Magnetic Field Boundaries (MagneticSolver)

[sebastien ROUQUETTE]

Hi everyone,

this is probably a simple question but... here it is:
I'm trying to add a lorentz force to a heat transfer and fluid flow problem.
I simulate the TIG (Tungsten Inert Gas) stationnary welding spot on a cylinder. I work on 2d axi symmetry. I've finished the heat transfer and fluid flow part. It works well.
I try to add the electromagnetic part (as it is a electric arc that melts the metal). I wanted to use the solver "magenticsolver" as i need both joules heating and lorentz force.
My geometry is a square. Top boundary, i've this conditions: d(r * Btheta)/dr = µ0 * r * J0(r) zith r is the coordinate 1, µ0 the magnetic permeability and B my magnetic field 2 (not quite sure anyway). Well i understand that if i say in boundary: "Magnetic Field 2 = 0" that means "Btheta = 0"
So what is the syntax for the condition: d(r*Btheta)/dr = µ0 * r *J0(r) .... ? any clues? My J0(r) is just a function of radius right now but i will vary it with time just after... so i wanted to used this solver.
Is there any other one... who gives the lorentz force then applied to the fluid?
Is it possible (yes i think) to solve only the magnetic induction equation then use the joule heating and lorentz force in the coupled heat transfer - fluid flow?
Cheers