  The magneto-centrifugal model for jet formation is studied by time-dependent
simulations reaching steady state in a cold gas with negligible fluid pressure,
in an axisymmetric geometry, using a modification of the Zeus3D code adapted to
parallel computers. The number of boundary conditions imposed at the coronal
base takes into account the existence of the fast and Alfvenic critical
surfaces, avoiding over-determination of the flow. The size and shape of the
computational box is chosen to include these critical surfaces, reducing the
influence of the outer boundary conditions. As there is a region, near the
origin, where the inclination of field lines to the axis is too small to drive
a centrifugal wind, we inject a thin, axial jet, expected to form
electromagnetically near black holes. Acceleration and collimation appear for
wide generic conditions. A reference run is shown in detail, with a wind
leaving the computational volume in the axial direction with a poloidal
velocity equal to 4 times the poloidal Alfven speed, collimated inside 11
degrees. Finally, the critical surfaces, fieldlines, thrust, energy, torque and
mass discharge of the outgoing wind are shown for simulations with various
profiles of mass and magnetic flux at the base of the corona.
