On Thu, May 19, 2016 at 12:43 PM, John Peterson <jwpeter...@gmail.com>
wrote:
>
>
> On Thu, May 19, 2016 at 10:19 AM, David Knezevic <
> david.kneze...@akselos.com> wrote:
>
>> I would like to add support for Exodus's SHELL elements to libMesh, e.g.
>> TRISHELL3 and SHELL4. See the attached figure from the Exodus standard for
>> a picture of a SHELL4 element.
>>
>> As you can see from the figure, the only difference here is that this
>> element has sidesets associated with the 2D faces as well as with the 1D
>> sides. This is useful when imposing loads on shell models, e.g. it allows
>> one to use Exodus sidesets (i.e. boundary_ids in libMesh) to impose surface
>> loads instead of Exodus blocks (i.e. subdomain_ids in libMesh).
>>
>> In order to support this, I think we'd need to change BoundaryInfo so
>> that we can get boundary_ids from an element (as opposed to only a side or
>> node of an element). Before I dive into working on this, I wanted to check
>> if others agree if this is the right approach, and if it makes sense to add
>> it to libMesh?
>>
>
> So once the elements are in libmesh, they will just be treated as TRI3 and
> QUAD4 types?
>
Yes, that's what I would suggest. The only difference between TRISHELL3 and
TRI3 in Exodus is in the sidesets, so that would just map to a change in
the the BoundaryInfo (we'd need boundary_ids on the elements themselves, as
I mentioned). No need to treat the element type itself any differently.
> You will have to look at and possibly take out the hacks I put in to work
> around the issue where Cubit 14+ automatically writes TRISHELL elements for
> TRI3 elements when dim==3 (search for "is_cubit14_plus" in
> exodusII_io_helper.C). Actually, I don't know how you will differentiate
> between the case where someone legitimately wanted a TRISHELL3 element and
> where one was incorrectly written to the file by Cubit...
>
I think once we support TRISHELL3 properly, this won't be an issue. We can
just read in the TRISHELL3 sideset data that Cubit wrote out, and store it
as BoundaryInfo data, and it should all work fine. I guess your hack had to
deal with the fact that sidesets 1 and 2 need to be ignored, but I'm
proposing to map those sidesets to element boundary IDs, so that should
smoothly resolve the hack.
David
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