[CIG-SHORT] ***UNCHECKED*** Re: Applying Gravitational Forces with Pylith

[Niloufar Abolfathian]

Thanks, Charles. You should be right. I am using hexahedral cells. The
model is a very simple vertical strike-slip fault. But gravity and finite
deformation may destort the cells. I have to run the model again to save
the vtk files in order to check the paraview. Also now I am trying to check
some finer cell sizes and tetrahedral mesh to see how they will affect the
results. Thanks for the suggestion.

I am still not sure how to check the quality of the mesh! Is there any
simple way to do that or any resources I can read from?

Best,
Niloufar



On Tue, Aug 14, 2018 at 10:02 PM, Charles Williams <willic3 at gmail.com>
wrote:

> Hi Niloufar,
>
> I can’t run your problem since I don’t have your mesh; however, it appears
> that this problem is bombing at about 7300 years.  You have given it a
> total_time of 30000 years, which is quite a long time.  I would see what
> the solution looks like running for 7300 years or so (so it doesn’t
> diverge).  One useful thing would be to look at the deformed mesh (I
> believe this is called something like ‘warp mesh’ in Paraview).  Use a
> magnification factor of 1 and see if the mesh is getting too deformed.  It
> might also be useful to look at the behavior of the solution with time to
> see if you can detect anything unusual.
>
> Cheers,
> Charles
>
> p.s.  Have you checked the quality of your mesh?
>
>
> On 15/08/2018, at 3:55 PM, Niloufar Abolfathian <
> niloufar.abolfathian at gmail.com> wrote:
>
> Hi,
>
> I followed the 2D gravity example and I could run my models with gravity
> and add initial stresses. But in models including finite strain, the
> nonlinear solver could not converge. I have tried running the model with
> gravitation on and off, applying depth dependent initial stress and no
> initial stress, applying multigrid preconditioner and also not applying the
> preconditioner and also modifying the linear and nonlinear tolerances, but
> could not converge the model. I have attached the setting when setting when
> I am using the gravity on, applying initial stress and using
> preconditioning, I am wondering why it is always giving the error after
> 6000 years. I really appreciate all your help solving these issues.
>
> Thanks,
> Niloufar
>
>
>
> On Thu, Aug 2, 2018 at 8:43 AM, Brad Aagaard <baagaard at usgs.gov> wrote:
>
>> Is this the gravity only problem to compute the initial stresses? If so,
>> then you should remove the fault.
>>
>> On 08/01/2018 08:59 PM, Niloufar Abolfathian wrote:
>>
>>> Thanks, Charles.
>>>
>>> My error is due to the convergence of the nonlinear solver. I have made
>>> some modifications but not sure if it is a good idea to decrease my
>>> residual norms.
>>>
>>> Best,
>>> Niloufar
>>>
>>>
>>> This is the setting I am using:
>>>
>>>
>>> [pylithapp.timedependent]
>>> formulation =pylith.problems.ImplicitLgDeform
>>>
>>>
>>> [pylithapp.timedependent.formulation]
>>> output =[domain,subdomain]
>>> output.subdomain =pylith.meshio.OutputSolnSubset
>>> solver =pylith.problems.SolverNonlinear
>>>
>>> [pylithapp.timedependent.formulation.time_step]
>>> total_time =50000.0*year
>>> dt =2.0*year
>>>
>>> [pylithapp.timedependent.interfaces]
>>> fault =pylith.faults.FaultCohesiveDyn
>>>
>>> [pylithapp.timedependent.interfaces.fault]
>>> label =fault
>>> edge =fault_edge
>>> zero_tolerance =1.0e-11
>>>
>>> # Use the slip-weakening friction model.
>>> friction.db_properties =spatialdata.spatialdb.UniformDB
>>> friction.db_properties.label =Slip weakening
>>> friction.db_properties.values =[static-coefficient,dynamic-c
>>> oefficient,slip-weakening-parameter,cohesion]
>>>
>>> friction.db_properties.data =[0.6,0.4,0.2*m,0.0*Pa]
>>>
>>> # ----------------------------------------------------------------------
>>> # PETSc settings
>>> # ----------------------------------------------------------------------
>>> [pylithapp.petsc]
>>> malloc_dump =
>>>
>>> # Preconditioner settings.
>>> pc_type =asm
>>> sub_pc_factor_shift_type =nonzero
>>>
>>
>> When you encounter convergence errors, a good strategy is to revert to
>> the direct solver. Note that this only works when you don't have a fault.
>>
>> pc_type = lu
>>
>>
>> For most real applications (after you have debugged the setup)l, we
>> recommend using the multigrid preconditioner. See
>> solver_algebraicmultigrid.cfg (no fault) and solver_fieldsplit.cfg )with
>> fault) in examples/3d/subduction.
>>
>>
>>> # Friction sensitivity solve used to compute the increment in slip
>>> # associated with changes in the Lagrange multiplier imposed by the
>>> # fault constitutive model.
>>> friction_pc_type =asm
>>> friction_sub_pc_factor_shift_type =nonzero
>>> friction_ksp_max_it =50
>>> friction_ksp_gmres_restart =30
>>>
>>> # Uncomment to view details of friction sensitivity solve.
>>> #friction_ksp_monitor = true
>>> #friction_ksp_view = true
>>> friction_ksp_converged_reason =true
>>>
>>> # Reduce convergence tolerances.
>>> ksp_rtol =1.0e-16
>>> ksp_atol =1.0e-12
>>> ksp_max_it =4000
>>> ksp_gmres_restart =100
>>>
>>> snes_rtol =1.0e-9
>>> snes_atol =1.0e-8
>>> snes_max_it =4000
>>>
>>>
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>
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