A numerical study is conducted to analyse the flow dynamics in a blade free planetary mixer (BFPM). The flow is simulated in the revolution reference frame. The analysis is focused on the departure from solid body rotation to a more complex 3D flow structure. Numerical calculations are realised using second order finite volume discretisation. The parameters investigated are the particle trajectories, velocity contours and streamlines. The results show that the flow is generally swirling with the presence of singular points on different specific planes. The vortical structures are found to be in spiral forms and their sizes, shapes, and rotation axes are dependent on the revolution rate. In addition, the dynamics of the flow is subject to significant changes at certain revolution rates. (C) 2015 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.