instructional workshop on openfoam programming lecture # 5€¦ · instructional workshop on...

Instructional workshop on OpenFOAMprogramming

LECTURE # 5

Pavanakumar Mohanamuraly

April 28, 2014

Outline

User defined boundary conditions - part I

User defined boundary conditions - part II

Recap

I fvMatrix class and boundaryCoeffs and internalCoeffsI Typos in Day 2 slides

I FVPatch should have been FvPatchI Make/files - missed an ‘s ′ in RobinFvPatchFields.C

Implementing Robins BC

I No need for two versions to be implemented fvm and fvc

I Need to read in three extra parameter φ′, a and b

aφ(0) + bφ′(0) and/or aφ(L) + bφ′(L) (1)

I This will introduce one extra RHS source term to theDirichlet BC

I Makes sense to use the Dirichlet BC and modify it for Robin

Hands on - Setting upI Copy the contents of

FOAM SRC/finiteVolume/fields/fvPatchFields/basic/fixedValueto a folder named MY FOLDER/RobinBC

I Rename all files having prefix fixedValueFvPatchField toRobinFvPatchField

for name in fixedValueFvPatchField*do

newname=RobinFvPatchField"$(echo "$name" | cut -c23-)"

mv "$name" "$newname"done

I Find and replace text fixedValueFvPatchField toRobinFvPatchField in all files

sed -i 's/fixedValueFvPatchField/RobinFvPatchField/g' RobinFvPatchField*

Hands on - Make changes

I Replace all fixedValue fields with Robin

sed -i 's/fixedValue/Robin/g' RobinFvPatchField*

I Runtime type information

TypeName("Robin");

I Runtime object selection

RobinFvPatchFields.C:37:makePatchFields(Robin);RobinFvPatchFields.H:39:makePatchTypeFieldTypedefs(

Robin)RobinFvPatchFieldsFwd.H:40:

makePatchTypeFieldTypedefs(Robin)

I wclean and

I wmake libso to create library libRobinBC .so

Hands on - Compile code

I Create the Make folder with files and options as follows

files

RobinFvPatchFields.C

LIB = libRobinBC

options

EXE_INC = \-I$(LIB_SRC)/finiteVolume/lnInclude -g

EXE_LIBS = -lfiniteVolume

I wmake libso to create library libRobinBC .so

Hands on - More changes

I Make the fixesValue() boolean function return false in fileRobinFvPatchField .H

virtual bool fixesValue() const{return false;

}

Hands on - Preliminary testing I

I Go to the 1d case folder and add the following tosystem/controlDict

libs ("libRobinBC.so");

I Set the library environment search path to theMake/linux ∗ ∗ ∗ ∗∗ folder (where the libRobinBC .so iscreated)

I Run the previous hands on example and check if you get errors

I If you get a warning as shown below

From function dlLibraryTable::open(const fileName&functionLibName)

in file db/dlLibraryTable/dlLibraryTable.C at line85

could not load dlopen(libRobinBC.so, 9): image notfound

I Check your library path and see if the lib file exists

Hands on - Preliminary testing II

I In the fields file replace all fixedValue types to Robin

I Re-run the code and it should give the same results as runusing fixedValue

I This ensures that the BC is compiled, loaded and setupcorrectly

Getting inputs - φ′, a and b

I Declare variables (RobinFvPatchField.H)

templateclass RobinFvPatchField: public fvPatchField{//- The $\phi'$ valueField gradPhiBoundary_;//- The const parameter a and bscalar a_, b_;

I gradPhiBoundary is of type ”Field < Type > ” (scalar ,vector or tensor)


I Constructor - 1 (RobinFvPatchField.C)

//- Construct from patch and internal fieldtemplateRobinFvPatchField::RobinFvPatchField(

const fvPatch& p,const DimensionedField& iF

):fvPatchField( p, iF ),gradPhiBoundary_( p.size(), pTraits::zero ),a_(), b_(){}



templateRobinFvPatchField::RobinFvPatchField(

const fvPatch& p,const DimensionedField& iF,const dictionary& dict

):fvPatchField( p, iF, dict, true ),gradPhiBoundary_( "gradient", dict, p.size() ),a_(dict.lookupOrDefault( "a", scalar(1.0))),b_(dict.lookupOrDefault( "b", scalar(0.0))){ }




const RobinFvPatchField& ptf,const fvPatch& p,const DimensionedField& iF,const fvPatchFieldMapper& mapper

