[CIG-SHORT] Mesh interpenetration

[Matthew Knepley]

Oh, that is not right. Either there is a bug, or the displacements are
being misinterpreted.

   Matt

On Wed, Nov 1, 2017 at 11:06 AM, Li, Teng <tengli2 at illinois.edu> wrote:

> Hi Matt,
>
> Please find the attachment which is the original mesh in the area where
> the left 60 degrees secondary fault link directly to the main fault. Two
> faults are highlighted. As we can see, all the mesh in this area is quad
> mesh. The reason why we see the triangular mesh in the left part is just
> that some meshes overlap each other. And according to my observation, part
> of the cells along the secondary fault on the right go into the cells along
> the secondary fault on the left part.
>
> Because the left 60-degree secondary fault link directly to the main
> fault, there will be a sharp triangular in the junction area. I choose
> 12.5m mesh size and use Trellis to mesh this area. And please find the new
> attachment for the mesh information in this junction triangular area. If
> this mesh is in a bad quality, what might be the solution? Can I use
> smaller mesh size?
>
> Thanks.
>
> Best,
> Teng
>
> Teng Li
>
> Master Candidate in Structures
>
> Department of Civil and Environmental Engineering
>
> University of Illinois at Urbana-Champaign
>
> 205 North Mathews Ave, Urbana, IL. 61801
>
> Phone:(217)8196210 <(217)%20819-6210>, Email: tengli2 at illinois.edu
>
>
>
> ------------------------------
> *From:* CIG-SHORT [cig-short-bounces at geodynamics.org] on behalf of
> Matthew Knepley [knepley at rice.edu]
> *Sent:* Wednesday, November 01, 2017 3:14 AM
> *To:* cig-short at geodynamics.org
> *Subject:* Re: [CIG-SHORT] Mesh interpenetration
>
> On Wed, Nov 1, 2017 at 12:05 AM, Li, Teng <tengli2 at illinois.edu> wrote:
>
>> Hi,
>>
>> Please see the attached picture which shows the junction of the secondary
>> fault and the main fault. I used paraview to visualize the vtk file. In the
>> paraview, I used wrap by vector filter to show the displacement of the
>> junction. As we can see, it seems interpenetration occurs in this area. And
>> two faces separate from each other.  I wonder whether this is a valid
>> result? And if it is not right, what might be the reason? Thanks.
>>
>
> 1) I do not understand why there are two triangles in the picture. Isn't
> this an all quad mesh?
>
> 2) If the fault is in tension, it will open. I am not sure why you would
> call that interpenetration, which means that two quads cross over each
> other, not leave a void.
>      You might increase the cohension at that interface if you want it to
> remain together, or look at the normal stress on the fault, which should
> ordinarily be more
>      than enough to keep it together.
>
> 3) The extremely narrow quads on the right are bad for your system
> condition number. Why did you mesh it that way?
>
>    Thanks,
>
>      Matt
>
> Best,
>> Teng
>>
>> Teng Li
>>
>> Master Candidate in Structures
>>
>> Department of Civil and Environmental Engineering
>>
>> University of Illinois at Urbana-Champaign
>>
>> 205 North Mathews Ave, Urbana, IL. 61801
>>
>> Phone:(217)8196210 <(217)%20819-6210>, Email: tengli2 at illinois.edu
>>
>>
>>
>>
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