CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > OpenFOAM > OpenFOAM Programming & Development

Zero Equation Turbulence models

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   April 9, 2013, 12:56
Default Zero Equation Turbulence models
  #1
New Member
 
Stefan Gracik
Join Date: Oct 2011
Location: Penn State
Posts: 8
Rep Power: 14
stefan.gracik is on a distinguished road
Has anyone implemented any zero equation turbulence models to OpenFOAM? That is, a turbulence model which uses algebraic equations to calculate turbulent viscosity rather than PDE's (k, ε etc.). The classic example of this is the Prandtl mixing length model.

I'm trying to implement a specialized model and am having trouble modifying the 2 and 1 eq models to remove the PDE's, so I figured having a zero equation model already implemented would help me understand what I need to do.

Thanks
stefan.gracik is offline   Reply With Quote

Old   April 16, 2013, 12:25
Default
  #2
New Member
 
Stefan Gracik
Join Date: Oct 2011
Location: Penn State
Posts: 8
Rep Power: 14
stefan.gracik is on a distinguished road
I've made some progress on this, but am stuck again. It is an equation designed for modeling external airflow over buildings. The turbulence model I'm trying to implement is depended on this distance to wall, where H is the average height of the building (implemented as a dimensionedScalar)

for walldist <= 1.3*H, nut = const*exp(walldist/H)*U

and

for walldist >1.3*H, nut = const*walldist ... etc.

I thought the best way to write this would be with an if statement. Currently I have written it like this (where d_ is the walldist)

Code:
 
 
    if
    (d_ <= (1.3*H_))
    {
    nut_ = a_*zh_*exp(-b_*d_/H_)*U_*pow((d_/H_),2);
    nut_.correctBoundaryConditions();
    }
    else
    {
    nut_ = 0.16*Uh_*(d_ + z0_)/Foam::log((d_ + z0_)/z0_);
    nut_.correctBoundaryConditions();
    }
but receive a pretty long error

