Hello every one,
I want to compute the Laplacian operator of a vector u in Vh (Th, P1) finite element space.
I use two different approaches:
- macro Laplacian(u) (dxx(u) + dyy(u)) //
Vh lap_U = Laplacian(u);
with this I always obtain a vector of zeros.
- macro div(u1,u2) (dx(u1) + dy(u2))//
Vh lap_U = div(u1,u2) ;
wirh this I obtain a vector different of zeros.
Is there any recommandations for the computation of the Laplacian operator.