  Numerical MHD codes have become extraordinarily powerful tools with which to
study accretion turbulence. They have been used primarily to extract values for
the classical $\alpha$ parameter, and to follow complex evolutionary
development. Energy transport, which is at the heart of classical disk theory,
has yet to be explored in any detail. Further topics that should be explored by
simulation include nonideal MHD, radiation physics, and outburst behavior
related to the temperature sensitivity of the resistivity.
