A review of the hydrodynamic models of fluidization is presented. Three hydrodynamic models have been programmed on supercomputers to predict the variation of void fractions, pressure, and gas and solid velocities as a function of position and time. The ability of the models to predict bubbles in fluidized beds, bed-to-wall heat transfer coefficients, and product distributions in gasifiers shows their great potential as new research and development tools. These supercomputer models should aid in improving the performance of chemical plants processing solids that are reported to have been performing below their design expectations for the last 20 years (Merrow, 1985).