Listed below are some key features of the numerical model that we employed in our study of accretion disks. We tested this model by simulating an accretion disk around a central gravitational source (i.e., no binary potential). The total angular momentum on the grid remained constant to within machine round-off, and the measured effective alpha was less than 0.001.

• Time-dependent ideal hydrodynamics: VH-1
• 2D cylindrical coordinates
• Isothermal equation of state
• simulation in rotating reference frame of binary system
• input parameters: sound speed, mass ratio, initial density profile
• periodic boundary conditions in phi, outflow in radius
• typicall grid of 200 radial zones by 115 azimuthal zones
• higher resolution used for high Mach numbers
• radial span of grid is typically 20 (e.g., .02 to .4)
• numerical code conserves angular momentum
• radial mass flux is monitered in order to compute and effective alpha
• grid is wiggled slightly in radial direction to suppress instabilities