For instance, Geldart and Clift observed that the bubble size distribution in 2D fluidized beds could not be directly applied to 3D beds due to differences in bubble coalescence and the presence of wall effects. More recently, the experimental results of Shen et al. corroborate these wall effects. In a different study, Briongos andGuardiola proposed a new method based on chaos scale-up
techniques to scale 2D hydrodynamics.