  We present three dimensional hydrodynamical simulations aimed at studying the
dynamical and chemical evolution of the interstellar medium (ISM) in isolated
dwarf spheroidal galaxies (dSphs). This evolution is driven by the explosion of
Type II and Type Ia supernovae, whose different contribution on both the
dynamics and chemical enrichment is taken into account. Radiative losses are
effective in radiating away the huge amount of energy released by SNe
explosions, and the dSph is able to retain most of the gas allowing a long
period (>2-3 Gyr) of star formation, as usually observed in this kind of
galaxies. We are able to reproduce the stellar metallicity distribution
function (MDF) as well as the peculiar chemical properties of strongly
O-depleted stars observed in several dSphs. The model also naturally predicts
two different stellar populations, with an anti-correlation between [Fe/H] and
velocity dispersion, similarly to what observed in the Sculptor and Fornax
dSphs. These results derive from the inhomogeneous pollution of the SNe Ia, a
distinctive characteristic of our model. We also applied the model to the
peculiar globular cluster (GC) Omega Cen in the hypothesis that it is the
remnant of a formerly larger stellar system, possibly a dSph.
