The present paper describes an experimental and numerical study conducted to investigate the particle movement inside an unbaffled rotary drum under different operating conditions and using particles of different shapes. The Discrete Element Method (DEM) was used in order to describe the granular flow pattern properly, along with the clumping method which enables the creation of particles of different shapes. A calibration and subsequent verification of the DEM calibrated model were performed. Experimental particle velocity distributions were determined by means of a high-speed video camera in order to validate the model in a scaled-up rotary drum. The drum length effect on the particle dynamics was also analyzed. It was observed that, besides the model parameter values, the particle shape plays an important role in particle motion and DEM granular flow prediction. The drum geometry also exhibited a major and nontrivial influence on particle dynamics since the greater the distance between front and back wall, the lower the dynamic angle of repose and the lower the particle velocity values in the active region. (C) 2016 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.