[CIG-SHORT] PyLith: Stresses not transmitted throughout the domain from Drichlet BCs on CUBIT Mesh

Thu Oct 15 14:26:40 PDT 2015

Charles,

Thanks again for your suggestion. I have reproduced the geometry and
improved the mesh quality by checking with 'Allmetrics' in Cubit (attached
below). Condition number is below 2 (1.606) and maximum aspect ratio is 3.
Still I am getting the same convergence errors. I have also tried the tips
found in the threads that Brad answered in the CIG-SHORT:

http://lists.geodynamics.org/pipermail/cig-short/2014-October/001885.html
http://lists.geodynamics.org/pipermail/cig-short/2012-September/001129.html

Hex quality, 810 elements:

------------------------------------

Function Name  Average  Std Dev   Minimum (id)    Maximum (id)

-----------------     ---------   ---------      --------------
-------------

Aspect Ratio 1.222e+00 6.289e-01 1.000e+00 (1) 3.000e+00 (724)

Skew 8.104e-16 8.536e-16 0.000e+00 (10) 6.821e-15 (733)

Taper 8.561e-16 8.748e-16 0.000e+00 (3) 6.845e-15 (736)

Element Volume 2.500e+07 5.660e+06 9.000e+06 (733) 2.700e+07 (505)

Stretch 9.330e-01 1.895e-01 3.974e-01 (782) 1.000e+00 (10)

Diagonal Ratio 1.000e+00 4.591e-08 1.000e+00 (372) 1.000e+00 (10)

Dimension 1.640e+02 2.602e+01 9.045e+01 (809) 1.732e+02 (315)

Condition No. 1.067e+00 1.907e-01 1.000e+00 (3) 1.606e+00 (737)

Jacobian 2.500e+07 5.660e+06 9.000e+06 (763) 2.700e+07 (315)

Scaled Jacobian 1.000e+00 0.000e+00 1.000e+00 (248) 1.000e+00 (1)

Shear 1.000e+00 0.000e+00 1.000e+00 (248) 1.000e+00 (1)

Shape 9.648e-01 9.963e-02 6.832e-01 (737) 1.000e+00 (1)

Relative Size 7.765e-01 2.288e-01 1.296e-01 (733) 8.573e-01 (487)

Shear And Size 7.765e-01 2.288e-01 1.296e-01 (733) 8.573e-01 (487)

Shape And Size 7.719e-01 2.418e-01 8.854e-02 (733) 8.573e-01 (487)

Distortion 1.000e+00 5.167e-08 1.000e+00 (367) 1.000e+00 (11)

Not sure what else I should try next. Please also see the attached files.

Thanks,
Mamun

On Wed, Oct 14, 2015 at 11:11 AM, Charles Williams <willic3 at gmail.com>
wrote:

