For the distances between cell centres, yes.

It feels like you're performing some operations that aren't particularly finite element-y?  Would you be using the approximate gradient in a variational form immediately, or are there further calculations you want to carry out?

In the former case, I think there's a nice FE way to get what you want.  In the latter case, we can probably hack something up if we're smart enough...

On 22 September 2015 at 18:42, Buesing, Henrik <HBuesing@eonerc.rwth-aachen.de> wrote:

---

Von: firedrake-bounces@imperial.ac.uk [firedrake-bounces@imperial.ac.uk]" im Auftrag von "Andrew McRae [A.T.T.McRae@bath.ac.uk]
Gesendet: Dienstag, 22. September 2015 18:59
An: firedrake@imperial.ac.uk
Betreff: Re: [firedrake] Cell center on extruded mesh

>>Can you say a bit more about how you plan to use this?
>>I wonder to what end you would like these values?
I would like to approximate \grad(pw) on a DG0 Function space by
(p('+') - p('-'))/|x('+')-x('-')|, where x are the cell centers. On a hexahedral mesh this should just give \Delta x, \Delta y, \Delta z, right?

Henrik

On 22 September 2015 at 17:52, Buesing, Henrik <HBuesing@eonerc.rwth-aachen.de> wrote:

Dear Firedrakers,

on an extruded mesh:

meshbase = RectangleMesh(Nx, Ny, Lx, Ly, quadrilateral=True)
mesh = ExtrudedMesh(meshbase, Nz, Delta_z)
horiz_elt = FiniteElement("DG", quadrilateral, 0)
vert_elt = FiniteElement("DG", interval, 0)
elt = OuterProductElement(horiz_elt, vert_elt)

How can I access the element center and the center of the element faces?
Thank you!

Henrik

--
Dipl.-Math. Henrik Büsing
Applied Geophysics and Geothermal Energy
E.ON Energy Research Center
RWTH Aachen University
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