  Observations of gravitational waves provide new opportunities to study our
Universe. In particular, mergers of stellar black holes are the main targets of
the current gravitational wave experiments. In order to make accurate
predictions, it is however necessary to simulate the mergers in numerical
general relativity, which requires high performance computing. While scaling
relations are used to rescale simulations for very massive black holes,
primordial black holes have specific properties which can invalidate the
rescaling. Similarly black holes in theories beyond Einstein's relativity can
have different scaling properties. In this article, we consider scaling
relations for the most general cases of primordial black holes, such as charged
and spinned black holes, and study the effects of the cosmological expansion
and of Hawking evaporation. We also consider more exotic black hole models and
derive the corresponding scaling relations, which can be compared to the
observations in order to identify the underlying black hole model and can be
used to rescale the numerical simulations of exotic black hole mergers.
