  Comparison of horizon-scale observations of Sgr A* and M87* with numerical
simulations has provided considerable insight in their interpretation. Most of
these simulations are variations of the same physical scenario consisting of a
rotation-supported torus seeded with poloidal magnetic fields. This setup has
several well known limitations, most notably, it differs in important ways from
what observed in simulations of accretion from large scales. We aim to study
the flow patterns that arise at horizon scales in more general scenarios, that
have a clearer connection with the large scale flow and are at the same time
controlled by a reduced set of parameters. As a first step in this direction,
we perform three dimensional general relativistic hydrodynamic simulations of
rotating transonic flows with velocity perturbations injected from a spherical
boundary located 1000 gravitational radii away from the central object. We
study the general properties of these flows with varying angular momentum and
perturbation amplitudes. We observe a rich phenomenology in accretion patterns,
that includes smooth Bondi-like flows, turbulent torus-like structures, shocks,
filaments, and complex sonic structures. For sufficiently large perturbations
and angular momentum, radial profiles deviate from the constant entropy and
angular momentum profiles used for initialization and resemble those of
advection dominated accretion flows, showing evidence of entropy generation and
angular momentum redistribution not mediated by magnetic fields. Fluctuations
are amplified and extend further in frequency than the injected white noise
spectrum, producing a red noise spectrum for synthetic Bremsstrahlung light
curves. Future inclusion of magnetic fields and radiative cooling could make
this type of simulations a viable alternative for numerical modeling of general
low-luminosity active galactic nuclei.
