[tzaht]

Hi,


I am at my wits end and would appreciate advice on my simpleFoam case.


I have got a basic room win which I am doing a ventilation study, there is an inlet and outlet and otherwise just a basic room with 4 walls. Indeed there is a Lagrangian phase in this case, but it is not relevant as I am first solving for a developed air phase.


As you can see, after only a few iterations, there is a blow up occurring in the case.

Time = 2

smoothSolver:  Solving for Ux, Initial residual = 0.211404, Final residual = 0.000810819, No Iterations 2
smoothSolver:  Solving for Uy, Initial residual = 0.572385, Final residual = 0.00430362, No Iterations 2
smoothSolver:  Solving for Uz, Initial residual = 0.735507, Final residual = 0.00371463, No Iterations 3
DICPCG:  Solving for p, Initial residual = 0.978743, Final residual = 0.0482656, No Iterations 14
time step continuity errors : sum local = 0.000722301, global = -5.1989e-05, cumulative = -5.19826e-05
smoothSolver:  Solving for epsilon, Initial residual = 0.971072, Final residual = 0.00924335, No Iterations 5
bounding epsilon, min: -8.40745e-06 max: 10 average: 0.00628978
smoothSolver:  Solving for k, Initial residual = 0.0730963, Final residual = 0.000527914, No Iterations 3
ExecutionTime = 1.45 s  ClockTime = 2 s

Time = 3

smoothSolver:  Solving for Ux, Initial residual = 0.369427, Final residual = 0.00263847, No Iterations 5
smoothSolver:  Solving for Uy, Initial residual = 0.264407, Final residual = 0.00211726, No Iterations 5
smoothSolver:  Solving for Uz, Initial residual = 0.618079, Final residual = 0.00482763, No Iterations 5
DICPCG:  Solving for p, Initial residual = 0.0736794, Final residual = 0.00308173, No Iterations 5
time step continuity errors : sum local = 0.384043, global = -0.000101108, cumulative = -0.00015309
smoothSolver:  Solving for epsilon, Initial residual = 0.926597, Final residual = 0.00811815, No Iterations 3
bounding epsilon, min: -0.051345 max: 10 average: 0.00115309
smoothSolver:  Solving for k, Initial residual = 0.125533, Final residual = 0.000602382, No Iterations 4
ExecutionTime = 1.82 s  ClockTime = 2 s

Time = 4

smoothSolver:  Solving for Ux, Initial residual = 0.736632, Final residual = 0.0068215, No Iterations 5
smoothSolver:  Solving for Uy, Initial residual = 0.642874, Final residual = 0.00635328, No Iterations 4
smoothSolver:  Solving for Uz, Initial residual = 0.607098, Final residual = 0.00551296, No Iterations 5
DICPCG:  Solving for p, Initial residual = 0.0779532, Final residual = 0.00282609, No Iterations 4
time step continuity errors : sum local = 7.69486, global = 0.058743, cumulative = 0.05859
smoothSolver:  Solving for epsilon, Initial residual = 0.206751, Final residual = 0.00197775, No Iterations 2
bounding epsilon, min: -0.326738 max: 14517.9 average: 1.68526
smoothSolver:  Solving for k, Initial residual = 0.26011, Final residual = 0.00143018, No Iterations 4
bounding k, min: -0.000992726 max: 10411.4 average: 1.66218
ExecutionTime = 2.21 s  ClockTime = 2 s

I cannot see any obvious error in the way I have posed the problem, and I have previously used a Spalart Allmaras set-up with this case, where it ran successfully.



Some more info:

internalField   uniform 0.00015;

boundaryField
{
    wall
    {
        type            kqRWallFunction;
        value           uniform 0.00015;
    }

    hva_inlet
    {
        type            fixedValue;
        value           $internalField;
    }

    hva_outlet
    {
        type            zeroGradient;
    }
}

internalField   uniform 10;

boundaryField
{
    wall
    {
        type            epsilonWallFunction;
        Cmu             0.09;
        kappa           0.41;
        E               9.8;
        value           uniform 10;
    }

    hva_inlet
    {
        type            fixedValue;
        value           $internalField;
    }

    hva_outlet
    {
        type            zeroGradient;
    }
}

Any help really appreciated, as I have toggled with the values of k and epsilon and the blow up always seems to occur after the 4th iteration.

[Tobermory]

Just a quick suggestion - how did you initialise the nut field? If with zero, then try put a non-zero initial value in for the field, since I have had problems with that in the past.

[tzaht]

Originally Posted by Tobermory

Just a quick suggestion - how did you initialise the nut field? If with zero, then try put a non-zero initial value in for the field, since I have had problems with that in the past.

Thanks! This did the trick!