Abstract
A discrete element method was applied for a two-dimensional fluidized bed. The calculation time rapidly increases as the number of particles increases. In order to decrease calculation time, imaginary spheres were used instead of actual particles. An imaginary sphere has a diameter grater than actual particles and a lower actual density. We compared the bubble diameter and minimum fluidization velocity between calculation and experiment. A good agreement of bubble diameter was obtained by using the assumption of a FCC (Face Centered Cubic) particles structure model.