We have seen that a body force, such as gravity, can be incorporated into the
lattice Boltzmann model. A method has been proposed which incorporates the
body force into the lattice Boltzmann equation. This method is seen to
produce very similar results to the method proposed by Martys et al.
[66]. The new method
is preferred because it introduces the gravitational
term directly into the governing equation in a straight forward manner.
The implementation of the new method
is also shown to be independent of the underlying grid. When
the body force is applied to the binary fluid model [9] the resulting
model has been shown to be, at worst, very close to Galilean invariant
for the correct choice of the relaxation parameter 
.