  A numerical simulation of a gas-fluidized bed is performed without
introduction of any empirical parameters. Realistic bubbles and slugs are
observed in our simulation. It is found that the convective motion of particles
is important for the bubbling phase and there is no convection in the slugging
phase. From the simulation results, non-Gaussian distributions are found in the
particle velocities and the relation between the deviation from Gaussian and
the local density of particles is suggested. It is also shown that the power
spectra of particle velocities obey power laws. A brief explanation on the
relationship between the simulation results and the Kolmogorov scaling argument
is discussed.
