[CIG-SHORT] Question about accuracy in Pylith
Tabrez Ali
stali at geology.wisc.edu
Fri Oct 14 17:16:29 PDT 2016
The displacements should not be noisy. Are you sure the solver converged
for the 3D case?
Tabrez
On 10/14/2016 02:17 PM, Demian Gomez wrote:
> Dear Brad, Matt and Charles,
>
> I have a question regarding the accuracy of the solution using tets. I
> have a model with a biased tet mesh (4 km at the fault and 160 km at
> the edges, ~2200 km away) from which I am trying to get the strain and
> stress on some depth profiles at ~ 400 km from the fault. I am running
> Pylith with the refiner on (only one level) to refine my mesh and
> improve the resolution.
>
> The problem I'm having is that when I plot the strains and stresses,
> the plots are very "noisy" (see profiles_70.png). The displacement
> looks ok, maybe a few bumps and kinks here and there, but acceptable.
> I think these small displacement kinks are translating into the
> "noise" and larger kinks in strain and stress. I did tests in 2D (on a
> cross section of my 3D model) to figure out the best discretization
> size, and if I use a mesh with constant element size (say, 1 km), then
> everything is smooth and nice (see profiles_70_2D.png). However, a 3D
> model of the size that I need meshed with 1 km elements is huge and
> very impractical. Moreover, there shouldn't be any problems with using
> a biased mesh since there are examples within Pylith were you guys use
> this type of mesh.
>
> I know that I can improve the accuracy by using hexes, but
> unfortunately I've been trying to mesh my model with hexes (in Trelis)
> without any success. The model has the shape of a spherical cap and
> apparently there is something that Trelis doesn't like about this
> geometry. No matter how I divide and subdivide the model to help the
> mesher, there is always one volume that I cannot mesh. With tets,
> however, it works fine.
>
> Do you have any suggestions on what can I try to improve these
> results, without increasing the number of elements? I am at the limit
> of resources in terms of the model size (right now I'm at 125 GB of
> required memory to run my model). I could start using the HPC but it
> seems that there should be another way to solve this problem other
> than "brute force", i.e. making the model larger and using a bigger
> computer. You may also have suggestions regarding the meshing process.
> I would appreciate any advise that can help me to solve my problem.
> Let me know if there is any additional information you may need that I
> did not include.
>
> Cheers,
> Demián
>
> PS: I've attached the cfg files, just in case you want to see how I'm
> running the problem.
>
> --
> *Dr. Demián D. Gómez*
> Postdoctoral Researcher
> The Ohio State University - School of Earth Sciences
> 275 Mendenhall Laboratory
> 125 South Oval Mall
> Columbus, Ohio 43210
> Cell: +1 (901) 900-7324
> email: gomez.124 at osu.edu <mailto:gomez.124 at osu.edu>
>
>
>
> _______________________________________________
> CIG-SHORT mailing list
> CIG-SHORT at geodynamics.org
> http://lists.geodynamics.org/cgi-bin/mailman/listinfo/cig-short
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.geodynamics.org/pipermail/cig-short/attachments/20161014/391db77c/attachment-0001.html>
More information about the CIG-SHORT
mailing list