[shikamaru]

Hello,

I am working on a problem where I have to take into account the temperature dependent viscosity of non-Newtonian fluids. I modified the solver to account for energy equation (similar to posts available in the forum) and tried to implement the power-law model available in FLUENT (http://aerojet.engr.ucdavis.edu/flue...ug/node340.htm).

I modified everything similar to work done here (http://www.tfd.chalmers.se/~hani/kur...nFoam%20v2.pdf), except to make it similar to the FLUENT implementation, I changed the part of the viscosity model equation.

The pdf file attached has the form in powerLaw.C file for CalcNu() function

Foam::tmp<Foam::volScalarField>
Foam::viscosityModels::powerLawTemp::calcNu() const
{
const volScalarField& T=U_.mesh().lookupObject<volScalarField>("T");

    return max
    (
        nuMin_,
        min
        (
            nuMax_,
            (k_-ko_*(T-To_))*pow
            (
                max
                (
                    dimensionedScalar("one", dimTime, 1.0)*strainRate(),
                    dimensionedScalar("VSMALL", dimless, VSMALL)
                ),
                n_.value() - scalar(1.0)
            )
        )
    );
}

I just modified it to the following form to match FLUENT's formulation-

Foam::tmp<Foam::volScalarField>
Foam::viscosityModels::powerLawTemp2::calcNu() const
{
const volScalarField& T=U_.mesh().lookupObject<volScalarField>("T");

    return max
    (
        nuMin_,
        min
        (
            nuMax_,
            (k_*exp(T/To_))*pow
            (
                max
                (
                    dimensionedScalar("one", dimTime, 1.0)*strainRate(),
                    dimensionedScalar("VSMALL", dimless, VSMALL)
                ),
                n_.value() - scalar(1.0)
            )
        )
    );
}

The 1st implementation works fine but for the second one I am getting errors that I can not resolve or understand why its happening. T is a volScalarField and To a scalar taken as input. I thought the exp() should be able to handle that. Here is the error log -

Create time

Create mesh for time = 0

Reading setFieldsDict

Setting field default values
    Setting internal values of volScalarField alpha.water
    Setting internal values of volScalarField T

Setting field region values
    Adding cells with center within boxes 1((0 0 -1) (0.1461 0.292 1))
    Setting internal values of volScalarField alpha.water
    Adding cells with center within boxes 1((0.2 0.3 -1) (0.3 0.4 1))
    Setting internal values of volScalarField T

End

#0  Foam::error::printStack(Foam::Ostream&) in "/projects/OpenFOAM/OpenFOAM-2.3.0/platforms/linux64GccDPOpt/lib/libOpenFOAM.so"
#1  Foam::sigFpe::sigHandler(int) in "/projects/OpenFOAM/OpenFOAM-2.3.0/platforms/linux64GccDPOpt/lib/libOpenFOAM.so"
#2   in "/lib64/libc.so.6"
#3   in "/lib64/libm.so.6"
#4  exp in "/lib64/libm.so.6"
#5  Foam::exp(Foam::Field<double>&, Foam::UList<double> const&) in "/projects/OpenFOAM/OpenFOAM-2.3.0/platforms/linux64GccDPOpt/lib/libOpenFOAM.so"
#6  void Foam::exp<Foam::fvPatchField, Foam::volMesh>(Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh>&, Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> const&) in "/home/OpenFOAM/2.3.0/platforms/linux64GccDPOpt/lib/libmyIncompressibleTransportModels.so"
#7  Foam::tmp<Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> > Foam::exp<Foam::fvPatchField, Foam::volMesh>(Foam::tmp<Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> > const&) in "/home/OpenFOAM/2.3.0/platforms/linux64GccDPOpt/lib/libmyIncompressibleTransportModels.so"
#8  Foam::viscosityModels::powerLawTemp2::calcNu() const in "/home/OpenFOAM/2.3.0/platforms/linux64GccDPOpt/lib/libmyIncompressibleTransportModels.so"
#9  Foam::viscosityModels::powerLawTemp2::correct() in "/home/OpenFOAM/2.3.0/platforms/linux64GccDPOpt/lib/libmyIncompressibleTransportModels.so"
#10  Foam::incompressibleTwoPhaseMixture::calcNu() in "/home/OpenFOAM/2.3.0/platforms/linux64GccDPOpt/lib/libmyIncompressibleTransportModels.so"
#11  
 at /projects/OpenFOAM/OpenFOAM-2.3.0/src/OpenFOAM/lnInclude/Switch.H:187
#12  __libc_start_main in "/lib64/libc.so.6"
#13  
 in "/home/OpenFOAM/2.3.0/platforms/linux64GccDPOpt/bin/interTempFoamV2"
Allrun.sh: line 8: 17499 Floating point exceptioninterTempFoamV2 > log.txt

I can see errors are coming from the calcNu() function but I cant figure out why. Would really appreciate some help if anyone has experience dealing with this before.

Regards

[jherb]

The error message shows that the problem is somehow related to the exp() function call. So search this site for help:
https://www.google.de/search?q=site%...foam+%22exp%22
Here are two threads, which might help:
http://www.cfd-online.com/Forums/ope...t-working.html
http://www.cfd-online.com/Forums/ope...ut-scalar.html

[shikamaru]

Thank you for the references, I will look them up.

[himanshu28]

Hi ,
I am trying to built a new viscosity model based on some scalar like alpha(concentration),T (Temperature)
I have tried the following approach given below

/*---------------------------------------------------------------------------*\
  =========                 |
  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
   \\    /   O peration     |
    \\  /    A nd           | Copyright (C) 2011 OpenFOAM Foundation
     \\/     M anipulation  |
-------------------------------------------------------------------------------
License
    This file is part of OpenFOAM.

