  We formally derive the hydrodynamic limit of a system modelling a bosons gas
having a condensed part, made of a quantum kinetic and a Gross-Pitaevskii
equation. The limit model, which is a two-fluids Euler system, is approximated
by an isentropic system, which is then studied. We find in particular some
conditions for the hyperbolicity, and we study the weak solutions. A numerical
example is given at the end.
