Growing supermassive black holes: sub-grid modelling and
  intermediate-scale processes
  The sheer range of scales in the Universe makes it impossible to model all at
once. It is necessary, therefore, when conducting numerical experiments, that
we employ sub-resolution prescriptions that can represent the scales we are
unable to model directly. In this article we present a prescription for black
hole growth that incorporates a different accretion regime from the standard
approach used in the literature, and discuss the results of dedicated
simulations of intermediate processes between small-scale accretion flows and
large-scale cosmological volumes that can strongly enhance the accretion rate
onto the black hole at the centre of a galaxy.
