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p_rgh and time step continuity error

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Old   June 16, 2019, 06:41
Default p_rgh and time step continuity error
  #1
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Raza Javed
Join Date: Apr 2019
Location: Germany
Posts: 180
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Hello Everyone,


I am using chtMultiRegionSimpleFoam and my OpenFoam version is 4.1.


I have multiple regions in my geometry and one region is the fluid region, and I am modelling turbulent flow in this.


I am a bit confused about that What is p_rgh?

And how to decide boundary conditions for this?


In my case, I have fixed inlet velocity and zeroGradient at the outlet. Pressure in the complete fluid region has calculated boundary condition.


But I am not sure about p_rgh, what boundary conditions to put?


My changeDictionaryDict file is below:


Code:
boundary
{
    inlet
    {
        type            patch;
    }
    outlet
    {
        type            patch;
    }
}

T
{
    internalField   uniform 300;

    boundaryField
    {
        inlet
        {
            type            fixedValue;
            value           $internalField;
            
        }

        outlet
        {
            type            zeroGradient;
            value           $internalField;

        }

        "fluid_to_box"
        {
            type            compressible::turbulentTemperatureCoupledBaffleMixed;
            Tnbr            T;
            kappaMethod     fluidThermo;
            value           uniform 300;
        }
    }
}

U
{
    internalField   uniform (0 0 0);

    boundaryField
    {
        inlet
        {
            type            fixedValue;
            value           uniform (0 0 -1.33);
        }

        outlet
        {
            type            zeroGradient;
        }
        "fluid_to_box"
        {
            type            noSlip;
        }
    }
}

epsilon
{
    internalField   uniform 0.01;

    boundaryField
    {
        inlet
        {
            type            fixedValue;
            value           uniform 0.01;
        }

        outlet
        {
            type            inletOutlet;
            inletValue      uniform 0.01;
        }

        ".*"
        {
            type            epsilonWallFunction;
            value           uniform 0.01;
        }
    }
}

k
{
    internalField   uniform 0.1;

    boundaryField
    {
        inlet
        {
            type            inletOutlet;
            inletValue      uniform 0.1;
        }

        outlet
        {
            type            zeroGradient;
            value           uniform 0.1;
        }

        ".*"
        {
            type            kqRWallFunction;
            value           uniform 0.1;
        }
    }
}


p_rgh
{
    internalField   uniform 0;

    boundaryField
    {
        inlet
        {
            type            zeroGradient;
            value           uniform 0;
        }

        outlet
        {
            type            fixedValue;
            value           uniform 0;
        }

        ".*"
        {
            type            fixedFluxPressure;
            value           uniform 0;
        }
    }
}

p
{
    internalField   uniform 0;

    boundaryField
    {
        ".*"
        {
            type            calculated;
            value           uniform 0;
        }
    }
}

/*p
{
    internalField   uniform 0;

    boundaryField
    {
        inlet
        {
            type            zeroGradient;//fixedValue;
            //value           uniform 10;
        }
        outlet
        {
            type            fixedValue;
            value           uniform 0;
        }
        "fluid_to_.*"
        {
            type            zeroGradient;

        }
    }
}*/

alphat
{
    internalField   uniform 0;

    boundaryField
    {
        inlet
        {
            type            calculated;//fixedValue;
            value           uniform 0;
        }

        outlet
        {
            type            calculated;
            value           uniform 0;
        }

        "fluid_to_box"
        {
            type            compressible::alphatWallFunction;
            value           uniform 0;
        }

        //#includeEtc "caseDicts/setConstraintTypes"
    }
}

nut
{
    internalField   uniform 0;

    boundaryField
    {
        inlet
        {
            type            calculated;
            value           uniform 0;
        }

        outlet
        {
            type            calculated;
            value           uniform 0;
        }

        "fluid_to_box"
        {
            type            nutkWallFunction;
            value           uniform 0;
        }

        //#includeEtc "caseDicts/setConstraintTypes"
    }
}

// ************************************************************************* //



When I am running the solver it gives me the following error.


Code:
--> FOAM FATAL ERROR: 
Maximum number of iterations exceeded

    From function Foam::scalar Foam::species::thermo<Thermo, Type>::T(Foam::scalar, Foam::scalar, Foam::scalar, Foam::scalar (Foam::species::thermo<Thermo, Type>::*)(Foam::scalar, Foam::scalar) const, Foam::scalar (Foam::species::thermo<Thermo, Type>::*)(Foam::scalar, Foam::scalar) const, Foam::scalar (Foam::species::thermo<Thermo, Type>::*)(Foam::scalar) const) const [with Thermo = Foam::hConstThermo<Foam::rhoConst<Foam::specie> >; Type = Foam::sensibleEnthalpy; Foam::scalar = double; Foam::species::thermo<Thermo, Type> = Foam::species::thermo<Foam::hConstThermo<Foam::rhoConst<Foam::specie> >, Foam::sensibleEnthalpy>]
    in file /home/ubuntu/OpenFOAM/OpenFOAM-4.1/src/thermophysicalModels/specie/lnInclude/thermoI.H at line 66.

