  The evolution of an accretion disk, formed as a consequence of the disruption
of a star by a black hole, is followed by solving numerically the hydrodynamic
equations. The present investigation aims to study the dependence of resulting
light curves on dynamical and physical properties of such a transient disk
during its existence. One of main results derived from our simulations is that
black body fits of X-ray data tend to overestimate the true mean disk
temperature. The temperature derived from black body fits should be identified
with the color X-ray temperature rather than the average value derived from the
true temperature distribution along the disk. The time interval between the
beginning of the circularization of the bound debris and the beginning of the
accretion process by the black hole is determined by the viscous timescale,
which fixes also the raising part of the resulting light curve. The luminosity
peak coincides with the beginning of matter accretion by the black hole and the
late evolution of the light curve depends on the evolution of the debris
fallback rate. Peak bolometric luminosities are in the range 10^45-10^46 erg
s^-1 whereas peak luminosities in soft X-rays (0.2-2.0 keV) are typically one
order of magnitude lower. The timescale derived from our preferred models for
the flare luminosity to decay by two orders of magnitude is about 3-4 years.
Predicted soft X-ray light curves were fitted to data on galaxies in which a
variable X-ray emission, related to tidal events, was detected.
