  The Kepler mission's discovery of a number of circumbinary planets orbiting
close (a_p < 1.1 au) to the stellar binary raises questions as to how these
planets could have formed given the intense gravitational perturbations the
dual stars impart on the disk. The gas component of circumbinary protoplanetary
disks is perturbed in a similar manner to the solid, planetesimal dominated
counterpart, although the mechanism by which disk eccentricity originates
differs. This is the first work of a series that aims to investigate the
conditions for planet formation in circumbinary protoplanetary disks. We
present a number of hydrodynamical simulations that explore the response of gas
disks around two observed binary systems: Kepler-16 and Kepler-34. We probe the
importance of disk viscosity, aspect-ratio, inner boundary condition, initial
surface density gradient, and self-gravity on the dynamical evolution of the
disk, as well as its quasi steady-state profile. We find there is a strong
influence of binary type on the mean disk eccentricity, e_d, leading to e_d =
0.02 - 0.08 for Kepler-16 and e_d = 0.10 - 0.15 in Kepler-34. The value of
alpha-viscosity has little influence on the disk, but we find a strong increase
in mean disk eccentricity with increasing aspect-ratio due to wave propagation
effects. The choice of inner boundary condition only has a small effect on the
surface density and eccentricity of the disk. Our primary finding is that
including disk self-gravity has little impact on the evolution or final state
of the disk for disks with masses less than 12.5 times that of the minimum-mass
solar nebula. This finding contrasts with the results of self-gravity relevance
in circumprimary disks, where its inclusion is found to be an important factor
in describing the disk evolution.
