Two-dimensional single-, two- and three-phase channel flows are investigated experimentally and numerically at the Reynolds numbers 1500, 6500 and 13,000. Local velocities of the continuous liquid and velocities and sizes of the dispersed gaseous and solid phases are measured separately with a phase-Doppler anemometer. Volume concentrations of the dispersed phases were 0.66% for gas bubbles and 0.054% for solid particles. Numerical simulations of the flow were performed with an Euler-Lagrangian model. The model included the relevant physical effects, namely phase interaction, particle dispersion by turbulence, lift forces on the particles, and particle-wall collisions. Comparisons between the measured and calculated data yield good agreement for the liquid and bubble velocity profiles and the bubble size and solid phase distributions. The turbulence levels in the liquid flow from measurement and computation agree well. Bubbles reduce the turbulence level slightly. With increasing Reynolds number the influence of bubbles on the liquid velocity decreases, while the influence of turbulence on the particle motion increases. (C) 2003 Elsevier Science Ltd. All rights reserved.