[CIG-SHORT] Linear convergence for nonplanar faults

[Matthew Knepley]

On Wed, Nov 9, 2016 at 9:42 AM, Josimar Alves da Silva <jsilva.mit at gmail.com
> wrote:

> Brad,
>
> I changed the boundary conditions for Dirichlet BC with constrained
> displacement perpendicular to the surfaces, but the problem still persists.
> I am starting to wonder if the nonplanar nature of the fault surface may be
> causing the problem.
>
> The reason for this hypothesis is that I have the same set up but now with
> flat surfaces, and then in this case I don't find any convergence issue.
> Everything else was kept the same, except the fault geometry was changed
> from slightly smoothed (the version I am having problems) to not smoothed.
>

You NEED to use the exact version of the solver and check for convergence,
just as in the slides. This will tell us whether your
formulation is screwed up.

   Matt


> Let me know what you think about this.
> Thank you
> Josimar
>
>
>
>
> On Wed, Nov 9, 2016 at 10:20 AM, Brad Aagaard <baagaard at usgs.gov> wrote:
>
>> On 11/09/2016 07:15 AM, Josimar Alves da Silva wrote:
>>
>>> Dear Brad, Matt and Charles,
>>>
>>> Thank you again for the suggestions. After reviewing your comments I
>>> performed the following task in order to solve my problem:
>>>
>>> Brad mentioned:
>>>
>>>  "1. Without a fault, check convergence with using ML for
>>> the preconditioned."
>>>
>>>          Result: the solver converges fine without the fault and using
>>> the specified preconditioned.
>>>
>>> "2. Add the fault and with zero prescribed slip (FaultCohesiveKin),
>>> examine the convergence with the solver_fault_fieldsplit.cfg parameters."
>>>
>>>          Results: no convergence for any solver. Error message:  Linear
>>> solve did not converge due to DIVERGED_ITS iterations 10000
>>>
>>
>> This suggests there is something wrong with your problem setup. Make sure
>> you have sufficient Dirichlet BC on each side of the fault to prevent rigid
>> body motion.
>>
>> Brad
>>
>>
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>
>
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