Three-dimensional CFD simulations of two-phase flow in a vertical pipe, a square cross-sectional bubble column and a large-scale plume are presented. A random dispersion model (RDM) is used to generate an instantaneous turbulent fluctuating velocity field by assuming that it is comprised of eddies, lifetimes and length-scales of which can be deduced from local mean flow properties. The RDM is used to describe turbulent dispersion of bubbles, and is validated here against the experimental data, and compared with predictions obtained by imposing an empirical turbulent dispersion force (TDF), but without introducing adjustable coefficients. The strictly mechanistic approach to bubble dispersion can offer better opportunities for the development of trustworthy, two-phase flow models. (C) 2007 Elsevier Ltd. All rights reserved.