Tidally-induced spiral waves may efficiently
  transport angular momentum out of the disk
  so that gas can fall into the black hole.

We use time-dependent hydrodynamical simulations of a two-dimensional isothermal accretion disk to measure the effects of binary tidal forces on transport within an accretion disk. These simulations were run for nearly a million timesteps on a grid of 200 x 120 zones, requiring tens of hours on a supercomputer.