through the calculated flow field but it also assumes that the particles does not affect the gas flow. To overcome this advantage Discrete Element Modeling (DEM) can be incorporated in CFD simulations.

DEM is a solid flow modeling at individual particle level. By using DEM model, particles movements are captured explicitly without using assumption based in kinetic theory of dense gases. There is no need to treat particle as pseudo-fluid where stresses are calculated using empirical or constitutive equations. Therefore coupling between DEM and CFD will give more accurate results. While local averaged Navier-Stokes equations in CFD solved the flow of continuum fluid flow, DEM approach can be used to solve the motion of discrete particles by applying Newton's law of motion to every particle. Numerically, DEM will give out the positions and velocities of individual particles and CFD will use these data to calculate the gas flow field which will then generate the fluid forces acting on each particle.

Results of CFD-DEM coupling can help to generate information leading to better understanding of the internal flow structure within a cyclone separator.