[petsc-users] Recommendations of possible preconditioner/ksp solver/snes solver for three phase flow reservoir simulator

[Chukwudi Chukwudozie]

 convergence_check.txt
<https://drive.google.com/file/d/1RXZX081zCvZ8FFEjRBWIkZXgmD0I0arR/view?usp=drive_web>
The non-convergence persists even after putting a KSP wrapper around the
ILU. I have attached a file that contains output of the KSPs for the global
model and that for the blocks. It shows convergence for the first two
newton steps. However, for the third step with no convergence, the KSP
residual norm reduces only minimally before the maximum ksp iteration
steps. Hence, the nonconvergence.



On Mon, Dec 17, 2018 at 9:55 AM Matthew Knepley <knepley at gmail.com> wrote:

> On Sun, Dec 16, 2018 at 10:12 PM Chukwudi Chukwudozie via petsc-users <
> petsc-users at mcs.anl.gov> wrote:
>
>> Barry,
>>
>> Thanks for the reply. I have attached two files with the information.
>>
>> On Sat, Dec 15, 2018 at 8:58 PM Smith, Barry F. <bsmith at mcs.anl.gov>
>> wrote:
>>
>>>
>>>   Chuks,
>>>
>>> 1)   Please run a successful case with -snes_view and send the output so
>>> we can see the exact solver options being used.
>>>
>>> 2)   Run a less successful case with -snes_monitor
>>> -ksp_monitor_true_residual -ksp_converged_reason
>>> -fieldsplit_ksp_monitor_true_residual -fieldsplit_ksp_converged reason so
>>> we can see how the linear solver (and the sub linear solves) are (not)
>>> converging.
>>>
>>
> The first thing I would do is to put Krylov wrappers around the ILU on the
> subblocks. ILU could be good enough
> for your simple case, but I bet the blocks are not begin accurately solved
> in the non-convergent case. You could
> turn on monitor for the blocks to confirm this:
>
>   -P_fieldsplit_0_ksp_type gmres
>   -P_fieldsplit_0_ksp_monitor_true_residual
>
>   Thanks,
>
>      Matt
>
>
>>
>>>     Barry
>>>
>>>
>>> > On Dec 15, 2018, at 7:54 PM, Chukwudi Chukwudozie via petsc-users <
>>> petsc-users at mcs.anl.gov> wrote:
>>> >
>>> > Hi,
>>> >
>>> > I am developing a fully implicit control volume finite element black
>>> oil reservoir simulator using petscdmplex and snes. So far, for 2 phase
>>> flow problems (3 by 3 block for pressure, saturation and bottomhole
>>> pressure), my simulator runs fine for small time step sizes in the order of
>>> less than 5 days. However, increasing the time step size, it doesn't
>>> converge with -3 (-5 sometimes) diverge reason. Considering that this is a
>>> fully implicit but nonlinear problem, I expect unconditional stability for
>>> reasonable time step sizes.
>>> >
>>> >  The background DM for the 3 block problem is a composite one with the
>>> first two being DMPLES's (bag->plexScalNode for pressure and saturation)
>>> and the last one, bag->WellRedun, a redundant DM for the wellbore
>>> pressures. See below.
>>> >
>>> >     ierr =
>>> DMRedundantCreate(PETSC_COMM_WORLD,0,bag->numWells,&bag->WellRedun);CHKERRQ(ierr);
>>> >     ierr =
>>> DMCompositeCreate(PETSC_COMM_WORLD,&bag->MultiPhasePacker);CHKERRQ(ierr);
>>> >         ierr =
>>> DMCompositeAddDM(bag->MultiPhasePacker,bag->plexScalNode);CHKERRQ(ierr);
>>> >         ierr =
>>> DMCompositeAddDM(bag->MultiPhasePacker,bag->plexScalNode);CHKERRQ(ierr);
>>> >         ierr =
>>> DMCompositeAddDM(bag->MultiPhasePacker,bag->WellRedun);CHKERRQ(ierr);
>>> >
>>> > I have used nested matrices as shown below. In addition, I used the
>>> fieldsplit (composite multiplicative) preconditioner with FGRES and least
>>> square for newton solver. See below.
>>> >
>>> > ierr =
>>> MatCreateNest(PETSC_COMM_WORLD,Msize,is,Msize,is,&bK[0],K);CHKERRQ(ierr);
>>> >
>>> >
>>> >     ierr = SNESGetKSP(bag->snesP,&kspP);CHKERRQ(ierr);
>>> >     ierr =
>>> KSPSetTolerances(kspP,1.e-8,1.e-8,PETSC_DEFAULT,PETSC_DEFAULT);CHKERRQ(ierr);
>>> >     ierr = KSPSetType(kspP,KSPFGMRES);CHKERRQ(ierr);
>>> >     ierr = KSPSetFromOptions(kspP);CHKERRQ(ierr);
>>> >     ierr = KSPGetPC(kspP,&pcP);CHKERRQ(ierr);
>>> >     ierr = PCSetType(pcP, PCFIELDSPLIT);CHKERRQ(ierr);
>>> >     ierr =
>>> DMCompositeGetGlobalISs(bag->MultiPhasePacker,&is);CHKERRQ(ierr);
>>> >     for(i = 0; i < Msize; i++)  ierr =
>>> PCFieldSplitSetIS(pcP,NULL,is[i]);CHKERRQ(ierr);
>>> >     ierr =
>>> PCFieldSplitSetType(pcP,PC_COMPOSITE_MULTIPLICATIVE);CHKERRQ(ierr);
>>> >
>>> > Any ideas on possible precoditioner options/solver
>>> options/combinations to improve stability will be appreciated.
>>> >
>>> > Chuks
>>> >
>>>
>>>
>
> --
> What most experimenters take for granted before they begin their
> experiments is infinitely more interesting than any results to which their
> experiments lead.
> -- Norbert Wiener
>
> https://www.cse.buffalo.edu/~knepley/
> <http://www.cse.buffalo.edu/~knepley/>
>
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