libmesh-devel

Re: [Libmesh-devel] [Libmesh-users] Averaging element fields to the nodes.

[Kirk, B. (JSC-EG311) <ben...@na...>]

That method lets you conveniently access all the elements sharing a given node, which is not what you want in this case. 

The usual way to do this is by solving an L2 projection onto a continuous field - think of this as finding the continuous gradient field that best approximates your discontinuous field in a least-squares sense. 

I don't think there are any examples that currently show this - I'll try to add one after the next release.

Given that it is a common-enough post processing task, we might start a discussion on the development list as to how to best provide this as a core library service...

-Ben

 

On Oct 29, 2012, at 3:41 AM, "Subramanya Gautam Sadasiva" <ssa...@pu...> wrote:

> Hi, 
> I need to extrapolate element fields to the nodes in order to compute approximate gradients for some quantities defined at the quadrature points. What is the easiest way to accomplish this?
> I saw meshtools has a nodes to elem map function.Does this work for parallel meshes?
> Thanks.
> Subramanya 
> 
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Re: [Libmesh-devel] [Libmesh-users] Averaging element fields to the nodes.

[Robert <li...@ro...>]

Hello,

within that topic I would throw in the idea to explicitly support
Gauss/quadrature-point storage. As far as I know this data is currently
stored using MONIMIAL variables. For the projection onto nodes and for
writing this data to output files, it would be nice to have a variable
type for that

Robert

On Mon, Oct 29, 2012 at 06:06:05AM -0500, Kirk, Benjamin (JSC-EG311) wrote:
> That method lets you conveniently access all the elements sharing a given node, which is not what you want in this case. 
> 
> The usual way to do this is by solving an L2 projection onto a continuous field - think of this as finding the continuous gradient field that best approximates your discontinuous field in a least-squares sense. 
> 
> I don't think there are any examples that currently show this - I'll try to add one after the next release.
> 
> Given that it is a common-enough post processing task, we might start a discussion on the development list as to how to best provide this as a core library service...
> 
> -Ben
> 
>  
> 
> On Oct 29, 2012, at 3:41 AM, "Subramanya Gautam Sadasiva" <ssa...@pu...> wrote:
> 
> > Hi, 
> > I need to extrapolate element fields to the nodes in order to compute approximate gradients for some quantities defined at the quadrature points. What is the easiest way to accomplish this?
> > I saw meshtools has a nodes to elem map function.Does this work for parallel meshes?
> > Thanks.
> > Subramanya 
> > 
> > ------------------------------------------------------------------------------
> > The Windows 8 Center - In partnership with Sourceforge
> > Your idea - your app - 30 days.
> > Get started!
> > http://windows8center.sourceforge.net/
> > what-html-developers-need-to-know-about-coding-windows-8-metro-style-apps/
> > _______________________________________________
> > Libmesh-users mailing list
> > Lib...@li...
> > https://lists.sourceforge.net/lists/listinfo/libmesh-users
> 
> ------------------------------------------------------------------------------
> The Windows 8 Center - In partnership with Sourceforge
> Your idea - your app - 30 days.
> Get started!
> http://windows8center.sourceforge.net/
> what-html-developers-need-to-know-about-coding-windows-8-metro-style-apps/
> _______________________________________________
> Libmesh-devel mailing list
> Lib...@li...
> https://lists.sourceforge.net/lists/listinfo/libmesh-devel

Re: [Libmesh-devel] [Libmesh-users] Averaging element fields to the nodes.

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

On Mon, 29 Oct 2012, Kirk, Benjamin (JSC-EG311) wrote:

> I don't think there are any examples that currently show this - I'll
> try to add one after the next release.

See the attached ~300 lines of code.  It reads a mesh and solution, L2
projects and then plots all gradient components of all solution
variables.  It needs to be changed to have more than just
Tecplot-or-GMV output, and as you may have guessed this implies I
haven't tested it in a couple years, but other than that it ought to
be ready to drop in as fem_system_ex2.
---
Roy