A detailed study of the internal flow field for the separation column in a circumfluent cyclone separator has been of great significance in understanding its separation mechanism and thus improving its efficiency. The turbulent flow viscidity theory and average velocity field were used, based upon the Reynolds and continuity equations for the column geometry and coordinate system. An approximate analysis of the velocity and pressure distribution of the flow field inside the separating column was carried out for which basic equations for three-dimensional velocity, pressure gradient and distribution of static pressure were given. Results obtained from experiments and prediction for tangential velocity and static pressure distribution are in very good agreement according to a specific set of experiments. More specifically, the tangential velocity of the inside separation column is characterized by its centrally symmetric distribution pattern, and the axial velocity is in basically axial symmetric distribution with the exception of the outlet vicinity. The value near the axial center reaches its maximum, which decreases gradually along the radial direction, and the value near the wall approaches zero. The value for static pressure near the axial center is the lowest one. When the length of the radius increases, the intensity of the pressure will also increase. Predictions showed that the axial line of the vortex core fishtails along the geometrical axial center when the gas in the separation column rotates at a high speed and results in an unstable flow field which reduces the separation efficiency. (C) 2012 Elsevier B.V. All rights reserved.