Hi Andrew, thanks for the response. I will definitely look into it. One more question I forgot: 5) For an anisotropic diffusion problem, I would like to use this diffusivity tensor: D(x) = [y^2+eps*x^2, -(1-eps)*x*y; -(1-eps)*x*y, eps*y^2+x^2] where eps is a user-defined scalar, and x and y correspond to the x and y coordinates of the cell. How would I express that? Thanks, Justin On Tue, Sep 22, 2015 at 12:18 PM, Andrew McRae <A.T.T.McRae@bath.ac.uk> wrote:

4) Do you guys support Hexahedron elements? When I look through the

...

documentation for UnitCubeMesh and BoxMesh, I see no option for non-tetrahedron elements.

We support semi-structured hexahedral meshes, though not *fully* unstructured. One has to go via the ExtrudedMesh functionality to get these.

For example, to quote Henrik in a different mailing list thread,

*meshbase = RectangleMesh(Nx, Ny, Lx, Ly, quadrilateral=True) mesh = ExtrudedMesh(meshbase, Nz, Delta_z)*

Or you can supply your own base quadrilateral mesh: m = Mesh("quadmesh.msh") mesh = ExtrudedMesh(m, ...)

For element families supported, see http://femtable.org/ to start with.

If your cells aren't perfect cuboids then some approximations are made in the quadrature calculations; if this seems to be hurting you badly then I can give further instructions.

_______________________________________________ firedrake mailing list firedrake@imperial.ac.uk https://mailman.ic.ac.uk/mailman/listinfo/firedrake