CFD Online Discussion Forums - [Other] Getting the cells next to a patch

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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 !!

Do patch.faceCells()

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

Enjoy,

Hrv

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

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]

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

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