A two-dimensional two-colour, nonlinear, Galilean-invariant, Boltzmann
cellular automaton is developed and used to study two-fluid hydrodyna
mics and to model fluid interfaces. The interfacial tension and interf
ace width are flexibly controlled by the parameters defining collision
rules for the colored particles. Results of studies of both the stati
c and dynamical relaxation of the surface tension and wetting properti
es are presented.