Code:
wmakeLnInclude: linking include files to ./lnInclude
Making dependency list for source file mykEpsilon.C
SOURCE=mykEpsilon.C ;  g++ -m64 -Dlinux64 -DWM_DP -Wall -Wextra -Wno-unused-parameter -Wold-style-cast -Wnon-virtual-dtor -O3  -DNoRepository -ftemplate-depth-100 -I/opt/openfoam211/src/turbulenceModels -I/opt/openfoam211/src/transportModels -I/opt/openfoam211/src/finiteVolume/lnInclude -I/opt/openfoam211/src/meshTools/lnInclude -I/opt/openfoam211/src/turbulenceModels/incompressible/RAS/lnInclude -IlnInclude -I. -I/opt/openfoam211/src/OpenFOAM/lnInclude -I/opt/openfoam211/src/OSspecific/POSIX/lnInclude   -fPIC -c $SOURCE -o Make/linux64GccDPOpt/mykEpsilon.o
mykEpsilon.H: In constructor ‘Foam::incompressible::RASModels::mykEpsilon::mykEpsilon(const volVectorField&, const surfaceScalarField&, Foam::transportModel&, const Foam::word&, const Foam::word&)’:
mykEpsilon.H:81:31: warning: ‘Foam::incompressible::RASModels::mykEpsilon::H_’ will be initialized after [-Wreorder]
mykEpsilon.H:77:31: warning:   ‘Foam::dimensionedScalar Foam::incompressible::RASModels::mykEpsilon::Uh_’ [-Wreorder]
mykEpsilon.C:47:1: warning:   when initialized here [-Wreorder]
mykEpsilon.C:160:19: error: no match for ‘operator<=’ in ‘((Foam::incompressible::RASModels::mykEpsilon*)this)->Foam::incompressible::RASModels::mykEpsilon::d_ <= Foam::operator*(const Foam::dimensioned<double>&, const Foam::dimensioned<Type>&) [with Type = double]((*(const Foam::dimensioned<double>*)(&((Foam::incompressible::RASModels::mykEpsilon*)this)->Foam::incompressible::RASModels::mykEpsilon::H_)))’
mykEpsilon.C:160:19: note: candidates are:
/opt/openfoam211/src/OpenFOAM/lnInclude/UList.C:224:6: note: bool Foam::UList<T>::operator<=(const Foam::UList<T>&) const [with T = double]
/opt/openfoam211/src/OpenFOAM/lnInclude/UList.C:224:6: note:   no known conversion for argument 1 from ‘Foam::dimensioned<double>’ to ‘const Foam::UList<double>&’
/opt/openfoam211/src/OpenFOAM/lnInclude/VectorSpaceI.H:693:13: note: template<class Form, class Cmpt, int nCmpt> bool Foam::operator<=(const Foam::VectorSpace<Form, Cmpt, nCmpt>&, const Foam::VectorSpace<Form, Cmpt, nCmpt>&)
mykEpsilon.C:162:50: error: no match for ‘operator=’ in ‘((Foam::incompressible::RASModels::mykEpsilon*)this)->Foam::incompressible::RASModels::mykEpsilon::nut_ = Foam::operator*(const Foam::tmp<Foam::GeometricField<Type, PatchField, GeoMesh> >&, const Foam::tmp<Foam::GeometricField<double, PatchField, GeoMesh> >&) [with Type = Foam::Vector<double>, PatchField = Foam::fvPatchField, GeoMesh = Foam::volMesh]((*(const Foam::tmp<Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> >*)(& Foam::pow(const Foam::tmp<Foam::GeometricField<double, PatchField, GeoMesh> >&, const scalar&) [with PatchField = Foam::fvPatchField, GeoMesh = Foam::volMesh, Foam::scalar = double]((* &2.0e+0)))))’
mykEpsilon.C:162:50: note: candidates are:
/opt/openfoam211/src/OpenFOAM/lnInclude/GeometricField.C:1083:6: note: void Foam::GeometricField<Type, PatchField, GeoMesh>::operator=(const Foam::GeometricField<Type, PatchField, GeoMesh>&) [with Type = double, PatchField = Foam::fvPatchField, GeoMesh = Foam::volMesh]
/opt/openfoam211/src/OpenFOAM/lnInclude/GeometricField.C:1083:6: note:   no known conversion for argument 1 from ‘Foam::tmp<Foam::GeometricField<Foam::Vector<double>, Foam::fvPatchField, Foam::volMesh> >’ to ‘const Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh>&’
/opt/openfoam211/src/OpenFOAM/lnInclude/GeometricField.C:1108:6: note: void Foam::GeometricField<Type, PatchField, GeoMesh>::operator=(const Foam::tmp<Foam::GeometricField<Type, PatchField, GeoMesh> >&) [with Type = double, PatchField = Foam::fvPatchField, GeoMesh = Foam::volMesh]
/opt/openfoam211/src/OpenFOAM/lnInclude/GeometricField.C:1108:6: note:   no known conversion for argument 1 from ‘Foam::tmp<Foam::GeometricField<Foam::Vector<double>, Foam::fvPatchField, Foam::volMesh> >’ to ‘const Foam::tmp<Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> >&’
/opt/openfoam211/src/OpenFOAM/lnInclude/GeometricField.C:1144:6: note: void Foam::GeometricField<Type, PatchField, GeoMesh>::operator=(const Foam::dimensioned<Form>&) [with Type = double, PatchField = Foam::fvPatchField, GeoMesh = Foam::volMesh]
/opt/openfoam211/src/OpenFOAM/lnInclude/GeometricField.C:1144:6: note:   no known conversion for argument 1 from ‘Foam::tmp<Foam::GeometricField<Foam::Vector<double>, Foam::fvPatchField, Foam::volMesh> >’ to ‘const Foam::dimensioned<double>&’
make: *** [Make/linux64GccDPOpt/mykEpsilon.o] Error 1
stefan@stefan-OpenFOAM:~/OpenFOAM/stefan-2.1.1/src/turbulenceModels/incompressible/RAS/mykEpsilon$
Any idea what the issue is? I have a feeling it has something to do with comparing walldist to a dimensionedScalar, but I'm really not sure.
stefan.gracik is offline   Reply With Quote

