A systematic study upon the Eulerian approach capability in predicting irregular particle (non-spherical) dynamics inside an unbaffled rotary drum was carried out through the investigation of different particle-particle interaction models and wall boundary conditions. The drum length effect on particle dynamics was also analyzed. The frictional viscosity, the wall movement method, and the particle boundary condition at the wall were shown to be of fundamental importance for irregular particles modelling in rotary drums. The moving mesh method did not represent well the experimental observation, regardless of the solid boundary condition used at the drum wall. The moving wall method combined with a no-slip boundary condition for the solid phase at the drum wall, and the frictional viscosity model using a critical particle concentration (alpha sc) of 0.4, satisfactory agreed with experiments. For the end-caps analyses, the higher the ratio L/ds, the lower the bed material surface slope and the lower the particle velocity values in the active region. From L/ds of 40.7 no differences were observed in particle dynamics behavior anymore. (C) 2018 Elsevier B.V. All rights reserved.