FOAM aborting

#0  Foam::error::printStack(Foam::Ostream&) at ??:?
#1  Foam::error::abort() at ??:?
#2  Foam::heRhoThermo<Foam::rhoThermo, Foam::pureMixture<Foam::constTransport<Foam::species::thermo<Foam::hConstThermo<Foam::rhoConst<Foam::specie> >, Foam::sensibleEnthalpy> > > >::calculate() at ??:?
#3  Foam::heRhoThermo<Foam::rhoThermo, Foam::pureMixture<Foam::constTransport<Foam::species::thermo<Foam::hConstThermo<Foam::rhoConst<Foam::specie> >, Foam::sensibleEnthalpy> > > >::correct() at ??:?
#4  ? at ??:?
#5  __libc_start_main in "/lib/x86_64-linux-gnu/libc.so.6"
#6  ? at ??:?
Aborted (core dumped)

The log file of the solver is also attached:


Code:
Solving for fluid region fluid
DILUPBiCG:  Solving for Ux, Initial residual = 0.9997355, Final residual = 0.08277523, No Iterations 2
DILUPBiCG:  Solving for Uy, Initial residual = 0.9999186, Final residual = 0.07461577, No Iterations 2
DILUPBiCG:  Solving for Uz, Initial residual = 0.999995, Final residual = 0.05243879, No Iterations 2
DILUPBiCG:  Solving for h, Initial residual = 1, Final residual = 0.04643201, No Iterations 2
Min/max T:-2938920 1665459
GAMG:  Solving for p_rgh, Initial residual = 0.1680867, Final residual = 0.0009985177, No Iterations 6
time step continuity errors : sum local = 19589.79, global = 1565.821, cumulative = 1565.819
Min/max rho:2 2
DILUPBiCG:  Solving for epsilon, Initial residual = 0.9999723, Final residual = 2.378201e-09, No Iterations 1
DILUPBiCG:  Solving for k, Initial residual = 0.9999912, Final residual = 0.06906627, No Iterations 2

Solving for solid region box
DICPCG:  Solving for h, Initial residual = 1, Final residual = 0.03971379, No Iterations 2
Min/max T:-264388.9 90652.27

Solving for solid region plate1
DICPCG:  Solving for h, Initial residual = 1, Final residual = 0.02562304, No Iterations 2
Min/max T:299.9961 300.0009

Solving for solid region plate2
DICPCG:  Solving for h, Initial residual = 1, Final residual = 0.03224597, No Iterations 2
Min/max T:299.9911 300.0009

Solving for solid region plate3
DICPCG:  Solving for h, Initial residual = 1, Final residual = 0.02419843, No Iterations 2
Min/max T:299.9997 300.0009

Solving for solid region hot1
DICPCG:  Solving for h, Initial residual = 0.8450844, Final residual = 0.005572694, No Iterations 2
Min/max T:300.0004 300.0031

Solving for solid region hot2
DICPCG:  Solving for h, Initial residual = 0.8459705, Final residual = 0.005387614, No Iterations 2
Min/max T:300.0005 300.003

Solving for solid region hot3
DICPCG:  Solving for h, Initial residual = 0.8490299, Final residual = 0.00578213, No Iterations 2
Min/max T:300.0004 300.003
ExecutionTime = 0.32 s  ClockTime = 0 s

Time = 0.3


Solving for fluid region fluid
DILUPBiCG:  Solving for Ux, Initial residual = 0.9586069, Final residual = 0.04442897, No Iterations 2
DILUPBiCG:  Solving for Uy, Initial residual = 0.9413187, Final residual = 0.02525996, No Iterations 2
DILUPBiCG:  Solving for Uz, Initial residual = 0.8798151, Final residual = 0.03200322, No Iterations 2
DILUPBiCG:  Solving for h, Initial residual = 0.9769101, Final residual = 0.01300722, No Iterations 2

From, the log file, it can be seen that the value of time step continuity error is very large, may be this error is because of that.


Any help would be highly appreciated.


Thank you
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Old   June 20, 2019, 06:07
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  #2
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Ingo Riess
Join Date: Jun 2019
Location: Switzerland
Posts: 30
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Here is an explanation of the term p_rgh:
Hydrostatic pressure effects

In your logfile for "solid region box", you get extraordinary temperatures min/max T:-264388.9 90652.27 K while everything else is at 300K. Could be that the trouble is caused there?
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chtmultiregionsimplefoam, openfoam, turbulence modelling

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