[efsolat]

Dear foamers,
I am doing a transient case using pimpleFoam. My geometry consists of a tube with constant input.

I have run the case with simpleFoam and it converged (even for various # cells). I have used the U and p fields resulted from simpleFoam as the initial values for pimpleFoam. pimpleFoam starts normally and converged in the first time step but at the next steps it doesn't converge and the problem is that the initial residual of p increases within the piso loop of pimpleFoam and avoids the convergence. It is notable that when i set nCorrectors 1 it doesn't converge even in the first time step. Maybe anybody knows the reason of piso fluctuations. please help.

Many thanks in advance!

fvSolution
solvers

{
   
   p
    {
        solver           PBiCGStab;// GAMG;//PCG;//
        preconditioner   DIC;
         tolerance       1e-06;
        relTol          0;
    }
    pFinal
    {
        $p;
        tolerance       1e-6;
        relTol          0;
    }
    "(U|k|epsilon)"
    {
        solver            smoothSolver;//PBiCGStab;//PBiCG;// GAMG;// 
      //  preconditioner    DILU;//   diagonal;//     
       smoother         DILU;// DILUGaussSeidel;// GaussSeidel;// nonBlockingGaussSeidel;// symGaussSeidel;//
       nSweeps          3;
        tolerance         1e-08;
        relTol            0;
        minItr            50;
    }
    UFinal
    {
        $U;
        tolerance       1e-8;
        relTol          0;
        minItr          50;
    }

    }

  PIMPLE
 {
    momentumPredictor   yes;
    correctPhi          yes;
    nOuterCorrectors    115;
    nCorrectors         3;
    nNonOrthogonalCorrectors 0;

    pRefCell        0;
    pRefValue       0;

    moveMeshOuterCorrectors false;

    consistent true;
    residualControl
     {
        U 
        {
            tolerance 1e-3;
            relTol 0;
        }
        p
        {
            tolerance 1e-2;
            relTol 0;
            
        }

             }
 }
relaxationFactors
  {
    fields
    {
        p              0.25;
       // p_rgh           0.9;
        pFinal          1;  // Last outer loop
    }
    equations
     {
       "U|k|epsilon"            0.2;
       "(U|k|epsilon)Final"     1;
                 }
   }

