CFD simulations have been carried out for the predictions of flow pattern in bubble column reactors using 1D, 2D and 3D k-epsilon models. An attempt has been made to develop a complete correspondence between the operation of a real column and the simulation. Attention has been focused on the cylindrical bubble columns because of their widespread applications in the industry. All the models showed good agreement with the experimental data for axial liquid velocity and the fractional gas hold-up profiles. However, as regards to eddy diffusivity, only the 3D model predictions agree closely with the experimental data. The CFD model has been extended for the estimation of an axial dispersion coefficient (D-L) using I D, 2D and 3D models. Excellent agreement was found only between the experimental values and the 3D predictions. The 1D and 2D simulations, however, yielded DL values, which were lower by 25-50%. For this, a mechanistic explanation has been provided. (c) 2005 Elsevier Ltd. All rights reserved.