):fvPatchField( ptf, p, iF, mapper ),gradPhiBoundary_( ptf.gradPhiBoundary_ ),a_( ptf.a_ ), b_( ptf.b_ ){}




const RobinFvPatchField& ptf):fvPatchField( ptf ),gradPhiBoundary_( ptf.gradPhiBoundary_ ),a_( ptf.a_ ), b_( ptf.b_ ){}




const RobinFvPatchField& ptf,const DimensionedField& iF

):fvPatchField( ptf, iF ),gradPhiBoundary_( ptf.gradPhiBoundary_ ),a_( ptf.a_ ), b_( ptf.b_ ){}


I Printing the boundary patch information(RobinFvPatchField.C)

templatevoid RobinFvPatchField::write(Ostream& os)

const{

fvPatchField::write(os);this->writeEntry( "value", os);gradPhiBoundary_.writeEntry( "gradient", os);os.writeKeyword("a")

Hands on - Testing BC inputI Compile code again to create libRobinBC .soI Modify example (laplacian solver) - loop over boundaryFields

and print field

Info

Some concepts - deltaCoeffs()

I deltaCoeffs() is the reciprocal distanceI Between owner and neighbour cell centroids of an internal face

surfaceInterpolation.C : lines (234 - 242)

// Set local references to mesh dataconst volVectorField& C = mesh_.C();const labelUList& owner = mesh_.owner();const labelUList& neighbour = mesh_.neighbour();

forAll(owner, facei){DeltaCoeffs[facei] = 1.0/mag(C[neighbour[facei]] -

C[owner[facei]]);}

Some concepts - deltaCoeffs()I deltaCoeffs() is the reciprocal distance

I Between owner and boundary face centroid of patch face

surfaceInterpolation.C : lines (244 - 248)

forAll(DeltaCoeffs.boundaryField(), patchi){DeltaCoeffs.boundaryField()[patchi] =1.0/mag(mesh_.boundary()[patchi].delta());

}

fvPatch.C : lines (141 - 143)

Foam::tmp Foam::fvPatch::delta()const

{return Cf() - Cn();

}

Some concepts - Patch gradient and value coefficients

Patch object should return the following to evaluate patch BC foroperators

I valueInternalCoeffs()I Return the matrix diagonal coefficients corresponding to the

evaluation of the value of the patchField with given weights

I valueBoundaryCoeffs()I Return the matrix source coefficients corresponding to the

evaluation of the value of the patchField with given weight

I gradientInternalCoeffs()I Return the matrix diagonal coefficients corresponding to the

evaluation of the gradient of the patchField

I gradientBoundaryCoeffs()I Return the matrix source coefficients corresponding to the

evaluation of the gradient of this patchField

Some concepts - Patch value coefficients example

Using the value internal/boundary coefficients to get fvMatrixentries (Gauss-Gradient scheme)

gaussConvectionScheme.C (::fvmDiv function)

forAll(fvm.psi().boundaryField(), patchI){

const fvPatchField& psf =fvm.psi().boundaryField()[patchI];

const fvsPatchScalarField& patchFlux =faceFlux.boundaryField()[patchI];

const fvsPatchScalarField& pw =weights.boundaryField()[patchI];

fvm.internalCoeffs()[patchI] =patchFlux*psf.valueInternalCoeffs(pw);

fvm.boundaryCoeffs()[patchI] =-patchFlux*psf.valueBoundaryCoeffs(pw);

}

Rationale behind value coefficients (face valueinterpolation)

i=Ni=1

i=Ni=1

R L

RL

f1 f2

L R

ii-1 i+1

iRL

f1 f2

R L

i-1 i+1

i = 1fx=0

R L

i = 2

i = NRL

fx=L

I Dirichlet type

φf = φ0︸︷︷︸RHS source

+ 0︸︷︷︸LHS coeff

I Neumann boundary conditions

δ∫0

fx=0dx =

δ∫0

φf − φ1δ

dx = φf − φ1

φf = 1︸︷︷︸LHS coeff

×φ1 + fx=0δ︸︷︷︸RHS source

(2)

