Fourier-Robin brick

This brick can be used to add boundary conditions of Fourier-Robin type like:

\[\frac{\partial u}{\partial \nu} = Qu\]

for scalar problems, or

\[\sigma\cdot \nu = Qu\]

for linearized elasticity problems. Q is a scalar field in the scalar case or a matrix field in the vectorial case. This brick works for both real or complex terms in scalar or vectorial problems.

The function adding this brick to a model is:

add_Fourier_Robin_brick(md, mim, varname, dataexpr, region);

where dataexpr is the data of the model which represents the coefficient \(Q\). It can be an arbitrary valid expression of GWFL, the generic weak form language (except for the complex version for which it should be a data of the model)

Note that an additional right hand side can be added with a source term brick.