We have examined the lattice gas model. There are a number of different variants but they all consider the evolution of fluid particles on a regular lattice.
The particle distribution tends to an equilibrium which is described by the
Fermi-Dirac distribution. The model has been seen to satisfy the continuity
equation and an equation similar to the Navier-Stokes equation. The lattice gas
Navier-Stokes equation differs from the standard Navier-Stokes equation through
the inclusion of a density dependent function 
and an additional
term, added to the pressure term, which is a function of density and velocity.
The viscosity of a lattice gas fluid is also a function of density. The
term, which represents the lack of Galilean invariance,
can be removed from the lattice gas
Navier-Stokes equation using a scaling technique, however the density
dependence remains. Multi-fluid models have also been discussed. It has
been seen that the lattice gas model is capable of simulating a binary
fluid mixture and a liquid-gas. The lack of Galilean invariance
can not be overcome by the scaling technique for such a model and the
unphysical density dependence can cause problems, particularly
in a liquid-gas model where there is a large density difference across
the simulation. Listed below are some of the main features of the
models.