A particle-based meshless method, the moving particle semi-implicit (MPS) method, is employed in this study to simulate the process of liquid film breakup and atomization in a rotary atomizer. The computational framework incorporates a specially designed inlet flow model, a centrifugal force calculation, and a surface tension model to allow the simulation of the unsteady flow with extreme deformations. To improve efficiency, the searching algorithm of the MPS method is modified by eliminating redundant calculations. The computational framework is further utilized to systematically study the transition of the liquid from the bulk phase to a film, then to multiple belts, and finally to numerous droplets under the low pressure and flow rate conditions in the rotary atomization. Key mass transfer mechanisms underlying the atomization process are elucidated by a comprehensive analysis of the flow trajectories. The computational work is expected to improve the fundamental understanding of the rotary atomization process and facilitate future process optimization efforts. (C) 2016 Elsevier Ltd. All rights reserved.