Old   April 17, 2013, 04:33
Default
  #3
Member
 
cosimo bianchini
Join Date: Mar 2009
Location: Florence, Tuscany, Italy
Posts: 88
Rep Power: 17
cosimobianchini is on a distinguished road
Send a message via Skype™ to cosimobianchini
If I did not misunderstand you should use your if statement within a loop on the internal cells of your volScalarField nut_. What the error is saying is that it makes no sense a statement like <= for a volScalarField in fact for some cells it will be > for others <.

In order to make it work write something like

forAll(nut_,cellI)
{
if(d_[cellI] <= (1.3*H_))
{
nut_[cellI] = a_*zh_*exp(-b_*d_[cellI]/H_)*mag(U_)*pow((d_[cellI]/H_),2);
}
else
{
nut_[cellI] = 0.16*Uh_*(d_[cellI] + z0_)/Foam::log((d_[cellI] + z0_)/z0_);
}
}

assuming that all other variables except for d_ and U_ are of type scalar this should work.
Another thing you should pay attention to is in the use of vector variables (I guessed U_ it is velocity vector) in a statement with scalars on the LHS, I added the operator mag(U_) to evaluate the magnitude of velocity but I'm not sure this is what you want. Change the operator accordingly to your needs but check that it returns a scalar.
__________________
Cosimo Bianchini

Ergon Research s.r.l.
Via Panciatichi, 92
50127 Florence - ITALY
Tel: +39 055 0763716
Mob: +39 320 9460153
e-mail: cosimo.bianchini@ergonresearch.it
URL: www.ergonresearch.it
cosimobianchini is offline   Reply With Quote

Old   April 17, 2013, 15:12
Default Thanks
  #4
New Member
 
Stefan Gracik
Join Date: Oct 2011
Location: Penn State
Posts: 8
Rep Power: 14
stefan.gracik is on a distinguished road
Thanks for the help!! but now I have a new error. d_ is generated from walldist.H, so it's the distance to the nearest wall. All of the other constants I've defined as dimensionedScalar

Code:
a_
    (
        dimensioned<scalar>::lookupOrAddToDict
        (
            "a",
            coeffDict_,
            0.09
        )
    ),
    b_
    (
        dimensioned<scalar>::lookupOrAddToDict
        (
            "b",
            coeffDict_,
            0.09
        )
    ),
    H_
    (
        dimensioned<scalar>//::lookupOrAddToDict
        (
            "H",
            dimensionSet(0, 1, 0, 0, 0, 0, 0),
            1.92
        )
    ),

    Uh_
    (
        dimensioned<scalar>//::lookupOrAddToDict
        (
            "Uh",
        dimensionSet(0, 1, -1, 0, 0, 0, 0),
            1.44
        )
    ),

    zh_
    (
        dimensioned<scalar>//::lookupOrAddToDict
        (
            "zh",
            dimensionSet(0, 1, 0, 0, 0, 0, 0),
            1.92
        )
    ),
    z0_
    (
        dimensioned<scalar>//::lookupOrAddToDict
        (
            "z0",
            dimensionSet(0,1,0,0,0,0,0),
            1.3
        )
    ),
but I still receive the error
"mykEpsilon.C:180:83: error: cannot convert ‘Foam::dimensioned<double>’ to ‘double’ in assignment"

Anyone have any idea why this could be?
stefan.gracik is offline   Reply With Quote

Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Turbulence postprocessing Mohsin FLUENT 2 October 3, 2016 15:18
Calculation of the Governing Equations Mihail CFX 7 September 7, 2014 07:27
Reynolds transport, turbulence model, etc Beginner Main CFD Forum 1 January 7, 2009 06:36
Solving the turbulence equation summer FLUENT 4 July 13, 2007 10:57
turbulence models? haider FLUENT 0 March 8, 2006 00:58


All times are GMT -4. The time now is 18:00.