Hi everyone!

I am sequentially solving two PDEs, correlated by the diffusion term:

After solving the first PDE (thus getting u) with

solve firstpde (u, v) = int3d (Th) ( A * grad(u)’ * grad(v) ) + BCs ) ;

where Th is the triangulation of the mesh Vh, I tried to define the diffusion coefficient B as

macro grad(f) [dx(f), dy(f), dz(f) ]

func B = int3d (Th) ( A * grad( u ) ) )

but it gives me error on the definition of B.

Does anyone can help me?

Thank you!