  We study the effects of initial and boundary conditions, taking
two-dimensional hydrodynamical numerical simulations of hot accretion flow as
an example. The initial conditions considered include a rotating torus, a
solution expanded from the one-dimensional global solution of hot accretion
flows, injected gas with various angular momentum distributions, and the gas
from a large-scale numerical simulation. Special attention is paid to the
radial profiles of the mass accretion rate and density. Both can be described
by a power-law function, $\dot{M}\propto r^s$ and $\rho\propto r^{-p}$. We find
that if the angular momentum is not very low, the value of $s$ is not sensitive
to the initial condition and lies within a narrow range, $0.47\la s \la 0.55$.
However, the value of $p$ is more sensitive to the initial condition and lies
in the range $0.48\la p \la 0.8$. The diversity of the density profile is
because different initial conditions give different radial profiles of radial
velocity due to the different angular momentum of the initial conditions. When
the angular momentum of the accretion flow is very low, the inflow rate is
constant with radius. Taking the torus model as an example, we have also
investigated the effects of inner and outer boundary conditions by considering
the widely adopted "outflow" boundary condition and the "mass flux
conservation" condition. We find that the results are not sensitive to these
two boundary conditions.
