CFD Online Discussion Forums - Understanding about updateCoeffs() in solidDisplacementFoam

CFD Online Discussion Forums (https://www.cfd-online.com/Forums/)

- OpenFOAM Programming & Development (https://www.cfd-online.com/Forums/openfoam-programming-development/)

- - Understanding about updateCoeffs() in solidDisplacementFoam (https://www.cfd-online.com/Forums/openfoam-programming-development/146503-understanding-about-updatecoeffs-soliddisplacementfoam.html)

Understanding about updateCoeffs() in solidDisplacementFoam

Hi,
In solidDisplacementFoam solver,at tractionDisplacementFvPatchVectorField.C, there is a following piece of code for updateCoeffs().

Code:

void tractionDisplacementFvPatchVectorField::updateCoeffs()

{

...

gradient() =

    (

        (traction_ - pressure_*n)/rho

      + twoMuLambda*fvPatchField<vector>::snGrad() - (n & sigmaD)

    )/twoMuLambda;

...

fixedGradientFvPatchVectorField::updateCoeffs();

}

Whereas, in stressedFoam solver, at tractionDisplacementFvPatchVectorField.C;the corresponding code is:

Code:

void tractionDisplacementFvPatchVectorField::updateCoeffs()

{

...

gradient() =

    (

        (traction_ - pressure_*n)/rho.value()

      - (n & (mu.value()*gradU.T() - (mu + lambda).value()*gradU))

      - n*tr(gradU)*lambda.value()

    )/(2.0*mu + lambda).value();



fixedGradientFvPatchVectorField::updateCoeffs();

}

1. What does the value() assign to mu in mu.value()?
2. Similarly, the meaning of gradU.T().
3. Do they convert a scalar to a matrix of given size?
4. Is there a layman way to understand the process of coefficients being updated?

Yours
Anil Kunwar

Greetings Anil Kunwar,

I'll only be able to answer a few of your questions:

Quote:

Originally Posted by Annier (Post 525532)

1. What does the value() assign to mu in mu.value()?

"mu" is a dimensioned scalar, the method "value()" gets access to only the value itself. Otherwise, the operations would try to do the necessary mathematics including units.

Quote:

Originally Posted by Annier (Post 525532)

2. Similarly, the meaning of gradU.T().

"T()" - Transposes the vector/matrix. For more details: http://openfoamwiki.net/index.php/Op...s_Guide_Errata

Quote:

Originally Posted by Annier (Post 525532)

3. Do they convert a scalar to a matrix of given size?

Uhm... the calculations are automatically made by taking into account all values in the patch or field, depending on the context. This is why there isn't a "for" loop in that code that goes along all faces of a patch or all the cells of a mesh.

Quote:

Originally Posted by Annier (Post 525532)

4. Is there a layman way to understand the process of coefficients being updated?

You'll have to be more specific to which coefficients you're referring to.

Best regards,
Bruno

Hi Bruno,
Thank you very much for making me understand more about OpenFOAM code structure.
I studied about updateCoeffs() in this thread http://www.cfd-online.com/Forums/ope...m-solvers.html
Some of my understandings are:

The updateCoeffs() ,is defined at the boundary for updating the coefficients as per the gradient specified in the BC file.
The updateCoeffs() is first defined virtually at the GeometricBoundaryField.C and overloaded (redefined) later in the specific derived classes such as fixedGradientFvPatchVectorField.C.
Another function evaluate(), are also defined at the Boundaries.
These functions are virtual functions of C++.
They are important functions associated with the boundary conditions subroutines.

Still, there are many things I need to know further, in order to conceptualize how the coefficients are updated [updateCoeffs()] and evaluated [evaluate()] at the boundaries.
Where is the source location of fixedGradientFvPatchVectorField.C?
Thank you.

Yours
Anil Kunwar

Quick answer:

You can search in the source code online here: https://github.com/OpenFOAM/OpenFOAM-2.3.x
You can search in the online code documentation: http://www.openfoam.com/docs/cpp/

You can search in the source code you are currently using, as explained here: http://openfoamwiki.net/index.php/In...with_the_Shell

Quote:

Finding all dictionary files that end with "Dict" in the tutorials folder:

Code:

find $FOAM_TUTORIALS -name "*Dict"
Finding all dictionary files that end with "Dict" in the applications folder:

Code:

find $FOAM_APP -name "*Dict"
Finding which tutorial files use the boundary condition "slip":

Code:

find $FOAM_TUTORIALS -type f | xargs grep -sl 'slip'
Find where the code for the boundary condition "slip" is located:

Code:

find $FOAM_SRC -name "*slip*"

Hi Bruno,

Thank you very much. I will try to learn the things.

Yours
Anil Kunwar