This study reports on the development of a complete solution methodology for the simulation of a hydrocyclone. A commercial software package, Ansys 12 Fluid Dynamics, is used to solve the governing conservation equations. Turbulence is modelled using the large eddy simulation, and the discrete particle model was used to predict the particle separation. Two hydrocyclones of differing geometries are explored, and the results compared with experimental values. It is shown that there are two key factors for obtaining a reliable result. The first is the domain discretisation, and the second is the generation of a consistent initial value, including the establishment of a stable air core. Using the methodology developed, superior agreement was obtained for predicted and experimental values of pressure, velocity distribution, air core profile and separation efficiency. (c) 2012 Canadian Society for Chemical Engineering