and the log results for final iterations of first and second time steps

PIMPLE: iteration 60
smoothSolver:  Solving for Ux, Initial residual = 0.000596143, Final residual = 1.68916e-11, No Iterations 3
smoothSolver:  Solving for Uy, Initial residual = 0.00048953, Final residual = 8.49394e-12, No Iterations 3
smoothSolver:  Solving for Uz, Initial residual = 0.000205322, Final residual = 2.13581e-11, No Iterations 3
DICPBiCGStab:  Solving for p, Initial residual = 0.0290384, Final residual = 9.97052e-07, No Iterations 120
time step continuity errors : sum local = 2.23685e-09, global = -2.09271e-10, cumulative = 1.22208e-08
DICPBiCGStab:  Solving for p, Initial residual = 0.0513252, Final residual = 9.98867e-07, No Iterations 165
time step continuity errors : sum local = 2.29943e-09, global = -9.46057e-10, cumulative = 1.12747e-08
DICPBiCGStab:  Solving for p, Initial residual = 0.0228054, Final residual = 9.56565e-07, No Iterations 102
time step continuity errors : sum local = 2.14037e-09, global = 2.6051e-10, cumulative = 1.15353e-08
PIMPLE: iteration 61
smoothSolver:  Solving for Ux, Initial residual = 0.000600401, Final residual = 1.68889e-11, No Iterations 3
smoothSolver:  Solving for Uy, Initial residual = 0.000489021, Final residual = 4.43221e-12, No Iterations 3
smoothSolver:  Solving for Uz, Initial residual = 0.000125419, Final residual = 1.99905e-11, No Iterations 3
DICPBiCGStab:  Solving for p, Initial residual = 0.0385374, Final residual = 9.62274e-07, No Iterations 226
time step continuity errors : sum local = 2.18719e-09, global = -1.86789e-09, cumulative = 9.66736e-09
DICPBiCGStab:  Solving for p, Initial residual = 0.015498, Final residual = 7.43952e-07, No Iterations 145
time step continuity errors : sum local = 1.65077e-09, global = -1.4565e-09, cumulative = 8.21086e-09
DICPBiCGStab:  Solving for p, Initial residual = 0.0227203, Final residual = 5.81333e-07, No Iterations 206
time step continuity errors : sum local = 1.29589e-09, global = -1.15134e-09, cumulative = 7.05952e-09
PIMPLE: iteration 62
smoothSolver:  Solving for Ux, Initial residual = 0.000604502, Final residual = 1.34418e-11, No Iterations 3
smoothSolver:  Solving for Uy, Initial residual = 0.0002945, Final residual = 4.25852e-12, No Iterations 3
smoothSolver:  Solving for Uz, Initial residual = 0.000180853, Final residual = 1.63934e-11, No Iterations 3
DICPBiCGStab:  Solving for p, Initial residual = 0.0125226, Final residual = 9.03802e-07, No Iterations 197
time step continuity errors : sum local = 1.99878e-09, global = -9.23917e-10, cumulative = 6.1356e-09
DICPBiCGStab:  Solving for p, Initial residual = 0.0165563, Final residual = 9.59857e-07, No Iterations 229
time step continuity errors : sum local = 2.12599e-09, global = 1.05918e-09, cumulative = 7.19478e-09
DICPBiCGStab:  Solving for p, Initial residual = 0.00870745, Final residual = 9.79781e-07, No Iterations 167
time step continuity errors : sum local = 2.15445e-09, global = -1.64654e-09, cumulative = 5.54824e-09
PIMPLE: iteration 63
smoothSolver:  Solving for Ux, Initial residual = 0.00207671, Final residual = 9.15617e-09, No Iterations 132
smoothSolver:  Solving for Uy, Initial residual = 0.00106387, Final residual = 8.38791e-09, No Iterations 90
smoothSolver:  Solving for Uz, Initial residual = 0.000734466, Final residual = 9.43681e-09, No Iterations 105
DICPBiCGStab:  Solving for p, Initial residual = 0.0160802, Final residual = 9.57418e-07, No Iterations 175
time step continuity errors : sum local = 6.38359e-08, global = 4.96666e-08, cumulative = 5.52149e-08
DICPBiCGStab:  Solving for p, Initial residual = 0.204943, Final residual = 9.94995e-07, No Iterations 142
time step continuity errors : sum local = 8.17283e-08, global = -1.66004e-08, cumulative = 3.86145e-08
DICPBiCGStab:  Solving for p, Initial residual = 0.321276, Final residual = 9.05519e-07, No Iterations 123
time step continuity errors : sum local = 8.7076e-08, global = -1.48197e-08, cumulative = 2.37949e-08
PIMPLE: converged in 63 iterations
Courant Number mean: 0.00221723 max: 16.9237
deltaT = 0.000170612
Time = 0.00594538

