Re: [Libmesh-devel] about shell element

[Roy S. <roy...@ic...>]

On Tue, 6 Mar 2007, Xi YUAN wrote:

> I am considering add shell elements to libmesh but not quite sure how to do
> it.

Could you post a few references for the element type you'd like to
add?

> The first probelm I encounter is how to build the shape function of such
> kind of elements. For shell elements, we need know the thickness and fiber
> vector of all FE nodes. But in libmesh, no such informations. I am
> considering add those variables into mesh_data and rewrite the function of
> shape function calculation like
>
> Real FE<2,LAGRANGE>::shape(const ElemType type,  const Order order,    const
> unsigned int i,
> 		   const Point& p, const real thickness, real* fibervector)
>
> But it looks a little awkward because it changes the basic structure of this
> soft. Is there any suggestion about it?

Well, we definitely don't want a new shape method signature.  The
thing to do will be to use the other shape function signature (which,
except for Lagrange mapping functions, is the one that gets called
anyway):

Real FE::shape(const Elem* elem, const Order o, const unsigned int i,
const Point& p)

But then the question becomes "how do we get that extra data from an
Elem *".  The closest analogous case we've got is the infinite element
support, but I'm not sure you'd like to add a new geometric Elem
subclass for every plate type you want.
---
Roy