Numerical simulations, based on an Eulerian approach, of a freely bubbling fluidized bed (131713) are performed where emphasis is put on the importance of the inlet boundary conditions (influence of the pressure drop of the air distributor on the state of fluidization). The numerical results are compared with local instantaneous pressure measurements and time-averaged measurements (bed height, mean particle concentration). The closure of the Eulerian model is treated as follows: the drift velocity is modelled with a binary dispersion coefficient, gas-phase (continuous phase) fluctuations are modelled with a modified two-equation k(1)-epsilon(1) model, and particle-phase (discrete phase) fluctuations are also described by a two-equation k(2)-k(12) model derived from the kinetic theory of granular flow (modified to account for the interstitial gas) and a Langevin equation. The numerical computations (of a bubbling fluidized bed) predict qualitatively the experimental values, which shows that there is a coupling between the bed and the air supply system.