> Dear Mamun,
>
> Your linear convergence looks very slow.  You could increase the number of
> iterations, but I’m not sure if that would solve your problem.  I would
> start with a higher quality mesh.  Ideally, you would like to have a mesh
> where the condition number quality measure is less than 2 for the entire
> mesh, particularly for problems involving fault friction.  If this is too
> difficult to achieve using hexahedral elements, you might need to try
> tetrahedral elements.
>
> Cheers,
> Charles
>
>
> On 15/10/2015, at 6:09 am, Mamun Miah <mmiah at go.olemiss.edu> wrote:
>
> Thanks, Charles. Your comments are very helpful. I have been going through
> each of your comments and discovered that both KSPSolve and SNESSolve do
> not converge when I uncommented corresponding flag options. So I figured
> the problem is with the mesh creation. Also set the the normalizer
> according to the smallest mesh dimension. Attached here is the log file in
> case you want to see.
>
> Thanks again,
> Mamun
>
> On Tue, Oct 13, 2015 at 12:37 PM, Charles Williams <willic3 at gmail.com>
> wrote:
>
>> Dear Mamun,
>>
>> It is a bit difficult to diagnose your problem without more information.
>> However, here are several potential problems:
>>
>>
>> 1.  First of all, the mesh you’re using is not of very high quality.  The
>> method you’ve used for refinement is pretty crude, and will never result in
>> high quality elements. Trelis/Cubit has a number of more powerful methods
>> for creating a high quality mesh, and I would take advantage of those.
>> 2.  It is unclear why you have set the normalization length scale to 1 m,
>> since I believe this is much smaller than your smallest element.
>> 3.  There is no indication of whether the linear and nonlinear solutions
>> are converging, since you have turned off all the solution monitoring
>> options, including the journal options.  You should never do this, as there
>> is then no way to tell what has happened with your solution.
>>
>> You should try running your problem again with all the solution
>> monitoring options turned back on, and save the results to a log file.
>> This will help us diagnose your problem further.  I would also try
>> improving your mesh quality and selecting a normalization length scale that
>> is appropriate for your mesh (~equal to the smallest cell dimension).
>>
>> Cheers,
>> Charles
>>
>>
>> On 14/10/2015, at 6:26 am, Mamun Miah <mmiah at go.olemiss.edu> wrote:
>>
>> Hello Developers,
>>
>> I have created the attached geometry (5kmx5kmx4.1km) in CUBIT. It has
>> three layer of materials (2000m+100m+200m) and a vertical fault (along Z
>> axis) 1000m to the left from the positive X-plane boundary. The exported
>> Exodus mesh is then used to run a PyLith simulation with Dirichlet
>> displacement and displacement rate BCs (e.g. PyLith Tutorial 'step12.cfg')
>> on +x and -x sides. The simulation runs fine but even after running for 100
>> years I don't see any stress being transmitted to the interior domain. All
>> I can see is the stress changes in the boundary elements where the
>> Dirichlet BCs are applied. I am not sure if it is caused by improper
>> meshing or boundary conditions.
>>
>> Attached also are the .cfg files, geometry journal file, and stress
>> output file from simulation. I would highly appreciate any help.
>>
>> --
>> Thanks & Best Regards,
>>
>> Mamun Miah
>> Graduate Research Assistant
>> Department of Civil Engineering
>> The University of Mississippi
>> Oxford, MS 38655
>> Phone: (662)-801-1904
>> Website: http://www.linkedin.com/pub/mamun-miah-eit/21/53/339
>> <geometry.jpg><application.cfg><pylithapp.cfg><visit0000.png>
>> <application.jou>_______________________________________________
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>>
>>
>> Charles A. Williams
>> Scientist
>> GNS Science
>> 1 Fairway Drive, Avalon
>> PO Box 30368
>> Lower Hutt  5040
>> New Zealand
>> ph (office): 0064-4570-4566
>> fax (office): 0064-4570-4600
>> C.Williams at gns.cri.nz
>>
>>
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>
>
>
> --
> Thanks & Best Regards,
>
> Mamun Miah
> Graduate Research Assistant
> Department of Civil Engineering
> The University of Mississippi
> Oxford, MS 38655
> Phone: (662)-801-1904
> Website: http://www.linkedin.com/pub/mamun-miah-eit/21/53/339
> <log>_______________________________________________
> CIG-SHORT mailing list
> CIG-SHORT at geodynamics.org
> http://lists.geodynamics.org/cgi-bin/mailman/listinfo/cig-short
>
>
> Charles A. Williams
> Scientist
> GNS Science
> 1 Fairway Drive, Avalon
> PO Box 30368
> Lower Hutt  5040
> New Zealand
> ph (office): 0064-4570-4566
> fax (office): 0064-4570-4600
> C.Williams at gns.cri.nz
>
>
> _______________________________________________
> CIG-SHORT mailing list
> CIG-SHORT at geodynamics.org
> http://lists.geodynamics.org/cgi-bin/mailman/listinfo/cig-short
>

-- 
Thanks & Best Regards,

Mamun Miah
Graduate Research Assistant
Department of Civil Engineering
The University of Mississippi
Oxford, MS 38655
Phone: (662)-801-1904
Website: http://www.linkedin.com/pub/mamun-miah-eit/21/53/339
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