CFD Online Discussion Forums - pimpleFoam screwed up with residual and courant number

I was trying to use pimpleFoam to obtain the transient solution of my simulation. In fvSolution, I followed: https://openfoamwiki.net/index.php/O...hm_in_OpenFOAM to setup.
And when I had my first timestep, the residuals went crazy. Here is the residuals plot just after the first timestep(50 iterations):
https://i.ibb.co/3kr8GZJ/resPlot.png

The velocity residuals blew up.

Also, in log.pimpleFoam, I found
1. forceCoeffs blew up;
2. courant blew up;
3. PIMPLE: Not converged within 50 iterations
4. last iteration take 1000 iterations for velocity
Here is part of the log:

Code:

...

PIMPLE: Iteration 49

smoothSolver:  Solving for Ux, Initial residual = 0.2628474, Final residual = 0.006348619, No Iterations 1

smoothSolver:  Solving for Uy, Initial residual = 0.3153633, Final residual = 0.009944488, No Iterations 1

smoothSolver:  Solving for Uz, Initial residual = 0.2931374, Final residual = 0.009416199, No Iterations 1

GAMG:  Solving for p, Initial residual = 1.737072e-05, Final residual = 9.476295e-08, No Iterations 4

time step continuity errors : sum local = 0.0003989904, global = 4.242985e-07, cumulative = 5.625885e-07

PIMPLE: Iteration 50

smoothSolver:  Solving for Ux, Initial residual = 0.6357956, Final residual = 0.0001464525, No Iterations 1000

smoothSolver:  Solving for Uy, Initial residual = 0.7345522, Final residual = 8.67146e-05, No Iterations 1000

smoothSolver:  Solving for Uz, Initial residual = 0.7207067, Final residual = 7.978962e-05, No Iterations 1000

GAMG:  Solving for p, Initial residual = 0.1127675, Final residual = 8.968816e-08, No Iterations 55

time step continuity errors : sum local = 0.004213623, global = -0.001068937, cumulative = -0.001068374

smoothSolver:  Solving for epsilon, Initial residual = 1, Final residual = 0.1651915, No Iterations 1000

smoothSolver:  Solving for k, Initial residual = 1, Final residual = 9.930172e-07, No Iterations 81

PIMPLE: Not converged within 50 iterations

ExecutionTime = 3608.8 s  ClockTime = 3653 s



forceCoeffs forceCoeffs1 write:

    Cm    = -1.194991e+17

    Cd    = -1.60657e+17

    Cl    = 1.946065e+17

    Cl(f) = -2.219587e+16

    Cl(r) = 2.168024e+17



Courant Number mean: 242261.2 max: 6.091332e+10

deltaT = 2.897077e-13

Time = 0.00588235

my questions are:
1. Why would my courant number go so large? I should have limited it in controlDict:

Code:

maxCo                3;

maxDaltaT        1;

2. Is 50 nOuterCorrector too few for this case?

3. Is any of my setup got wrong?(I will post it at the end)

Thank you very much!!

fvSolution:

Code:

solvers

{

    p

    {

        solver          GAMG;

        smoother        DICGaussSeidel;

        tolerance       1e-7;

        relTol          0.01;

    }



    pFinal

    {

        $p;        

        relTol                0;



    }



    "(U|k|epsilon)"

    {

        solver                smoothSolver;

        smoother        symGaussSeidel;

        tolerance        1e-06;

        relTol                0.1;

    }



    "(U|k|epsilon)Final"

    {

        $U;

        tolerance        1e-06;

        relTol                0;

    }

}





PIMPLE

{

        nOuterCorrectors         50;

        nCorrectors                 1;

        nNonOrthogonalCorrectors 0;



        outerCorrectorResidualControl

        {

                U

                {

                        tolerance        1e-5;

                        relTol                0;

                }

                p

                {

                        tolerance        5e-4;

                        relTol                0;

                }

        }

}





relaxationFactors

{

    fields

    {

        p        0.3;

        pFinal        1;

    }



    equations

    {

        "U|k|epsilon"        0.3;        

        "(U|k|epsilon)Final"        1;

    }

}

controlDict:

Code:

application     pimpleFoam;



startFrom       latestTime;



startTime       0;



stopAt          endTime;



endTime         400;



deltaT          0.005;



writeControl    adjustableRunTime;



writeInterval   0.1;



purgeWrite      0;



writeFormat     binary;



writePrecision  7;



writeCompression off;



timeFormat      general;



timePrecision   6;



runTimeModifiable yes;



adjustTimeStep        yes;



maxCo                3;

maxDaltaT        1;



functions

{

    #include "streamLines"

    #include "cuttingPlane"

    #include "forceCoeffs"

}