It is assumed that the
macroscopic
behaviour of a fluid does not depend directly on the
detailed microscopic behaviour. This is similar to the BGK assumption
in the classical Boltzmann theory, see section 2.4.
Thus in general any system which satisfies the
continuity equation (1.1) and the Navier-Stokes
equation (1.2) can be used to model a fluid, the detail of the
microscopic behaviour is not important. A cellular automata approach to
modelling the microscopic behaviour has the advantage that it can be
implemented efficiently and quickly on a computer. The fluid properties
are incorporated into the update rules.