Granular gases and flows of granular particles have been studied well d
ue to the importance in technol-
ogy, geophysics, astrophysics, and science. The peculiar propertie
s of the granular gases are mainly
caused by the energy dissipation during the collisions of particles. Due to the
dissipative collisions, the
equilibrium state does not exist and the steady state or steady flow of granu
lar particles can be retained
only if the external force fields exist. In this sense, the granular gases a
re intrinsically
non-equilibrium
and quite di
ff
erent from molecular gases and usual fluids.