The separation performance of the hydrocyclone is affected by its flow field characteristic, based on this reason, the study of flow field is very important. But because of various restrictive conditions, application of the experiment method to detect the flow field of all hydrocyclones is not possible, 3D computational fluid dynamics algorithms is an efficient method, the flow field and the turbulent flow characteristics are predicted here by a Reynolds stress model and SIMPLEC calculation method, the results give some new understanding on three-dimensional velocity distribution. Furthermore, the calculation results indicated that the main separation area existed asymmetry and unsteady flow field which was produced by inlet velocity and inlet arrangement structure, as well as the cone angle of hydrocyclones. Besides, the simulation results showed that the pressure gradient was existed within air core from the underflow orifice to vortex finder, this is a reason of the gas flow inside air core. Depending on the aforementioned flow field characteristics, the factors of forming high concentration area were analyzed. Those above provided the evidence for new understanding of a hydrocycloe flow field and separation mechanism.
