  The purpose of this communication is to discuss the simulation of a free
surface compressible flow between two fluids, typically air and water. We use a
two fluid model with the same velocity, pressure and temperature for both
phases. In such a numerical model, the free surface becomes a thin three
dimensional zone. The present method has at least three advantages: (i) the
free-surface treatment is completely implicit; (ii) it can naturally handle
wave breaking and other topological changes in the flow; (iii) one can easily
vary the Equation of States (EOS) of each fluid (in principle, one can even
consider tabulated EOS). Moreover, our model is unconditionally hyperbolic for
reasonable EOS.
