Three-dimensional simulation of a multiphase flow is performed using the EulerianEulerian finite volume method in order to evaluate the separation efficiency and velocity field of deoiling hydrocyclones.The solution is developed using a mass conservation-based algorithm(MCBA) with collocated grid arrangement.The mixture approach of the Reynolds stress model is also employed in order to capture features of turbulent multiphase swirling flow.The velocity field and separation efficiency of two different configurations of deoiling hydrocyclones are compared with available experimental data.The comparison shows that the separation efficiency can be predicted with high accuracy using computational fluid dynamics.The velocity fields are also in good agreement with available experimental velocity measurements.Special attention is drawn to swirl intensity in deoiling hydrocyclones and it is shown that the differences in velocity and volume fraction fields of different configurations are related to swirl distribution. Three-dimensional simulation of a multiphase flow is performed using the Eulerian Eulerrian finite volume method in order to evaluate the separation efficiency and velocity field of deoiling hydrocyclones. The solution is developed using a mass conservation-based algorithm (MCBA) with collocated grid arrangement. mixture approach of the Reynolds stress model is also employed in order to capture features of turbulent multiphase swirling flow. velocity field and separation efficiency of two different configurations of deoiling hydrocyclones are compared with available experimental data. the comparison shows that the separation efficiency can be predicted with high accuracy using computational fluid dynamics. Velocity fields are also in good agreement with available experimental velocity measurements. Special attention drawn to swirl intensity in deoiling hydrocyclones and it is shown that the differences in velocity and volume fraction fields of different configurations are related to swirl distribution.