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-   -   Getting the cells next to a patch (http://www.cfd-online.com/Forums/openfoam-meshing/82881-getting-cells-next-patch.html)

arkangel December 8, 2010 10:05

Getting the cells next to a patch
 
Dear Foamers,

I want to get the indexes of the cells right next to a patch. In other words, I want to access the owner index of a face that conforms a patch

something like this

Code:

foreach (patchList , patchI){
    foreach (patchList[patchI].faces(), facesI){
        mesh.C[patchList[patchI].faces[facesI].owner] =val;

  }
 }

or maybe you have a better idea of how can I do it

thanks !!

hjasak December 20, 2010 13:43

Do patch.faceCells()

That will give you cell indices for cells next to patch faces.

Enjoy,

Hrv

arkangel January 25, 2011 12:33

Thanks a lot Hrv!

Now I want to access the face values of a boundary patch in a specific scalarField/vectorField using these indexes.

I mean, let says that
forAll ( patch.faceCells(),cellI) gives me indexes cellI=1 2 ....

then cell[1] has a face on this patch whose b value is -1.0, where b is an scalar field
I want to recover this -1.0.

I hope I was clear enough

Regards

nygbook April 13, 2011 21:21

I suggest you read the code in wallViscosity
HTML Code:

  const fvPatchList& patches = mesh.boundary();
    forAll(patches, patchi)
    {
        const fvPatch& currPatch = patches[patchi];
        if (isType<wallFvPatch>(currPatch))
        {
            scalarField& nutw = nutb.boundaryField()[patchi];
            forAll(currPatch, facei)
            {
                label faceCelli = currPatch.faceCells()[facei];
                // calculate yPlus
                scalar yPlus =
                    Cmu25*y[patchi][facei]
                  *::sqrt(k[faceCelli])
                  /nub_;
                if (yPlus > 11.6)
                {
                    nutw[facei] =
                        yPlus*nub_*kappa_
                      /::log(E_*yPlus)
                      - nub_;
                }
                else
                {
                    nutw[facei] = 0.0;
                }
            }
        }
    }
}

where k[faceCelli] is the turbulent kinetic in cell close to wall. However, I have another question. What is y[patchi][facei] and nutw[facei]? According to wall function theory, y[patchi][facei] and nutw[facei] should be distance between center of cell and wall and viscosity in cell close to wall. why cann't write nutw[faceCelli]

nygbook April 13, 2011 21:34

:)another question
what different is betweent U.boundaryField( )[patchi].patchInternalField( ) and U[faceCelli]

darlopez April 23, 2012 08:10

Hi everybody.

I try to program the Simpson's rule in order to obtain the pressure force on a patch. To do it I should obtain the value of the pressure in all cells next to the patch. I have programed:



forAll(forcePatches, patchi)
{
const fvPatch& curPatch = forcePatches[patchi];
label forcePatchID = mesh.boundaryMesh().findPatchID(forcePatches[patchi]);

if (isType<wallFvPatch>(forcePatches[patchi]))
{
scalarField& pp = p.boundaryField()[patchi];

forAll(forcePatches[patchi], facei)
{
label faceCelli = curPatch.faceCells()[facei];
P[faceCelli]=pp[faceCelli]; // I save the values of pressure in vector P
}
}

// Now, Simpson's rule:
int i = 1;
for(int i = 1; i <= 374; i++) // I have 750 cells on each patch
{
A = A + 2 * P[2*i]*0.02*0.02; // where 0.02*0.02 is the area of the face of each cell
}
int j = 2;
for(int j = 2; j <= 375; j++)
{
B = B + 4 * P[2*j-1]*0.02*0.02;
}
a0 = P[1];
an = P[750];

scalar PressForce = 0.02/3*(a0 + A + B + an);

vector patchPressForce = PressForce * gSum(mesh.Sf().boundaryField()[forcePatchID])/gSum(mesh.magSf().boundaryField()[forcePatchID]);

// Multiply the resulting force by density to account for normalisation in
// incompressible solvers, and get component in direction of motion
scalar totPatchPressForce = (patchPressForce
* mediumRho.value()
) & aVector;

Info << "Area of patch " << forcePatches[patchi] << " [m^2] = "
<< gSum(mesh.magSf().boundaryField()[forcePatchID]) << endl;

Info << "Pressure force on patch " << forcePatches[patchi] << " [N] = " << totPatchPressForce << endl;

totPressureForce += totPatchPressForce;
}

Info << "Total Pressure Force along motion vector [N] = " << totPressureForce << endl;
}


But this loop does not work. Any ideas?? Where is the problem??

Thanks a lot.

Darío


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