This modelling tool can be extremely useful to improve the understanding of milling processes where either the experimental limitations or the complexity of the system hinders the ability to get valuable insights. In the last decades, the number of publications using DEM simulations to address granular engineering problems, such as granular flow [13], powder mixing [14; 15; 16], powder mechanics [17] and milling [18; 19; 20; 21; 22; 23], has vastly increased. Although the DEM approach to milling still has limitations due to the computational costs of modelling the small particle size of the feed material, the simulations have been useful to drive the mill optimisation as function of operating conditions, to predict the effect of the mill design on the media motion and to support the transition from the lab scale to the industrial scale [24; 25; 26; 27; 28; 29]. The validation of the DEM model is a necessary step to use the simulations not only as a cost- and time-saving tool for the design of experiments, but also to the quantity of the grinding media motion and its energetics. In this context, PEPT measurements can be used to generate experimental data for the validation of the numerical simulations. [PERSON] et al. (2011) validated the results of a CFD-DEM model of the Isa mill against PEPT measurements [30]. The work showed a reasonably good agreement between the two techniques and it also highlighted some discrepancies which were attributed to the differences between the experimental set-up and the DEM model such as the lower sampling rate of PEPT compared to the simulations. A very interesting study has been conducted by [PERSON] et al. (2013) [6], where the authors validated the predictions of a dry DEM model by statistical comparison with the PEPT measurements carried out in a wet tumbling mill. This work demonstrated the effectiveness of an adjusted-friction DEM model to accurately reproduce the motion of the solid charge, without the explicit representation of either the powder particles or the fluid phase. In the current work, PEPT experiments and DEM simulations are combined to improve the understanding of dry milling. PEPT experiments are used to investigate the motion of the grinding media inside a laboratory-scale vertical stirred mill (Union Process HD01) as a function of the impeller rotational speed, impeller clearance and bead fill level. As the ultimate aim is to match the experimental results to DEM simulations, the experiments were conducted by using only the grinding media ignoring the effect of the powder on the media motion. Consequently, in the absence of powder the set of data generated by PEPT can be directly compared to the results of the DEM simulations. In fine and ultra-fine grinding the characteristic particle size of a powder is too fine to be modelled by DEM simulations in a reasonable computational time [3; 22; 26]. However, the effect of the powder on the grinding media motion can be taken into account without modelling the particles. According to several studies, good model predictions can be obtained either by adjusting the DEM input parameters (friction and rolling coefficients, coefficient of restitution) or by scaling-up the size of the powder particles [25; 31; 32; 33; 34]. To validate the DEM simulations, for a chosen set of experimental conditions the grinding media static friction coefficient used in the DEM model is adjusted to match the velocity distribution generated by PEPT. Once the optimal static friction coefficient is determined, the velocity fields generated by DEM simulations and PEPT measurements are compared both qualitatively and quantitatively. The resulting validated model will be utilised in future work to link the milling conditions of dry milling to the final material properties.