I have a scalar field defined on the nodes of a mesh, and I need to
compute the tensor field of its gradient on the mesh's nodes.
(For now I use continuous elements, so the gradient is discontinuous at
the cells' borders, so what I want to compute is, on each node, the
average for all neighbor cells of the node of the gradient's projection
on the node. I may later use discontinuous elements, but I guess the
problems I have will still be there...)
I have tried to use the functions
compute_projection_from_quadrature_points_matrix and
compute_projection_from_quadrature_points.
Sorry for that not-so-smart question. Actually, the right way to do it
seems to be the following:
- \phi is the known scalar field for which I can compute the gradient
on each integration point
- w is the unknown vector field that is expressed on the nodes through
w = N^t . W
- the equation simply writes: w = \grad(\phi)
- taking its weak form and discretizing, one obtains W = M\Q where M =
\int(N . N^t) and Q = \int(N . \grad(\phi))
Easy!
Martin.
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