PIMPLE: iteration 1
smoothSolver:  Solving for Ux, Initial residual = 0.000726623, Final residual = 3.21501e-12, No Iterations 3
smoothSolver:  Solving for Uy, Initial residual = 0.00353084, Final residual = 9.0885e-12, No Iterations 3
smoothSolver:  Solving for Uz, Initial residual = 0.000171417, Final residual = 6.08206e-12, No Iterations 3
DICPBiCGStab:  Solving for p, Initial residual = 0.547564, Final residual = 9.87219e-07, No Iterations 291
time step continuity errors : sum local = 1.38683e-10, global = 8.50819e-11, cumulative = 2.38799e-08
DICPBiCGStab:  Solving for p, Initial residual = 0.338699, Final residual = 3.90249e-07, No Iterations 255
time step continuity errors : sum local = 4.52846e-11, global = -4.5126e-12, cumulative = 2.38754e-08
DICPBiCGStab:  Solving for p, Initial residual = 0.380801, Final residual = 8.73685e-07, No Iterations 240
time step continuity errors : sum local = 1.15928e-10, global = -9.86046e-12, cumulative = 2.38656e-08
PIMPLE: iteration 2
smoothSolver:  Solving for Ux, Initial residual = 0.000918823, Final residual = 1.84937e-11, No Iterations 3
smoothSolver:  Solving for Uy, Initial residual = 0.0102808, Final residual = 5.02138e-11, No Iterations 3
smoothSolver:  Solving for Uz, Initial residual = 0.00029521, Final residual = 1.8008e-11, No Iterations 3
DICPBiCGStab:  Solving for p, Initial residual = 0.269734, Final residual = 9.15093e-07, No Iterations 252
time step continuity errors : sum local = 1.04702e-10, global = -2.08214e-11, cumulative = 2.38447e-08
DICPBiCGStab:  Solving for p, Initial residual = 0.309119, Final residual = 4.23408e-07, No Iterations 238
time step continuity errors : sum local = 4.7834e-11, global = -3.87096e-11, cumulative = 2.3806e-08
DICPBiCGStab:  Solving for p, Initial residual = 0.220623, Final residual = 4.8042e-07, No Iterations 253
time step continuity errors : sum local = 5.0209e-11, global = -3.04463e-11, cumulative = 2.37756e-08
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PIMPLE: iteration 112
smoothSolver:  Solving for Ux, Initial residual = 0.000654905, Final residual = 5.10987e-11, No Iterations 3
smoothSolver:  Solving for Uy, Initial residual = 0.008963, Final residual = 4.70701e-10, No Iterations 3
smoothSolver:  Solving for Uz, Initial residual = 0.002707, Final residual = 1.98632e-10, No Iterations 3
DICPBiCGStab:  Solving for p, Initial residual = 0.508875, Final residual = 8.70705e-07, No Iterations 259
time step continuity errors : sum local = 1.35272e-10, global = 8.35666e-11, cumulative = 2.39468e-08
DICPBiCGStab:  Solving for p, Initial residual = 0.636816, Final residual = 9.83226e-07, No Iterations 239
time step continuity errors : sum local = 1.94442e-10, global = 1.66498e-10, cumulative = 2.41133e-08
DICPBiCGStab:  Solving for p, Initial residual = 0.216246, Final residual = 9.04256e-07, No Iterations 239
time step continuity errors : sum local = 9.22798e-11, global = 5.99732e-11, cumulative = 2.41732e-08
PIMPLE: iteration 113
smoothSolver:  Solving for Ux, Initial residual = 0.000786775, Final residual = 5.61967e-11, No Iterations 3
smoothSolver:  Solving for Uy, Initial residual = 0.014052, Final residual = 2.9613e-10, No Iterations 3
smoothSolver:  Solving for Uz, Initial residual = 0.00341111, Final residual = 2.98654e-10, No Iterations 3
DICPBiCGStab:  Solving for p, Initial residual = 0.30737, Final residual = 4.81297e-07, No Iterations 267
time step continuity errors : sum local = 5.46339e-11, global = -2.44855e-11, cumulative = 2.41488e-08
DICPBiCGStab:  Solving for p, Initial residual = 0.318505, Final residual = 5.74335e-07, No Iterations 238
time step continuity errors : sum local = 6.78318e-11, global = 2.74993e-11, cumulative = 2.41763e-08
DICPBiCGStab:  Solving for p, Initial residual = 0.316076, Final residual = 9.71893e-07, No Iterations 271
time step continuity errors : sum local = 1.17822e-10, global = 2.19671e-11, cumulative = 2.41982e-08
PIMPLE: iteration 114
smoothSolver:  Solving for Ux, Initial residual = 0.000839459, Final residual = 6.56314e-11, No Iterations 3
smoothSolver:  Solving for Uy, Initial residual = 0.0113558, Final residual = 2.80627e-10, No Iterations 3
smoothSolver:  Solving for Uz, Initial residual = 0.00402269, Final residual = 2.05148e-10, No Iterations 3
DICPBiCGStab:  Solving for p, Initial residual = 0.255311, Final residual = 9.42784e-07, No Iterations 260
time step continuity errors : sum local = 1.05578e-10, global = 5.01809e-11, cumulative = 2.42484e-08
DICPBiCGStab:  Solving for p, Initial residual = 0.416368, Final residual = 9.32197e-07, No Iterations 254
time step continuity errors : sum local = 1.44675e-10, global = -2.3226e-11, cumulative = 2.42252e-08
DICPBiCGStab:  Solving for p, Initial residual = 0.305066, Final residual = 7.54257e-07, No Iterations 238
time step continuity errors : sum local = 9.33397e-11, global = 7.98126e-12, cumulative = 2.42332e-08
PIMPLE: iteration 115
smoothSolver:  Solving for Ux, Initial residual = 0.00383473, Final residual = 9.00047e-09, No Iterations 126
smoothSolver:  Solving for Uy, Initial residual = 0.0347903, Final residual = 8.96059e-09, No Iterations 135
smoothSolver:  Solving for Uz, Initial residual = 0.0268389, Final residual = 8.99541e-09, No Iterations 135
DICPBiCGStab:  Solving for p, Initial residual = 0.250735, Final residual = 6.17735e-07, No Iterations 283
time step continuity errors : sum local = 2.71463e-09, global = 2.64751e-09, cumulative = 2.68807e-08
DICPBiCGStab:  Solving for p, Initial residual = 0.981904, Final residual = 9.85822e-07, No Iterations 129
time step continuity errors : sum local = 2.2477e-07, global = 4.54504e-08, cumulative = 7.23311e-08
DICPBiCGStab:  Solving for p, Initial residual = 0.988755, Final residual = 9.79718e-07, No Iterations 119
time step continuity errors : sum local = 4.52153e-07, global = -2.04961e-09, cumulative = 7.02815e-08
PIMPLE: not converged within 115 iterations