We present a two-dimensional grid-based hydrodynamic simulation of a thin , viscous , locally-isothermal corotating disk orbiting an equal-mass Newtonian binary point mass on a fixed circular orbit .
We study the structure of the disk after multiple viscous times .
The binary maintains a central hole in the viscously-relaxed disk with radius equal to about twice the binary semimajor axis .
Disk surface density within the hole is reduced by orders of magnitude relative to the density in the disk bulk .
The inner truncation of the disk resembles the clearing of a gap in a protoplanetary disk .
An initially circular disk becomes elliptical and then eccentric .
Disturbances in the disk contain a component that is stationary in the rotating frame in which the binary is at rest ; this component is a two-armed spiral density wave .
We measure the distribution of the binary torque in the disk and find that the strongest positive torque is exerted inside the central low-density hole .
We make connection with the linear theory of disk forcing at outer Lindblad resonances ( OLRs ) and find that the measured torque density distribution is consistent with forcing at the 3:2 ( m = 2 ) OLR , well within the central hole .
We also measure the time dependence of the rate at which gas accretes across the hole and find quasi-periodic structure .
We discuss implications for variability and detection of active galactic nuclei containing a binary massive black hole .