The internal shock model for gamma-ray bursts involves shocks taking place in
a relativistic wind with a very inhomogeneous initial distribution of the
Lorentz factor. We have developed a 1D lagrangian hydrocode to follow the
evolution of such a wind and the results we have obtained are compared to those
of a simpler model presented in a recent paper (Daigne & Mochkovitch 1998)
where all pressure waves are suppressed in the wind so that shells with
different velocities only interact by direct collisions. The detailed
hydrodynamical calculation essentially confirms the conclusion of the simple
model: the main temporal and spectral properties of gamma-ray bursts can be
reproduced by internal shocks in a relativistic wind.Comment: 10 pages, 15 figures, to be published in A&
