Effective boundary conditions for magnetohydrodynamic flows with thin Hartmann layers

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 models 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 small 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. (C) 2002 American Institute of Physics.