Gas-fluidization of Geldart A particles was simulated for a domain of lab-scale dimensions. Hydrodynamics of homogeneous regime and transition to bubbling were studied. In this context a detailed fine mesh simulation study is presented for the first time, using the state-of-the-art two-fluid model (TFM). The effect of particle density was investigated. The fine mesh simulations were analyzed for insights into bed transition from homogeneous to bubbling regime and the effect of interparticle forces (IPFs). Simulations reveal that transition to bubbling occurs over a velocity range rather than at a discrete velocity. We propose an index to quantify the effect of IPFs on bed expansion. During homogeneous expansion this IPF index was found to drop exponentially with velocity. It became negligible as bubbling ensued which is in line with the, literature. The simulated average bed voidage was found comparable to the corresponding Eulerian Lagrangian and experimental data.