[NilsTilton]

Dear OpenFoam Community,

As part of learning OpenFoam, I am solving a simple steady heat conduction problem using laplacianFoam, and I am systematically experimenting with different methods of applying nonuniform Dirichlet boundary conditions. From the OpenFoam documentation and online sources, I have grasped how to apply a polynomial temperature profile using "fixedProfile" and "polynomial." For example, along a patch named west, I can apply the temperature T =1 + 2y using the following entry in my 0/T file:

west
{
type fixedProfile;
profile polynomial
(
(1 0)
(2 1)
);
direction (0 1 0);
origin 0;
}

My question is the following. Can I use a similar approach to apply the condition T = cos(y) along the same west boundary? The online documentation for fixedProfile mentions that I can apply a <Function1<Type>> for profile. Meanwhile, I see in the source code files (src/OpenFOAM/primitives/functions/Function1/) that there is a cosine. However, the .H file for cosine seems to imply it's reserved for taking the cosine of time, and not a spatial coordinate. So in summary, is there a way to use "fixedProfile" and "cosine" to apply the condition, or am I barking up the wrong tree? I plan to explore using codeStream next, but didn't like this conceptual issue left hanging.

[tomf]

Hi Nils,

If you are on the openfoam.com version, you may want to look into some examples of expressions.

Best regards,
Tom

[NilsTilton]

Hi Tom,

Thanks for the link. It has some great info I was missing.

Best Wishes,
Nils

[NilsTilton]

Hi All,

For those interested in applying general Dirichlet conditions, here are three ways of applying the sinusoidal temperature profile T=273+80*cos(4*pi*x/Lx) on a boundary patch called north. The first uses OpenFOAM's fixedProfile. The second uses fixedValue with codeStream. The third uses codedFixedProfile

Option 1 using fixedProfile with coded:

north
{
type fixedProfile;
profile coded
name CosineT;

codeInclude
#{
#include "mathematicalConstants.H"
#};

code
#{
scalar Lx = 1;
scalar pi = 3.141592653589793;
return scalar
(
273 + 80*cos(4.0*pi*x/Lx)
);
#};
direction (1 0 0);
origin 0;

}

Option 2 using fixedValue with codeStream:


north
{
type fixedValue;
value #codeStream
{

// optional include files
codeInclude
#{
#include "fvCFD.H"
#};

// optional compile options
codeOptions
#{
-I$(LIB_SRC)/finiteVolume/lnInclude \
-I$(LIB_SRC)/meshTools/lnInclude
#};

// optional libraries
codeLibs
#{
-lfiniteVolume \
-lmeshTools
#};


code
#{

//----------- required to access patch data ------------//
const IOdictionary& d = static_cast<const IOdictionary&>
(
dict.parent().parent()
);

const fvMesh& mesh = refCast<const fvMesh>(d.db());
const label id = mesh.boundary().findPatchID("north");
const fvPatch& patch = mesh.boundary()[id];
//------------------------------------------------------//


scalar pi = 3.141592653589793;
scalar Lx = 1;

scalarField TN(patch.size(), 0.0);
forAll(TN, i)
{
const scalar x = patch.Cf()[i][0];
TN[i] = 273 + 80*cos(4.0*pi*x/Lx);
}

TN.writeEntry("", os);


#};

};

}

Option 3 using codedFixedProfile:

north
{
type codedFixedValue;
value uniform 0; // optional
name CosineCondition;

// optional include files
codeInclude
#{
#include "fvCFD.H"
#};

// optional compile options
codeOptions
#{
-I$(LIB_SRC)/finiteVolume/lnInclude \
-I$(LIB_SRC)/meshTools/lnInclude
#};

// optional libraries
codeLibs
#{
-lfiniteVolume \
-lmeshTools
#};


code
#{
scalar Lx = 1.0;
scalar pi = 3.141592653589793;
vector xdir(1,0,0);
scalarField x( patch().Cf()&xdir );

operator==(
273 + 80*Foam::cos( 4.0*pi*x/Lx )
);

#};

}