The theoretical modelling of flow in a rotary drum is still a great challenge. In this study, the charge of solids in the flights as a function of angular position, rotational speed, number of flights, and granular material was investigated. The prediction of the flow of solids by simulation using a Euler-Euler approach was also investigated. The simulated results were compared with experimental data using granulated sugar and glass beads as material, with the rotary drum operating with 12 and 15 flights. The results showed that the Eulerian approach along with the kinetic theory of granular flow (KTGF) agreed with the experimental results obtained with the rotary drum operating in several configurations, with average deviations between numerical and experimental data being smaller than 15 %. The CFD approach allowed the development of a more generalized model compared to the empirical and geometrical equations used in the literature to predict the solids holdup.