  Stationary magnetohydrodynamic (MHD) outflows from a rotating, conducting
Keplerian accretion disk threaded by B-field are investigated numerically by
time-dependent, axisymmetric (2.5D) simulations using a Godunov-type code. A
large class of stationary magneto-centrifugally driven winds are found where
matter is accelerated from a thermal speed at the disk to much larger velocity,
greater than the fast magnetosonic speed and larger than the escape speed. The
flows are approximately spherical outflows with only small collimation within
the simulation region. Numerical results are shown to coincide with the
theoretical predictions of ideal, axisymmetric MHD to high accuracy.
Investigation of the influence of outer boundary conditions, particularly that
on the toroidal component of magnetic field shows that the commonly used
``free'' boundary condition leads to artificial magnetic forces which can act
to give spurious collimation. New boundary conditions are proposed which do not
generate artificial forces. Artificial results may also arise for cases where
the Mach cones on the outer boundaries are partially directed into the
simulation region.
