The hydrodynamic behavior of a 3D liquid-solid fluidized bed (LSFB) operating in the intermediate stability flow regime was extensively analyzed by applying stability analysis, coupled CFD-DEM, and tomography. The particle volume fraction (PVF) profiles measured by electrical resistance tomography (ERT) as well as the bed height were employed to validate the CFD-DEM model. A close agreement between the simulation and experimental results was achieved. The porosity values obtained from the simulations along with the stability criterion exhibited the intermediate flow regime for all liquid superficial velocities and number of particles tested. It was also found that in intermediate flow regimes (when superficial velocity was greater than 0.12 m/s), two unique hydrodynamic behaviors occurred: vortices (responsible for homogeneous flow behavior) and gulf-streaming effects (an indication of nonhomogeneity). It was also observed that the trend of particle and liquid mean axial velocity profiles were dependent on the superficial liquid velocity and number of particles.