    OpenFOAM is free software: you can redistribute it and/or modify it
    under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
    for more details.

    You should have received a copy of the GNU General Public License
    along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.

\*---------------------------------------------------------------------------*/

#include "alphaTLaw.H"
#include "addToRunTimeSelectionTable.H"
#include "surfaceFields.H"

// * * * * * * * * * * * * * * Static Data Members * * * * * * * * * * * * * //

namespace Foam
{
namespace viscosityModels
{
    defineTypeNameAndDebug(alphaTLaw, 0);

    addToRunTimeSelectionTable
    (
        viscosityModel,
        alphaTLaw,
        dictionary
    );
}
}


// * * * * * * * * * * * * Private Member Functions  * * * * * * * * * * * * //

Foam::tmp<Foam::volScalarField>
Foam::viscosityModels::alphaTLaw::calcNu() const
{
const volScalarField& T = U_.mesh().lookupObject<volScalarField>("T");
const volScalarField& alpha = U_.mesh().lookupObject<volScalarField>("alpha");


        return ((1/Re_)*exp(alpha*(ln(m_))-T));


}
// * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //

Foam::viscosityModels::alphaTLaw::alphaTLaw
(
    const word& name,
    const dictionary& viscosityProperties,
    const volVectorField& U,
    const surfaceScalarField& phi
)
:
    viscosityModel(name, viscosityProperties, U, phi),
    //alphaTLawCoeffs_(viscosityProperties.subDict(typeName + "Coeffs")),
    Re_(alphaTLawCoeffs_.lookup("Re")),
    m_(alphaTLawCoeffs_.lookup("m")),
    //nuMin_(alphaTLawCoeffs_.lookup("nuMin")),
    //nuMax_(alphaTLawCoeffs_.lookup("nuMax")),

    nu_
    (
        IOobject
        (
            name,
            U_.time().timeName(),
            U_.db(),
            IOobject::NO_READ,
            IOobject::AUTO_WRITE
        ),
        calcNu()
    )
{}

// * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * * //

bool Foam::viscosityModels::alphaTLaw::read
(
    const dictionary& viscosityProperties
)
{
    viscosityModel::read(viscosityProperties);

    alphaTLawCoeffs_ = viscosityProperties.subDict(typeName + "Coeffs");

    alphaTLawCoeffs_.lookup("Re") >> Re_;
    alphaTLawCoeffs_.lookup("m") >> m_;
    //alphaTLawCoeffs_.lookup("nuMin") >> nuMin_;
    //alphaTLawCoeffs_.lookup("nuMax") >> nuMax_;

    return true;
}


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

But I am getting following error in wmake libso.

Making dependency list for source file alphaTLaw.C
SOURCE=alphaTLaw.C ;  g++ -m64 -Dlinux64 -DWM_DP -Wall -Wextra -Wno-unused-parameter -Wold-style-cast -Wnon-virtual-dtor -O3  -DNoRepository -ftemplate-depth-100 -I/home/himanshu/OpenFOAM/OpenFOAM-2.3.0/src/transportModels/incompressible/lnInclude/ -I.. -I../twoPhaseMixture/lnInclude -I/home/himanshu/OpenFOAM/OpenFOAM-2.3.0/src/finiteVolume/lnInclude -IlnInclude -I. -I/home/himanshu/OpenFOAM/OpenFOAM-2.3.0/src/OpenFOAM/lnInclude -I/home/himanshu/OpenFOAM/OpenFOAM-2.3.0/src/OSspecific/POSIX/lnInclude   -fPIC -c $SOURCE -o Make/linux64GccDPOpt/alphaTLaw.o
alphaTLaw.C: In member function ‘Foam::tmp<Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> > Foam::viscosityModels::alphaTLaw::calcNu() const’:
alphaTLaw.C:57:33: error: invalid initialization of reference of type ‘const Foam::fileName&’ from expression of type ‘const dimensionedScalar {aka const Foam::dimensioned<double>}’
  return ((1/Re_)*exp(alpha*ln(m_)-T));
                                 ^
In file included from /home/himanshu/OpenFOAM/OpenFOAM-2.3.0/src/OpenFOAM/lnInclude/regIOobject.H:43:0,
                 from /home/himanshu/OpenFOAM/OpenFOAM-2.3.0/src/OpenFOAM/lnInclude/GeometricField.H:42,
                 from /home/himanshu/OpenFOAM/OpenFOAM-2.3.0/src/OpenFOAM/lnInclude/GeometricScalarField.H:38,
                 from /home/himanshu/OpenFOAM/OpenFOAM-2.3.0/src/OpenFOAM/lnInclude/GeometricFields.H:34,
                 from /home/himanshu/OpenFOAM/OpenFOAM-2.3.0/src/finiteVolume/lnInclude/volFields.H:37,
                 from alphaTLaw.H:40,
                 from alphaTLaw.C:26:
/home/himanshu/OpenFOAM/OpenFOAM-2.3.0/src/OpenFOAM/lnInclude/OSspecific.H:170:6: error: in passing argument 1 of ‘bool Foam::ln(const Foam::fileName&, const Foam::fileName&)’
 bool ln(const fileName& src, const fileName& dst);
      ^
alphaTLaw.C:60:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^
make: *** [Make/linux64GccDPOpt/alphaTLaw.o] Error 1

I not getting any clue why the following error in Bold is appearing.
Thank you
Regards