Some concepts - fixedValue patch coefficients

fixedValueFvPatchField.C

templatetmp fixedValueFvPatchField::

valueInternalCoeffs( const tmp& ) const{

return tmp( new Field(this->size(), pTraits::zero) );

}


templatetmp fixedValueFvPatchField::

valueBoundaryCoeffs( const tmp& ) const{ return *this; } /// this has base class Field

Some concepts - fixedGradient patch coefficients

fixedGradientFvPatchField.C

templatetmp fixedGradientFvPatchField::

valueInternalCoeffs( const tmp& ) const{

return tmp(new Field(this->size(), pTraits::one));

}


templatetmp fixedGradientFvPatchField::

valueBoundaryCoeffs( const tmp& ) const{ return gradient()/this->patch().deltaCoeffs(); }

Some concepts - Patch gradient coefficients example

Using the value internal/boundary coefficients to get fvMatrixentries (Gauss-Laplacian scheme)

gaussLaplacianScheme.C (::fvmLaplacianUncorrected function)

forAll(fvm.psi().boundaryField(), patchI){

const fvPatchField& psf = fvm.psi().boundaryField()[patchI];

const fvsPatchScalarField& patchGamma =gammaMagSf.boundaryField()[patchI];

fvm.internalCoeffs()[patchI] = patchGamma*psf.gradientInternalCoeffs();

fvm.boundaryCoeffs()[patchI] = -patchGamma*psf.gradientBoundaryCoeffs();

}

Rationale behind gradient coefficients (one-sided facegradient)

i=Ni=1

i=Ni=1

R L

RL

f1 f2

L R

ii-1 i+1

iRL

f1 f2

R L

i-1 i+1

i = 1fx=0

R L

i = 2

i = NRL

fx=L

I Dirichlet type

fx=0 =φfdx

=φf − φ1

δ=

φfδ︸︷︷︸

RHS source

− 1δ︸︷︷︸

LHS coeff

φ1

I Neumann boundary conditions

fx=0 = φ′x=0︸︷︷︸

RHS source

+ 0︸︷︷︸LHS coeff

Some concepts - fixedValue patch coefficients


templatetmp fixedValueFvPatchField::gradientInternalCoeffs() const{

return -pTraits::one*this->patch().deltaCoeffs();}


templatetmp fixedValueFvPatchField::gradientBoundaryCoeffs() const{

return this->patch().deltaCoeffs()*(*this);}

Some concepts - fixedGradient patch coefficients


templatetmp fixedGradientFvPatchField::gradientInternalCoeffs() const{

return tmp( new Field(this->size(), pTraits::zero) );

}


templatetmp fixedGradientFvPatchField::gradientBoundaryCoeffs() const{

return gradient();}

Hands on - RobinBC implementation

I Use the value and gradient coefficients shown in previousslides and implement the following Robin BC

I At x = 0aφ(0) + bφ′(0) (3)

I At x = Laφ(L) + bφ′(L) (4)

I Compile the libRobinBC .so and test the code

Custom BC done !

Robin BC

i=Ni=1

i=Ni=1

R L

RL

f1 f2

L R

ii-1 i+1

iRL

f1 f2

R L

i-1 i+1

i = 1fx=0

R L

i = 2

i = NRL

fx=L

I Value Coefficients

aφdirf + bφneuf = a︸︷︷︸

LHS

×φ1 + bfx=0δ + aφ0︸︷︷︸RHS

I Gradient Coefficients

aφ′dirf + bφ′neuf = −

a

δ︸︷︷︸LHS

×φ1 +aφfδ

+ bφ′x=0︸︷︷︸RHS

(5)

I Remember a and b are between [0, 1] 0 ≤ a, b ≤ 1

End of Week 2 Day 3

User defined boundary conditions - part IUser defined boundary conditions - part II

instructional workshop on openfoam programming lecture # 5€¦ · instructional workshop on...

Documents