Magnetic field inside and outside the rectangular conductor

[merro]

Hi
I want to find the magnetic field result from DC current flow through the rectangular transmission line numerically by using the finite difference.
the solved equation is curl curl A =µ J , with div A=0, and J is a uniform current on the crosssection.
I implement the MATLAB code , but the result is not logical, so i think the boundary condition is the problem
I take the symmetry plans , one vertical and other Horzi. and solve the problem for quarter conductor.
my question the boundary conditions for that problem

thank you in advance

 

[cragar]

Couldn't you just use amperes law and model it as a sheet current, at least that would give you an approximation.