[CIG-SHORT] Problems with viscoelastic model with Pylith

[Brad Aagaard]

Francisco,

Check to make sure the solver is converging at every time step. This is 
easiest if you include

ksp_error_if_not_converged = true

so that the simulation will abort with an error if convergence is not 
reached.

If you still don't understand what the problem is, send a sketch/diagram 
of the problem you are trying to solve along with the 
pylith_parameters.json file generated (which contains all of your 
parameters).

Regards.
Brad



On 07/12/2017 11:49 AM, Francisco Delgado wrote:
> Dear Pylith developers,
> 
> I've been running simulations of a pressurised magma chamber surrounded 
> by a viscoelastic shell with an exponential pressure function of the 
> form P=Pf(1-exp(-t/tau)) but the solutions yields numerical 
> instabilities like in the attached plot. I suspect it's an issue with 
> the solver, but I don't know what to look for. My solver parameters are 
> the following which work well for static linear elastic problems
> 
> [pylithapp.petsc]
> 
> # Preconditioner settings.
> 
> pc_type = asm
> 
> sub_pc_factor_shift_type = nonzero
> 
> # Convergence parameters.
> 
> ksp_rtol = 1.0e-12
> 
> ksp_atol = 1.0e-12
> 
> ksp_max_it = 500
> 
> ksp_gmres_restart = 50
> 
> # Linear solver monitoring options.
> 
> ksp_monitor = true
> 
> ksp_view = true
> 
> ksp_converged_reason = true
> 
> log_summary = true
> 
> # start_in_debugger = true
> 
> 
> 
> Any insight is appreciated
> 
> Thanks
> 
> -- 
> --------------------------------------------------------
> Francisco Delgado
> PhD candidate, Geological Sciences
> Cornell University