  Supernovae of Type II is a phenomenon that occurs at the end of evolution of
massive stars when the iron core of the star exceeds a mass limit. After
collapse of the core under gravity the shock wave alone does not succeed in
expelling the mass of the star and in this sense the role of neutrinos is the
most important mechanism to do so. During the emission of neutrinos flavor
conversion is possible, related the phenomenon of oscillations, which however
depends directly on the particular density profile of the medium. In this paper
we present results of numerical simulations of neutrino flavor conversion in
protoneutron stars and after collapse. The probabilities of survival for a
given flavor in a complete three-flavors framework is estimated through an
algorithm which conserves unitarity to a high degree of accuracy. The
sensitivity of the results to the different adopted models for the protoneutron
star structure is examined in detail demonstrating how the neutrino signal
could be used to check the validity of models.
