  Here we build some effective boundary conditions to be used in numerical
calculations in order to avoid the thin meshing usually required in problems
involving Hartmann layers near a locally plane wall. Wall model are provided
for both tangential and normal electric current density and velocity. In
particular, a condition on the normal derivative of the tangential velocity is
derived. A wide variety of problems is covered as the only restriction is that
the magnetic Reynolds number has to be large at the scale of the Hartmann
layer. The cases of perfectly conducting or insulating wall are examined, as
well as the case of a thin conducting wall. The newest result is a condition on
the normal velocity accounting for inertial effects in the Hartmann layer.
