### Abstract

We study the evolution of circumbinary disks under the gravitational
influence of the binary using two-dimensional hydrodynamical simulations to
investigate the impact of disk and binary parameters on the dynamical aspects
of the disk. To distinguish between physical and numerical effects we apply
three hydrodynamical codes. First we analyse in detail numerical issues
concerning the conditions at the boundaries and grid resolution. We then
perform a series of simulations with different binary (eccentricity, mass
ratio) and disk parameters (viscosity, aspect ratio) starting from a reference
model with Kepler-16 parameters.
Concerning the numerical aspects we find that the inner grid radius must be
of the order of the binary semi-major axis, with free outflow conditions
applied such that mass can flow onto the central binary. A closed inner
boundary leads to unstable evolutions.
We find that the inner disk turns eccentric and precesses for all
investigated physical parameters. The precession rate is slow with periods
($T_prec$) starting at around 500 binary orbits ($T_bin$) for
high viscosity and large $H/R$ where the inner hole is smaller and more
circular. Reducing $\alpha$ and $H/R$ increases the gap size and
$T_prec$ reaches 2500 $T_bin$. For varying binary mass ratios
$q_bin$ the gap size remains constant whereas $T_prec$
decreases for increasing $q_bin$.
For varying binary eccentricities $e_bin$ we find two separate
branches in the gap size and eccentricity diagram. The bifurcation occurs at
around $e_crit 0.18$ where the gap is smallest with the
shortest $T_prec$. For $e_bin$ smaller and larger than
$e_crit$ the gap size and $T_prec$ increase. Circular
binaries create the most eccentric disks.

### Users

Please

log in to take part in the discussion (add own reviews or comments).