A liquid-solid fluidization system was investigated with Computational Fluid Dynamics (CFD) by using a transient Eulerian-Eulerian model. The study focused on various drag models between the phases and how the results vary when simulating the system 2-dimensional or 3-dimensional. Also the grid dependencies to the results were investigated. The simulation results were validated experimentally using a digital imaging method. The suitability of this experimental method is also investigated in this paper. The CFD results show that the outcome from different drag models vary considerably and therefore the used model has to be chosen with care. (C) 2012 Elsevier B.V. All rights reserved.