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 u;

Vh lap_U = Laplacian(u);

with this I always obtain a vector of zeros.

- macro div(u1,u2) (dx(u1) + dy(u2))//

Vh u;

Vh u1=dx(u);

Vh u2=dy(u);

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.

Best regards.