How to: Coupling Ferrite to an external problem

^{Originally posted by **jfbarthelemy** October 11, 2023}
Dear Ferrite devs and users,

Would it be possible to add a global scalar (not a field attached to any interpolation system) as dof in a problem? I explain a case where I would need this. Consider a stready-state heat equation problem (possibly with non linear conductivity to avoid invoking linearity as a workaround later) on a domain such that one part Γ of the boundary is submitted to an unknown uniform temperature but the resulting heat flux (integral over Γ) is known. This problem is well posed and could for example be handled by introducing a new variable which is the unknown temperature and a Lagrange multiplier field on Γ to ensure the condition of uniformity of T on Γ. Is this feasible with Ferrite?

Thanks in advance